TECHNICAL NOTES
Vol. 130
bronchial foreign object: any lesion partially obstructing a bronchus may result in this finding. Asthma with mucus plugging is the most common condition simulating foreign-body aspiration, both clinically and radiographically; however, it can be distinguished by the somewhat slower onset of wheezing, repeated episodes of respiratory distress, and response to bronchodilator therapy. Only one of the 10 patients studied by Burrington and Cotton who presented with clinical and radiographic signs of foreign-body aspiration was ultimately shown to have asthma. Other conditions causing air trapping, such as congenital lobar emphysema, bullous emphysema, congenital lung cyst, cystic adenomatoid malformation, Swyer-James syndrome, and aberrant right pulmonary artery, all cause abnormalities on the inspiratory chest radiograph-usually hyperexpansion of the lung or lesion plus other specific findings (6). In contrast, the inspiratory radiograph is frequently normal in foreign-body aspiration.
539
Technical Notes
REFERENCES 1. Benjamin B, Vandeleur T: Inhaled foreign bodies in children. Met J Aust 1:355-358, 9 Mar 1974 2. Burrington JO, Cotton EK: Removalof foreign bodies from the tracheobronchial tree. J Pediatr Surg 7:119-122, Apr 1972 3. Campbell JB: Personal communication 4. Friedberg SA, BluestoneCD: Foreignbodyaccidents involving the air and food passagesin children. Otol Clin North Am 3:395-403, Jun 1970 5. Holinger PH: Foreign bodies in the air andfood passages. Trans Am Acad Ophthalmol OtoI66:193-210, Mar-Apr 1962 6. Wesenberg RL: The NewbornChest. Hagerstown, Md., Harper & Row, 1973, pp 187-219 1 From the Departments of Radiology (R.L.W., J.D.B.)and Pediatrics (R.L.W.), Universityof ColoradoMedicalCenter, Denver, Colo. 80262. Accepted for publication in February 1978. 2 Presentaddress: Departmentof Radiology, Children's Orthopedic Hospital and Medical Center, Seattle, Wash. 98105. sjh
Use of CT Scans in Manual Radiotherapy Treatment Planning 1 Ben M. Birkhead, M.D., Thomas E. Banks, M.S., and Dwight B. Short, M.D. The use of CT scans in radiotherapy treatment planning need not depend on the availability of a computer. The authors describe a quick method of converting CT images to scale-corrected cross-sectional contours suitable for manual treatment planning in less than an hour. INDEX TERMS: Computed tomography, treatment planning. Treatment plan-
ning Radiology 130:539-540, February 1979
The rapid dissemination of computed tomographic scanners has made them relatively accessible to most radiotherapy facilities. Although the cross-sectional images obtained with these machines can be of invaluable assistance in treatment planning, their use need not depend on the availability of a computer. If the radiotherapist can be presented with scale-corrected cross-sectional CT images, manual treatment planning can proceed to whatever degree of complexity he desires. We offer a step-by-step procedure for converting CT data into a form satisfactory for this purpose. This method is applicable to any region except the head. TECHNIQUE 1. Prior to scanning, opaque catheters are taped to the patient's back in a staggered fashion as shown in Figure 1. A standard 183-cm (6-ft.) anteroposterior (AP) radiograph is taken to serve as a reference. 2. With the opaque catheters in place, the appropriate region is scanned in the normal fashion. When the scan is completed, the opaque catheters can be removed and the patient returned to the radiotherapy department together with the CT images and the reference radiograph. 3. The radiotherapist outlines the treatment area on the reference radiograph and determines its center (Fig. 1). The AP and lateral dimensions of the patient are then measured at the level of the central axis of the treatment area. If necessary, the patient can be fluoroscoped, using bony landmarks to locate the body level corresponding to the central axis. Once these measurements are obtained, the patient may leave.
Fig. 1. Reference radiograph showing the treatment area with the central axis marked. 4. Using the reference radiograph as a guide, one then estimates how many opaque catheters would be traversed by a cut through the central axis. On the CT images, the opaque catheters are clearly seen end-on as small white dots on the posterior surface of the patient (Fig. 2). The cut showing the appropriate number of dots (9 in this case) represents the desired central axis level. 5. The chosen CT scan is then photographed on direct positive film 2 with a 35mm camera. We suggest that the CT scan occupy only the central half of the transparency to avoid the distortion arising from the lack of recti linearity in most projector lens systems. The film can be developed in a rapid processor and then mounted. 6. Using a standard 35mm projector, the transparency is
540
TECHNICAL NOTES
February 1979
DISCUSSION
Fig. 2. Cross-sectional CT image of the central axis. The arrow indicates the opaque catheters.
