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1946 IMPACT OF UROLOGY RESIDENTS ON THE FLUOROSCOPY TIME USED DURING URETEROSCOPY
Vol. 187, No. 4S, Supplement, Tuesday, May 22, 2012
THE JOURNAL OF UROLOGY姞
e785
CONCLUSIONS: The reduced function of the staghorn bearing renal unit is multifactorial and likely to be due to associated obstruction and infection. The usual complications of PNL like bleeding, infection, adjacent organ injury are almost equivalent to PNL for simple stones. PNL does improve the function of the affected unit despite using multiple tracts. However multi-tract & relook PNL were the major determining factors for short term functional deterioration in minority. Source of Funding: None
1945 FEASIBILITY OF DISCRIMINATING URIC ACID FROM NON-URIC ACID RENAL STONES USING A SINGLE-SOURCE CT SCANNER AND 3D ANATOMIC REGISTRATION: IN VITRO AND IN VIVO STUDIES
Source of Funding: This work was partially supported by a research grant (P50 DK083007) from the National Institutes of Health.
Shuai Leng*, Katharine Grant, Terri Vrtiska, Rochester, MN; Bernhard Krauss, Forchheim, Germany; Maria Shiung, Samantha Hansen, Jia Wang, Xinhui Duan, Cynthia McCollough, rochester, MN INTRODUCTION AND OBJECTIVES: To prospectively demonstrate in phantoms and patients the feasibility of differentiating uric acid (UA) and non-uric acid (NUA) renal stones using two consecutive scans on a single source CT scanner and a 3D registration algorithm. METHODS: A total of 30 UA and 30 NUA renal stones were placed in individual vials filled with water, emerged in a 35 cm water phantom and scanned on a 128 slice single source CT scanner. An 80 kV scan was first performed and followed by a 140 kV scan. To simulate patient motion, stone vials were shifted by 7 mm in cranial caudal direction and rotated by 5° between the two scans. Images from the two scans were registered using a 3D registration program, followed by dual-energy processing to differentiate UA (in red) and NUA (in blue) stones. For the IRB approved in vivo patient study, a total of 20 patients undergoing clinically-indicated dual-source (DS), dual-energy CT scanning for UA and NUA kidney stone differentiation were recruited. On the same day as the clinically-indicated DS exam, the patient was scanned on the single source CT scanner with an 80 kV scan followed by a 140 kV scan with scan range limited to the areas with stones detected. The same dual energy analysis as that in the phantom exam was performed. Accuracy of stone classification was calculated using the results from DS scanner as reference standard. A GU radiologist recorded the number, size and composition of stones in each patient, and compared the image quality of the single-source and dual-source exams. The combined radiation dose for the 80 and 140 kV scans was set to be equivalent to that applied with the DS CT scan. RESULTS: All stones were correctly classified with 100% accuracy in the phantom. For the patient study, a total of 215 stones (122 NUA, 1 UA, and 79 unclassified) were identified from the DS CT exams. The accuracy was 82% considering all stones, and 94% considering only stones ⬎ 2mm (n⫽79, all NUA). Image quality of single source CT exam was considered similar to or slightly better than that of the dual source exam for all patients. CONCLUSIONS: Using a 3D registration algorithm on two consecutive single energy scans at different beam energies, UA and NUA stones can be accurately differentiated using a single source CT scanner, which is more available and has a wide clinic impact.
1946 IMPACT OF UROLOGY RESIDENTS ON THE FLUOROSCOPY TIME USED DURING URETEROSCOPY Mohamed Elkoushy*, Sero Andonian, Montreal, Canada INTRODUCTION AND OBJECTIVES: Endourological procedures resulted in dramatic rise in radiation exposure for both the patient and surgeon. Therefore, monitoring and awareness of fluoroscopic dose are critical. The aim of the present study was to assess the impact of urology residents on fluoroscopy time (FT) during ureteroscopy (URS). METHODS: A retrospective review of prospectively collected data was performed for consecutive patients undergoing URS by urology residents between July 2009 and February 2011. Residents in the Post-Graduate Year 4 (PGY-4) performed these cases under the direct supervision of a single endourologist. Standard fluoroscopic unit using 30 frames per second was used in these cases. Patient and stone characteristics together with operative data were compared among residents using univariate and multivariate analyses. RESULTS: Seven residents (A, B, C, D, E, F, and G) performed 106 URS with a median (range) of 16 (9-20) procedures per resident. Although a trend of decreasing mean FT over successive residents was observed, there were significant differences among the residents in their use of fluoroscopy (p⫽0.001) (Figure 1). The mean FT (95% CI) for residents A through G were 200 (128-272), 104 (65-144), 98 (72-124), 117 (58-175), 91 (52-131), 127 (89-166) and 64 (36-91) seconds, respectively. There were significant differences among residents in the use of access sheath (p⫽0.001) and pre-operative stenting (p⫽0.03). However, there were no significant differences regarding patients (age, sex) and stone characteristics (size, laterality, location, multiplicity) (p⬎0.05). Likewise, operative time, type of ureteroscopes and balloon dilation were all comparable among residents (p⬎0.05). FT (p⬍0.001), preoperative stenting (0.006) and use of access sheath (0.03) maintained their significance in the multivariate analysis after correction for all confounders. CONCLUSIONS: Urology residents vary significantly in their use of fluoroscopy during URS. Whether these differences are intrinsic to residents themselves or due to peri-operative factors remain to be clarified.
