- Email: [email protected]
Radiation Exposure to Operators during Vertebroplasty
Radiation Exposure to Operators during Vertebroplasty Atsushi Komemushi, MD, PhD, Noboru Tanigawa, MD, PhD, Shuji Kariya, MD, Hiroyuki Kojima, MD, Yuzo Shomura, MD, PhD, and Satoshi Sawada, MD, PhD
PURPOSE: To measure the radiation received by physicians during percutaneous vertebroplasty with use of two types of injection devices with the interventional equipment guided by computed tomography (CT) and an angiographic/CT system. MATERIALS AND METHODS: Twenty consecutive patients who underwent percutaneous vertebroplasty were included in this study. The patients were divided into two groups, the 1-mL syringe group and the bone cement injector group. Percutaneous vertebroplasties were performed with the IVR-CT system, which combines angiographic and CT equipment with a single fluoroscopy table. Radiation dose to operators was measured as equivalent dose penetrating at a 10-mm tissue depth with use of electronic personal dosimeters attached outside and inside lead aprons. Effective radiation dose (HE) was estimated based on the radiation dose outside the lead apron (Ha) and the radiation dose inside the lead apron (Hb). Differences between the groups in doses and fluoroscopic duration were analyzed. RESULTS: In the 1-mL syringe group and bone cement injector group, mean Ha measurements were 320.8 Sv and 116.2 Sv, respectively. Mean Hb measurements were 14.5 Sv versus 7.8 Sv and mean HE measurements were 48.2 Sv versus 19.7 Sv. Significant differences were found in Ha, Hb, and HE. However, duration of fluoroscopy did not differ significantly between groups. CONCLUSIONS: Radiation dose was relatively high for operators performing percutaneous vertebroplasty. The bone cement injector was useful in reducing the level of radiation exposure to operators during vertebroplasty. J Vasc Interv Radiol 2005; 16:1327–1332 Abbreviations: Ha ⫽ radiation dose received outside the lead apron, Hb ⫽ radiation dose received inside the lead apron, HE ⫽ effective radiation dose, PMMA ⫽ polymethylmethacrylate
PERCUTANEOUS vertebroplasty, a procedure in which bone cement is injected percutaneously into vertebrae affected by compression fracture, is increasingly performed for analgesia (1– 9). In general, bone cement is injected during percutaneous vertebroplasty
From the Department of Radiology, Kansai Medical University, 10-15 Fumizono, Moriguchi, Osaka 5708507, Japan. Received July 8, 2005; revision requested July 11; final revision received and accepted July 27. From the SIR 2005 Annual Meeting. Address correspondence to A.K., E-mail: [email protected] None of the authors have identified a conflict of interest. © SIR, 2005 DOI: 10.1097/01.RVI.0000179794.65662.01
under lateral fluoroscopic guidance and, as a result, operators may be exposed to a high level of radiation. In recent years, bone cement injectors have become available that feature a long tube with which the operator can inject bone cement while standing outside the field of fluoroscopy. The objective of the present study was to compare the levels of radiation exposure to operators during percutaneous vertebroplasty performed with use of two different bone cement injectors.
MATERIALS AND METHODS All patients received explanations of percutaneous vertebroplasty and handling of clinical data, and written
informed consent was obtained from each patient. The procedure of percutaneous vertebroplasty was approved by the institutional review board. It does not require such approval for each prospective clinical study. Patient Group The study included 20 patients who underwent 20 consecutive percutaneous vertebroplasty procedures at our institution from April 22 to September 2, 2004. With the envelope method described later, participants were randomly divided into a 1-mL syringe group and a bone cement injector group. Twenty envelopes that could not be distinguished from the exterior were made, 10 for a 1-mL syringe and
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Radiation Exposure to Operators during Vertebroplasty
Part
Tissue or Organ
Tissue Weighting Factor
Part Weighting Factor
Head and neck
Thyroid Bone marrow (red) Bone surface Lung Esophagus Breast Stomach Liver Bone marrow (red) Bone surface Gonads Bladder Colon Bone marrow (red) Bone surface Skin
0.05 0.12 (0.013) 0.01 (0.002) 0.12 0.05 0.05 0.12 0.05 0.12 (0.04) 0.01 (0.002) 0.20 0.05 0.12 0.12 (0.07) 0.01 (0.003) 0.05 (0.01)
0.065 (0.075)
Lower abdomen
Remainder tissues
JVIR
culated according to the following formula:
Table 1 Tissue Weighting Factors
Upper abdomen
October 2005
0.43 (0.44)
0.44 (0.45)
0.05 (0.025)
The values in parentheses were distributed as 0.01 of skin and 0.025 of remaining tissues tissue weighting factors in accordance with Nuclear Safety Technology Center in Japan.
