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Range —A technique for lumbar computerized tomography
Co,nputeri;ed Radio/. Vol. 6. pp. 371
Printed
in the
U.S.A.All
to 376, 1982
0730~1862/82,'060371-J6EO3.OO.O
Copyright
rights reserved
0 1982 Pergamon
Press Ltd
RANGE-A TECHNIQUE FOR LU COMPUTERIZED TOMOGRAPHY LEROY M. KOTZEN and KALAVATHY BALAKUMAR Department of Radiology, Hackensack Medical Center, Hospital Place. Hackensack, NJ 07601. U.S.,4 (Received
11 December
1981: received for puhlimtion
5 May 1982)
technique for lumbar CT scanning for the diagnosis of discogenic disease called Range techAbstract-A nique is described. This technique was formulated to minimize false positive and negative interpretation. while producing an examination which affords patients comfort and technical ease. Computed
tomography
Lumbar
spinal canal
Discogenic
disease
Range technique
Parallel
cuts
INTRODUCTION High resolution, nonenhanced computerized tomography is a promising method for non-invasive evaluation of the lumbar spinal canal [l]. The value of nonenhanced computed tomography in diagnosis of herniated disc [2,3], lumbar stenosis, lateral recess syndrome and lumbar facet abnormalities has been reported in literature [4].
The initial and perhaps the most important phase of CT scanning of the lumbar spine to diagnose discogenic disease, is the development of a technique which decreases the false positive calls secondary to equipment limitations, anatomy and artifact. Range technique was developed to minimize diagnostic problems, provide rapid patient thru-put and provide patient comfort.
MATERIALS
A-ND METHODS
Three hundred and thirty-nine patients were scanned on the General Electric CT/T 8800 during the period of December 1980-July 1981. A 25cm Algorithm 9.6 set scan time, 120KV, 320MA were used. The patient is placed symmetrically on the table top with concave gantry pads in supine position (Fig. 1). A lateral digital radiograph (scout view) of the lumbosacral spine is then obtained. The digital cursor is placed in a parallel plane to the inferior cortex of L5. The computer is programmed to range parallel 5 mm slices at 3 mm intervals commencing below the cortex of Sl, finishing above the inferior cortex of L5, where single pedicular and foraminal slices of L.5 are obtained (Fig. 2). The digital cursor is then placed parallel to the inferior cortex of L4, parallel 5 mm slices at ,3mm intervals commencing below the superior cortex of L5 and finishing above the inferior cortex of L4 are obtained, including the foramen (Fig. 3). Singles slices of the L4 pedicle, L3-4 interspace and L3 foramen complete the examination (Fig. 4). The examination time is approximately 20min per patient. The images are filmed at both soft tissue and bone windows.
DISCUSSION The literature deals with technique partially, [S] and does not adequately outline the important problems in interpretation created by the shortcomings in the existing technology. Hirschy’s series shows 96% of L5-Sl angles were greater than the maximum gantry angulation in the GE, CT/T8800 of 15”. This produces a situation where posterior bone, either osteophytic or normal body, can be projected with partial volume effect, and masquerade as a soft tissue density. This may not be differentiated from a herniated disc. To avoid these false positive calls, Hirschy suggests 1.5 mm cuts 371
LEROY M. KOTZEN and KALAYATHY
372
Fig. 1. Patient
position
BALAXUMAR
for scanning.
with arrange-off axis reformating to parallel cnts. This soft ware is experimental and only available at selected sites, it also produces loss of resolution and is time consuming. The second large diagnostic problem is to differentiate real pathology from artifact of any type. It was felt that parallel overlapping slices would show almost all abnormalities on more than one slice,
Fig. 2. Lateral posterior
digital radiograph L5-Sl interspace.
of lumbar spine. Electronic lines indicate the parallel slices covering The upper two slices cover the foraminal and pedicular area of L5.
the
Range- -a technique
for lumbar
CT
373
Fig. 3. Lateral
dlgital radiograph of lumbar spine. Electronic lines indicate the parallel slices covering posterior L4-5 interspace. The uppermost slice includes the foraminal area.
