Detection of bone metastases in patients with endocrine gastroenteropancreatic tumors: bone scintigraphy compared with somatostatin receptor scintigraphy.

UNLABELLED: Scintigraphy with somatostatin analogs is a sensitive method for the staging and therapeutic management of patients with endocrine gastroenteropancreatic (GEP) tumors. The aim of this study was to compare prospectively somatostatin receptor scintigraphy (SRS) using 111n-pentetreotide with bone scintigraphy using 99mTc-hydroxymethylene diphosphonate for the detection of bone metastases. METHODS: One-hundred-forty-five patients with proven endocrine GEP tumors were investigated. Patients were classified according to the presence of bone metastases as indicated by CT, MRI or histologic data. Group I included 19 patients with confirmed bone metastases, and group II included 126 patients without bone metastases. RESULTS: In group I, SRS was positive in all 19 patients with bone metastases, and bone scintigraphy was positive in 17 patients. Bone metastases were found to occur predominantly in patients with liver metastases. In group 11, 5 patients had recent bone surgery for fracture or arthritis. SRS showed bone uptake in 4 of these patients, and bone scanning showed abnormal uptake in 5. In 7 of the remaining 121 group II patients, SRS was negative and bone scanning showed abnormal bone uptake suggesting bone metastases. The detection of bone metastases was of major prognostic value, because 42% of group 1 patients died during a 2-y follow-up. CONCLUSION: In patients with GEP tumors, the accuracy of SRS appears to be similar to that of bone scintigraphy for the detection of bone metastases.

Quantitative autoradiography using a radioimager based on a multiwire proportional chamber.

Determination of the biodistribution of radiopharmaceuticals is an important issue for the evaluation of their performance in diagnosis and therapy. In this study, we evaluated a digital radioimager (RI) based on a multiwire proportional chamber for quantitative autoradiography (AR). The RI allows direct detection of electronic emissions of gamma emitters. Its qualitative and quantitative performances were tested on 99mTc and (111)In labelled sections and compared with conventional film AR. Linearity of count rate versus activity was verified over a 104 range of activity. As compared with film AR, a substantial improvement of the detection limit was obtained even for acquisition periods up to 20 times less than film exposure times. We provided the basis for quantitative analysis with tissue equivalent paste standards: the 99mTc and (111)In RI counting efficiencies were respectively 1.19% and 2.35%. We illustrated the respective values of RI and film AR in two rat studies: 99mTc-DMSA in kidney and dual-isotope 99mTc-MIBI and (111)In-antimyosin in heart. Calculated activity concentrations on sections of rat organs confirmed good correlation to gamma counting (deviation less than 12%). We suggest RI as a convenient technique for fast localization of single or dual-isotope tracers and determination of activity distribution.

Iodine-131 ablation therapy for a patient receiving peritoneal dialysis.

The authors describe a patient with follicular thyroid carcinoma who was receiving continuous ambulatory peritoneal dialysis to manage end-stage renal disease. To deliver radioiodine therapy to ablate thyroid remnants safely and under optimal conditions, the behavior of 37 MBq (1 mCi) I-131 was followed daily for 3 days. Blood activity and total body count decreased with a half-life of 100 hours (4.17 days). The daily iodide removal rate, estimated as a percentage of the total administrated activity, was low: 5.3% to 8.6% in peritoneal dialysate and 1.3% to 2.2% in urine. The thyroid uptake, measured using a probe, was 2.4% to 2.1% from day 1 to day 3 and 1.9% later at day 8. The volume of thyroid remnants was determined by ultrasonography to be 0.6 g. The patient received a reduced ablative I-131 dose of 814 MBq (22 mCi). Radiation emitted from the patient after I-131 therapy, monitored using a radiation monitor probe located at a distance of 1 meter, decreased with an effective half-life of 70 hours (2.9 days). The integration of the curve from t = 0 showed a level always less than 25 microSv/hour as early as 24 hours after treatment. Because the iodine removal rate is continuous but low in a case of peritoneal dialysis, smaller therapeutic doses must be administered to deliver maximal radiation to residual thyroid tissue while minimizing excessive radiation exposure to patients, their families, and medical staff.