Inr. J. Rcrdiafion Onroloyy 0 Pergamon Pm\ Inc..
Biol. Phys.. Vol. 5. pp. W-103 Printed in the U.S.A. 1979.
??Technical Innovation
036&3016/79/01014iMG02.00/0
and Note
THE USE OF COMPUTERIZED TOMOGRAPHY SCANNING TREATMENT PLANNING FOR BLADDER CARCINOMA
IN
BARBARA SCHLAGER, M.D.,? SUCHA 0. ASBELL, M.D.,* ALAN S. BAKER, M.S.,§ DAVID M. SKLAROFF, M.D.,7 H. GUNTER SEYDEL, M.D." and BERNARD J. OSTRUM, M.D.?? Albert Einstein Medical Center, York & Tabor Roads, Philadelphia, PA 19141, U.S.A. Computerized tomography (CT) scans of the pelvis were performed in 50 patients with and without known pelvic malignancies at the Afhert Einstein Medical Center, Northern Mvfsion, between September 1976 and September 1977. Each scan was reviewed systematically to determine size, location and interrelationship of pelvic structures as well as to evaluate the possible extent of tumor. For the 21 patients who were to receive radiation therapy for carcinoma of the bladder, the treatment plans, which were based on the patient contour and diagnostic studies, were compared to the information gained from the CT scan. Twenty nine per cent of the original treatment plans were altered after reviewing the CT scans. Ten patients with a diagnosis of bladder carcinoma underwent pre- and post-voiding scans. The area of the bladder at the level of the femoral heads which remained after voiding was on the average 69% of the original (range, 5441%). The CT scan provided information which permitted better understanding of the dynamics of physiologic anatomy. It could replace the more invasive techniques presently used for localization in carcinoma of the urinary bladder. Computerized
tomography
scanning, Therapy treatment
INTRODUCTION
planning, Carcinoma
of the urinary bladder.
For patients who were to receive radiation therapy for carcinoma of the bladder, the treatment plans, which were based on the patient contour and the diagnostic studies, were compared to the information gained from the CT scan. This comparison determined if any alterations should be considered.
The clinical application of computerized tomography (CT) scanning was first introduced to the United States in 1973 with Hounsfield’s original EM1 (Electrical Musical Instrument) unit which was limited to scanning of the head and neck.‘,5 In 1974, total body scanning became available. The potential use of these scans for definitive tumor localization and treatment planning was obvious. Much of the present literature deals with the physical and mechanical aspects of obtaining data.4.‘2 Articles concerning clinical application or whole body scanning to treatment planning for radiation therapy are few.2*6.7 We obtained CT scans of the pelvis in patients with and without known pelvic malignancies. Each scan was reviewed systematically to determine size, location and the interrelationship of pelvic structures, as well as to evaluate the possible extent of the tumor.
METHODS
AND MATERIALS
The Ohio Nuclear Corporation total body scanner was employed in this study. The images were formed on a 256 x 256 matrix producing two adjacent 1.3 cm thick sections in 2.5 min. These images were displayed on a t.v. monitor, and Polaroid photographs were obtained from the data display. A cursor circle is a pointer which permits evaluation of density at a point or within a given area encompassed by the circle.” This was used to define the limits of various structures by relating the change
tResident, Department of Radiation Therapy. SClinical Assistant Professor, in Radiology,
of Radiation Therapy. ‘Attending, Radiology Department, Thomas Jefferson University Hospital, 1 lth & Walnut Streets, Philadelphia, Pa 19107, U.S.A. ttClinica1 Professor of Radiology, Temple University School of Medicine, and Chairman, Division of Radiology. Reprint requests to: Sucha 0. Asbell, M.D. Accepted for publication 31 May 1978.