10 for a bone cement injector. An operator selected one envelope for each participant just before vertebroplasty, thereby assigning 10 patients to the 1-mL syringe group and 10 to the bone cement injector group. Because whether the 1-mL syringe or bone cement injector was used had no detrimental effect on the patients, it does not require approval from the ethical review board for this grouping method. Radiation Dose Measurement Radiation doses to operators during the procedure were measured with use of electronic personal dosimeters (PDM-117; Aloka, Tokyo, Japan; energy threshold, 20 keV; detector, silicon solid-state; energy response, 30 keV to 3 MeV within 30% calibrated by 40 keV of x rays with use of a slab phantom; accuracy within 20%, 10 –9,999 mSv calibrated by 40 keV of x rays with use of a slab phantom; linearity within 10% to a maximum of 30 mSv/h, within 20% from 30 to 100 mSv/h; in compliance with International Committee on Radiological Protection Publication 74) attached on the outside and inside of their 0.50-mm Pb lead aprons at the upper sternal level. Dose was assessed in terms of equivalent dose penetrating at 10-mm tissue
depth outside the lead apron (Ha; detailed later) and inside the lead apron (Hb; detailed later). Dosimeters were attached at the start of percutaneous vertebroplasty and level of radiation exposure was recorded after completion of the procedure. Effective radiation dose (HE) was calculated according to the following formula in accordance with the 1990 Recommendation of the International Commission on Radiological Protection (10) and the Nuclear Safety Technology Center in Japan (Table 1). HE ⫽ 0.08Ha ⫹ 0.44Hb ⫹ 0.45Hc ⫹ 0.03Hm Where HE is the effective dose from external exposure, Ha is the head and neck equivalent dose penetrating at a 10-mm tissue depth; Hb is the chest and upper-limb equivalent dose penetrating at a 10-mm tissue depth; Hc is the abdomen and femoral region equivalent dose penetrating at a 10-mm tissue depth; and Hm is the equivalent dose penetrating at a 10-mm tissue depth of the potential maximum external exposure in the head and neck, chest and upper limb, and abdomen and femoral region. Therefore, the HE estimated by personal dosimeters on the outside and inside of the lead apron was cal-
HE ⫽ 0.11Ha ⫹ 0.89Hb Vertebroplasty Technique Percutaneous vertebroplasty procedures were performed with guidance of the IVR-CT system (Advantx-ACT; GE Medical Systems, Milwaukee, WI), which combines angiographic equipment (Advantx-LCA⫹, GE Medical Systems) and computed tomography (CT) equipment (HiSpeed LX/i; GE Medical Systems) with a single fluoroscopy table (Omega4 Angio Step; GE Medical Systems; Fig 1). The x-ray tube unit (Maxiray150TH; GE Medical Systems; Nominal anode input power, 16/47/115 kW; target material, tungsten; nominal focal spot value, 0.3/ 0.6/1.2 mm; minimal inherent filtration, 0.85; aluminum equivalent at 70 kV; nominal high voltage, 125 kV; maximum current filament, 6.5 A) was used with a 0.6-mm ⫻ 0.6-mm focal spot in normal-sized patients and a 1.2-mm ⫻ 1.2-mm focal spot in large patients. Four image intensifier formats are available: 40 cm, 32 cm, 22 cm, and 17 cm in diameter. An additional inherent aluminum filter 1.3 mm thick, movable filters of 1.0 mm aluminum and 0.5 mm copper, and an x-ray grid built into carbon fiber cover plates (Smitrontgen; Eindhoven, The Netherlands; lead grid lines, 44 lines/ cm; grid ratio, 10/1; focal distance, 110 cm; interspacer, fiber) were always applied. The system was calibrated by the manufacturer to deliver an image intensifier input dose of 12.32 Gy/ min with a 40-cm field of view in fluoroscopy and 4.4 Gy/frame with a 22-cm field of view in digital radiography. All fluoroscopic procedures were performed under automatic brightness control in which the tube potential (60 – 120 kV) and tube current are adjusted. The fluoroscopy mode was standard conventional fluoroscopy mode with an interventional digital fluoroscopy module without high-level control function. Pulse fluoroscopy was used at a rate of 60 pulses per second. Digital radiography was performed with the tube potential of 80 –90 kV, tube current of 800 mA. and frame ratio of 7.5 frames per second under automatic exposure-rate control in which the pulse windows (1.0 –10 msec) are ad-
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Figure 1. The IVR-CT system combines angiographic and CT equipment with a single fluoroscopy table.
justed. Last image hold function and collimation were used as much as possible. The system was not equipped with CT fluoroscopy function. Table shields were mounted on the fluoroscopy table to protect the operator’s body and used during all procedures. No additional shielding was used during the procedures. In the present study, percutaneous vertebroplasty was performed by four operators. All were specialists in interventional radiology with a minimum of 8 years of experience in the field, and each had performed at least 50 percutaneous vertebroplasty procedures. In each procedure, all procedures other than preparation of the bone cement were carried out by one operator. The bone cement was prepared by an assistant. All operators attempted to minimize radiation exposure during the procedure. In the 1-mL syringe group, bone cement was injected into vertebrae with use of screw-type 1-mL syringes (Medallion 1-mL syringe; Merit Medical, Salt Lake City, UT; Fig 2). In the bone cement injector group, bone cement was injected with use of a bone cement injector (Osteoject Bone Ce-
ment Delivery System; Integra Neuro Sciences, Hampshire, UK), which allows operators to keep their hands 34 cm (23 cm as tube and 11 cm as syringe) outside the fluoroscopy field (Fig 3). After intramuscular injection of 25 mg of hydroxyzine hydrochloride (Atarax P; Pfizer Japan, Tokyo, Japan), 0.5 mg of atropine sulfate (Tanabe Seiyaku, Osaka, Japan) and 10 mg of morphine hydrochloride (Sankyo, Tokyo, Japan), the patient was positioned prone on the fluoroscopy table. Continuous blood pressure monitoring and pulse oximetry were performed. The location of vertebrae to be treated was reconfirmed with lateral fluoroscopy. Plain vertebral CT was performed to reference the puncture site and angle. The skin overlying the vertebral body to be injected was cleaned and draped. The skin, subcutaneous tissues, and periosteum over the pedicle to be punctured were then anesthetized with 1% lidocaine hydrochloride (Xylocaine polyamp 1%; AstraZeneca, Osaka, Japan) with use of a 22-gauge, 70-mm Cathelin needle (Terumo, Leuven, Belgium) with reference to CT images and lat-
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eral fluoroscopic guidance, and the needle tip was retained adjacent to the pedicle. CT was then performed to confirm the needle location. With this needle as a guide, a 13-gauge needle (Osteo-site Bone Biopsy Needle Murphy M2; 13-gauge, 10 cm; Cook, Bloomington, IN) was advanced without fluoroscopic guidance until its tip penetrated the cortex. CT was again performed to verify the needle position. Under lateral fluoroscopic guidance, the needle was then advanced into the vertebral body. Ideally, the tip of the needle was placed in the anterior third of the vertebral body, close to the midline. More posterior needle positions occasionally had to be accepted when treating severely compressed vertebral bodies with steep pedicle angulation. Venography was then performed with use of CO2 as a contrast agent. CO2 was drawn from a CO2 generator through a sterile filter into a 10-mL or 20-mL syringe (Gaster; Asahi Keiki, Osaka, Japan). After connecting the syringe containing CO2 to the bone biopsy needle via 50 cm of extensible tubing, the operator manually injected CO2 while keeping as far from the fluoroscopic field as possible. Frontal and lateral venograms were obtained with use of digital subtraction angiography. The amount of CO2 used in venography was 10 mL for thoracic vertebrae and 20 mL for lumbar vertebrae (9). Data collection for digital subtraction angiography was performed with a 12-inch image intensifier at nine frames per second. After this, 20 g of methylmethacrylate powder (Osteobond copolymer bone cement; Zimmer, Warsaw, IN) was mixed with 5 g of dry heat-sterilized barium sulfate powder (Horii, Osaka, Japan) to increase its opacity (11). Next, 10 mL of liquid methylmethacrylate monomer was added to the powder, and the resulting polymethylmethacrylate (PMMA) mixture was blended to a toothpaste-like consistency. The PMMA was loaded into a 10-mL syringe (Terumo) and backfilled into a screw-type 1-mL syringe or bone cement injector system, ensuring that air was expelled from the PMMA. The PMMA was injected with lateral fluoroscopic guidance (Figs 2,3). Injection was terminated when adequate filling of the vertebral body was
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Radiation Exposure to Operators during Vertebroplasty
JVIR
tion. Total fluoroscopy time during vertebroplasty and fluoroscopy time during cement injection were recorded. After the CT procedure, all patients were observed in the supine position for 2 hours. To avoid radiation exposure associated with CT scanning, CT was performed while the operator was in the adjacent control room. Statistical Analysis.