The entire transfer of information from the minified CT scan to the 1:1 scale tracing on graph paper requires less than an hour. Given the traced cross-section, treatment planning may proceed to whatever degree of complexity the radiotherapist desires. Some possible considerations are: (a) Tissue inhomogeneities may be accounted for by including bone and air-filled cavities on the tracing. (b) Off-axis dosimetry is possible by choosing additional levels (e.g., the top and bottom of the portal) for transfer to graph paper. It should be noted, however, that central-axis isodose data may not be appropriate for these off-axis contours. (c) Interval CT studies may be done so that the treatment plan may be changed to account for shrinking tumor volumes. (d) If treatment is repeated, old portals can be marked with opaque catheters, thereby making it possible to locate them on the tracing. These steps enable the radiotherapist to use the valuable information available only on CT scans to his patient's best advantage. This method is quick, cheap, and applicable in virtually any radiotherapy department.
projected onto graph paper taped on a wall. By varying the distance from projector to graph paper, the size of the image can be changed until it exactly fits the AP and lateral dimensions obtained in Step 3. The image is thereby scale-corrected and a tracing of the projected image can be made on the graph paper. Body outline, tumor extent, and normal surroundingorgans are illustrated in whatever detail desired by the treatment planner. The treatment volume is then drawn onto this cross-sectional image and treatment planning can proceed.
1 From the Radiation Center, University of Louisville School of Medicine, 500 S. Floyd St. (B.M.B., T.E.B.), and the Department of Radiology, Jewish Hospital (D.B.S.),Louisville, Ky. 40202 (Reprint requests to University of Louisville). Accepted for publication in February 1978. 2 SO-185 rapid-processing copy film, Eastman Kodak, Rochester, N.Y. sjh
Radiographic Localization of the Acetabular Component of a Hip Prosthesis 1 Bernard Ghelman, M.D. The degree of anterior or posterior tilt of the acetabular cup can be established using fluoroscopy in patients with total hip prostheses. Since the technique is fast, painless, and requires minimal cooperation, it can be performed immediately following surgery. This method is suitable for postoperative evaluation of patients with total hip replacement and is also reproducible for serial analysis. INDEX TERM: Hip, prosthesis, 4 [4].454
Radiology 130:540-542, February 1979
The placement of total hip prostheses is essential in determining the postsurgical prognosis. Radiographic evaluation essentially involves assessment of (a) the position of the femoral and acetabular components; (b) the relationship of the prosthesis to the pelvis; and (c) the relative position of the prosthesis and standard imaginary planes. The relationship between the acetabular cup and the pelvic bones is radiographically uncertain at present because of anatomical variation of bony landmarks and the difficulty in reproducing patient position for periodic radiographic measurements. I have developed a fluoroscopic method which can determine the exact position of the acetabular component (cup) relative to specific planes of orientation. With this method, anatomical variation between patients is unimportant and little if any cooperation of the patient is necessary.
METHODS AND MATERIAL An adult pelvis was fitted with a prosthetic acetabular cup and examined under fluoroscopy. The circular wire in the base of the cup was examined with cephalad, neutral, and caudadangulation of the x-ray tube. When the anterior and posterior halves of the wire overlapped, the angle of the tube was recorded along with its cephalad or caudad direction. Overlap indicates that the beam is tangential to the plane passing through the opening of the cup. The angle of the tube indicates the degree of anteroposterior tilt of the cup in relation to a 'cross-section transverse or transaxial plane. When the halves of the wire overlap, the position of the tube determines which way the opening of the cup is facing, i.e., it is tilted forward (anterior) if overlap is observed with the tube caudad or backward (posterior) if the tube is pointing cephalad. The position of the acetabular component in relation to the horizontal plane affects measurements made by this method. The farther vertical the cup is inserted in respect to the ischioischial line (a line drawn between the farthest inferior tips of the ischial bones), the greater the apparent anteroposterior tilt in relation to the transverse plane. As the angle of the cup in relation to the ischio-ischial line is increased to 90°. a point is reached where overlap is impossible unless the base is parallel to the sagittal plane. The relationship between the fluoroscopic measurement of the anteroposterior tilt of the cup and the angulation of the cup to the ischio-ischial line was observed.
