Robert A. Cooper

Tc-99m sestamibi uptake in metastatic prostate carcinoma

Chest pain developed in a 67-year-old man with a history of prostate carcinoma and he was referred for a myocardial perfusion scan. A Tc-99m sestamibi-dipyridamole study showed impaired coronary artery flow reserve to the interventricular septum and a fixed perfusion defect in the inferior wall of the left ventricle, consistent with previous myocardial infarction. Increased sestamibi uptake in an irregular pattern in multiple ribs was noted incidentally. The serum prostate-specific antigen concentration was markedly elevated at 84.3 μg/l (normal, <4.0 μg/l). A whole-body bone scan showed corresponding multiple foci of increased tracer accumulation in the ribs and elsewhere in the axial and appendicular skeleton, consistent with widespread prostatic carcinoma metastases in bone. Tc-99m sestamibi uptake has been reported in a wide range of benign and malignant tumors, but accumulation in prostate carcinoma has not been previously described.

Generation of planar images from lung ventilation/perfusion SPECT

ObjectiveTo develop a method of producing lung ventilation and perfusion (V/Q) planar images using forward projection of reconstructed single-photon emission computed tomography (SPECT) images through approximate attenuation (µ) maps generated from the lung emission scans alone, as transmission-based µ maps may not be routinely available.MethodsSynthetic µ maps are derived from 99mTc photopeak and “scatter” windows for the attenuation correction of the SPECT images. The attenuation-corrected SPECT images are forward projected at appropriate angles to give the equivalent of planar images. This method allows high-count planar images, as well as the SPECT images, to be produced from a single SPECT acquisition. In addition, isolated “single lung” views of lateral and medial projections without “shine-through” from the contra-lateral lung, which have not been available previously, can be formed.ResultsComparison of reprojected images produced from CT-derived or synthetic µ maps displayed similar detail and radiopharmaceutical distribution. In a blinded comparison of “true” planar images with those from reprojecting the SPECT data using the synthetic µ maps, no difference in mismatched defect detection was found, and hence it was confirmed that the reprojected planar images could replace true planar images with no loss in planar diagnostic sensitivity.ConclusionsThe reprojected planar images provide high-count, high-quality images, which are comparable with conventional 2D images.

Cardiac function in acute hypothyroidism

It has been established that chronic hypothyroidism may affect cardiac function by several mechanisms. It is not known how long the patient has to be hypothyroid for cardiac involvement to develop. This study was undertaken to assess the effect of a short period of hypothyroidism (10 days) on cardiac function. Nine patients who had had total thyroidectomy, had received ablative radioiodine for thyroid cancer and were euthyroid on replacement therapy were studied while both euthyroid and hypothyroid. Cardiac assessment was performed by X-ray, ECG, echocardiography and gated blood-pool scans. After 10 days of hypothyroidism, the left-ventricular ejection fraction failed to rise after exercise in 4 of the 9 patients studied, which was significant (P0.002). No significant changes in cardiac size or function at rest were detected. This functional abnormality in the absence of any demonstrable change in cardiac size and the absence of pericardial effussion with normal basal function suggest that short periods of hypothyroidism may reduce cardiac reserve, mostly because of alterations in metabolic function.

A comparative study of 99mTc and 131I in thyroid scanning

Thyroid scans performed with both 99mTc pertechnetate (99mTcO4) and (131I) were compared in 46 patients with palpable thyroid nodules to determine whether 131I scanning is any longer a necessary procedure. A discrepancy between the two types of scan existed in only three cases, in one of which the thyroid nodule showed uptake of 99mTcO4 but not of 131I. Subsequent surgery revealed a thyroid malignancy in this patient. In each of the other two discrepancies a nodule ‘cold’ on 99mTcO4 scanning was apparently functioning on 131I scanning, and was found to be benign at surgery. As the convenience and lower radiation absorbed dose of 99mTcO4 compared with 131I make it a better scanning agent, it is recommended that 99mTcO4 scans of the thyroid be first performed in the assessment of patients with thyroid nodules. If these nodules prove to be functioning equally with paranodular tissue, a 131I scan should also be performed to help exclude a possible thyroid malignancy.

The estimation of liver triglyceride content by 133Xe clearance.

Abstract A prospective study of 41 patients undergoing liver biopsy was performed to investigate the relationship between liver 133Xe time-activity curves and a biochemical assay of liver triglyceride concentration. A good correlation was obtained between the half time of the faster component in the xenon washout curve and the triglyceride concentration measured by gas liquid chromatography (r = 0.79). This method may be useful for predicting clinically significant fatty infiltration of the liver.

The lung scan appearance of a "coughed-up" endobronchial tumor.

A case of obstruction of the left main bronchus detected by a ventilation-perfusion lung scan is presented. This occured following bronchoscopic biopsy of a lung tumor. Repeat bronchoscopy the following morning showed that the mobile endobronchial tumor seen 2 days earlier had disappeared leaving only a small ulcer. Presumably the tumor had been coughed up-a rare occurence for lung tumors