e786
THE JOURNAL OF UROLOGY姞
Vol. 187, No. 4S, Supplement, Tuesday, May 22, 2012
1948 ORGAN SPECIFIC RADIATION DOSE RATES AND EFFECTIVE DOSE DURING PERCUTANEOUS NEPHROLITHOTOMY Michael Lipkin*, John Mancini, Agnes Wang, Greta Toncheva, Colin Anderson-Evans, Michael Ferrandino, Terry Yoshizumi, Glenn Preminger, Durham, NC
Source of Funding: This work was supported in part by the Northeastern AUA Young Investigator Award and Montreal General Hospital Foundation Award to Sero Andonian.
1947 HOW MUCH RADIATION EXPOSURE DOES A UROLOGIST RECEIVE DURING ENDOSCOPIC PROCEDURES? Seth A. Cohen, Sriram S. Rangarajan*, Kerrin L. Palazzi, Thomas R. Nelson, Roger L. Sur, San Diego, CA INTRODUCTION AND OBJECTIVES: The literature lacks data offering urologists a reference for the amount of radiation exposure received while surgically managing urolithiasis. This study examines the cumulative radiation exposure of a urologist during endourologic procedures. METHODS: A single urologist at a tertiary kidney stone center recorded his radiation exposure over 5 consecutive months, as determined by a thermoluminescent dosimeter (TLD) worn on the outside of the thyroid shield. A 0.5mm lead thyroid shield and lead apron were worn during all procedures. The monthly fluoroscopy times for all surgeries were recorded as well. Estimations of radiation exposure (mrem) per month were then charted with fluoroscopy times, using scatter plots to estimate Spearman’s rank correlation coefficients. RESULTS: The total 5-month radiation exposure was 25 mrems for deep dose equivalent (DDE), 84 mrem for lens dose equivalent (LDE), and 81 mrem for shallow dose equivalent (SDE). Total fluoroscopy time during this period was 148 minutes for 15 percutaneous nephrolithotomies (PNL), 40 ureteroscopies (URS), and 6 shock wave lithotripsies (SWL). Spearman’s rank correlation coefficients were not significant for DDE (p⫽0.391), LDE (p⫽0.391), or SDE (p⫽0.391). CONCLUSIONS: Over a 5-month period, total radiation exposures were below annual accepted limits (DDE 5000 mrem, LDE 15,000 mrem and SDE 50,000 mrem). Although fluoroscopy time did not correlate with radiation exposure, an ongoing prospective study will account for other co-variates such as patient obesity and urologist distance from radiation source. Month April
Flouroscopy Time and Radiation Exposure Over 5 Months Time (mins) DDE LDE 36 9 31
SDE 30
May
43
5
17
June
17
0
0
0
July
13
4
14
13
August
39
7
22
22
Source of Funding: None
16
INTRODUCTION AND OBJECTIVES: Fluoroscopy time has been used to report on radiation exposure during urologic procedures. However, it is difficult to determine actual radiation dose delivered to patients based on fluoroscopy time. Effective dose relates absorbed radiation to the risk of developing a malignancy. We determined organ specific dose rates and calculated effective dose rates (EDR) during right and left sided percutaneous nephrolithotomy (PNL) using a validated phantom model. We determined effective dose (ED) for right and left PNL performed at our institution. METHODS: A validated anthropomorphic adult male phantom was placed prone on an operating room table. Metal Oxide Semiconductor Field Effect Transistor dosimeters were placed at 20 organ locations to measure the organ dosages. A portable C-arm was used to provide continuous fluoroscopy for three 10 minute runs each to simulate a left and right PNL. Organ dose rate (mGy/s) was determined by dividing organ dose by fluoroscopy time. The organ dose rates were multiplied by their tissue weighting factor and summed to determine EDR (mSv/s). We retrospectively reviewed 210 PNL procedures performed at our institution over a two year period. A total of 20 procedures on non-obese males with information on fluoroscopy time were included. Non-obese males most closely match the physical characteristics of our model. The ED was calculated by multiplying the fluoroscopy time by the EDR. RESULTS: The EDR for a left and right sided PNL were 0.021 mSv/s and 0.014 mSv/s, respectively. The skin entrance was exposed to the greatest amount of radiation during left and right PNL, 0.24 mGy/s and 0.26 mGy/s respectively. The stomach was exposed to the second greatest amount of radiation on the left (0.07 mGy/s) and the gallbladder was exposed to the second greatest amount of radiation on the right (0.12 mGy/s). The median fluoroscopy time and ED for left PNL were 386.3 s (142.2 – 1364.6) and 8.11 mSv (2.99 – 28.66). The median fluoroscopy time and ED for a right PNL were 545.0 s (236.8 – 1269.5) and 7.63 mSv (3.32 – 17.77). CONCLUSIONS: The EDR is higher for a left sided PNL compared to a right sided PNL. This is due to the fact that distribution of radiation exposure during PNL is not uniform. The patient ED for left and right PNL in non-obese males is greater than that of a computed tomography of the abdomen/pelvis. This radiation contributes to the overall amount patients with stones are exposed to. Further studies are needed to determine ways to reduce radiation exposure during PNL. Source of Funding: None