Figure 2. In the 1-mL syringe group, bone cement was injected into vertebrae with use of screw-type 1-mL syringes with lateral fluoroscopic guidance.
With a Mann-Whitney U test, we analyzed the differences between the 1-mL syringe group and the bone cement injector group with respect to the following parameters: equivalent dose penetrating at 10-mm tissue depth outside lead apron (ie, Ha) and inside lead apron (ie, Hb), HE, total fluoroscopy duration, and fluoroscopy duration during cement injection. A P value less than .05 was considered to indicate significance. All analyses were performed using StatView (Version 5.0; SAS, Cary, NC) for Windows (Microsoft, Redmond, WA).
RESULTS
Figure 3. In the bone cement injector group, bone cement was injected with use of a bone cement injector system, which allows operators to keep their hands 34 cm outside the fluoroscopy field, with lateral fluoroscopic guidance.
achieved or when leakage outside the vertebral body occurred. When leakage occurred, the needle was repositioned and additional PMMA was in-
jected to fill the remaining part of the vertebral body. The needle was then removed and plain vertebral CT was performed to confirm PMMA distribu-
In the 1-mL syringe group, 19 vertebrae were treated during 10 procedures, and in the bone cement injector group, 16 vertebrae were treated during 10 procedures. All procedures were carried out without complications. The average number of treated vertebrae per procedure was 1.75 ⫾ 0.79 (SD) for the 20 subjects: 1.90 ⫾ 0.88 for the 1-mL syringe group and 1.60 ⫾ 0.70 for the bone cement injector group. Student t test did not reveal a significant difference between groups. Average total fluoroscopy time did not differ significantly between the 1-mL syringe group and the bone cement injector group (7.54 min ⫾ 3.50 vs 6.66 min ⫾ 2.45). Average fluoroscopy time for bone cement injection did not differ significantly between the 1-mL syringe group and the bone cement injector group (3.57 min ⫾ 1.73 vs 2.40 min ⫾ 0.91). Average Ha measurements were 320.8 Sv ⫾ 232.2 for the 1-mL syringe group and 116.2 Sv ⫾ 92.8 for the bone cement injector group. Average Hb measurements for these two groups were 14.5 Sv ⫾ 11.3 and 7.8 Sv ⫾ 9.7, respectively. Average HE
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Table 2 Fluoroscopy Times and Radiation Doses
Total fluoroscopy time (min) Fluoroscopy time for bone cement injection (min) Ha (Sv) Hb (Sv) HE (Sv)
1-ml Syringe
Bone Cement Injector
P Value
7.54 ⫾ 3.50 3.57 ⫾ 1.73
6.66 ⫾ 2.45 2.40 ⫾ 0.91
NS NS
320.8 ⫾ 232.2 14.5 ⫾ 11.3 48.2 ⫾ 33.8
116.2 ⫾ 92.8 7.8 ⫾ 9.7 19.7 ⫾ 18.3
⬍.05 ⬍.05 ⬍.05
Note.—Values presented as means ⫾ SD.
measurements for the two groups were 48.2 Sv ⫾ 33.8 and 19.7 Sv ⫾ 18.3, respectively. Ha, Hb, and HE for the 1-mL syringe group were significantly higher than for the bone cement injector group (Table 2).
DISCUSSION According to the 1990 Recommendation of the International Commission on Radiological Protection (10), the HA limit is 100 mSv per 5 years or 50 mSv/y, the dose limit for the lens is 150 mSv/y, and the dose limit for the skin is 500 mSv/y. In our study, the HA measurements for the 1-mL syringe and bone cement injector groups were 48.2 Sv ⫾ 33.8 and 19.7 Sv ⫾ 18.3, respectively. Hence, the dose limit for the HE could be reached over a 5-year period with 2,074.7 procedures (95% CI, 1,219.5– 6,944.4) for the 1-mL syringe group and with 5,076.1 procedures (95% CI, 2,631.6 –7,1426.6) for the bone cement injector group. The Ha measurements for the 1-mL syringe and bone cement injector groups were 320.8 Sv ⫾ 232.2 and 116.2 Sv ⫾ 92.8, respectively. Without a lens protector, the dose limit for the lens could be reached over a 1-year period with 467.6 procedures (95% CI, 271.2–1,693.0) for the 1-mL syringe group and with 1,290.9 procedures (95% CI, 717.7– 6,410.3) for the bone cement injector group. By using the lower limit of the 95% CI to emphasize safety, the upper limit of HE could be reached with 1,219.5 procedures over a period of 5 years (243.9 procedures per year) with use of the 1-mL syringe and 2,631.6 procedures over a period of 5 years (526.3 procedures per year) with use of the bone cement injector. Without the use of lead glasses, the dose limit for the lens could be
reached with 271.2 procedures per year with use of the 1-mL syringe and with 717.7 procedures per year with use of the bone cement injector. In other interventional radiology procedures, the HE for operators is 8.8 Sv for transcatheter arterial embolization in the treatment of hepatocellular carcinoma (12), 0.4 –28 Sv for transjugular intrahepatic portosystemic shunt creation (13), 8 Sv for pediatric cardiac catheterization (14), 50 Sv for percutaneous transluminal coronary angioplasty (15), 40 Sv for neuroembolization (16), 40 Sv for percutaneous coronary intervention (16), and 40 Sv for hepatic infusion catheter implantation (16). There have been substantial changes in fluoroscopic beam quality and management since the mid-1990s, so some procedures yield lower doses recently. In the present study, the HE measurements for operators performing percutaneous vertebroplasty was 48.2 Sv for the 1-mL syringe group and 19.7 Sv for the bone cement injector group, thereby suggesting that percutaneous vertebroplasty is a technique associated with relatively high radiation exposure to operators. In percutaneous vertebroplasty, operators can be exposed to radiation during the following stages: confirming affected vertebrae under the guidance of lateral fluoroscopy, locally anesthetizing puncture sites under the guidance of lateral fluoroscopy, inserting the needle into the vertebra under the guidance of lateral fluoroscopy, conducting venography, and injecting bone cement under the guidance of lateral fluoroscopy. Because the last image hold function is used as much as possible, the level of radiation exposure to operators is very low while performing the first two stages. The
