Parathyroid adenoma radiation dose simulator.

INTRODUCTION: As the number of radioisotope localization cases increased at our facility, the pathologists expressed concern regarding radiation exposure from parathyroid specimens. The radiation safety officer was consulted to analyze personnel radiation protection issues. METHODS: Analysis of simulated specimens was performed for a range of activities and masses corresponding to the values that have been observed. The radiation dose rates from these samples were measured using a Ludlum Model 14C survey meter with a Model 44-38 energy compensated GM probe and a Ludlum Model 3 Geiger counter with a Model 44-9 "pancake" style GM probe (Ludlum Measurements, Inc., Sweetwater, Texas). Additionally, 3 consecutive 10-second counts were performed using a USSC Navigator Gamma Guidance System (United States Surgical Corporation, Norwalk, CT). The per-second average readings were recorded. RESULTS: Our sample count-rates ranged from 139 to 2,830 counts/second. The majority of these values fell within the 100 to 1,000 count/second range typically observed during surgery. Based on our sample set, our dose rates at contact with these samples ranged from 0.17 to 4.0 mR/hour depending on the instrument, sample activity, and sample volume. The variation between count rate and dose rate for each observed volume varied linearly with activity. CONCLUSION: Based on these observed radiation doses, we concluded that there is no need to hold parathyroid specimens for 24 to 48 hours after surgical removal for handling because the typical radiation doses are quite low and would not result in significant radiation exposure to pathology personnel.

Positron emission tomography and Paget disease: hot is not necessarily malignant.

The authors imaged a lung cancer patient with an enlarging solitary pulmonary nodule and incidentally found intense activity in the right proximal humerus consistent with known Paget disease confirmed via plain film and computed tomography (CT) without change in the CT appearance or symptoms during the next 7 months. The alkaline phosphatase and alanine amino transferase (ALT) levels were in the normal ranges. Their findings of high uptake with normal alkaline phosphatase and ALT are contradictory to previous reports. The authors present a case of Paget disease that appeared "hot" on positron emission tomography initially thought to be a malignant transformation that typically demonstrated high uptake.

The day of contamination.

OBJECTIVE: We present 3 cases of suspected radioisotope urinary contamination that occurred on a single day. Because net clearance is via the kidneys, the injected dose is excreted in patients' urine. It is important to recognize the patterns of urinary contamination to avoid reporting false-positive abnormalities. MATERIALS AND METHODS: (99m)Tc-Medronate was administered intravenously and whole-body bone scans and spot views were obtained 2-3 h later. RESULTS: Two cases of urinary contamination were confirmed, and the third case was false-positive with a urinary collection leg bag seen in an orthogonal view. CONCLUSION: We believe that urinary contamination is probably the most common type of contamination. There are distinct urinary contamination patterns among male and female patients. It is unusual to find so many cases of contamination on a single day in our institution. Few statistics are widely available on the number or percentages of contamination for specific radiopharmaceuticals.

Thyroid carcinoma: iodine-131-negative whole-body scan reverses to positive after a combination of thyrogen stimulation and withdrawal.

PURPOSE: Reports state that scan results for as many as 25% of patients with differentiated thyroid carcinoma will convert to iodine-131 (I-131) negative over time with positive thyroglobulin levels. Tl-201, positron emission tomography (PET), and sestamibi or tetrofosmin have all helped to identify I-131-negative thyroid carcinomas. The authors have identified a case of reversal of I-131 findings from negative to positive after short-term thyroxine withdrawal combined with treatment with recombinant human thyroid-stimulating hormone (rhTSH). MATERIALS AND METHODS: The authors obtained multiple I-131 whole-body scans with 4-week thyroid hormone withdrawal, post-I-131 therapy scans, nonthyroid withdrawal Tl-201 chloride whole-body tumor images, and finally combined 2.5-week thyroid hormone withdrawal and rhTSH-stimulation I-131 whole-body scans before and after therapy. RESULTS: The authors examined one patient during a period of 9 years whose I-131 whole-body scan results were at first positive and then became negative. After a combination of rhTSH stimulation and thyroid hormone withdrawal, the results changed again to I-131 positive. CONCLUSIONS: This is the first known case in which I-131 findings changed from negative to positive. A combination of rhTSH stimulation and nearly adequate withdrawal may help convert more I-131-negative whole-body scans to positive.

Penile implant on bone scan imaging: a case study.

We present an unusual case of the incidental finding of a penile implant on a whole-body bone scan obtained for back pain in a patient with osteoporosis and vertebral body fractures. On 2 separate occasions, this patient underwent 3-h delayed whole-body bone scanning with (99m)Tc-methylene diphosphonate. The images showed acute and then subacute vertebral body fractures. On both imaging occasions, the bone scan that included the region of the implant clearly showed the penis, but visualization was better on the second scan. Penile implants have not been described in the nuclear medicine literature, and it is important to recognize the diagnostic possibilities when penile photopenia is identified.