Temple Attending Staff,
University School of Medicine, and Department of Radiation Therapy. QClinical Assistant Professor in Radiology, Temple University School of Medicine, and Physicist, Division of Radiology. (Clinical Associate Professor of Radiology, Temple University School of Medicine, and Chairman, Department 99
100
Radiation
Oncology
0 Biology
0 Physics
in their densities. The computer also was equipped with the dynamic spatial measurement program which enabled us to make accurate measurements of organ size. This program functioned by placing a marker at the points of interest and automatically measured the distance between them. These markers could be utilized to evaluate organs in a specific position on the computer display throughout consecutive levels. When radio-opaque contrast material was utilized, no additional information was gained and frequently resulted in the production of artifacts. The use of contrast was, therefore, abandoned. Computerized tomography scans of the pelvis were performed on 50 patients at the Albert Einstein Medical Center between September 1976 and September 1977. Five of these patients were excluded from this study because of motion or artifact. The remaining 45 patients were composed of 30 males and 15 females. The mean age was 64.4 years. Twenty eight patients were examined for radiation therapy of pelvic malignancies. Fifteen were studied for tumors which arose outside of the true pelvis with possible extension into the pelvis and 7 were studied for non-radiotherapeutic reasons. All patients were placed in the supine position without being instructed to void or prepared in any special fashion for the scan. Scans were taken at 13 mm intervals from the level of the iliac crest to below the femoral heads. Treatment fields, when present, were outlined on the patient by means of radio-opaque markers (angiographic catheter). The boundaries of these portals had been localized previously by the use of a simulator and appropriate contrast materials. Scans at the level of the center of the femoral heads 2 6.2 mm were used to evaluate the size and position of pelvic structures with particular attention to the bladder. The anterior margin of the bladder was marked at the level of its greatest AP diameter and scans were obtained of successively inferior levels; the marker was maintained in its original position until the symphysis pubis was visualremained equal. ized , and all other parameters Therefore, any alteration secondary to voiding in the relationship of the anterior margin of the bladder to pubic symphysis could be measured. The result of the dimensional analysis of cross-sectional pelvic anatomy and its application for more accurate treatment planning in carcinoma of the bladder is presented. Table 1. Dimensional No. of patients 45
January
1979, Volume
5, Number
I
RESULTS Table 1 presents the analysis of the cross-sectional anatomical data of 45 patients at the level of the femoral heads. Column A shows the measurements of the anterior abdominal wall to the anterior aspect of the bladder in both males and females. There is a wide variation around the mean (+47%) which is compatible with different body types and variable deposition of adipose tissue within the anterior abdominal wall. Columns B and C demonstrate that the AP and lateral dimensions of the bladder vary little and suggest that a portal of 10 cm in width X 10 cm in anterior posterior dimension will encompass the bladder adequately in most patients. A constant relationship of the posterior aspect of the bladder to the overall pelvic AP diameter is represented by the ratio (A + B)/D as Fig. 1 demonstrates; this is 0.560 + 1l%(Table 1). This verifies that the posterior aspect of the bladder is located near the mid-plane of the pelvis. Utilizing this ratio, a simple method of checking the adequacy of the posterior margin of the treatment portal is established, in whom contrast material particularly in patients cannot be used. The anterior margin of the bladder was evaluated in 10 patients with bladder carcinoma. In 6 of these patients, the bladder not only extended to 2.0cm beyond the symphysis pubis anteriorly, but also failed to show positional changes after voiding.
)A
I
I
B
Fig. 1. Cross-sectional diagram of the anatomy at the level of the femoral heads. A is the measurement from the anterior abdominal wall to the anterior bladder wall, B is the anterior-posterior diameter of the bladder, C is the bladder width and D is the anterior-posterior diameter of the patient.
analysis of bladder and pelvis at the level of femoral heads.