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level of radiation exposure should be low while conducting venography because the operator stands away from the radiation source and uses an extension tube (17). Radiation exposure is high while inserting the needle into the vertebra and injecting bone cement under lateral fluoroscopic guidance because the operator must stand near the radiation source and fluoroscopy is continuously used. When the bone cement injector is used, bone cement can be injected from a 34-cm distance, thereby reducing the level of radiation exposure to the operator. There are some reports about radiation dose to the operator during vertebroplasty under only fluoroscopic guidance. Kallmes et al (6) reported left wrist doses of 1,280 Sv per procedure with use of 1-mL syringes and 980 Sv per procedure with use of an injection device in 39 vertebroplasty procedures. However, they did not report HE, they used a radiation shield in only cases in which the injection device was used, and the operators stood to the lateral x-ray tube side during injection. In addition, they described that some error might have occurred from variation in positioning of the dosimeters on the operator’s wrist or from other variables, as seven of 39 vertebroplasty procedures yielded zero dose. We reported radiation dose outside and inside lead aprons and HE, and it was similar to their data that the use of an injection device significantly decreased the radiation dose. Mehdizade et al (7) measured radiation dose in 11 vertebroplasty procedures. However, they did not report mean radiation dose but only maximum and minimum doses of 22–3,256 Sv per procedure outside and 10 – 470 Sv per procedure inside the lead apron. Kruger et al (8) measured whole-body dose in 36 vertebroplasty procedures with or without lead shields and lead aprons placed on the patients as shielding devices. The shielding devices greatly reduced whole-body dose from 1,440 Sv per vertebra to 4 Sv per vertebra. We are aware of no reports on radiation dose to the operator during vertebroplasty under IVR-CT guidance. The IVR-CT system can reduce fluoroscopy duration and position the needle safely. We measured radiation dose in 40 vertebroplasty procedures under IVR-CT guidance. In the present
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study, HE measurements were 48.2 Sv ⫾ 33.8 per procedure in the 1-mL syringe group and 19.7 Sv ⫾ 18.3 per procedure in the bone cement injector group. These radiation exposures are relatively low. The shielding devices described by Kruger et al (8) may further reduce radiation exposure In percutaneous vertebroplasty, high-quality fluoroscopic imaging is necessary when injecting bone cement, but not during the other stages. Hence, to reduce the level of radiation exposure to operators, it may be useful to reduce the quality of fluoroscopic images aside from when conducting this step. As to limitations of the present study, this study was conducted at a single facility, and because the IVR-CT system was used, it is difficult to apply the results to percutaneous vertebroplasty with fluoroscopic guidance alone. In addition, although the level of radiation exposure for the entire percutaneous vertebroplasty was measured, levels were not measured at each stage. In conclusion, the present study investigated the level of radiation exposure to operators during percutaneous vertebroplasty with use of the IVR-CT system by randomly using a 1-mL syringe or a bone cement injector. The findings indicated that the level of radiation exposure to operators during percutaneous vertebroplasty is relatively high and that the maximum recommended HE could be reached over a 1-year period with 243.9 procedures with use of the 1-mL syringe or 526.3 procedures with use of the bone cement injector. Hence, the bone cement injector was found to be useful in re-
ducing the level of radiation exposure to operators during percutaneous vertebroplasty. References 1. Mathis JM, Wong W. Percutaneous vertebroplasty: technical considerations. J Vasc Interv Radiol 2003; 14:953–960. 2. McGraw JK, Cardella J, Barr JD, et al. Society of Interventional Radiology quality improvement guidelines for percutaneous vertebroplasty. J Vasc Interv Radiol 2003; 14:827–831. 3. Stallmeyer MJ, Zoarski GH, Obuchowski AM. Optimizing patient selection in percutaneous vertebroplasty. J Vasc Interv Radiol 2003; 14:683–696. 4. McGraw JK, Lippert JA, Minkus KD, et al. Prospective evaluation of pain relief in 100 patients undergoing percutaneous vertebroplasty: results and follow-up. J Vasc Interv Radiol 2002;13: 883–886. 5. Zoarski GH, Snow P, Olan WJ, et al. Percutaneous vertebroplasty for osteoporotic compression fractures: quantitative prospective evaluation of longterm outcomes. J Vasc Interv Radiol 2002; 13:139–148. 6. Kallmes DF, O E, Roy SS, et al. Radiation dose to the operator during vertebroplasty: prospective comparison of the use of 1-cc syringes versus an injection device. AJNR Am J Neuroradiol 2003; 24:1257–1260. 7. Mehdizade A, Lovblad KO, Wilhelm KE, et al. Radiation dose in vertebroplasty. Neuroradiology 2004; 46:243–245. 8. Kruger R, Faciszewski T. Radiation dose reduction to medical staff during vertebroplasty: a review of techniques and methods to mitigate occupational dose. Spine 2003; 28:1608–1613. 9. Tanigawa N, Komemushi A, Kariya S, et al. Intraosseous venography with carbon dioxide contrast agent in percutaneous vertebroplasty. AJR Am J Roentgenol 2005; 184:567–570. 10. International Commission on Radio-
11.
12.
13.
14.
15.
16.
17.
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logical Protection. 1990 Recommendation of the International Commission on Radiological Protection, ICRP Publication 60. Ann ICRP 1991; 21:No. 1–3. Leibold RA, Gilula LA. Sterilization of barium for vertebroplasty: an effective, reliable, and inexpensive method to sterilize powders for surgical procedures. AJR Am J Roentgenol 2002; 179: 198–200. Ishiguchi T, Nakamura H, Okazaki M, et al. Radiation exposure to patient and radiologist during transcatheter arterial embolization for hepatocellular carcinoma Nippon Igaku Hoshasen Gakkai Zasshi 2000; 60:839–844. Zweers D, Geleijns J, Aarts NJ, et al. Patient and staff radiation dose in fluoroscopy-guided TIPS procedures and dose reduction, using dedicated fluoroscopy exposure settings. Br J Radiol 1998; 71:672–676. Li LB, Kai M, Takano K, et al. Occupational exposure in pediatric cardiac catheterization. Health Phys 1995; 69: 261–264. Karppinen J, Parvianinen T, Servomaa A, et al. Radiation risk and exposure of radiologists and patients during coronary angiography and percutaneous transluminal coronary angioplasty (PTCA). Radiat Prot Dosimetry 1995; 57:481–485. Suzuki S, Furui S, Yamaguchi I, et al. Radiation exposure to physicians during interventional radiologic procedures: evaluation for neuroembolization, percutaneous coronary intervention, and hepatic infusion catheter implantation. Jpn J Intervent Radiol 2004; 19:377–382. Hayashi N, Sakai T, Kitagawa M, et al. Radiation exposure to interventional radiologists during manual-injection digital subtraction angiography. Cardiovasc Intervent Radiol 1998; 21:240– 243.
