Left inguinal hernia mimicking metastasis on bone scan.

Inguinal hernia is a well-known entity that usually affects males. The most common herniated organs are parts of the bowel, omentum, or fat. Urinary bladder herniation into the inguinal region is very rare and is often diagnosed during inguinal hernia surgery. This case highlights the importance of additional views and anatomic imaging to accurately interpret the unusual scan findings.

I-131 SPECT/CT elucidates cryptic findings on planar whole-body scans and can reduce needless therapy with I-131 in post-thyroidectomy thyroid cancer patients.

BACKGROUND: Interpreting I-131 whole-body scans (WBSs) after thyroidectomy for thyroid cancer is not simple. There are scans in which interpretation is speculative because of cryptic findings (CF). Complexity is added in scans that are done a week after an ablative or therapeutic dose of I-131 because not only is I-131-labeled thyroxine (T4) distributed throughout the body, but inorganic I-131 that is derived from the de-iodination of T4 may be also detected. We present our observations regarding the analysis of CF on WBS using I-131 single-photon emission computed tomography (SPECT) in fusion with noncontrast computed tomography (CT), referred to here and elsewhere as I-131 SPECT/CT. METHODS: Forty of 184 WBSs in 38 thyroidectomized thyroid cancer patients were followed up with I-131 SPECT/CTs. The SPECT/CT images were acquired after a tracer dose of I-131 (n=82) or a week after an ablative or therapeutic dose of I-131 (n=102). RESULTS: Among 184 WBSs, 40 (22%) had CF. In 35 patients the WBS was negative for metastatic disease except for the CF and 5 patients had evidence of thyroid cancer in addition to the CF. There were 49 CF in the planar scans that were localized by SPECT/CT. These were characterized as physiological uptake in gingiva, thymus, gall bladder, menstrual blood, uterine fibroid, recto-sigmoid, colon, and bladder. Also observed was uptake in sites that represented nonthyroidal pathology including dental abscess, hiatal hernia, renal cyst, and struma ovarii. SPECT/CT suggested that 10 of the CF were actually of thyroid origin. In 40 SPECT/CT scans, the images contributed to interpreting the scan. In 15 of 40 patients the SPECT/CT analysis of WBS was performed with tracer doses of I-131 and was important for determining whether to administer ablative I-131 treatment. In another 25 patients, in whom SPECT/CT was performed after ablative or therapeutic doses of 131-I, information regarding the characterization of CF by SPECT/CT was useful in determining if thyroid cancer metastases or thyroid remnants were present. CONCLUSIONS: I-131 SPECT/CT is a useful tool to characterize atypical or CF on WBS by differentiating thyroid remnant or cancer from physiologic activity or nonthyroid pathology. In the past, uptake on a WBS that was not explicable as physiologic activity was identified as putative or possible thyroid cancer and generally was treated with I-131. Now, by identifying activity in some possible cancer sites as not thyroid cancer, SPECT/CT can reduce inappropriate treatment with I-131. SPECT/CT of WBS performed after ablative doses of 131-I is useful in determining the nature of CF and therefore likely providing prognostic information.

Recognition of dose infiltration on pulmonary ventilation-perfusion scintigraphy.

Pulmonary scintigraphy has a well-established role in the diagnosis of pulmonary embolism (PE). The diagnostic specificity is increased if the perfusion study is combined with assessment of regional ventilation. VQ scans interpreted as either normal, near-normal, or high probability are reasonably diagnostic. Misinterpretation of the VQ scan can result in failure of this simple and noninvasive modality to diagnose a PE. Dose infiltration of the perfusion tracer is one of the rare causes of the misinterpretation of the VQ scan study. We present the VQ scan images of two patients and discuss the findings when Tc99m macroaggregated serum albumin (MAA) dose infiltration was recognized and the perfusion study was repeated for optimal interpretation.

Follicular variant of papillary thyroid carcinoma presenting as a toxic nodule by I-123 scintigraphy.

