Symposium on Pediatric Oncology

Nuclear Medicine and Pediatric Neoplasia

David L. Gilday, M.D., B. Eng., F.R.C.P.(C)*

Nuclear medicine has developed some highly specialized techniques for investigating the child suspected of having a neoplastic process. This is due to the development of improved gamma camera systems with high resolution and the establishment of technetium-99m radiopharmaceuticals, especially technetium phosphate compounds for bone imaging. This has resulted in rapid growth and use of nuclear techniques for the investigation of pediatric neoplasia.

THE RADIONUCLIDE SKELETAL SURVEY Since the advent of technetium-99m phosphate bone imaging radiopharmaceuticals, the utilization of the radionuclide skeletal survey has become available to any nuclear medicine department. Thus any child should be able to have this evaluation for bone metastases. Using the gamma camera, it is fast and simple to image all parts of the body including both anterior views and posterior views of the torso. The approach in our hospital is to perform the radionuclide skeletal survey as the primary screening procedure for bone metastases. If a definite or suspicious lesion is identified then a complete radiological examination of that area is conducted. Metastases from primary bone sarcomas to the skeleton do occur. In addition these and the histiocytosis X group may have multicentric involvement of the skeleton. The search for metastases may yield lesions in an unusual location such as the calcaneus (Fig. lA) or in more common locations such as the ribs (Fig. IB). The multicentric nature of histiocytosis X has sometimes proven difficult to evaluate without the bone scan. This is demonstrated vividly in a child with multiple lesions in the skull where only the orbital lesion was definitely seen radiologically (Fig. 2). Text continued on page 46 'Head, Division of Nuclear Medicine, The Hospital for Sick Children, Toronto, Ontario; Assistant Professor of Radiology, University of Toronto, Toronto, Ontario, Canada

Pediatric Clinics of North America-Vol. 23, No.1, February 1976












Figure 1. A, Osteogenic sarcoma solitary metastasis. The total body scan done with a whole body scanner demonstrates a very hot right calcaneus, was normal on the routine views of the calcaneus; however, the tangential views showed a lyticlesion in the medial border. The patient had a primary osteogenic sarcoma of the pelvis causing obstruction of the bladder outflow. B, Osteogenic sarcoma multiple metastases. The whole body scan shows that the right leg has been amputated just below the intertrochanteric region. There are multiple areas of increased activity throughout the ribs seen posteriorly.



Figure 1 (Continued). C, The views using a gamma camera demonstrate the rib lesions to a much better effect as they are superficial and thus better resolved by the gamma camera. D, The chest radiograph demonstrates multiple lesions throughout the lungs but no rib lesions.







Figure 2. Histiocytosis X. A, The right orbital lesion is seen best in the anterior view using the gamma camera. Band C, The lateral views demonstrate not only the involvement in the orbit but also in the petrous pyramid. D, This is confirmed in the posterior view where the lesion is seen to be lateral.



Figure 2 (Continued). The whole body scan perfonned with the rectilinear scanner depicts a lesion in the right ribs posteriorly (E), was not seen radiologically (F).





The pediatric neoplasm which most frequently metastasizes to bone is the neuroblastoma. 3 This frequently results in multiple metastases. Usually these are seen as multiple areas of increased activity in the metaphysis or adjacent regions. The bone marrow scan in such circumstances shows that the neuroblastoma has replaced the marrow as its starting point to involve the bone (Fig. 3). Not infrequently this tumor can be so invasive that it inhibits the blood supply so that the bone cannot respond to the tumor. Hodgkin's disease and leukemia are somewhat similar neoplastic processes in that they cause bony lesions secondary to marrow involvement. In such circumstances the bony involvement may be multicentric or solitary. The scan has proved to be at least as sensitive as the radiograph. In our experience the usual location is in the long bones and is readily identified (Fig. 4).

