Tumor scanning

The search continues for a general tumor-scanning agent. Although several radionuclides have been found to localize tumors of widely different types and regions of the body, current interest is in the use of 67 Ga-citrate, which is undergoing a wide clinical trial and may prove to be useful in the localization of lymphomas as well as some adenocarcinomas. Medical imaging techniques arc discussed in several articles of this encyclopedia. Consult alphabetical index. 

Hisada K and Ando A (1973) Radiolanthanides as promising tumor scanning agents. J Nucl Med 14 615-617. 

The major uses of lndlum-111 in medicine are listed in Table 2. Indium-111 labeled DTPA is the preferred agent for the study of cerebral spinal fluid kinetics (cisternography)( ). Indium-labeled bleomycin has been used for tumor scanning C2.), although citrate has achieved greater clinical use. It appears that indium bleomycin is in fact a weak chelate and the in vivo distribution is very similar to that of indium transferrin. 

Deoxyglucose labeled with fluorine-18 is commonly used in PET scans to locate tumors. Fluorine-18 has a half-life of 109 min. How long will it take for the level of fluorine-18 in the body to drop to 10% of its initial value ... 

Brain scans are used to study epiiepsy, brain tumors, strokes, Aizheimer s disease, and mentai iiiness. Each of these disorders generates a unique brain activity pattern that differs from the pattern seen in normai brains. Physicians interpret these patterns both for diagnosis and to indicate appropriate treatment. 

It has been forty-five minutes since CH s arrival, and he has been given lorazepam 4 mg twice and loaded with 1500 mg of phenytoin. He received another 400 mg dose of phenytoin 15 minutes ago, but is still unarousable. His jerking movements have slowed down, but his temperature is now 39.9°C (103.8°F), and his blood pressure has dropped to 124/62 mm Hg. His oxygen saturation is 91% on 4 L oxygen via nasal cannula. Bilateral crackles are heard upon auscultation of his lungs. A CT scan of his head is obtained which shows no evidence of hemorrhage, tumor, or mass effect. 

MRI and CT scan Both reveal a pituitary tumor approximately 5 mm in diameter. 

Further evaluation with CT and PET scans reveal a T2N0M0 tumor. 

Overall survival is affected by the success of the initial surgery to debulk the tumor to less than 1 cm of disease and response to first-line chemotherapy. The CA-125 level should be monitored with each cycle, and at least a 50% reduction in CA-125 after four cycles of taxane/platinum chemotherapy is related to an improved prognosis. Patients who achieve a complete response should have follow-up examinations every 3 months, including CA-125 determination, physical examination, pelvic examination, and appropriate diagnostic scans (e.g., CT scan, MRI, or PET scan) and should be evaluated for the detection of disease. Evaluate patients for resolution of any residual chemotherapy-related side effects, including neuropathies, nephrotoxicity, ototoxicity, myelosuppression, and nausea/vomiting. 

Repeat CT scans of the chest after the first cycle of chemotherapy, surgical stenting, or radiotherapy to assess tumor response. 

Tumor response is measured by clinical chemistry (e.g., liver enzyme elevation in patients with hepatic metastases) or imaging techniques (e.g., bone scans or chest x-rays). 

Frmctional imaging such as PET scanning and SPECT scanning is also likely to be explored for detecting early activity of these cytostatic agents just as PET scanning documented the early activity of Gleevec in patients with G1 stromal tumors. ... 

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