A
B
C
(A + B)/D
Mean age (yrs)
Ant.abd. wall to ant.bladder (cm)
A.P. diameter bladder (cm)
Bladder width (cm)
A+B A.P. dia. pelvis
64.4 (22-81)
4.8 + 47% (2.2-l 1.9)
6.9 2 22% (3.9-9.8)
7.3 + 19% (4.6-10.6)
0.5605 11% (0.436-0.653)
Computerized
tomography
scanning
in treatment
Further analysis of the pre- and post-voiding studies of these 10 patients showed that the mean residual bladder area was 69% k 10 (range, 54-81%) of the original (Table 2). This suggests that most patients with bladder cancer have some residual urine. This was delineated by means of the cursor circle defining water density area. Several causes are postulated: 1. Tumor invasion of the vesicular muscularis, decreasing its ability to contract. 2. Prostatic hypertrophy or prostatic invasion by tumor causing obstruction. 3. Inability of a patient to void on command or significant delay between urination and the scan. Therefore, the actual area of the urinary bladder at any given time is variable, even in post-voiding conditions (Figs 2a and 2b). Current methods used to determine bladder volume may be inadequate because they cannot simulate anatomy of the bladder under actual treatment conditions. Radiation therapy texts suggest cystograms using a catheter for vesicular emptying followed by installation of contrast material or they are vague, giving no specific directions for localizaThe introduction of the catheter tion procedures3.‘.”
planning
for bladder
carcinoma
B.
SCHLAGER
(b)
scan at the level of the femoral heads. (b) Post-void scan of same patient femoral heads showing no significant change from the previous study.
Table 2. Mean bladder
Sex Male Female Mean of both
et al.
Pre-void (cm?
cross-sectional Post-void (cm*)
101
alone alters the physiological anatomy and does not reproduce actual treatment conditions. In addition to defining average bladder dimensions and the presence of residual urine, the CT scan yielded additional information concerning unusual contour and possible extension of tumor outside the vesicular wall. An intraluminal defect is demonstrated on IVP and cystogram in Fig. 3a. The clinical evaluation of this patient suggested extension of tumor outside the bladder wall. The CT scan (Fig. 3b) confirmed the suspicion of a large extraluminal component of this tumor. Figure 4 demonstrates the bladder as outlined by the contrast studies with the cross hatched area representing the volume, added by analysis of the CT scan. A retrograde cystogram demonstrated a bladder diverticulum which appeared to be located centrally with extension superiorly. This abnormality was unsuspected on the patient’s intravenous pyelogram Fig. 5a. All lateral films were difficult to interpret because of the patient’s obesity. A CT scan (Fig. 5b) was obtained. It not only verified the presence of this abnormality, but also showed that the diverticulum extended beyond the previously anticipated bladder margin.
(4 Fig. 2. (a) Pre-void
0
area through
the level of the femoral
Postlpre residual area (%)
at the level of the
heads.
Range (yr)
58.5 40.6
48.5 23.6
82 61
548 1 56-65
53.1
41.0
694 10
54-81
102
Radiation
Oncology
0 Biology
0 Physics
January
1979, Volume
5, Number
1
(4
Fig. 3. (a) An intraluminal defect in the bladder visualized on the intravenous pyelogram demonstrated irregular right margin. (b) The CT scan showed extension of this lesion to the pelvic wall.
/
/
/
,_--
___--‘..
,
\ \ \
/
EXTRA LUMINAL TUMOR MASS
I /
\
/
Fig. 4. Patient contour with diagram of bladder as localized by cystogram and intravenous pyelogram. Cross-hatched area is the volume added by analysis of multi-level CT scans.
Fig. Sa. An intravenous urogram showing no evidence of an abnormality within the bladder.
by the
Of the 45 patients who were reviewed, 21 had carcinoma of the bladder. In each of these patients the treatment portals, which had been based on diagnostic studies, were re-evaluated in light of the results of the CT scan. In 15 of the 21 patients, no additional information was gained from the CT scan, but the CT scan did include all the information obtained from the diagnostic studies. Six of the patients had changes in their treatment portals as a direct result of the CT scans. That is, 29% of the patients with bladder malignancies had changes in treatment planning. Most of these changes were the result of previous
Fig. 5b. Extension of bladder diverticulum anteriorly. (Radio-opaque dots an anterior abdominal wall outline treatment portal.)