1949 LOW-DOSE FLUOROSCOPY DURING PERCUTANEOUS NEPHROSTOLITHOTOMY: FEASIBILITY, OUTCOMES, AND EFFECTS ON RADIATION EXPOSURE Kirk Anderson*, Amy Schlaifer, Roger Li, Brian Blair, Catherine Chen, Don Arnold, Damien Smith, D. Duane Baldwin, Loma Linda, CA INTRODUCTION AND OBJECTIVES: Patients with large renal stones are subjected to radiation exposure during pre and postoperative imaging and during fluoroscopy used during percutaneous nephrostolithotomy (PCNL). The use of low dose CT imaging for pre and postoperative imaging is now well established, but there is little data regarding the feasibility of low-dose fluoroscopy protocols during PCNL. The purpose of this study is to compare fluoroscopy times and treatment outcomes before and after implementation of a low-dose fluoroscopy protocol during PCNL. METHODS: A retrospective chart review was conducted of patients treated with PCNL at a single academic institution by a single
THE JOURNAL OF UROLOGY姞
e785
CONCLUSIONS: The reduced function of the staghorn bearing renal unit is multifactorial and likely to be due to associated obstruction and infection. The usual complications of PNL like bleeding, infection, adjacent organ injury are almost equivalent to PNL for simple stones. PNL does improve the function of the affected unit despite using multiple tracts. However multi-tract & relook PNL were the major determining factors for short term functional deterioration in minority. Source of Funding: None
1945 FEASIBILITY OF DISCRIMINATING URIC ACID FROM NON-URIC ACID RENAL STONES USING A SINGLE-SOURCE CT SCANNER AND 3D ANATOMIC REGISTRATION: IN VITRO AND IN VIVO STUDIES
Source of Funding: This work was partially supported by a research grant (P50 DK083007) from the National Institutes of Health.
Shuai Leng*, Katharine Grant, Terri Vrtiska, Rochester, MN; Bernhard Krauss, Forchheim, Germany; Maria Shiung, Samantha Hansen, Jia Wang, Xinhui Duan, Cynthia McCollough, rochester, MN INTRODUCTION AND OBJECTIVES: To prospectively demonstrate in phantoms and patients the feasibility of differentiating uric acid (UA) and non-uric acid (NUA) renal stones using two consecutive scans on a single source CT scanner and a 3D registration algorithm. METHODS: A total of 30 UA and 30 NUA renal stones were placed in individual vials filled with water, emerged in a 35 cm water phantom and scanned on a 128 slice single source CT scanner. An 80 kV scan was first performed and followed by a 140 kV scan. To simulate patient motion, stone vials were shifted by 7 mm in cranial caudal direction and rotated by 5° between the two scans. Images from the two scans were registered using a 3D registration program, followed by dual-energy processing to differentiate UA (in red) and NUA (in blue) stones. For the IRB approved in vivo patient study, a total of 20 patients undergoing clinically-indicated dual-source (DS), dual-energy CT scanning for UA and NUA kidney stone differentiation were recruited. On the same day as the clinically-indicated DS exam, the patient was scanned on the single source CT scanner with an 80 kV scan followed by a 140 kV scan with scan range limited to the areas with stones detected. The same dual energy analysis as that in the phantom exam was performed. Accuracy of stone classification was calculated using the results from DS scanner as reference standard. A GU radiologist recorded the number, size and composition of stones in each patient, and compared the image quality of the single-source and dual-source exams. The combined radiation dose for the 80 and 140 kV scans was set to be equivalent to that applied with the DS CT scan. RESULTS: All stones were correctly classified with 100% accuracy in the phantom. For the patient study, a total of 215 stones (122 NUA, 1 UA, and 79 unclassified) were identified from the DS CT exams. The accuracy was 82% considering all stones, and 94% considering only stones ⬎ 2mm (n⫽79, all NUA). Image quality of single source CT exam was considered similar to or slightly better than that of the dual source exam for all patients. CONCLUSIONS: Using a 3D registration algorithm on two consecutive single energy scans at different beam energies, UA and NUA stones can be accurately differentiated using a single source CT scanner, which is more available and has a wide clinic impact.
