Clinical value of iodine-123-alpha-methyl-L-tyrosine single-photon emission tomography in the differential diagnosis of recurrent brain tumor in patients pretreated for glioma at follow-up.

PURPOSE: To assess the clinical potential of iodine-123-alpha-methyl-L-tyrosine (IMT) and single-photon emission tomography (SPET) in the differential diagnosis of recurrences in patients pretreated for gliomas at follow-up. PATIENTS AND METHODS: Seventy-eight patients were examined after primary therapy over 36 months. Histopathologic diagnoses of all patients was known at first treatment; magnetic resonance and/or computed tomography examination was performed in addition to IMT-SPET. Cerebral SPET images were acquired 20 minutes after intravenous application of 190 +/- 10 MBq of IMT. SPET images were classified as positive or negative for recurrent tumor visually and by calculating the ratios between tracer accumulation in the lesion and the unaffected contralateral regions of reference using region of interest. Final diagnoses were based on prospective clinicopathologic findings obtained independently of IMT-SPET. RESULTS: IMT-SPET detected all high-grade recurrent gliomas (grade 4; sensitivity, 100%). A difference could be demonstrated in grade 2 and 3 recurrences (sensitivity, 84% and 92%, respectively). Moreover, benign posttherapeutic lesions (postoperative scars, radiation necrosis) were correctly diagnosed as negative for tumor recurrence. In general, IMT uptake in grade 2 (1.45 +/- 0.24) was significantly lower than that in grades 3 (1.70 +/- 0.41) and 4 (1.88 +/- 0.32). However, it was difficult to evaluate tumor grade only from the IMT accumulation in individual cases. CONCLUSION: IMT-SPET seems highly useful for detecting and delineating recurrent gliomas and differentiating between benign posttherapeutic lesions and malignant tumor tissue. It may be a valuable clinical tool to diagnose recurrences in patients pretreated for gliomas at follow-up. However, it showed limitations in determining histologic tumor grade.

Localization of extramedullary hematopoiesis with Tc-99m-labeled monoclonal antibodies (BW 250/183).

Extramedullary hematopoiesis is of special interest to physicians because of its relation to hematologic disease. Because it normally remains asymptomatic, sites are typically found by chance. Effective diagnosis involves a specific, reliable, whole-body and low-cost method of screening. Although radiologic methods such as computed tomography and magnetic resonance imaging can only suggest the presence of extramedullary hematopoiesis, apart from invasive and therefore risky biopsy procedures, only scintigraphy can detect and confirm the nature of hematopoietic tissue. Although radioactive tracers commonly in use partly lack the demands for specific diagnosis, Tc-99m-labeled antibodies (NCA-95) seem to combine the advantages of different scintigraphic approaches. Two patients with dyserythropoetic anemia and paravertebrally situated pelvic and thoracic tumor masses were studied for extramedullary hematopoiesis. Planar and SPECT images were obtained 6 and 24 hours after injection of 800 to 850 MBq (22 to 23 mCi) Tc-99m-labeled monoclonal antibodies (BW 250/183). In both patients, tracer accumulated in the masses, thereby revealing hematopoietic tissue. Biopsy confirmed these findings. By using Tc-99m-labeled monoclonal antibodies to detect extramedullary hematopoiesis, the demands of diagnosis were met. As an alternative to invasive diagnostic procedures, this tracer combines the advantages of other radioactive substances previously used, such as radioiron, In-111 chloride, and Tc-99m colloids. This low-cost agent is readily available and when applied, reliable, and delivers whole-body images free of additional uptake in the liver or spleen.

Local platelet trapping as the cause of thrombocytopenia after hepatic cryotherapy.

Cryosurgery has been shown to be an effective approach to destruction of unresectable hepatic tumors. However, hepatic cryoablation may also be associated with local and systemic side effects, including thrombocytopenia and clotting dysfunction. Although thrombocytopenia is known to relate to the magnitude of hepatocellular injury, its etiology is still unknown. With the use of whole-body scintigraphy after injection of indium-111-labeled platelets we here demonstrated in six patients undergoing cryoablation of hepatic tumors that manifestation of systemic thrombocytopenia after cryosurgery is associated with excessive platelet trapping and destruction within the cryolesion. We therefore conclude that local platelet trapping represents a major cause of cryothermia-induced systemic thrombocytopenia.