Computerized
tomography
scanning
in treatment
under-estimation of size and/or position of the bladder by standard localization procedures. Both size and position of the bladder were factors in 4 patients resulting in an increase in the size of the treatment portal. An extremely anterior location of the bladder in one case resulted in a change in the orientation of the treatment fields. Another required an increase in the size of his boost field based on extraluminal extent of his tumor mass. DISCUSSION Analysis of the CT scans of 45 patients indicates the following conclusions regarding treatment planning for carcinoma of the urinary bladder: 1. Pelvic anatomy shows certain constant relationships concerning bladder size. This suggests that for treatment purposes the 10 cm x 1Ocm area on a treatment plan for limited bladder therapy should be an adequate size in most patients. 2. There is a wide variation from patient to patient in the location of the anterior bladder wall. But in any individual, there is little change in the anterior margin even after voiding. Since there is such a wide variation in the positions of the anterior bladder margins, the centering of the treatment portal cannot depend routinely on bony landmarks (i.e. symphysis pubis, femoral heads). When CT scans are not used, diagnostic studies must be analyzed carefully. It cannot be assumed that the anterior margin, as outlined by
planning
for bladder
carcinoma
0 B. SCHLAGER
et al.
103
double contrast studies (air and radio-opaque material), will change after voiding. 3. Because of residual urine and decreased contractility, the margins of the bladder may not be defined adequately by the instillation of contrast material. The recommended 30-60 cm3 of contrast material may not simulate the patient’s anatomy.“” If CT scanning is not available, it might be useful to measure the amount of urine post natural voiding in the catheter specimen and replace at least that amount with contrast. 4. Any abnormality such as an irregular bladder wall, bladder diverticula, or an intraluminal defect should warrant additional studies. A CT scan in particular would help to determine the extent of the tumor or the bladder mucosa, which otherwise could be excluded from a treatment portal. 5. Munzenrider et al. have suggested that CT scanning for treatment planning in pelvic malignancies, while having little effect on the treatment volume in whole pelvis irradiation, may play a significant role in limited field irradiation.’ Twenty nine per cent of our patients had some alteration of their treatment portals (the majority of these changes were on the limited field) as a result of the information obtained from the CT scan. However, follow-up evaluation of these patients is necessary to determine if those treatment portal changes will have any effect on recurrent disease or overall patient survival.
REFERENCES 1. Ambrose, J.A.: Computerized transverse axial scanning (tomography)-II. Clinical application. Br. J. Radiol. 46: 1023-1047, 1973. 2. Chernak, B.S., Rodriquez-Antunez, A., Jeldin, G.L., Daluval, R.S., Lavick, P.S.: The use of computed tomography for radiation therapy treatment planning. Radiology 117: 613-614, 1975. 3. Fletcher, G.: Textbook of Radiation Therapy, 2nd Edn. Philadelphia, Lea & Febiger, 1973, pp. 726-728. 4. Geise, R.A., McCullough, E.C.: The use of CT scanners megavoltage photon beam therapy planning. iadiology 124: 143-149, 1977. 5. Hounsfield, G.N.: Computerized transverse axial scanning (tomography)-I. Description of system. Br. J. Radial. 46: 1016-1022, 1973. 6. Jelden, G.L., Chernak, ES., Rodriquez-Antunez, A., Hagga, J.R., Lavik, P.S., Dhaliwal, R.S.: Further progress in CT scanning and computerized radiation therapy treatment planning. Am. J. Roentgen01 127: 179-185, 1976.
