Biomedical subjects
Publications and source records attributed to R D Karl.
Radionuclide scanning is a valuable diagnostic tool based on metabolic and anatomic imaging. When used in the appropriate clinical setting, radionuclide imaging is a sensitive, minimally invasive imaging modality that detects and differentiates skeletal from nonskeletal pathology in the painful foot. Isotopic scanning is of particular value in the evaluation of the diabetic foot and in the subsequent follow-up of response to therapy.
New lesions were shown by Tc99m bone scans to have developed in sixty patients with known metastatic cancer or high-risk primary cancer and normal neurologic examinations; they were further evaluated with plain radiographs, spinal computed tomography (CT), and CT myelography (CT-M) according to an algorithm. Three groups were identified based on plain radiographs: group 1 (normal radiograph), group 2 (compression fracture as indicated by radiograph), group 3 (evidence of metastasis as indicated by radiograph). In group 1 (n = 18), spinal CT revealed that 33% of the patients had benign disease and 67%, metastases; epidural compression was seen in 25% of the patients with metastasis as indicated by CT-M. In group 2 (n = 26), CT-M disclosed that 38% had a benign compression fracture and 62% had metastases and that 63% of the patients with metastases had an epidural compression. In group 3 (n = 16), spinal CT revealed that 15 patients had metastases (one patient had benign disease). Epidural cord compression was seen in 47% of the patients with metastatic disease. In all groups, the presence of cortical bone discontinuity around the neural canal (seen in 31 patients) was highly associated with epidural compression (seen in 20 patients). Our approach allowed the early and accurate diagnosis of spinal metastasis and epidural tumor as well as the diagnosis of benign disease and was useful in planning optimal local therapy.
An unsuspected false aneurysm of the ascending aorta was discovered during a first pass, left-to-right shunt study.
The differential diagnosis of a solitary photopenic defect in the renal fossa observed at renal scintigraphy is extensive. A case of one of the most unusual causes for this finding, renal agenesis, is presented. Additional cases that illustrate the similarity in the radionuclide appearance of other pathologic entities are also presented. Correlation with clinical findings and other imaging modalities is required to accurately distinguish these conditions.
A Xe-133 hepatic study was misleading when the absence of Xe-133 localization in an area of low CT numbers was considered to be negative for a diagnosis of focal fatty infiltration.
This is the first report in the nuclear medicine literature of the scintigraphic appearance of the piriformis muscle syndrome. This syndrome previously has been thought to be a purely clinical diagnosis and imaging modalities have been ignored. However, its confusing clinical presentation can lead to unnecessary surgical exploration. This case is presented to illustrate the characteristic scintigraphic pattern and suggest the role of nuclear medicine scanning in establishing the diagnosis.
Four methods of Tc-99m red blood cell labeling were tested for labeling efficiency and kinetics in normal adults. From a perspective of the gastrointestinal hemorrhage study, the in vivo method was least appropriate because of extravascular loss of pertechnetate. The modified in vitro method was disadvantageous because of long labeling intervals in a syringe fixed to the patient's forearm (45 minutes). The pure in vitro methods produced the highest labeling efficiency (95% +) and are preferred by the authors.
The interpretation of Ga-67 scans is limited by the complex anatomic and physiologic distribution of Ga-67 and by the low resolution possible with this isotope. The use of a second isotope Tc-99m, tagged to an appropriate pharmaceutical allows the identification of anatomic landmarks. Computer acquisition of both the Ga-67 and Tc-99m images allows for subtraction of the Tc-99m images from the Ga-67 images and leads to precise localization of abnormal Ga-67 accumulations. Only a small percentage of the counts in the Tc-99m window are due to Ga-67 scatter and do not degrade the Tc-99m images. Cases illustrating the value of the dual-isotope technique are presented.
To compare the accuracy of single-photon emission computed tomography (SPECT) with that of contrast cineangiography in measuring left ventricular end-diastolic volume, 25 consecutive patients undergoing catheterization for coronary artery or valvular heart disease were first evaluated scintigraphically. A simple, count-corrected voxel counting technique was used to derive left ventricular end-diastolic volume from transaxial SPECT slices. SPECT volume values showed a high degree of correlation with those determined by angiography (r = 0.969), with a standard error of the estimate of 23 ml. SPECT offers a highly accurate and essentially noninvasive method for measuring chamber volumes that is independent of geometric assumptions about ventricular configuration and chest wall attenuation and does not require blood sample counting.
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A retrospective analysis of 104 chest radionuclide angiography (CRNA) studies establishes the utility of this procedure in the evaluation of pulmonary malignancies and benign masses. Remarkable abnormalities in the perfusion of the lungs were identified in 36 (58%) of 62 cases that were not predictably normal or predictably abnormal form the clinical setting. While 60 of these 62 cases involved malignancy being evaluated for metastases, only 21 (34%) had metastases identified by radionuclide bone or liver-spleen scintigraphy. In addition to diagnosis of superior vena cava obstruction, the CRNA may have a more frequent application as an adjunct to routine scintigraphic studies directed to the identification of metastatic disease.
The authors report a case of "hot spot" localization on SPECT hepatic scintigraphy secondary to IVC obstruction. The tomographic slices demonstrated the location of the focal increase in radiotracer activity as anterior, within the medial segment of the left lobe of the liver. Radionuclide angiography confirmed the extensive collateral vasculature of IVC obstruction.
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A new cholescintigraphic finding, the "hot rim" sign, is reported in a case of acute cholecystitis. Local inflammation in the gallbladder fossa may be the cause of this phenomenon.
Single harmonic Fourier amplitude and phase (FA/P) analyses of 129 radionuclide angiographic (RNA) studies were found to reflect accurately the sequence and quantity of perfusion determined in the independently interpreted RNA studies. In addition, the anatomic detailing in peripheral studies (hands, feet, etc.) was considered superior to that obtained in RNA studies.
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