Faculty Bibliography

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

A 75-year-old man with prostate cancer was referred for metastatic workup. A Tc-99m methylene diphosphonate bone scan was performed which revealed diffusely increased radiopharmaceutical uptake in the muscles of the arms and thighs. The patient was taking simvastatin 80 mg per day and gemfibrozil 600 mg twice a day for high cholesterol. The patient reported myalgias, and laboratory evaluation was consistent with rhabdomyolysis. After discontinuation of the anticholesterol medications, the clinical and laboratory evaluations normalized. Bone scan performed 1 year later demonstrated complete resolution of muscle uptake

PURPOSE: To determine if contrast material-enhanced magnetic resonance (MR) imaging is useful for assessment of myocardial viability in patients with equivocal stress-rest results from single photon emission computed tomographic (SPECT) examination with technetium 99m sestamibi. MATERIALS AND METHODS: Twenty patients underwent stress-rest SPECT examinations with sestamibi. Results were considered equivocal for assessment of myocardial infarct on the basis of fixed perfusion defects that either had normal wall motion or exceeded any wall motion abnormalities. Patients then underwent (a). contrast-enhanced MR imaging for assessment of myocardial infarct and (b). cine MR imaging for assessment of wall motion. For image analyses, the left ventricle was divided into 14 segments. Wall motion and extent of infarct were assessed independently and compared. RESULTS: Forty-one segments were equivocal for infarct at SPECT, and most (21 of 41 [51%]) involved the posterior or inferior wall. Infarct was confirmed with MR imaging in 10 of 41 (24%) equivocal segments in eight patients (40%). An additional 29 segments in eight patients had infarct at MR imaging that was not suspected at SPECT, including segments in three patients with no clinical history of myocardial infarct prior to imaging. All cases of infarct except one that were equivocal or undetected with sestamibi at SPECT were nontransmural at MR imaging, and most of the unsuspected subendocardial infarcts (15 of 28 [54%]) had no associated wall motion abnormalities. CONCLUSION: Patients with radionuclide examination findings that are equivocal for infarct may benefit from contrast-enhanced MR imaging, particularly in the setting of nontransmural infarct

BACKGROUND. Although computed tomography and magnetic resonance imaging have improved the staging and evaluation of non-small cell lung cancer (NSCLC), mediastinal staging lacks adequate specificity and sensitivity. Radioimmunodetection may augment computed tomography and magnetic resonance imaging. The authors evaluated the ability of the technetium 99m-anticarcinoembryonic antigen IMMU-4 Fab' fragment to localize NSCLC in vivo, measured its pharmacokinetics, and estimated its radiation dose. METHODS. Seventeen patients with carcinoembryonic antigen-positive NSCLC received 16-30 mCi of technetium 99m IMMU-4 Fab'. Planar imaging was performed at 1-7 hours and 20-24 hours. Single-photon emission computed tomography (SPECT) was performed within 8 hours after injection. In 10 patients, blood sampling, urine collection, and quantitative imaging were performed to determine blood and urine pharmacokinetics and radiation dose estimates. Human anti-mouse antibody response was measured for as long as 3 months after administration. RESULTS. Planar and/or SPECT imaging detected 72% of 32 known lesions. SPECT was more sensitive than planar imaging. T1/2 alpha averaged 0.18 +/- 0.33 hours; T1/2 beta averaged 8.02 +/- 5.53 hours. The mean concentration versus time value was 1.11 +/- 0.56 mg.h. The average whole body dose estimated for administration of 30 mCi was 0.45 +/- 0.08 rads. No human anti-mouse antibody responses were detected. CONCLUSION. The tumor detection rate was high, but the persistent blood pool at < 8 hours complicated image interpretation. An intermediate imaging time point (12-16 hours) might be preferable. SPECT is an important adjunct to imaging with this radioimmunoconjugate. The acceptable dosimetry estimated for 30 mCi Technetium 99m IMMU-4 Fab' and the lack of human anti-mouse antibody responses suggest this is a promising localizing tool for NSCLC

Consecutive gallium-67 scans (n = 237) of 180 human immunodeficiency virus-seropositive patients with suspected pulmonary infections were evaluated for intensity and pattern of gallium distribution. Scan findings were correlated with the history, chest radiographic findings, and clinicopathologic diagnoses. Pneumocystis carinii pneumonia (PCP) occurred significantly more often with heterogeneous diffuse uptake than with homogeneous diffuse uptake. Heterogeneous diffuse uptake had an 87% positive predictive value for PCP, which was higher than that of other patterns. Localized pulmonary uptake was most commonly due to bacterial pneumonia or PCP; ill-defined, perihilar uptake, to cytomegalovirus or PCP; and focal (lymph node) uptake, to tuberculosis or lymphoma. The positive predictive value of any pulmonary uptake for lung pathology was 93%, and the negative predictive value of a negative scan was 96%. These findings confirm the utility of gallium scanning in the detection of lung pathology related to acquired immunodeficiency syndrome, particularly PCP. Furthermore, identification of a diffuse pattern may permit the use of a less invasive test more specifically directed at the confirmation of a diagnosis of PCP

A case of unilateral mismatch on a ventilation/perfusion lung scan due to aortic aneurysm dissection is presented. Pulmonary embolism should not be considered the sole cause of unilateral lung mismatch. Clinical evaluation and pulmonary angiography should be used for a definitive diagnosis

Eighty-six [67Ga]citrate chest scans were performed in 71 adult patients with the acquired immunodeficiency syndrome. Forty-five of these patients also had Kaposi's sarcoma. Only 29 of 57 abnormal scans were correlated with abnormal chest radiographs. Chest radiographs were negative for 27 scans and unavailable for one. Several scan patterns were seen. Diffusely increased lung uptake was seen most commonly with Pneumocystis carinii pneumonia, but also other infections and noninfectious inflammatory conditions. Focal uptake corresponding to regional lymph node groups occurred most often with Mycobacterium avium-intracellulare but aslo with lymphoma. Localized intrapulmonary uptake was seen in bacterial pneumonias. Perihilar activity occurred in two cases. When chest radiographs were abnormal and 67Ga scans negative, the most common diagnosis was pulmonary Kaposi's sarcoma