7. Laughlin, J.S., Chu, F., Simpson, L., Watson, R.C.: Radiation treatment planning. Cancer 39: 719-728, 1977. 8. Moss, W.T., Brand, W.N.: Therapeutic Radiology, 4th Edn. St. Louis, Mosby, 1973, p. 370. 9. Munzenrider, J.E., Pilepick, M., Rene-Ferrero, J.B., Tchcekarova, I., Carter, B.L.: Use of body scanner in radiotherapy treatment planning. Cancer 40: 170-179, 1977. 10. Ohio-Nuclear, Inc., Solon, Ohio, Operators Manual-A Scan 50, Manual 961000, Revision C, Change 1; pp. 4-12, 1977. 11. Rotman, M. & A. Rafla: (New York Med. College, N.Y.) Monograph: Carcinoma of Urinary Bladder, pp. 50-53, (RSNA 1975 meeting, Chicago). 12. Sontag, M.R., Battista, J., Bronskill, M.J., Cunningham, J.R.: Implications of computed tomography for inhomogeneity corrections in photon beam dose calculations. Radiology 124: 143-149, 1977.
Biol. Phys.. Vol. 5. pp. W-103 Printed in the U.S.A. 1979.
??Technical Innovation
036&3016/79/01014iMG02.00/0
and Note
THE USE OF COMPUTERIZED TOMOGRAPHY SCANNING TREATMENT PLANNING FOR BLADDER CARCINOMA
IN
BARBARA SCHLAGER, M.D.,? SUCHA 0. ASBELL, M.D.,* ALAN S. BAKER, M.S.,§ DAVID M. SKLAROFF, M.D.,7 H. GUNTER SEYDEL, M.D." and BERNARD J. OSTRUM, M.D.?? Albert Einstein Medical Center, York & Tabor Roads, Philadelphia, PA 19141, U.S.A. Computerized tomography (CT) scans of the pelvis were performed in 50 patients with and without known pelvic malignancies at the Afhert Einstein Medical Center, Northern Mvfsion, between September 1976 and September 1977. Each scan was reviewed systematically to determine size, location and interrelationship of pelvic structures as well as to evaluate the possible extent of tumor. For the 21 patients who were to receive radiation therapy for carcinoma of the bladder, the treatment plans, which were based on the patient contour and diagnostic studies, were compared to the information gained from the CT scan. Twenty nine per cent of the original treatment plans were altered after reviewing the CT scans. Ten patients with a diagnosis of bladder carcinoma underwent pre- and post-voiding scans. The area of the bladder at the level of the femoral heads which remained after voiding was on the average 69% of the original (range, 5441%). The CT scan provided information which permitted better understanding of the dynamics of physiologic anatomy. It could replace the more invasive techniques presently used for localization in carcinoma of the urinary bladder. Computerized
tomography
scanning, Therapy treatment
INTRODUCTION
planning, Carcinoma
of the urinary bladder.
For patients who were to receive radiation therapy for carcinoma of the bladder, the treatment plans, which were based on the patient contour and the diagnostic studies, were compared to the information gained from the CT scan. This comparison determined if any alterations should be considered.
The clinical application of computerized tomography (CT) scanning was first introduced to the United States in 1973 with Hounsfield’s original EM1 (Electrical Musical Instrument) unit which was limited to scanning of the head and neck.‘,5 In 1974, total body scanning became available. The potential use of these scans for definitive tumor localization and treatment planning was obvious. Much of the present literature deals with the physical and mechanical aspects of obtaining data.4.‘2 Articles concerning clinical application or whole body scanning to treatment planning for radiation therapy are few.2*6.7 We obtained CT scans of the pelvis in patients with and without known pelvic malignancies. Each scan was reviewed systematically to determine size, location and the interrelationship of pelvic structures, as well as to evaluate the possible extent of the tumor.
METHODS
AND MATERIALS
The Ohio Nuclear Corporation total body scanner was employed in this study. The images were formed on a 256 x 256 matrix producing two adjacent 1.3 cm thick sections in 2.5 min. These images were displayed on a t.v. monitor, and Polaroid photographs were obtained from the data display. A cursor circle is a pointer which permits evaluation of density at a point or within a given area encompassed by the circle.” This was used to define the limits of various structures by relating the change
tResident, Department of Radiation Therapy. SClinical Assistant Professor, in Radiology,
of Radiation Therapy. ‘Attending, Radiology Department, Thomas Jefferson University Hospital, 1 lth & Walnut Streets, Philadelphia, Pa 19107, U.S.A. ttClinica1 Professor of Radiology, Temple University School of Medicine, and Chairman, Division of Radiology. Reprint requests to: Sucha 0. Asbell, M.D. Accepted for publication 31 May 1978.