Fig. 4. Lateral
digital
radiography of lumbar spine. Electronic lines indicate slices covering area of L4, L3-4 interspace and foraminal area of L3.
the
the pedicuiar
374
Lxoy
M.
and
K~TZEN
KALAVATHY
%AL~RLMAR
thus differentiating real positives from false positives except in the rare instance when the disc is herniated totally above or below the affected interspace and might be seen on only the most cephalad of caudal slices. Efforts to reduce this L5-Sl angle have included elevation of the lumbar spine by cushions, pad or pneumatic air devices. All such attempts have resulted in a slight reduction of the L5-Sl angle, however, the patient is placed in an anteverted position causing great discomfort to the patient with low back pain or sciatica, resulting in patient movement. Such movement may result in lack of correlation between the digital cursor placement on the scout view and the actual anatomic slice at the time of scan, asymmetry and motion artifact. The above di.fficulties render the scan technically unpopular and diagnostically unreliable. Furthermore, repeatability is not possible. The Range Method is designed to: 1. Decrease patient movement. 2. The parallel 5 mm slices at 3 mm intervals in most instances display the abnormality in more than one slice, thus decreasing false positive interpretations due to artifact or anatomic variation (Figs 5 and 6). 3. Increased speed of examination through decrease in asymmetric slices, decreasing the need for repeat slices. The examination requires in most patients 15-17 slices (Fig. 7). 4. Good foraminal evaluation. 5. Evaluation of discs that have herniated above and below the interspace. 6. Allows reformating in sagittal plane (Table 1).
Table
1. CT
with
surgical correlation
and
myelographic
Patients
with positive
surgery
for disc disease
Patients
30 CT positive 6 CT negative with negative surgery
for disc disease
Patients
2 CT negative with CT and myelograms cases
in nonsurgical
12 positive CT, positive myelograms 13 negative CT, negative myelograms 7 positive CT, negative myelograms 3 negative CT, positive myelograms
Imaging 5 mm slices at 3 mm intervals was felt to be preferable following reasons.
to 9.5 mm imaging for the
1. Increased speed of examination with increased thru-put. 2. Less radiation. 3. Less noise on the image. In a small percentage of cases, the L5-Sl angle will be so severe that images will contain the body of L5 and the posterior elements of Sl. Evaluation for spinal stenosis or lateral recess encroachment is not possible in these cases.
SUMMARY Range is a simple, technically reproducible, fast, comfortable and diagnostically reliable method for high resolution CT of the spine. The 5 mm slices at 3 mm intervals provide parallel overlapping slices which display the pathology in more than one slice, providing the abnormality is not seen only in the first or last cut at the L5-Sl or L4-L5 interspace, thus decreasing false positives due to artifact of normal anatomic structures.
Range-a
technique
for lumbar
CT
gs 5 and 6. Two consecutive slices at the level of L4-5 interspace reveals extruded ventral disc. Visualization of the findings on two consecutive slices removes artifact as a diagnostic possibility.
376
&COY hf. KOTZEN
and KALAVATHY
Fig. 7. Usual levels, plans and number
BALAKUMAR
of slices by the range method
REFERENCES 1. G. F. Carrera, A. L. Williams and V. M. Haughton. Computed tomography in sciatica, Radio&y 837, 433-437 (1980). 2. G. A. Meyer, V. M. Haughton and A. L. Williams, Diagnosis of herniated lumbar disc with computed tomography, New Engl. J. Med. 301, 11661167 (1979). 3. A. L. Williams, V. M. Haughton and A. Syvertsen: Computed tomography with the diagnosis of herniated pulposis, Radiologg 135, 95599 (1980). 4. G. F. Carrera, V. M. Haughton: A. Syvertsen and A. William, Computed tomography of the lumbar facet, J. RudI’oI. 134, 145-148 (1980). 5. J. C. Hirschy. W. M. Leue and W. H. Berhinger, CT of the lumbosacral spine: importance of tomographic planes parallel to vertebra end plate, Am. J. Roentg. 136, 47-52 (1981). About the Author--- LEROYi’d. KOTZEN, M.D. graduated from the State University of New York, Downstate Division in 1963 and did a Medical Internship at Jefferson Medical College Hospital. Philadelphia, PA in 1964. From 19641967 he did a Radiology Residency at New York Hospital, Cornell Medical Center. He was attending Radiologist at Columbia Presbyterian Medical Center. NY and also attending Radiologist at Hackensack Medical Center until 1968. From 1976 till present he is associate Director of Radiology, Hackensack Medical Center 1976present and a Member of Board of Governors. Hackensack Medical Center since 1975. About the Author-KALAVATHY BALAKLMAR, M.D. graduated from Madras Medical College, Madras University, India in 1975. She did a year of Rotating Internship in Government General Hospital, Madras, India. She was a General Practitioner in her hometown for a year. She came to this country at the end of 1977. She started her residency in Diagnostic Radiology in July 1979 at Misericordia Hospital Medical Center, New York and did her first year there. She is continuing her residency in Diagnostic Radiology at Hackensack Medical Center and is doing her third year of Diagnostic Radiology now.