The risk of malignancy in a "hot" thyroid nodule detected by radioiodine scintigraphy is rare. We report a case of a 63-year-old man with a hyperfunctioning nodule demonstrated by radioiodine scintigraphy and cytology suspicious for follicular variant of papillary thyroid carcinoma (FVPTC). There were no locoregional or distant metastases at initial diagnosis. Histopathologic examination following thyroidectomy confirmed the presence of an encapsulated FVPTC. A year into follow-up, his I-131 whole body scan performed following the withdrawal from exogenous thyroid hormone was negative, whereas his serum thyroglobulin (Tg) levels were intermediate. A subsequent PET/CT scan revealed a small, but stable, metabolically active pretracheal lymph node, which on biopsy was confirmed to be stage III FVPTC. In conclusion, the presence of hyperfunctioning thyroid nodule(s) does not preclude malignancy and, therefore, proper cytohistologic evaluation in such patients may help to exclude a coexistent thyroid carcinoma. Patients treated for localized PTC may benefit from serial PET/CT follow-up in the early detection and management of recurrence or distant metastases.

Effect of proton pump inhibitors and H2 antagonists on the stomach wall in 99mTc-sestamibi cardiac imaging.

UNLABELLED: On the basis of previously unpublished observations, we hypothesized that prolonged use of proton pump inhibitors (PPIs) causes an increase in (99m)Tc-sestamibi uptake in the stomach wall, manifested as curvilinear activity surrounding the photopenic fundus of the stomach cavity. We prospectively evaluated the frequency of stomach wall uptake in patients undergoing myocardial perfusion SPECT who were taking PPIs or H(2) antagonists. METHODS: Patients (n = 138) who were scheduled for single-day rest/stress (99m)Tc-sestamibi SPECT were randomly selected. Poststress SPECT was performed 30 min after treadmill exercise or 45 min after dipyridamole infusion. The rest scan was obtained 45 min after tracer injection. All patients drank 473 mL of water 5-10 min after both the rest and the stress radiotracer injections. Patients were questioned regarding their use of PPIs and H(2) antagonists. The significant use of either was defined as more than 2 wk of continuous therapy before cardiac SPECT. Masked observers assessed poststress planar projection images in endless-loop cinematic format for the following 3 patterns: stomach cavity uptake, attributable to duodenogastric reflux of tracer; stomach wall uptake; and no stomach uptake. A 2-tailed chi(2) test with Yates correction was used to calculate statistically significant associations among variables. RESULTS: Only patients with observed patterns of stomach wall uptake (n = 30) and no stomach wall uptake (n = 91) were included. Patients with stomach cavity uptake (n = 17) were excluded because the assessment of the adjacent stomach wall uptake was not possible. Of the patients included (n = 121), 30 were men and 91 were women. Sixty-seven patients were older than 60 y; 26 patients were taking PPIs. Of the 95 patients not taking PPIs, 14 were taking H(2) antagonists. No patients were taking both medications. Stomach wall uptake was strongly associated with prolonged use of PPIs (chi(2) = 51.9, P < 0.0001). No statistically significant association was noted among age, sex, or use of H(2) antagonists (P = NS). CONCLUSION: Prolonged PPI therapy, but not H(2) antagonist therapy, contributes to a significant increase in stomach wall activity, potentially resulting in Compton scatter or ramp filter artifacts affecting the inferior wall of the left ventricle. Stomach wall activity, unlike the stomach cavity activity, cannot be prevented by the ingestion of water before imaging. Therefore, it is important to elicit a history of prolonged PPI use to better anticipate the possibility of increased stomach wall activity, which can confound the image quality and interpretation.

Tetracyclic Antidepressant Causing Altered Biodistribution of MIBG.

We present the case of a 61-year-old man who underwent I-123 metaiodobenzylguanidine (MIBG) scintigraphy based on clinical suspicion of pheochromocytoma. The study was nondiagnostic secondary to diffuse muscle uptake. On review of his medications, the patient was found to be taking mirtazapine, a tetracyclic antidepressant (Remeron). We hypothesize that the MIBG biodistribution was altered by mirtazapine-mediated blockade of the presynaptic alpha-2 receptor. To our knowledge, tetracyclic antidepressants have not been previously reported to cause altered biodistribution on I-123 MIBG scans.

Abnormal FDG Uptake in the Pericardial Adipose Tissue Mimicking Malignancy.

Focal mediastinal F-18 FDG uptake may be from potential adenopathy requiring biopsy confirmation or benign active brown adipose tissue to be left untouched. Knowledge of this potential pitfall and precise localization with fusion PET/CT are important in preventing misinterpretation as malignancy. Our case report is important in the aspect that CT was not able to confirm the uptake as benign finding, which led to invasive biopsy and biopsy confirmed it to be a benign brown adipose tissue.