Temple Attending Staff,
University School of Medicine, and Department of Radiation Therapy. QClinical Assistant Professor in Radiology, Temple University School of Medicine, and Physicist, Division of Radiology. (Clinical Associate Professor of Radiology, Temple University School of Medicine, and Chairman, Department 99
100
Radiation
Oncology
0 Biology
0 Physics
in their densities. The computer also was equipped with the dynamic spatial measurement program which enabled us to make accurate measurements of organ size. This program functioned by placing a marker at the points of interest and automatically measured the distance between them. These markers could be utilized to evaluate organs in a specific position on the computer display throughout consecutive levels. When radio-opaque contrast material was utilized, no additional information was gained and frequently resulted in the production of artifacts. The use of contrast was, therefore, abandoned. Computerized tomography scans of the pelvis were performed on 50 patients at the Albert Einstein Medical Center between September 1976 and September 1977. Five of these patients were excluded from this study because of motion or artifact. The remaining 45 patients were composed of 30 males and 15 females. The mean age was 64.4 years. Twenty eight patients were examined for radiation therapy of pelvic malignancies. Fifteen were studied for tumors which arose outside of the true pelvis with possible extension into the pelvis and 7 were studied for non-radiotherapeutic reasons. All patients were placed in the supine position without being instructed to void or prepared in any special fashion for the scan. Scans were taken at 13 mm intervals from the level of the iliac crest to below the femoral heads. Treatment fields, when present, were outlined on the patient by means of radio-opaque markers (angiographic catheter). The boundaries of these portals had been localized previously by the use of a simulator and appropriate contrast materials. Scans at the level of the center of the femoral heads 2 6.2 mm were used to evaluate the size and position of pelvic structures with particular attention to the bladder. The anterior margin of the bladder was marked at the level of its greatest AP diameter and scans were obtained of successively inferior levels; the marker was maintained in its original position until the symphysis pubis was visualremained equal. ized , and all other parameters Therefore, any alteration secondary to voiding in the relationship of the anterior margin of the bladder to pubic symphysis could be measured. The result of the dimensional analysis of cross-sectional pelvic anatomy and its application for more accurate treatment planning in carcinoma of the bladder is presented. Table 1. Dimensional No. of patients 45
January
1979, Volume
5, Number
I
RESULTS Table 1 presents the analysis of the cross-sectional anatomical data of 45 patients at the level of the femoral heads. Column A shows the measurements of the anterior abdominal wall to the anterior aspect of the bladder in both males and females. There is a wide variation around the mean (+47%) which is compatible with different body types and variable deposition of adipose tissue within the anterior abdominal wall. Columns B and C demonstrate that the AP and lateral dimensions of the bladder vary little and suggest that a portal of 10 cm in width X 10 cm in anterior posterior dimension will encompass the bladder adequately in most patients. A constant relationship of the posterior aspect of the bladder to the overall pelvic AP diameter is represented by the ratio (A + B)/D as Fig. 1 demonstrates; this is 0.560 + 1l%(Table 1). This verifies that the posterior aspect of the bladder is located near the mid-plane of the pelvis. Utilizing this ratio, a simple method of checking the adequacy of the posterior margin of the treatment portal is established, in whom contrast material particularly in patients cannot be used. The anterior margin of the bladder was evaluated in 10 patients with bladder carcinoma. In 6 of these patients, the bladder not only extended to 2.0cm beyond the symphysis pubis anteriorly, but also failed to show positional changes after voiding.
)A
I
I
B
Fig. 1. Cross-sectional diagram of the anatomy at the level of the femoral heads. A is the measurement from the anterior abdominal wall to the anterior bladder wall, B is the anterior-posterior diameter of the bladder, C is the bladder width and D is the anterior-posterior diameter of the patient.
analysis of bladder and pelvis at the level of femoral heads.
