Use of sentinel node lymphoscintigraphy in malignant melanoma.

Lymphoscintigraphy is a sensitive, inexpensive, relatively noninvasive method of identifying lymphatic drainage patterns and sentinel lymph nodes in patients with malignant melanoma. Lymphoscintigraphy with filtered technetium-99m sulfur colloid allows prompt visualization of the lymphatic system, produces high-quality images, and delivers a low radiation dose to the patient. In addition, good regional lymph node retention is seen with filtered Tc-99m sulfur colloid, improving the success rate of intraoperative gamma probe localization. In combination with surgical localization, lymphoscintigraphy allows preoperative and intraoperative identification of the sentinel node in patients with intermediate thickness melanomatous lesions, obviating radical lymph node dissection in most patients and possibly prolonging their survival. Variables such as tumor location, type and preparation of radiopharmaceutical, injection technique, imaging technique, and prior surgical intervention influence the efficacy of lymphoscintigraphy. Nevertheless, lymphoscintigraphy is recommended as a cost-effective preoperative procedure in all patients planning to undergo elective lymph node dissection. Because of the unpredictability of lymphatic drainage, preoperative scintigraphic findings may lead to changes in surgical management.

Single-photon emission computed tomography of the brain in acute mania and schizophrenia.

Single-photon emission computed tomography (SPECT) imaging with n-isopropyliodoamphetamine (IMP) was performed on 11 patients with bipolar mania, 21 acute schizophrenics, and 15 healthy control subjects. Subjects were evaluated with neuropsychological tests and psychiatric rating scales. SPECT brain studies were blindly evaluated to assess the degree of radiopharmaceutical uptake in three neuroanatomical regions of interest in each hemisphere. All the control subjects, 1 manic patient, and 1 schizophrenic patient had normal brain SPECT uptake patterns. The scans of all others were read as abnormal. Hypofrontality was noted in some schizophrenics and maniacs. A significant increase in tracer uptake in temporal lobes was observed in both patient groups, more prominently in the manic patients. Increased and decreased basal ganglia uptake was also observed in patients. Both manic and schizophrenic patients showed cortical tracer heterogeneity of varying degree. The patterns of cerebral SPECT uptake seen in these acute psychoses were not specific for a diagnosis, but may be associated with dimensions of psychopathology. Because the patterns are different from those seen in cerebrovascular disease and the dementias, they may prove to be helpful in differential diagnosis.

Tc-99m DISIDA hepatobiliary scintigraphy in AIDS cholangitis.

Sixteen patients with documented AIDS cholangitis who underwent Tc-99m DISIDA hepatobiliary scintigraphy were retrospectively reviewed to assess the spectrum of changes observed in this disease. AIDS cholangitis was documented by either ERCP with aspiration/biopsy or the presence of typical sonographic/CT abnormalities with positive stool culture and a minimum of 6 months follow-up. Images were graded as regards parenchymal function (blood pool clearance, peak parenchymal activity, and degree of parenchymal retention), gallbladder visualization, presence of ductal dilatation, and time of intestinal activity. Three patterns were identified: 1) focal ductal dilatation with focal narrowing and focal or diffuse parenchymal retention; 2) ductal dilatation, without narrowing, and diffuse parenchymal retention; and 3) severe diffuse parenchymal retention with or without ductal abnormality. All 16 studies revealed abnormal parenchymal retention. Gallbladder nonvisualization was demonstrated in nine studies and delayed in two. The hepatobiliary scan is a very sensitive technique for evaluating AIDS cholangitis. Although a spectrum of findings may be observed, parenchymal retention with some degree of ductal abnormality is the most commonly observed pattern.

Hepatic SPECT imaging in the detection and clinical assessment of hepatocellular disease.

A total of 95 patients, including 45 people with no evidence of liver disease and 50 documented hepatocellular disease patients, were studied to assess the value of planar and SPECT scintigraphy in the evaluation of hepatocellular disease. The accuracy and concordance between techniques was assessed using two criteria. Criterion 1, heterogeneity of the tracer in liver, yielded a concordance of 64%, whereas with criterion 2, liver and spleen tracer pattern, concordance was 78%. SPECT was significantly more accurate than planar imaging (P < 0.01), using both criteria. The clinical severity of the hepatocellular disease was further assessed in 72 of the patients and correlated with a liver scan severity rating scale. The SPECT technique showed a good correlation (r = 0.89) with the composite clinical severity score; however, no significant relationship with planar imaging was noted. The results of this study suggest that liver SPECT is a reliable technique for the assessment of hepatocellular disease.

Interventions and functional brain imaging.

Assessment of regional cerebral blood flow (rCBF) is useful in the evaluation of cerebral vascular disease. However, a single resting study has limitations in that a normal rCBF may be present with diminished cerebral vascular flow reserve and regions of decreased rCBF may be seen with diaschisis or selective neuronal loss and an intact vascular supply. To help differentiate these conditions a stress rCBF study can be obtained following the administration of vasodilatory stimulus. The topic of this review is the discussion of single photon emission computed tomography (SPECT) and vascular intervention, primarily, acetazolamide (Diamox, Lederle Laboratory Division, Pearl River, NY) augmented SPECT in the evaluation of cerebral vascular disease.

The potential value of serial cerebral SPECT scanning in the evaluation of psychiatric illness.