PURPOSE: To measure the radiation received by physicians during percutaneous vertebroplasty with use of two types of injection devices with the interventional equipment guided by computed tomography (CT) and an angiographic/CT system. MATERIALS AND METHODS: Twenty consecutive patients who underwent percutaneous vertebroplasty were included in this study. The patients were divided into two groups, the 1-mL syringe group and the bone cement injector group. Percutaneous vertebroplasties were performed with the IVR-CT system, which combines angiographic and CT equipment with a single fluoroscopy table. Radiation dose to operators was measured as equivalent dose penetrating at a 10-mm tissue depth with use of electronic personal dosimeters attached outside and inside lead aprons. Effective radiation dose (HE) was estimated based on the radiation dose outside the lead apron (Ha) and the radiation dose inside the lead apron (Hb). Differences between the groups in doses and fluoroscopic duration were analyzed. RESULTS: In the 1-mL syringe group and bone cement injector group, mean Ha measurements were 320.8 Sv and 116.2 Sv, respectively. Mean Hb measurements were 14.5 Sv versus 7.8 Sv and mean HE measurements were 48.2 Sv versus 19.7 Sv. Significant differences were found in Ha, Hb, and HE. However, duration of fluoroscopy did not differ significantly between groups. CONCLUSIONS: Radiation dose was relatively high for operators performing percutaneous vertebroplasty. The bone cement injector was useful in reducing the level of radiation exposure to operators during vertebroplasty. J Vasc Interv Radiol 2005; 16:1327–1332 Abbreviations: Ha ⫽ radiation dose received outside the lead apron, Hb ⫽ radiation dose received inside the lead apron, HE ⫽ effective radiation dose, PMMA ⫽ polymethylmethacrylate
PERCUTANEOUS vertebroplasty, a procedure in which bone cement is injected percutaneously into vertebrae affected by compression fracture, is increasingly performed for analgesia (1– 9). In general, bone cement is injected during percutaneous vertebroplasty
From the Department of Radiology, Kansai Medical University, 10-15 Fumizono, Moriguchi, Osaka 5708507, Japan. Received July 8, 2005; revision requested July 11; final revision received and accepted July 27. From the SIR 2005 Annual Meeting. Address correspondence to A.K., E-mail: [email protected] None of the authors have identified a conflict of interest. © SIR, 2005 DOI: 10.1097/01.RVI.0000179794.65662.01
under lateral fluoroscopic guidance and, as a result, operators may be exposed to a high level of radiation. In recent years, bone cement injectors have become available that feature a long tube with which the operator can inject bone cement while standing outside the field of fluoroscopy. The objective of the present study was to compare the levels of radiation exposure to operators during percutaneous vertebroplasty performed with use of two different bone cement injectors.
MATERIALS AND METHODS All patients received explanations of percutaneous vertebroplasty and handling of clinical data, and written
informed consent was obtained from each patient. The procedure of percutaneous vertebroplasty was approved by the institutional review board. It does not require such approval for each prospective clinical study. Patient Group The study included 20 patients who underwent 20 consecutive percutaneous vertebroplasty procedures at our institution from April 22 to September 2, 2004. With the envelope method described later, participants were randomly divided into a 1-mL syringe group and a bone cement injector group. Twenty envelopes that could not be distinguished from the exterior were made, 10 for a 1-mL syringe and
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Part
Tissue or Organ
Tissue Weighting Factor
Part Weighting Factor
Head and neck
Thyroid Bone marrow (red) Bone surface Lung Esophagus Breast Stomach Liver Bone marrow (red) Bone surface Gonads Bladder Colon Bone marrow (red) Bone surface Skin
0.05 0.12 (0.013) 0.01 (0.002) 0.12 0.05 0.05 0.12 0.05 0.12 (0.04) 0.01 (0.002) 0.20 0.05 0.12 0.12 (0.07) 0.01 (0.003) 0.05 (0.01)
0.065 (0.075)
Lower abdomen
Remainder tissues
JVIR
culated according to the following formula:
Table 1 Tissue Weighting Factors
Upper abdomen
October 2005
0.43 (0.44)
0.44 (0.45)
0.05 (0.025)
The values in parentheses were distributed as 0.01 of skin and 0.025 of remaining tissues tissue weighting factors in accordance with Nuclear Safety Technology Center in Japan.
10 for a bone cement injector. An operator selected one envelope for each participant just before vertebroplasty, thereby assigning 10 patients to the 1-mL syringe group and 10 to the bone cement injector group. Because whether the 1-mL syringe or bone cement injector was used had no detrimental effect on the patients, it does not require approval from the ethical review board for this grouping method. Radiation Dose Measurement Radiation doses to operators during the procedure were measured with use of electronic personal dosimeters (PDM-117; Aloka, Tokyo, Japan; energy threshold, 20 keV; detector, silicon solid-state; energy response, 30 keV to 3 MeV within 30% calibrated by 40 keV of x rays with use of a slab phantom; accuracy within 20%, 10 –9,999 mSv calibrated by 40 keV of x rays with use of a slab phantom; linearity within 10% to a maximum of 30 mSv/h, within 20% from 30 to 100 mSv/h; in compliance with International Committee on Radiological Protection Publication 74) attached on the outside and inside of their 0.50-mm Pb lead aprons at the upper sternal level. Dose was assessed in terms of equivalent dose penetrating at 10-mm tissue
depth outside the lead apron (Ha; detailed later) and inside the lead apron (Hb; detailed later). Dosimeters were attached at the start of percutaneous vertebroplasty and level of radiation exposure was recorded after completion of the procedure. Effective radiation dose (HE) was calculated according to the following formula in accordance with the 1990 Recommendation of the International Commission on Radiological Protection (10) and the Nuclear Safety Technology Center in Japan (Table 1). HE ⫽ 0.08Ha ⫹ 0.44Hb ⫹ 0.45Hc ⫹ 0.03Hm Where HE is the effective dose from external exposure, Ha is the head and neck equivalent dose penetrating at a 10-mm tissue depth; Hb is the chest and upper-limb equivalent dose penetrating at a 10-mm tissue depth; Hc is the abdomen and femoral region equivalent dose penetrating at a 10-mm tissue depth; and Hm is the equivalent dose penetrating at a 10-mm tissue depth of the potential maximum external exposure in the head and neck, chest and upper limb, and abdomen and femoral region. Therefore, the HE estimated by personal dosimeters on the outside and inside of the lead apron was cal-