BRAIN SCANNING To adequately evaluate the brain one must do not only a radionuclide angiogram and delayed brain scans but also blood pool images immediately after the injection. This permits complete evaluation of any lesion which is seen. It is not only important to note the presence of a lesion but also to determine whether the lesion is vascular or cystic. 2 To adequately visualize the posterior fossa, meticulous positioning must be adhered to. The posterior fossa tumors are easily detected unless they are deep in the brain stem. 1 The characteristic appearance is seen in the delayed brain scans at three hours. The usual appearance is that of moderate to very active uptake of the radiopharmaceutical within the tumor (Fig. 5). Cystic gliomas occur in the cerebral and cerebellar hemispheres and these are often not only detected but characterized as to their cystic nature by the complete brain scan (Fig. 6). The one tumor which is very poorly detected compared with the rest is the primary craniopharyngioma. This tumor is frequently very difficult to detect unless there is a considerable amount of solid tumor above the membrane of the sella (6 of 10). The recurrent craniopharyngioma is almost always detected (5 of 5).1

LIVER AND SPLEEN SCANNING The most valuable addition to the routine liver and spleen scan is the radionuclide angiogram which can be performed as part of the study. This frequently will help to differentiate those lesions which are basically cystic from those which are solid with a good blood flow to them. In addition to the routine four orthagonal views at least the two anterior and two posterior oblique views must be added. Metastatic disease to the liver is relatively uncommon in children compared with adults, however, Wilms' tumor and neuroblastoma do metastasize to the liver (Fig. 7). These usually produce multiple focal Text continued on page 52



Figure 3. Neuroblastoma metastases. Multiple lesions are seen in the skull (A), left shoulder (B), right distal femoral metaphysis (C). This is utilizing the bone scan. The radionuclide assessment of the marrow using Technetium sulphur colloid demonstrates that the right knee as seen on the posterior projection demonstrates no activity in the distal femoral metaphyseal region. This is due to the metastasis seen also on the bone scan (D).



Figure 4. Hodgkin's disease. The lesions in the right upper third of the femur and mid third of the tibia on the right side are both seen on the bone scan and were seen on the radiograph.



Figure 5. Vennis astrocytoma. The astrocytoma is seen as a moderately active lesion in the midline in the vennis. It is seen to be separated from the basal activity, thus it cannot be a fourth ventricular or brain stem lesion.




Figure 6. Cystic astrocytoma. A, The blood pool images demonstrate an area of increased activity which is seen to be in the right temporal region. B, The delayed brain scan shows not only the lesion seen in the blood pool image, but also a large lesion above it and contiguous with it. The lesion seen in the blood pool image which was the more active area on the delayed scan is the solid component, the other is a cystic component. The radioactivity leaked from the solid tumor into the cystic fluid causing the cystic to become apparent.











Figure 7. Neuroblastoma metastases. Multiple areas of decreased activity which are well defined especially in the left anterior oblique view (D) are seen in all views of the liver. This is the typical appearance.







c Figure 8. Malignant hepatoblastoma. A discrete solitary lesion is seen posteriorly in the right lobe of the liver. This proved to be a viralizing hepatoblastoma.

lesions within the liver. On the other hand, primary liver tumors usually cause only a well defined local area of decreased activity (Fig. 8).

CONCLUSION By far the most important recent event in pediatric nuclear medicine is the recent availability of high quality bone scanning radiopharmaceuticals which results in extremely sensitive detection of skeletal abnormalities. The brain scan has proven to be a valuable investigative tool for intracranial and cranial tumors. The use of computed tomography should replace the brain scan as the initial screening procedure for intracranial neoplasms; the total radionuclide study is proving to be valuable in acquiring additional information when computed tomography is not definitive. The liver and spleen scan, although much maligned in the past, is now becoming appreciated.




REFERENCES J. M.: Accuracy of brain scanning in pediatric craniocerebral neoplasms. Radiology, 117:93-97, 1975. 2. Gilday, D. L., and Harwood-Nash, D. C. F.: Co-ordinated investigation of cystic astrocytomas by nuclear medicine and neurological techniques. Child's Brain, 1 :34-45, 1975. 3. Rosenfield, N., and Treves, S.: Osseous and extra-osseous uptake of fluorine-18 and technetium-99m polyphosphate in children with neuroblastoma. Radiology, 111 :127133,1974. 1. Gilday, D. L., and Ash,

Division of Nuclear Medicine The Hospital for Sick Children 555 University Avenue Toronto, Ontario M5G lX8 Canada

Nuclear medicine and pediatric neoplasia.

Symposium on Pediatric Oncology Nuclear Medicine and Pediatric Neoplasia David L. Gilday, M.D., B. Eng., F.R.C.P.(C)* Nuclear medicine has develope...
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