1946 IMPACT OF UROLOGY RESIDENTS ON THE FLUOROSCOPY TIME USED DURING URETEROSCOPY Mohamed Elkoushy*, Sero Andonian, Montreal, Canada INTRODUCTION AND OBJECTIVES: Endourological procedures resulted in dramatic rise in radiation exposure for both the patient and surgeon. Therefore, monitoring and awareness of fluoroscopic dose are critical. The aim of the present study was to assess the impact of urology residents on fluoroscopy time (FT) during ureteroscopy (URS). METHODS: A retrospective review of prospectively collected data was performed for consecutive patients undergoing URS by urology residents between July 2009 and February 2011. Residents in the Post-Graduate Year 4 (PGY-4) performed these cases under the direct supervision of a single endourologist. Standard fluoroscopic unit using 30 frames per second was used in these cases. Patient and stone characteristics together with operative data were compared among residents using univariate and multivariate analyses. RESULTS: Seven residents (A, B, C, D, E, F, and G) performed 106 URS with a median (range) of 16 (9-20) procedures per resident. Although a trend of decreasing mean FT over successive residents was observed, there were significant differences among the residents in their use of fluoroscopy (p⫽0.001) (Figure 1). The mean FT (95% CI) for residents A through G were 200 (128-272), 104 (65-144), 98 (72-124), 117 (58-175), 91 (52-131), 127 (89-166) and 64 (36-91) seconds, respectively. There were significant differences among residents in the use of access sheath (p⫽0.001) and pre-operative stenting (p⫽0.03). However, there were no significant differences regarding patients (age, sex) and stone characteristics (size, laterality, location, multiplicity) (p⬎0.05). Likewise, operative time, type of ureteroscopes and balloon dilation were all comparable among residents (p⬎0.05). FT (p⬍0.001), preoperative stenting (0.006) and use of access sheath (0.03) maintained their significance in the multivariate analysis after correction for all confounders. CONCLUSIONS: Urology residents vary significantly in their use of fluoroscopy during URS. Whether these differences are intrinsic to residents themselves or due to peri-operative factors remain to be clarified.
e786
THE JOURNAL OF UROLOGY姞
Vol. 187, No. 4S, Supplement, Tuesday, May 22, 2012
1948 ORGAN SPECIFIC RADIATION DOSE RATES AND EFFECTIVE DOSE DURING PERCUTANEOUS NEPHROLITHOTOMY Michael Lipkin*, John Mancini, Agnes Wang, Greta Toncheva, Colin Anderson-Evans, Michael Ferrandino, Terry Yoshizumi, Glenn Preminger, Durham, NC
Source of Funding: This work was supported in part by the Northeastern AUA Young Investigator Award and Montreal General Hospital Foundation Award to Sero Andonian.