HE ⫽ 0.11Ha ⫹ 0.89Hb Vertebroplasty Technique Percutaneous vertebroplasty procedures were performed with guidance of the IVR-CT system (Advantx-ACT; GE Medical Systems, Milwaukee, WI), which combines angiographic equipment (Advantx-LCA⫹, GE Medical Systems) and computed tomography (CT) equipment (HiSpeed LX/i; GE Medical Systems) with a single fluoroscopy table (Omega4 Angio Step; GE Medical Systems; Fig 1). The x-ray tube unit (Maxiray150TH; GE Medical Systems; Nominal anode input power, 16/47/115 kW; target material, tungsten; nominal focal spot value, 0.3/ 0.6/1.2 mm; minimal inherent filtration, 0.85; aluminum equivalent at 70 kV; nominal high voltage, 125 kV; maximum current filament, 6.5 A) was used with a 0.6-mm ⫻ 0.6-mm focal spot in normal-sized patients and a 1.2-mm ⫻ 1.2-mm focal spot in large patients. Four image intensifier formats are available: 40 cm, 32 cm, 22 cm, and 17 cm in diameter. An additional inherent aluminum filter 1.3 mm thick, movable filters of 1.0 mm aluminum and 0.5 mm copper, and an x-ray grid built into carbon fiber cover plates (Smitrontgen; Eindhoven, The Netherlands; lead grid lines, 44 lines/ cm; grid ratio, 10/1; focal distance, 110 cm; interspacer, fiber) were always applied. The system was calibrated by the manufacturer to deliver an image intensifier input dose of 12.32 Gy/ min with a 40-cm field of view in fluoroscopy and 4.4 Gy/frame with a 22-cm field of view in digital radiography. All fluoroscopic procedures were performed under automatic brightness control in which the tube potential (60 – 120 kV) and tube current are adjusted. The fluoroscopy mode was standard conventional fluoroscopy mode with an interventional digital fluoroscopy module without high-level control function. Pulse fluoroscopy was used at a rate of 60 pulses per second. Digital radiography was performed with the tube potential of 80 –90 kV, tube current of 800 mA. and frame ratio of 7.5 frames per second under automatic exposure-rate control in which the pulse windows (1.0 –10 msec) are ad-
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Figure 1. The IVR-CT system combines angiographic and CT equipment with a single fluoroscopy table.
justed. Last image hold function and collimation were used as much as possible. The system was not equipped with CT fluoroscopy function. Table shields were mounted on the fluoroscopy table to protect the operator’s body and used during all procedures. No additional shielding was used during the procedures. In the present study, percutaneous vertebroplasty was performed by four operators. All were specialists in interventional radiology with a minimum of 8 years of experience in the field, and each had performed at least 50 percutaneous vertebroplasty procedures. In each procedure, all procedures other than preparation of the bone cement were carried out by one operator. The bone cement was prepared by an assistant. All operators attempted to minimize radiation exposure during the procedure. In the 1-mL syringe group, bone cement was injected into vertebrae with use of screw-type 1-mL syringes (Medallion 1-mL syringe; Merit Medical, Salt Lake City, UT; Fig 2). In the bone cement injector group, bone cement was injected with use of a bone cement injector (Osteoject Bone Ce-
ment Delivery System; Integra Neuro Sciences, Hampshire, UK), which allows operators to keep their hands 34 cm (23 cm as tube and 11 cm as syringe) outside the fluoroscopy field (Fig 3). After intramuscular injection of 25 mg of hydroxyzine hydrochloride (Atarax P; Pfizer Japan, Tokyo, Japan), 0.5 mg of atropine sulfate (Tanabe Seiyaku, Osaka, Japan) and 10 mg of morphine hydrochloride (Sankyo, Tokyo, Japan), the patient was positioned prone on the fluoroscopy table. Continuous blood pressure monitoring and pulse oximetry were performed. The location of vertebrae to be treated was reconfirmed with lateral fluoroscopy. Plain vertebral CT was performed to reference the puncture site and angle. The skin overlying the vertebral body to be injected was cleaned and draped. The skin, subcutaneous tissues, and periosteum over the pedicle to be punctured were then anesthetized with 1% lidocaine hydrochloride (Xylocaine polyamp 1%; AstraZeneca, Osaka, Japan) with use of a 22-gauge, 70-mm Cathelin needle (Terumo, Leuven, Belgium) with reference to CT images and lat-
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eral fluoroscopic guidance, and the needle tip was retained adjacent to the pedicle. CT was then performed to confirm the needle location. With this needle as a guide, a 13-gauge needle (Osteo-site Bone Biopsy Needle Murphy M2; 13-gauge, 10 cm; Cook, Bloomington, IN) was advanced without fluoroscopic guidance until its tip penetrated the cortex. CT was again performed to verify the needle position. Under lateral fluoroscopic guidance, the needle was then advanced into the vertebral body. Ideally, the tip of the needle was placed in the anterior third of the vertebral body, close to the midline. More posterior needle positions occasionally had to be accepted when treating severely compressed vertebral bodies with steep pedicle angulation. Venography was then performed with use of CO2 as a contrast agent. CO2 was drawn from a CO2 generator through a sterile filter into a 10-mL or 20-mL syringe (Gaster; Asahi Keiki, Osaka, Japan). After connecting the syringe containing CO2 to the bone biopsy needle via 50 cm of extensible tubing, the operator manually injected CO2 while keeping as far from the fluoroscopic field as possible. Frontal and lateral venograms were obtained with use of digital subtraction angiography. The amount of CO2 used in venography was 10 mL for thoracic vertebrae and 20 mL for lumbar vertebrae (9). Data collection for digital subtraction angiography was performed with a 12-inch image intensifier at nine frames per second. After this, 20 g of methylmethacrylate powder (Osteobond copolymer bone cement; Zimmer, Warsaw, IN) was mixed with 5 g of dry heat-sterilized barium sulfate powder (Horii, Osaka, Japan) to increase its opacity (11). Next, 10 mL of liquid methylmethacrylate monomer was added to the powder, and the resulting polymethylmethacrylate (PMMA) mixture was blended to a toothpaste-like consistency. The PMMA was loaded into a 10-mL syringe (Terumo) and backfilled into a screw-type 1-mL syringe or bone cement injector system, ensuring that air was expelled from the PMMA. The PMMA was injected with lateral fluoroscopic guidance (Figs 2,3). Injection was terminated when adequate filling of the vertebral body was
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tion. Total fluoroscopy time during vertebroplasty and fluoroscopy time during cement injection were recorded. After the CT procedure, all patients were observed in the supine position for 2 hours. To avoid radiation exposure associated with CT scanning, CT was performed while the operator was in the adjacent control room. Statistical Analysis.