Cerebral SPECT imaging has the potential to make an important contribution to clinical psychiatry. Cerebral SPECT scanning, stimulated by the work with PET, is readily available and much less expensive than PET. This paper reports a case demonstrating the potential value of cerebral SPECT scanning with I-123 IMP, specifically in the serial evaluation of a schizophrenic patient with auditory hallucinations. The initial scan revealed focal areas of increased uptake in the caudate nuclei of the basal ganglia, and in the right temporal lobe. After pharmacological treatment with clinical improvement, the follow-up SPECT scan demonstrated significant improvement in the distribution of the radiopharmaceutical.

The value of SPECT imaging in the diagnosis of hepatic hemangioma.

Radionuclide flow studies, planar, and SPECT hepatic blood pool imaging were performed in 23 patients with 39 hepatic hemangiomas, 23 patients with primary and secondary liver tumors, 12 patients with hepatocellular disease, two patients with hepatic cysts, and 10 patients with no evidence of liver disease. The hepatic SPECT imaging identified all 39 hemangiomas as having a sequestration pattern compared with a yield of 69% (27 of 39 cases) for the planar imaging. None of the 47 other patients demonstrated this pattern. The SPECT approach is considered superior to planar blood pool imaging because of improved diagnostic yield, reduced patient imaging time, and greater ease of correlation with other cross-sectional imaging modalities.

Single photon emission computed tomography and transmission computed tomography in the evaluation of liver disease.

To assess the relative strengths of hepatic SPECT and transmission computed tomography (TCT), a comparison of these methods was made in 88 patients during a 20-month period. The scans were classified into four categories: normal, solitary focal, multifocal, or diffuse hepatocellular patterns. The final disease category was determined by histologic evaluation-biopsy/autopsy, surgery, or a combination of ultrasound, laboratory, and clinical follow-up for a minimum of 6 months. Both SPECT and TCT were normal in the 47 patients classified as normal. Of the 16 patients with diffuse hepatocellular disease, SPECT correctly identified 16 and TCT identified two patients. Eleven patients had solitary focal disease; 11 were detected by SPECT and 10 by TCT. Fourteen patients were in the multifocal disease group; 13 were detected by SPECT and 10 by TCT. Overall, SPECT and TCT findings were in agreement in 68 (77%) of the cases. This study demonstrates that SPECT is equal to TCT in the assessment of the liver parenchyma in normal and focal disease states and that SPECT is superior in the assessment of diffuse disease.

Quantitative autoradiography of parathyroid glands in rats with carbon-14-labeled amino acids.

We have utilized a quantitative autoradiographic method as a means of evaluating amino acid uptake of the rat parathyroid gland for the ultimate purpose of finding agents potentially suitable for position emission tomographic scanning of parathyroid glands. L-[1-14C]leucine and L-[guanido-14C]arginine were evaluated because of their relatively high content in the synthetic products of the parathyroid glands compared with other neck tissues, thyroid gland, and muscle. Carbon-14 leucine disappeared rapidly from plasma following intravenous injection and there was relatively selective uptake of the [14C]leucine and [14C]arginine by the parathyroid glands when compared with uptake by the thyroid gland and neck muscle. These data suggest that both agents warrant further investigation for their potential utility in positron emission tomographic scanning of the parathyroid gland.

Abdominal SPECT imaging.

Over the past several years, abdominal single photon emission computed tomography (SPECT) imaging has evolved from a research tool to an important clinical imaging modality that is helpful in the diagnostic assessment of a wide variety of disorders involving the abdominal viscera. Although liver-spleen imaging is the most popular of the abdominal SPECT procedures, blood pool imaging is becoming much more widely utilized for the evaluation of cavernous hemangiomas of the liver as well as other vascular abnormalities in the abdomen. Adjunctive indium leukocyte and gallium SPECT studies are also proving to be of value in the assessment of a variety of infectious and neoplastic diseases. As more experience is acquired in this area, SPECT should become the primary imaging modality for both gallium and indium white blood cells in many institutions. Renal SPECT, on the other hand, has only recently been used as a clinical imaging modality for the assessment of such parameters as renal depth and volume. The exact role of renal SPECT as a clinical tool is, therefore, yet to be determined.

Visualization of arterial grafts on a gastrointestinal bleeding scan.

A case of patent arterial grafts causing an abnormal Tc-99m sulfur colloid bleeding scan is presented. This finding has not been reported previously.

Identification of retinal isomers isolated from bacteriorhodopsin.

The purple membrane of Halobacterium halobium contains the protein bacteriorhodopsin which resembles the visual pigment, rhodopsin, in many aspects. The isomeric configurations of its chromophore, retinal, were studied by a combination of methylene chloride extraction and analysis by high-pressure liquid chromatography. The light-adapted form bR570LA yields solely all-trans-retinal, while the dark-adapted form of bacteriorhodopsin, bR560DA, yields a mixture of 13-cis and all-trans with a ratio of similar to 1;1. The photointermediate M412 in a membrane modified by ether at high NaCl concentration also yields an approximately 1:1 mixture of 13-cis-and all-trans-retinals, while a similar M405 species produced by illumination in 2 M guanidine hydrochloride at high pH yields mainly 13-cis-retinal. These results indicate that the photochemical cycle of bR570LA may involve an isomerization of the retinal chromophore from the all-trans to the 13-cis form.