Vol. 130
bronchial foreign object: any lesion partially obstructing a bronchus may result in this finding. Asthma with mucus plugging is the most common condition simulating foreign-body aspiration, both clinically and radiographically; however, it can be distinguished by the somewhat slower onset of wheezing, repeated episodes of respiratory distress, and response to bronchodilator therapy. Only one of the 10 patients studied by Burrington and Cotton who presented with clinical and radiographic signs of foreign-body aspiration was ultimately shown to have asthma. Other conditions causing air trapping, such as congenital lobar emphysema, bullous emphysema, congenital lung cyst, cystic adenomatoid malformation, Swyer-James syndrome, and aberrant right pulmonary artery, all cause abnormalities on the inspiratory chest radiograph-usually hyperexpansion of the lung or lesion plus other specific findings (6). In contrast, the inspiratory radiograph is frequently normal in foreign-body aspiration.
539
Technical Notes
REFERENCES 1. Benjamin B, Vandeleur T: Inhaled foreign bodies in children. Met J Aust 1:355-358, 9 Mar 1974 2. Burrington JO, Cotton EK: Removalof foreign bodies from the tracheobronchial tree. J Pediatr Surg 7:119-122, Apr 1972 3. Campbell JB: Personal communication 4. Friedberg SA, BluestoneCD: Foreignbodyaccidents involving the air and food passagesin children. Otol Clin North Am 3:395-403, Jun 1970 5. Holinger PH: Foreign bodies in the air andfood passages. Trans Am Acad Ophthalmol OtoI66:193-210, Mar-Apr 1962 6. Wesenberg RL: The NewbornChest. Hagerstown, Md., Harper & Row, 1973, pp 187-219 1 From the Departments of Radiology (R.L.W., J.D.B.)and Pediatrics (R.L.W.), Universityof ColoradoMedicalCenter, Denver, Colo. 80262. Accepted for publication in February 1978. 2 Presentaddress: Departmentof Radiology, Children's Orthopedic Hospital and Medical Center, Seattle, Wash. 98105. sjh
Use of CT Scans in Manual Radiotherapy Treatment Planning 1 Ben M. Birkhead, M.D., Thomas E. Banks, M.S., and Dwight B. Short, M.D. The use of CT scans in radiotherapy treatment planning need not depend on the availability of a computer. The authors describe a quick method of converting CT images to scale-corrected cross-sectional contours suitable for manual treatment planning in less than an hour. INDEX TERMS: Computed tomography, treatment planning. Treatment plan-
ning Radiology 130:539-540, February 1979
The rapid dissemination of computed tomographic scanners has made them relatively accessible to most radiotherapy facilities. Although the cross-sectional images obtained with these machines can be of invaluable assistance in treatment planning, their use need not depend on the availability of a computer. If the radiotherapist can be presented with scale-corrected cross-sectional CT images, manual treatment planning can proceed to whatever degree of complexity he desires. We offer a step-by-step procedure for converting CT data into a form satisfactory for this purpose. This method is applicable to any region except the head. TECHNIQUE 1. Prior to scanning, opaque catheters are taped to the patient's back in a staggered fashion as shown in Figure 1. A standard 183-cm (6-ft.) anteroposterior (AP) radiograph is taken to serve as a reference. 2. With the opaque catheters in place, the appropriate region is scanned in the normal fashion. When the scan is completed, the opaque catheters can be removed and the patient returned to the radiotherapy department together with the CT images and the reference radiograph. 3. The radiotherapist outlines the treatment area on the reference radiograph and determines its center (Fig. 1). The AP and lateral dimensions of the patient are then measured at the level of the central axis of the treatment area. If necessary, the patient can be fluoroscoped, using bony landmarks to locate the body level corresponding to the central axis. Once these measurements are obtained, the patient may leave.
Fig. 1. Reference radiograph showing the treatment area with the central axis marked. 4. Using the reference radiograph as a guide, one then estimates how many opaque catheters would be traversed by a cut through the central axis. On the CT images, the opaque catheters are clearly seen end-on as small white dots on the posterior surface of the patient (Fig. 2). The cut showing the appropriate number of dots (9 in this case) represents the desired central axis level. 5. The chosen CT scan is then photographed on direct positive film 2 with a 35mm camera. We suggest that the CT scan occupy only the central half of the transparency to avoid the distortion arising from the lack of recti linearity in most projector lens systems. The film can be developed in a rapid processor and then mounted. 6. Using a standard 35mm projector, the transparency is
540
TECHNICAL NOTES
February 1979
DISCUSSION
Fig. 2. Cross-sectional CT image of the central axis. The arrow indicates the opaque catheters.