Figure 2. In the 1-mL syringe group, bone cement was injected into vertebrae with use of screw-type 1-mL syringes with lateral fluoroscopic guidance.
With a Mann-Whitney U test, we analyzed the differences between the 1-mL syringe group and the bone cement injector group with respect to the following parameters: equivalent dose penetrating at 10-mm tissue depth outside lead apron (ie, Ha) and inside lead apron (ie, Hb), HE, total fluoroscopy duration, and fluoroscopy duration during cement injection. A P value less than .05 was considered to indicate significance. All analyses were performed using StatView (Version 5.0; SAS, Cary, NC) for Windows (Microsoft, Redmond, WA).
RESULTS
Figure 3. In the bone cement injector group, bone cement was injected with use of a bone cement injector system, which allows operators to keep their hands 34 cm outside the fluoroscopy field, with lateral fluoroscopic guidance.
achieved or when leakage outside the vertebral body occurred. When leakage occurred, the needle was repositioned and additional PMMA was in-
jected to fill the remaining part of the vertebral body. The needle was then removed and plain vertebral CT was performed to confirm PMMA distribu-
In the 1-mL syringe group, 19 vertebrae were treated during 10 procedures, and in the bone cement injector group, 16 vertebrae were treated during 10 procedures. All procedures were carried out without complications. The average number of treated vertebrae per procedure was 1.75 ⫾ 0.79 (SD) for the 20 subjects: 1.90 ⫾ 0.88 for the 1-mL syringe group and 1.60 ⫾ 0.70 for the bone cement injector group. Student t test did not reveal a significant difference between groups. Average total fluoroscopy time did not differ significantly between the 1-mL syringe group and the bone cement injector group (7.54 min ⫾ 3.50 vs 6.66 min ⫾ 2.45). Average fluoroscopy time for bone cement injection did not differ significantly between the 1-mL syringe group and the bone cement injector group (3.57 min ⫾ 1.73 vs 2.40 min ⫾ 0.91). Average Ha measurements were 320.8 Sv ⫾ 232.2 for the 1-mL syringe group and 116.2 Sv ⫾ 92.8 for the bone cement injector group. Average Hb measurements for these two groups were 14.5 Sv ⫾ 11.3 and 7.8 Sv ⫾ 9.7, respectively. Average HE
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Table 2 Fluoroscopy Times and Radiation Doses
Total fluoroscopy time (min) Fluoroscopy time for bone cement injection (min) Ha (Sv) Hb (Sv) HE (Sv)
1-ml Syringe
Bone Cement Injector
P Value
7.54 ⫾ 3.50 3.57 ⫾ 1.73
6.66 ⫾ 2.45 2.40 ⫾ 0.91
NS NS
320.8 ⫾ 232.2 14.5 ⫾ 11.3 48.2 ⫾ 33.8
116.2 ⫾ 92.8 7.8 ⫾ 9.7 19.7 ⫾ 18.3
⬍.05 ⬍.05 ⬍.05
Note.—Values presented as means ⫾ SD.
measurements for the two groups were 48.2 Sv ⫾ 33.8 and 19.7 Sv ⫾ 18.3, respectively. Ha, Hb, and HE for the 1-mL syringe group were significantly higher than for the bone cement injector group (Table 2).
DISCUSSION According to the 1990 Recommendation of the International Commission on Radiological Protection (10), the HA limit is 100 mSv per 5 years or 50 mSv/y, the dose limit for the lens is 150 mSv/y, and the dose limit for the skin is 500 mSv/y. In our study, the HA measurements for the 1-mL syringe and bone cement injector groups were 48.2 Sv ⫾ 33.8 and 19.7 Sv ⫾ 18.3, respectively. Hence, the dose limit for the HE could be reached over a 5-year period with 2,074.7 procedures (95% CI, 1,219.5– 6,944.4) for the 1-mL syringe group and with 5,076.1 procedures (95% CI, 2,631.6 –7,1426.6) for the bone cement injector group. The Ha measurements for the 1-mL syringe and bone cement injector groups were 320.8 Sv ⫾ 232.2 and 116.2 Sv ⫾ 92.8, respectively. Without a lens protector, the dose limit for the lens could be reached over a 1-year period with 467.6 procedures (95% CI, 271.2–1,693.0) for the 1-mL syringe group and with 1,290.9 procedures (95% CI, 717.7– 6,410.3) for the bone cement injector group. By using the lower limit of the 95% CI to emphasize safety, the upper limit of HE could be reached with 1,219.5 procedures over a period of 5 years (243.9 procedures per year) with use of the 1-mL syringe and 2,631.6 procedures over a period of 5 years (526.3 procedures per year) with use of the bone cement injector. Without the use of lead glasses, the dose limit for the lens could be
reached with 271.2 procedures per year with use of the 1-mL syringe and with 717.7 procedures per year with use of the bone cement injector. In other interventional radiology procedures, the HE for operators is 8.8 Sv for transcatheter arterial embolization in the treatment of hepatocellular carcinoma (12), 0.4 –28 Sv for transjugular intrahepatic portosystemic shunt creation (13), 8 Sv for pediatric cardiac catheterization (14), 50 Sv for percutaneous transluminal coronary angioplasty (15), 40 Sv for neuroembolization (16), 40 Sv for percutaneous coronary intervention (16), and 40 Sv for hepatic infusion catheter implantation (16). There have been substantial changes in fluoroscopic beam quality and management since the mid-1990s, so some procedures yield lower doses recently. In the present study, the HE measurements for operators performing percutaneous vertebroplasty was 48.2 Sv for the 1-mL syringe group and 19.7 Sv for the bone cement injector group, thereby suggesting that percutaneous vertebroplasty is a technique associated with relatively high radiation exposure to operators. In percutaneous vertebroplasty, operators can be exposed to radiation during the following stages: confirming affected vertebrae under the guidance of lateral fluoroscopy, locally anesthetizing puncture sites under the guidance of lateral fluoroscopy, inserting the needle into the vertebra under the guidance of lateral fluoroscopy, conducting venography, and injecting bone cement under the guidance of lateral fluoroscopy. Because the last image hold function is used as much as possible, the level of radiation exposure to operators is very low while performing the first two stages. The