1947 HOW MUCH RADIATION EXPOSURE DOES A UROLOGIST RECEIVE DURING ENDOSCOPIC PROCEDURES? Seth A. Cohen, Sriram S. Rangarajan*, Kerrin L. Palazzi, Thomas R. Nelson, Roger L. Sur, San Diego, CA INTRODUCTION AND OBJECTIVES: The literature lacks data offering urologists a reference for the amount of radiation exposure received while surgically managing urolithiasis. This study examines the cumulative radiation exposure of a urologist during endourologic procedures. METHODS: A single urologist at a tertiary kidney stone center recorded his radiation exposure over 5 consecutive months, as determined by a thermoluminescent dosimeter (TLD) worn on the outside of the thyroid shield. A 0.5mm lead thyroid shield and lead apron were worn during all procedures. The monthly fluoroscopy times for all surgeries were recorded as well. Estimations of radiation exposure (mrem) per month were then charted with fluoroscopy times, using scatter plots to estimate Spearman’s rank correlation coefficients. RESULTS: The total 5-month radiation exposure was 25 mrems for deep dose equivalent (DDE), 84 mrem for lens dose equivalent (LDE), and 81 mrem for shallow dose equivalent (SDE). Total fluoroscopy time during this period was 148 minutes for 15 percutaneous nephrolithotomies (PNL), 40 ureteroscopies (URS), and 6 shock wave lithotripsies (SWL). Spearman’s rank correlation coefficients were not significant for DDE (p⫽0.391), LDE (p⫽0.391), or SDE (p⫽0.391). CONCLUSIONS: Over a 5-month period, total radiation exposures were below annual accepted limits (DDE 5000 mrem, LDE 15,000 mrem and SDE 50,000 mrem). Although fluoroscopy time did not correlate with radiation exposure, an ongoing prospective study will account for other co-variates such as patient obesity and urologist distance from radiation source. Month April
Flouroscopy Time and Radiation Exposure Over 5 Months Time (mins) DDE LDE 36 9 31
SDE 30
May
43
5
17
June
17
0
0
0
July
13
4
14
13
August
39
7
22
22
Source of Funding: None
16
INTRODUCTION AND OBJECTIVES: Fluoroscopy time has been used to report on radiation exposure during urologic procedures. However, it is difficult to determine actual radiation dose delivered to patients based on fluoroscopy time. Effective dose relates absorbed radiation to the risk of developing a malignancy. We determined organ specific dose rates and calculated effective dose rates (EDR) during right and left sided percutaneous nephrolithotomy (PNL) using a validated phantom model. We determined effective dose (ED) for right and left PNL performed at our institution. METHODS: A validated anthropomorphic adult male phantom was placed prone on an operating room table. Metal Oxide Semiconductor Field Effect Transistor dosimeters were placed at 20 organ locations to measure the organ dosages. A portable C-arm was used to provide continuous fluoroscopy for three 10 minute runs each to simulate a left and right PNL. Organ dose rate (mGy/s) was determined by dividing organ dose by fluoroscopy time. The organ dose rates were multiplied by their tissue weighting factor and summed to determine EDR (mSv/s). We retrospectively reviewed 210 PNL procedures performed at our institution over a two year period. A total of 20 procedures on non-obese males with information on fluoroscopy time were included. Non-obese males most closely match the physical characteristics of our model. The ED was calculated by multiplying the fluoroscopy time by the EDR. RESULTS: The EDR for a left and right sided PNL were 0.021 mSv/s and 0.014 mSv/s, respectively. The skin entrance was exposed to the greatest amount of radiation during left and right PNL, 0.24 mGy/s and 0.26 mGy/s respectively. The stomach was exposed to the second greatest amount of radiation on the left (0.07 mGy/s) and the gallbladder was exposed to the second greatest amount of radiation on the right (0.12 mGy/s). The median fluoroscopy time and ED for left PNL were 386.3 s (142.2 – 1364.6) and 8.11 mSv (2.99 – 28.66). The median fluoroscopy time and ED for a right PNL were 545.0 s (236.8 – 1269.5) and 7.63 mSv (3.32 – 17.77). CONCLUSIONS: The EDR is higher for a left sided PNL compared to a right sided PNL. This is due to the fact that distribution of radiation exposure during PNL is not uniform. The patient ED for left and right PNL in non-obese males is greater than that of a computed tomography of the abdomen/pelvis. This radiation contributes to the overall amount patients with stones are exposed to. Further studies are needed to determine ways to reduce radiation exposure during PNL. Source of Funding: None
1949 LOW-DOSE FLUOROSCOPY DURING PERCUTANEOUS NEPHROSTOLITHOTOMY: FEASIBILITY, OUTCOMES, AND EFFECTS ON RADIATION EXPOSURE Kirk Anderson*, Amy Schlaifer, Roger Li, Brian Blair, Catherine Chen, Don Arnold, Damien Smith, D. Duane Baldwin, Loma Linda, CA INTRODUCTION AND OBJECTIVES: Patients with large renal stones are subjected to radiation exposure during pre and postoperative imaging and during fluoroscopy used during percutaneous nephrostolithotomy (PCNL). The use of low dose CT imaging for pre and postoperative imaging is now well established, but there is little data regarding the feasibility of low-dose fluoroscopy protocols during PCNL. The purpose of this study is to compare fluoroscopy times and treatment outcomes before and after implementation of a low-dose fluoroscopy protocol during PCNL. METHODS: A retrospective chart review was conducted of patients treated with PCNL at a single academic institution by a single