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The aortic homograft has become the replacement valve of choice in the treatment of complicated endocarditis involving native and prosthetic aortic valves. Complications are rare, typically involving chronic leaflet degeneration causing valvular insufficiency or rarely chronic calcific stenosis. We present a case in which functional stenosis of the homograft valve was caused by compression and distortion by blood transmitted directly from the left ventricle into a space between the homograft and an external cavity formed by a Dacron wrap. The latter had been placed to help control suture-line bleeding. This case presentation demonstrates an unusual cause of homograft failure and suggests that wrapping of a homograft conduit by native aorta or an external Dacron wrap is not a substitute for meticulous surgical technique to assure a hemostatic suture line.

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Left ventricular hypertrophy (LVH) is frequently present in patients referred for radionuclide ventriculography (RVG) for evaluation of left ventricular function. During interpretation of these studies, the nuclear medicine physician may have the subjective impression that increased septal thickening is present because of the abnormally prominent separation of the right and left ventricular blood pools. To examine the diagnostic reliability of this finding, we retrospectively reviewed the RVG studies of 43 consecutive patients and correlated the finding of subjectively increased septal thickness with established echocardiographic (ECHO) criteria and commonly used electrocardiographic (ECG) indices of LVH. Using standard ECHO measurements of septal thickness as a gold standard, RVG interpretation of septal thickening demonstrated a sensitivity of 0.69, specificity of 0.70, and accuracy of 0.70. When compared with standard ECG criteria for LVH, RVG performed quite favorably in the diagnosis of LVH confirmed by ECHO left ventricular mass index. We conclude that scintigraphic evidence of LVH should be reported when RVG studies are interpreted.

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Right aortic arch is a rare congenital anomaly associated with abnormal development of the paired embryological aortic arches. While various abnormalities of the great vessels have been described using both first-pass and multigated radionuclide ventriculographic studies, diagnosis of a right-sided aortic arch has typically required a radiographic contrast technique. We present a case of a patient with a suspected right-sided aortic arch diagnosed by radionuclide methods.

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False-positive findings suggestive of metastatic functioning thyroid carcinoma have been well documented in I-131 whole-body imaging. These artifacts are often associated with contamination from radioiodine-containing body secretions. Recently, a contaminated handkerchief on an iodine-131 whole-body scan was reported. In the following study, two additional cases involving the sequestration of I-131 contaminated handkerchiefs in patients' pockets are presented, and the literature regarding these false-positive findings is reviewed. Although rare, this "radioactive handkerchief sign" may cause serious misinterpretation of a focal radioiodine accumulation.

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A case of idiopathic pulmonary fibrosis with multiple areas of mismatch on ventilation-perfusion lung imaging in the absence of pulmonary embolism is presented. Idiopathic pulmonary fibrosis is one of the few nonembolic diseases producing a pulmonary ventilation-perfusion mismatch. In this condition, chest radiographs may not detect the full extent of disease, and xenon-133 ventilation imaging may be relatively insensitive to morbid changes in small airways. Thus, when examining patients with idiopathic pulmonary fibrosis, one should be aware that abnormal perfusion imaging patterns without matching ventilation abnormalities are not always due to embolism. In this setting, contrast pulmonary angiography is often needed for accurate differential diagnosis.

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For many years it has been known that the sensitivity of bone scanning to the presence of destructive bony lesions favors its use in screening for bone metastases and osteomyelitis. More recently bone scanning has been routinely employed in evaluating benign skeletal pathology that may be the cause of low back pain. Bone scanning can play an important part in (1) identifying the cause of pain, (2) clarifying the significance of radiographic findings, and (3) evaluating the results of spinal surgery. This expansion of the role of nuclear medicine in diagnosing and managing low back pain is based in part upon novel diagnostic applications of 99mTc-methylene diphosphonate, a radiopharmaceutical that has been available for over 15 years. Equally important for this development, however, has been the recent availability of SPECT, a tomographic imaging technique that can be used to display the spine in a series of 6- to 8-mm thick sections. Slightly more than one-half of newly purchased gamma cameras are rotating systems suitable for bone SPECT studies. Thus, many community hospitals can now perform state-of-the-art bone scans for low back pain.

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