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level of radiation exposure should be low while conducting venography because the operator stands away from the radiation source and uses an extension tube (17). Radiation exposure is high while inserting the needle into the vertebra and injecting bone cement under lateral fluoroscopic guidance because the operator must stand near the radiation source and fluoroscopy is continuously used. When the bone cement injector is used, bone cement can be injected from a 34-cm distance, thereby reducing the level of radiation exposure to the operator. There are some reports about radiation dose to the operator during vertebroplasty under only fluoroscopic guidance. Kallmes et al (6) reported left wrist doses of 1,280 Sv per procedure with use of 1-mL syringes and 980 Sv per procedure with use of an injection device in 39 vertebroplasty procedures. However, they did not report HE, they used a radiation shield in only cases in which the injection device was used, and the operators stood to the lateral x-ray tube side during injection. In addition, they described that some error might have occurred from variation in positioning of the dosimeters on the operator’s wrist or from other variables, as seven of 39 vertebroplasty procedures yielded zero dose. We reported radiation dose outside and inside lead aprons and HE, and it was similar to their data that the use of an injection device significantly decreased the radiation dose. Mehdizade et al (7) measured radiation dose in 11 vertebroplasty procedures. However, they did not report mean radiation dose but only maximum and minimum doses of 22–3,256 Sv per procedure outside and 10 – 470 Sv per procedure inside the lead apron. Kruger et al (8) measured whole-body dose in 36 vertebroplasty procedures with or without lead shields and lead aprons placed on the patients as shielding devices. The shielding devices greatly reduced whole-body dose from 1,440 Sv per vertebra to 4 Sv per vertebra. We are aware of no reports on radiation dose to the operator during vertebroplasty under IVR-CT guidance. The IVR-CT system can reduce fluoroscopy duration and position the needle safely. We measured radiation dose in 40 vertebroplasty procedures under IVR-CT guidance. In the present
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study, HE measurements were 48.2 Sv ⫾ 33.8 per procedure in the 1-mL syringe group and 19.7 Sv ⫾ 18.3 per procedure in the bone cement injector group. These radiation exposures are relatively low. The shielding devices described by Kruger et al (8) may further reduce radiation exposure In percutaneous vertebroplasty, high-quality fluoroscopic imaging is necessary when injecting bone cement, but not during the other stages. Hence, to reduce the level of radiation exposure to operators, it may be useful to reduce the quality of fluoroscopic images aside from when conducting this step. As to limitations of the present study, this study was conducted at a single facility, and because the IVR-CT system was used, it is difficult to apply the results to percutaneous vertebroplasty with fluoroscopic guidance alone. In addition, although the level of radiation exposure for the entire percutaneous vertebroplasty was measured, levels were not measured at each stage. In conclusion, the present study investigated the level of radiation exposure to operators during percutaneous vertebroplasty with use of the IVR-CT system by randomly using a 1-mL syringe or a bone cement injector. The findings indicated that the level of radiation exposure to operators during percutaneous vertebroplasty is relatively high and that the maximum recommended HE could be reached over a 1-year period with 243.9 procedures with use of the 1-mL syringe or 526.3 procedures with use of the bone cement injector. Hence, the bone cement injector was found to be useful in re-
ducing the level of radiation exposure to operators during percutaneous vertebroplasty. References 1. Mathis JM, Wong W. Percutaneous vertebroplasty: technical considerations. J Vasc Interv Radiol 2003; 14:953–960. 2. McGraw JK, Cardella J, Barr JD, et al. Society of Interventional Radiology quality improvement guidelines for percutaneous vertebroplasty. J Vasc Interv Radiol 2003; 14:827–831. 3. Stallmeyer MJ, Zoarski GH, Obuchowski AM. Optimizing patient selection in percutaneous vertebroplasty. J Vasc Interv Radiol 2003; 14:683–696. 4. McGraw JK, Lippert JA, Minkus KD, et al. Prospective evaluation of pain relief in 100 patients undergoing percutaneous vertebroplasty: results and follow-up. J Vasc Interv Radiol 2002;13: 883–886. 5. Zoarski GH, Snow P, Olan WJ, et al. Percutaneous vertebroplasty for osteoporotic compression fractures: quantitative prospective evaluation of longterm outcomes. J Vasc Interv Radiol 2002; 13:139–148. 6. Kallmes DF, O E, Roy SS, et al. Radiation dose to the operator during vertebroplasty: prospective comparison of the use of 1-cc syringes versus an injection device. AJNR Am J Neuroradiol 2003; 24:1257–1260. 7. Mehdizade A, Lovblad KO, Wilhelm KE, et al. Radiation dose in vertebroplasty. Neuroradiology 2004; 46:243–245. 8. Kruger R, Faciszewski T. Radiation dose reduction to medical staff during vertebroplasty: a review of techniques and methods to mitigate occupational dose. Spine 2003; 28:1608–1613. 9. Tanigawa N, Komemushi A, Kariya S, et al. Intraosseous venography with carbon dioxide contrast agent in percutaneous vertebroplasty. AJR Am J Roentgenol 2005; 184:567–570. 10. International Commission on Radio-
11.
12.
13.
14.
15.
16.
17.
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logical Protection. 1990 Recommendation of the International Commission on Radiological Protection, ICRP Publication 60. Ann ICRP 1991; 21:No. 1–3. Leibold RA, Gilula LA. Sterilization of barium for vertebroplasty: an effective, reliable, and inexpensive method to sterilize powders for surgical procedures. AJR Am J Roentgenol 2002; 179: 198–200. Ishiguchi T, Nakamura H, Okazaki M, et al. Radiation exposure to patient and radiologist during transcatheter arterial embolization for hepatocellular carcinoma Nippon Igaku Hoshasen Gakkai Zasshi 2000; 60:839–844. Zweers D, Geleijns J, Aarts NJ, et al. Patient and staff radiation dose in fluoroscopy-guided TIPS procedures and dose reduction, using dedicated fluoroscopy exposure settings. Br J Radiol 1998; 71:672–676. Li LB, Kai M, Takano K, et al. Occupational exposure in pediatric cardiac catheterization. Health Phys 1995; 69: 261–264. Karppinen J, Parvianinen T, Servomaa A, et al. Radiation risk and exposure of radiologists and patients during coronary angiography and percutaneous transluminal coronary angioplasty (PTCA). Radiat Prot Dosimetry 1995; 57:481–485. Suzuki S, Furui S, Yamaguchi I, et al. Radiation exposure to physicians during interventional radiologic procedures: evaluation for neuroembolization, percutaneous coronary intervention, and hepatic infusion catheter implantation. Jpn J Intervent Radiol 2004; 19:377–382. Hayashi N, Sakai T, Kitagawa M, et al. Radiation exposure to interventional radiologists during manual-injection digital subtraction angiography. Cardiovasc Intervent Radiol 1998; 21:240– 243.