A
B
C
(A + B)/D
Mean age (yrs)
Ant.abd. wall to ant.bladder (cm)
A.P. diameter bladder (cm)
Bladder width (cm)
A+B A.P. dia. pelvis
64.4 (22-81)
4.8 + 47% (2.2-l 1.9)
6.9 2 22% (3.9-9.8)
7.3 + 19% (4.6-10.6)
0.5605 11% (0.436-0.653)
Computerized
tomography
scanning
in treatment
Further analysis of the pre- and post-voiding studies of these 10 patients showed that the mean residual bladder area was 69% k 10 (range, 54-81%) of the original (Table 2). This suggests that most patients with bladder cancer have some residual urine. This was delineated by means of the cursor circle defining water density area. Several causes are postulated: 1. Tumor invasion of the vesicular muscularis, decreasing its ability to contract. 2. Prostatic hypertrophy or prostatic invasion by tumor causing obstruction. 3. Inability of a patient to void on command or significant delay between urination and the scan. Therefore, the actual area of the urinary bladder at any given time is variable, even in post-voiding conditions (Figs 2a and 2b). Current methods used to determine bladder volume may be inadequate because they cannot simulate anatomy of the bladder under actual treatment conditions. Radiation therapy texts suggest cystograms using a catheter for vesicular emptying followed by installation of contrast material or they are vague, giving no specific directions for localizaThe introduction of the catheter tion procedures3.‘.”
planning
for bladder
carcinoma
B.
SCHLAGER
(b)
scan at the level of the femoral heads. (b) Post-void scan of same patient femoral heads showing no significant change from the previous study.
Table 2. Mean bladder
Sex Male Female Mean of both
et al.
Pre-void (cm?
cross-sectional Post-void (cm*)
101
alone alters the physiological anatomy and does not reproduce actual treatment conditions. In addition to defining average bladder dimensions and the presence of residual urine, the CT scan yielded additional information concerning unusual contour and possible extension of tumor outside the vesicular wall. An intraluminal defect is demonstrated on IVP and cystogram in Fig. 3a. The clinical evaluation of this patient suggested extension of tumor outside the bladder wall. The CT scan (Fig. 3b) confirmed the suspicion of a large extraluminal component of this tumor. Figure 4 demonstrates the bladder as outlined by the contrast studies with the cross hatched area representing the volume, added by analysis of the CT scan. A retrograde cystogram demonstrated a bladder diverticulum which appeared to be located centrally with extension superiorly. This abnormality was unsuspected on the patient’s intravenous pyelogram Fig. 5a. All lateral films were difficult to interpret because of the patient’s obesity. A CT scan (Fig. 5b) was obtained. It not only verified the presence of this abnormality, but also showed that the diverticulum extended beyond the previously anticipated bladder margin.
(4 Fig. 2. (a) Pre-void
0
area through
the level of the femoral
Postlpre residual area (%)
at the level of the
heads.
Range (yr)
58.5 40.6
48.5 23.6
82 61
548 1 56-65
53.1
41.0
694 10
54-81
102
Radiation
Oncology
0 Biology
0 Physics
January
1979, Volume
5, Number
1
(4
Fig. 3. (a) An intraluminal defect in the bladder visualized on the intravenous pyelogram demonstrated irregular right margin. (b) The CT scan showed extension of this lesion to the pelvic wall.
/
/
/
,_--
___--‘..
,
\ \ \
/
EXTRA LUMINAL TUMOR MASS
I /
\
/
Fig. 4. Patient contour with diagram of bladder as localized by cystogram and intravenous pyelogram. Cross-hatched area is the volume added by analysis of multi-level CT scans.