The entire transfer of information from the minified CT scan to the 1:1 scale tracing on graph paper requires less than an hour. Given the traced cross-section, treatment planning may proceed to whatever degree of complexity the radiotherapist desires. Some possible considerations are: (a) Tissue inhomogeneities may be accounted for by including bone and air-filled cavities on the tracing. (b) Off-axis dosimetry is possible by choosing additional levels (e.g., the top and bottom of the portal) for transfer to graph paper. It should be noted, however, that central-axis isodose data may not be appropriate for these off-axis contours. (c) Interval CT studies may be done so that the treatment plan may be changed to account for shrinking tumor volumes. (d) If treatment is repeated, old portals can be marked with opaque catheters, thereby making it possible to locate them on the tracing. These steps enable the radiotherapist to use the valuable information available only on CT scans to his patient's best advantage. This method is quick, cheap, and applicable in virtually any radiotherapy department.
projected onto graph paper taped on a wall. By varying the distance from projector to graph paper, the size of the image can be changed until it exactly fits the AP and lateral dimensions obtained in Step 3. The image is thereby scale-corrected and a tracing of the projected image can be made on the graph paper. Body outline, tumor extent, and normal surroundingorgans are illustrated in whatever detail desired by the treatment planner. The treatment volume is then drawn onto this cross-sectional image and treatment planning can proceed.
1 From the Radiation Center, University of Louisville School of Medicine, 500 S. Floyd St. (B.M.B., T.E.B.), and the Department of Radiology, Jewish Hospital (D.B.S.),Louisville, Ky. 40202 (Reprint requests to University of Louisville). Accepted for publication in February 1978. 2 SO-185 rapid-processing copy film, Eastman Kodak, Rochester, N.Y. sjh
Radiographic Localization of the Acetabular Component of a Hip Prosthesis 1 Bernard Ghelman, M.D. The degree of anterior or posterior tilt of the acetabular cup can be established using fluoroscopy in patients with total hip prostheses. Since the technique is fast, painless, and requires minimal cooperation, it can be performed immediately following surgery. This method is suitable for postoperative evaluation of patients with total hip replacement and is also reproducible for serial analysis. INDEX TERM: Hip, prosthesis, 4 [4].454
Radiology 130:540-542, February 1979
The placement of total hip prostheses is essential in determining the postsurgical prognosis. Radiographic evaluation essentially involves assessment of (a) the position of the femoral and acetabular components; (b) the relationship of the prosthesis to the pelvis; and (c) the relative position of the prosthesis and standard imaginary planes. The relationship between the acetabular cup and the pelvic bones is radiographically uncertain at present because of anatomical variation of bony landmarks and the difficulty in reproducing patient position for periodic radiographic measurements. I have developed a fluoroscopic method which can determine the exact position of the acetabular component (cup) relative to specific planes of orientation. With this method, anatomical variation between patients is unimportant and little if any cooperation of the patient is necessary.
METHODS AND MATERIAL An adult pelvis was fitted with a prosthetic acetabular cup and examined under fluoroscopy. The circular wire in the base of the cup was examined with cephalad, neutral, and caudadangulation of the x-ray tube. When the anterior and posterior halves of the wire overlapped, the angle of the tube was recorded along with its cephalad or caudad direction. Overlap indicates that the beam is tangential to the plane passing through the opening of the cup. The angle of the tube indicates the degree of anteroposterior tilt of the cup in relation to a 'cross-section transverse or transaxial plane. When the halves of the wire overlap, the position of the tube determines which way the opening of the cup is facing, i.e., it is tilted forward (anterior) if overlap is observed with the tube caudad or backward (posterior) if the tube is pointing cephalad. The position of the acetabular component in relation to the horizontal plane affects measurements made by this method. The farther vertical the cup is inserted in respect to the ischioischial line (a line drawn between the farthest inferior tips of the ischial bones), the greater the apparent anteroposterior tilt in relation to the transverse plane. As the angle of the cup in relation to the ischio-ischial line is increased to 90°. a point is reached where overlap is impossible unless the base is parallel to the sagittal plane. The relationship between the fluoroscopic measurement of the anteroposterior tilt of the cup and the angulation of the cup to the ischio-ischial line was observed.