Printed
in the
U.S.A.All
to 376, 1982
0730~1862/82,'060371-J6EO3.OO.O
Copyright
rights reserved
0 1982 Pergamon
Press Ltd
RANGE-A TECHNIQUE FOR LU COMPUTERIZED TOMOGRAPHY LEROY M. KOTZEN and KALAVATHY BALAKUMAR Department of Radiology, Hackensack Medical Center, Hospital Place. Hackensack, NJ 07601. U.S.,4 (Received
11 December
1981: received for puhlimtion
5 May 1982)
technique for lumbar CT scanning for the diagnosis of discogenic disease called Range techAbstract-A nique is described. This technique was formulated to minimize false positive and negative interpretation. while producing an examination which affords patients comfort and technical ease. Computed
tomography
Lumbar
spinal canal
Discogenic
disease
Range technique
Parallel
cuts
INTRODUCTION High resolution, nonenhanced computerized tomography is a promising method for non-invasive evaluation of the lumbar spinal canal [l]. The value of nonenhanced computed tomography in diagnosis of herniated disc [2,3], lumbar stenosis, lateral recess syndrome and lumbar facet abnormalities has been reported in literature [4].
The initial and perhaps the most important phase of CT scanning of the lumbar spine to diagnose discogenic disease, is the development of a technique which decreases the false positive calls secondary to equipment limitations, anatomy and artifact. Range technique was developed to minimize diagnostic problems, provide rapid patient thru-put and provide patient comfort.
MATERIALS
A-ND METHODS
Three hundred and thirty-nine patients were scanned on the General Electric CT/T 8800 during the period of December 1980-July 1981. A 25cm Algorithm 9.6 set scan time, 120KV, 320MA were used. The patient is placed symmetrically on the table top with concave gantry pads in supine position (Fig. 1). A lateral digital radiograph (scout view) of the lumbosacral spine is then obtained. The digital cursor is placed in a parallel plane to the inferior cortex of L5. The computer is programmed to range parallel 5 mm slices at 3 mm intervals commencing below the cortex of Sl, finishing above the inferior cortex of L5, where single pedicular and foraminal slices of L.5 are obtained (Fig. 2). The digital cursor is then placed parallel to the inferior cortex of L4, parallel 5 mm slices at ,3mm intervals commencing below the superior cortex of L5 and finishing above the inferior cortex of L4 are obtained, including the foramen (Fig. 3). Singles slices of the L4 pedicle, L3-4 interspace and L3 foramen complete the examination (Fig. 4). The examination time is approximately 20min per patient. The images are filmed at both soft tissue and bone windows.
DISCUSSION The literature deals with technique partially, [S] and does not adequately outline the important problems in interpretation created by the shortcomings in the existing technology. Hirschy’s series shows 96% of L5-Sl angles were greater than the maximum gantry angulation in the GE, CT/T8800 of 15”. This produces a situation where posterior bone, either osteophytic or normal body, can be projected with partial volume effect, and masquerade as a soft tissue density. This may not be differentiated from a herniated disc. To avoid these false positive calls, Hirschy suggests 1.5 mm cuts 371
LEROY M. KOTZEN and KALAYATHY
372
Fig. 1. Patient
position
BALAXUMAR
for scanning.
with arrange-off axis reformating to parallel cnts. This soft ware is experimental and only available at selected sites, it also produces loss of resolution and is time consuming. The second large diagnostic problem is to differentiate real pathology from artifact of any type. It was felt that parallel overlapping slices would show almost all abnormalities on more than one slice,
Fig. 2. Lateral posterior
digital radiograph L5-Sl interspace.
of lumbar spine. Electronic lines indicate the parallel slices covering The upper two slices cover the foraminal and pedicular area of L5.
the
Range- -a technique
for lumbar
CT
373
Fig. 3. Lateral
dlgital radiograph of lumbar spine. Electronic lines indicate the parallel slices covering posterior L4-5 interspace. The uppermost slice includes the foraminal area.