Fig. Sa. An intravenous urogram showing no evidence of an abnormality within the bladder.
by the
Of the 45 patients who were reviewed, 21 had carcinoma of the bladder. In each of these patients the treatment portals, which had been based on diagnostic studies, were re-evaluated in light of the results of the CT scan. In 15 of the 21 patients, no additional information was gained from the CT scan, but the CT scan did include all the information obtained from the diagnostic studies. Six of the patients had changes in their treatment portals as a direct result of the CT scans. That is, 29% of the patients with bladder malignancies had changes in treatment planning. Most of these changes were the result of previous
Fig. 5b. Extension of bladder diverticulum anteriorly. (Radio-opaque dots an anterior abdominal wall outline treatment portal.)
Computerized
tomography
scanning
in treatment
under-estimation of size and/or position of the bladder by standard localization procedures. Both size and position of the bladder were factors in 4 patients resulting in an increase in the size of the treatment portal. An extremely anterior location of the bladder in one case resulted in a change in the orientation of the treatment fields. Another required an increase in the size of his boost field based on extraluminal extent of his tumor mass. DISCUSSION Analysis of the CT scans of 45 patients indicates the following conclusions regarding treatment planning for carcinoma of the urinary bladder: 1. Pelvic anatomy shows certain constant relationships concerning bladder size. This suggests that for treatment purposes the 10 cm x 1Ocm area on a treatment plan for limited bladder therapy should be an adequate size in most patients. 2. There is a wide variation from patient to patient in the location of the anterior bladder wall. But in any individual, there is little change in the anterior margin even after voiding. Since there is such a wide variation in the positions of the anterior bladder margins, the centering of the treatment portal cannot depend routinely on bony landmarks (i.e. symphysis pubis, femoral heads). When CT scans are not used, diagnostic studies must be analyzed carefully. It cannot be assumed that the anterior margin, as outlined by
planning
for bladder
carcinoma
0 B. SCHLAGER
et al.
103
double contrast studies (air and radio-opaque material), will change after voiding. 3. Because of residual urine and decreased contractility, the margins of the bladder may not be defined adequately by the instillation of contrast material. The recommended 30-60 cm3 of contrast material may not simulate the patient’s anatomy.“” If CT scanning is not available, it might be useful to measure the amount of urine post natural voiding in the catheter specimen and replace at least that amount with contrast. 4. Any abnormality such as an irregular bladder wall, bladder diverticula, or an intraluminal defect should warrant additional studies. A CT scan in particular would help to determine the extent of the tumor or the bladder mucosa, which otherwise could be excluded from a treatment portal. 5. Munzenrider et al. have suggested that CT scanning for treatment planning in pelvic malignancies, while having little effect on the treatment volume in whole pelvis irradiation, may play a significant role in limited field irradiation.’ Twenty nine per cent of our patients had some alteration of their treatment portals (the majority of these changes were on the limited field) as a result of the information obtained from the CT scan. However, follow-up evaluation of these patients is necessary to determine if those treatment portal changes will have any effect on recurrent disease or overall patient survival.
REFERENCES 1. Ambrose, J.A.: Computerized transverse axial scanning (tomography)-II. Clinical application. Br. J. Radiol. 46: 1023-1047, 1973. 2. Chernak, B.S., Rodriquez-Antunez, A., Jeldin, G.L., Daluval, R.S., Lavick, P.S.: The use of computed tomography for radiation therapy treatment planning. Radiology 117: 613-614, 1975. 3. Fletcher, G.: Textbook of Radiation Therapy, 2nd Edn. Philadelphia, Lea & Febiger, 1973, pp. 726-728. 4. Geise, R.A., McCullough, E.C.: The use of CT scanners megavoltage photon beam therapy planning. iadiology 124: 143-149, 1977. 5. Hounsfield, G.N.: Computerized transverse axial scanning (tomography)-I. Description of system. Br. J. Radial. 46: 1016-1022, 1973. 6. Jelden, G.L., Chernak, ES., Rodriquez-Antunez, A., Hagga, J.R., Lavik, P.S., Dhaliwal, R.S.: Further progress in CT scanning and computerized radiation therapy treatment planning. Am. J. Roentgen01 127: 179-185, 1976.
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