PMC5724631_01
Patient is a 48-year-old male with node-positive papillary thyroid carcinoma with adverse pathologic features and evidence for distant metastases s/p thyroidectomy. (a) Initial total body I-123 scan of the patient on "Day 1" obtained 1 h after I-123 but prior to voiding. A low-activity "standard" source (50-100 microCi) of I-123 is placed near the patient's ankle to correct for changes in scanner speed and sensitivity between the two scans. Separate regions of interest (ROIs) are drawn around the whole body and "standard" on both anterior and posterior views (not shown). (b) Total body I-123 scan of patient on "Day 2" at 24 h. ROIs are drawn around the total body and "standard" (not shown) and integral ROI counts are used to compute total body burden and "standard" content. (c) CT shows innumerable pulmonary nodules. Although not radioiodine-avid, they were FDG-avid on positron emission tomography and wedge resection confirmed metastatic disease.
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This protocol was employed in a 48-year-old man with T4 N1 M1 papillary thyroid cancer and innumerable pulmonary metastases (see Figure 1).
Data entry form of the web-based calculator that computes the effective clearance half-time for I-131 using data from two total body iodine scans. Provision is made using a standard source to correct for variations in scanner sensitivity. The I-131 effective clearance half-time is used to estimate the maximum administered activities to avoid marrow and pulmonary toxicity.
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Our web-based software (see Figure 2) calculated his biological clearance half-life to be 18.8 h and I-131 clearance effective half-life to be 17.1 h ("Normal" Duke reference value is 18 h).