I-131 Metastatic Survey PDF

Whole-Body 1-131 Metastatic Survey as an Aide in Determining Functional Thyroid Metastases Leo R. LaRocque Hartford Hospital. Hartford. Connecticut Whole-body metastatic sun ey scans are performed in whenever possible. for two reasons: it usually requires order to determine t...

Whole-Body 1-131 Metastatic Survey as an Aide in Determining Functional Thyroid Metastases Leo R. LaRocque Hartford Hospital. Hartford. Connecticut Whole-body metastatic sun ey scans are performed in whenever possible. for two reasons: it usually requires order to determine the extent of metastases, the quality of only 3-5 min to take camera images. and so minimal tumor uptake, and whether the patient will benefit from disruption in patient scheduling is achieved: and, at the therapeutic doses of radioiodine. Periodic whole-body scans same time. the scanner is readily available for the next also help to evaluate the success of radioiodine therapy or the patient. By performing a 48- or 72-hr study, we are necessity to repeat therapeutic treatments. Using a dual-probe allowing for some of the radioiodine to be excreted by rectilinear scanner and supplementing with scintillation camera images, we have found this procedure useful in detecting the urinary system. thereby decreasing body background. metastatic and focal thyroid cancer. Discussion Following surgery for some forms of thyroid carcino- The best available treatment for carcinoma of the thy- ma, patients may be evaluated with radioiodine so- roid is surgery (2) and there are two important reasons dium iodide for residual functioning tissue by various why surgery should precede radioiodine therapy. First, a methods. These include imaging techniques, 1-131-PBI large specimen of the tumor is provided for pathological conversion rates, and excretion studies ( /). It is assumed examination because some parts of the gland portion of that there will be little or no accumulation of radioiodine the tumor may concentrate T-131 and other parts may by any remaining thyroid tissue. These studies are also not. Secondly, uptake of the remaining cancerous tissue based on the premise that the tracer dose of 1-131 is is increased when part or all of the gland is removed. De- cleared by the thyroid. kidneys. gastric mucosa, and the pending upon the outcome of the pathological examina- salivary glands. The presence of metastases and evidence tion, a variety of paths may be taken (Fig. 2) that the lesion concentrates iodine sufficiently are two primary indications when selecting patients for radio- iodine therapy. Method and Materials Whole-body scans are usually performed 48 or 72 hr following the oral administration of 1-3 mCi of[ 11 1J] so- dium iodide. The images arc recorded by an Ohio- Nuclear model 84 dual-probe rectilinear scanner (Ohio Nuclear. Solon, OH) using 38-M medium energy collimators. Whole-body minified scans arc obtained by using the 5: I ratio and 5: I light aperatures with a 1/x-in. line spacing (Fig. 1). Neither backgrou11d erase nor contrast enhancement is used in order that we may be able to detect all areas of radioiodine concentration. The scanner is set at a speed of 700 (53~ em min) and the total elapsed time of the procedure is approximately 40 min. The lower distal extremities are excluded. At the conclusion of the scan the patient is requested to remain in the department until the images have been re- viewed by a nuclear medicine physician. Additional images may be requested of abnormal areas of raJio- iodine accumulation with either pinhole or medium energy collimators attached to a scintillation camera. When additional views are requested, we use the camera, For rerrinb contact: Leo R. LaR