Fig. 4. Lateral
digital
radiography of lumbar spine. Electronic lines indicate slices covering area of L4, L3-4 interspace and foraminal area of L3.
the
the pedicuiar
374
Lxoy
M.
and
K~TZEN
KALAVATHY
%AL~RLMAR
thus differentiating real positives from false positives except in the rare instance when the disc is herniated totally above or below the affected interspace and might be seen on only the most cephalad of caudal slices. Efforts to reduce this L5-Sl angle have included elevation of the lumbar spine by cushions, pad or pneumatic air devices. All such attempts have resulted in a slight reduction of the L5-Sl angle, however, the patient is placed in an anteverted position causing great discomfort to the patient with low back pain or sciatica, resulting in patient movement. Such movement may result in lack of correlation between the digital cursor placement on the scout view and the actual anatomic slice at the time of scan, asymmetry and motion artifact. The above di.fficulties render the scan technically unpopular and diagnostically unreliable. Furthermore, repeatability is not possible. The Range Method is designed to: 1. Decrease patient movement. 2. The parallel 5 mm slices at 3 mm intervals in most instances display the abnormality in more than one slice, thus decreasing false positive interpretations due to artifact or anatomic variation (Figs 5 and 6). 3. Increased speed of examination through decrease in asymmetric slices, decreasing the need for repeat slices. The examination requires in most patients 15-17 slices (Fig. 7). 4. Good foraminal evaluation. 5. Evaluation of discs that have herniated above and below the interspace. 6. Allows reformating in sagittal plane (Table 1).
Table
1. CT
with
surgical correlation
and
myelographic
Patients
with positive
surgery
for disc disease
Patients
30 CT positive 6 CT negative with negative surgery
for disc disease
Patients
2 CT negative with CT and myelograms cases
in nonsurgical
12 positive CT, positive myelograms 13 negative CT, negative myelograms 7 positive CT, negative myelograms 3 negative CT, positive myelograms
Imaging 5 mm slices at 3 mm intervals was felt to be preferable following reasons.
to 9.5 mm imaging for the
1. Increased speed of examination with increased thru-put. 2. Less radiation. 3. Less noise on the image. In a small percentage of cases, the L5-Sl angle will be so severe that images will contain the body of L5 and the posterior elements of Sl. Evaluation for spinal stenosis or lateral recess encroachment is not possible in these cases.
SUMMARY Range is a simple, technically reproducible, fast, comfortable and diagnostically reliable method for high resolution CT of the spine. The 5 mm slices at 3 mm intervals provide parallel overlapping slices which display the pathology in more than one slice, providing the abnormality is not seen only in the first or last cut at the L5-Sl or L4-L5 interspace, thus decreasing false positives due to artifact of normal anatomic structures.
Range-a
technique
for lumbar
CT
gs 5 and 6. Two consecutive slices at the level of L4-5 interspace reveals extruded ventral disc. Visualization of the findings on two consecutive slices removes artifact as a diagnostic possibility.
376
&COY hf. KOTZEN
and KALAVATHY
Fig. 7. Usual levels, plans and number
BALAKUMAR
of slices by the range method
REFERENCES 1. G. F. Carrera, A. L. Williams and V. M. Haughton. Computed tomography in sciatica, Radio&y 837, 433-437 (1980). 2. G. A. Meyer, V. M. Haughton and A. L. Williams, Diagnosis of herniated lumbar disc with computed tomography, New Engl. J. Med. 301, 11661167 (1979). 3. A. L. Williams, V. M. Haughton and A. Syvertsen: Computed tomography with the diagnosis of herniated pulposis, Radiologg 135, 95599 (1980). 4. G. F. Carrera, V. M. Haughton: A. Syvertsen and A. William, Computed tomography of the lumbar facet, J. RudI’oI. 134, 145-148 (1980). 5. J. C. Hirschy. W. M. Leue and W. H. Berhinger, CT of the lumbosacral spine: importance of tomographic planes parallel to vertebra end plate, Am. J. Roentg. 136, 47-52 (1981). About the Author--- LEROYi’d. KOTZEN, M.D. graduated from the State University of New York, Downstate Division in 1963 and did a Medical Internship at Jefferson Medical College Hospital. Philadelphia, PA in 1964. From 19641967 he did a Radiology Residency at New York Hospital, Cornell Medical Center. He was attending Radiologist at Columbia Presbyterian Medical Center. NY and also attending Radiologist at Hackensack Medical Center until 1968. From 1976 till present he is associate Director of Radiology, Hackensack Medical Center 1976present and a Member of Board of Governors. Hackensack Medical Center since 1975. About the Author-KALAVATHY BALAKLMAR, M.D. graduated from Madras Medical College, Madras University, India in 1975. She did a year of Rotating Internship in Government General Hospital, Madras, India. She was a General Practitioner in her hometown for a year. She came to this country at the end of 1977. She started her residency in Diagnostic Radiology in July 1979 at Misericordia Hospital Medical Center, New York and did her first year there. She is continuing her residency in Diagnostic Radiology at Hackensack Medical Center and is doing her third year of Diagnostic Radiology now.