Myocardial fatty acid utilisation during exercise induced ischemia in patients with coronary artery disease.

AIM: Reversible or irreversible myocardial damage due to ischemia correlates with altered membrane functions of the cells. To compare myocardial free fatty acid (FFA) metabolism and flow during exercise induced ischemia we studied ten patients with coronary artery disease but without previous myocardial infarction. METHODS: A series of post-exercise single-photon emission computed tomography (SPECT) measurements was performed after injection of 123I labelled heptadecanoic acid (HDA). Myocardial perfusion was estimated from the separately performed exercise-redistribution thallium study. Fatty acid metabolic rate, thallium uptake and washout were calculated for anterior, lateral, posterior and septal segments. RESULTS: The more reduced post-exercise FFA metabolic rate (-63 +/- 18%, mean +/- 1 SD) compared to flow (-36 +/- 16%) was related to the severity of myocardial ischemia and wall motion abnormalities. CONCLUSION: In this small group of patients, the reduced post-exercise FFA metabolic rate tentatively suggests a parsimonious workload of the exercising myocardium by reducing oxygen consumption in patients with coronary artery disease.

Interictal brain 99Tc-HM-PAO SPECT hypoperfusion in patients with unstable partial epilepsy and normal CT.

Brain perfusion was studied interictally with 99mTc-HM-PAO SPECT in 47 adult patients with partial epilepsy and normal brain CT. Epilepsy was classified as secondarily generalized in 24 patients, as complex partial in 17 patients and as simple partial in 6 patients. In 24 patients good seizure control was not achieved as these patients had a median number of 78 seizures during the preceding month, while in the rest of the patients seizure control was relatively good (less than 6 seizures during preceding month). Local brain hypoperfusion was observed in 41 or 87% of the patients. Hypoperfusion was located close to the EEG foci in 76% and equally often with temporal and frontal foci. Hypoperfusion and the EEG focus were located on the same side in 83%. Hypoperfusion was more frequent in secondarily generalized epilepsy and simple partial epilepsy than in complex partial epilepsy. Left-sided hypoperfusion was especially associated with complex partial epilepsy. It is likely that the significant epileptogenic brain area was revealed in patients with SPECT focus and EEG focus in the same brain area. In one of our patients MRI showed a small temporal lesion which on successful removal was identified as a low-grade oligodendroglioma. Abnormalities of regional brain uptake of HM-PAO demonstrated by SPECT in patients with partial epilepsy and normal brain CT give further information about pathophysiology in partial epilepsy; this may be of use both for selecting appropriate therapy and in presurgical localization of foci.

99Tcm-HMPAO SPECT in suspected dementia.

To evaluate the usefulness of 99Tcm-hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) in suspected dementia we studied 160 consecutively imaged elderly patients from our hospital's memory disorder clinic. The diagnosis was based on clinical data, laboratory tests, neuropsychological examination, computed tomography (CT) and EEG. The patients were divided into six diagnostic categories: Alzheimer's disease (AD), multi-infarct dementia (MID), frontal lobe-type dementia (FTD), vascular encephalopathy not fulfilling the criteria of dementia, specific organic conditions, and psychiatric disorders. SPECT images were assessed without knowing the clinical diagnosis, and divided into AD pattern, FTD pattern, MID pattern, abnormal but unclassifiable, and normal. Twenty-three of 36 patients with clinical AD, 25/33 patients with clinical MID, and 2/5 patients with clinical TFD had compatible SPECT patterns. SPECT distinguished AD from MID in the majority (80%) of cases. In patients with depression or anxiety SPECT was abnormal in 16/21 cases, suggesting that SPECT may give early clues to the presence of an underlying organic disease in such elderly patients. Thus, SPECT with 99Tcm-HMPAO seems to be useful in the diagnosis of suspected dementia.

Regional cerebral blood flow after human cardiac arrest. A hexamethylpropyleneamine oxime single photon emission computed tomographic study.

We studied 30 patients 24 hours after out-of-hospital cardiac arrest and 13 age-matched normal controls with the use of technetium Tc 99m-hexamethylpropyleneamine oxime single photon emission computed tomography. All patients were followed up for 12 months or until death. Frontal hypoperfusion (anteroposterior perfusion ratio, less than 0.90) was observed in 23 patients (77%). In eight patients who remained comatose and died, the total size of perfusion defects was larger (38% +/- 20%) than in the 21 patients who recovered consciousness (24% +/- 14%), but the anteroposterior ratio was similar in both of these patient groups (0.83 +/- 0.09) and significantly lower than in the controls (0.96 +/- 0.03). During follow-up, both the anteroposterior perfusion ratio and the relative defect size improved, but frontal hypoperfusion was still observed in seven of 13 patients. After cardiac arrest, regional cerebral blood flow is characterized by frontal hypoperfusion that tends to improve over time but that persists in most patients.

Anti-melanoma antibodies bind preferentially to diploid metastases in immunoscintigraphy.

Immunoscintigraphy with 99Tcm-labelled anti-melanoma monoclonal antibody F(ab')2- fragments was performed in 23 patients with histologically verified metastatic melanoma. Immunoscintigraphy was positive in 14 patients and all known metastases were detected in eight patients, five of whom had only one lesion. Lesion localization and detectability were as follows: 12/13 (92%) cutaneous and subcutaneous, 11/14 (79%) lymph node, 5/7 (71%) bone, 3/6 (50%) lung and 1/5 (20%) abdominal metastases were visualized. Despite its high specificity--no false positive immunoscintigrams--the low sensitivity of this method in detecting deep metastases hampers its usability. The false negative results were not due to lack of antigen expression as positive immunostaining results were observed also in specimens from patients with negative immunoscintigrams. Flow cytometric analysis of the metastases revealed that in 7/8 (88%) patients with diploid tumours had positive immunoscintigrams but only 7/15 (47%) patients with aneuploid tumours. These results show that the diagnostic accuracy of melanoma immunoscintigraphy can be improved by selecting patients not only by testing for the antigen but also on the basis of DNA analysis of an accessible lesion.

A comparison of 131I-labeled antibodies, 2-deoxy-2-[18F]fluoro-D-glucose and 68Ga-EDTA in the imaging of human tumor xenografts in nude mice.

Three different biological properties--glucose metabolism, gallium imaging and antigen-antibody interaction--have been targeted to image human tumor xenografts implanted in nude mice. Seventy-two experiments were performed in 25 nude mice. Two types of human tumors were used: colorectal carcinoma SW 1116 and melanoma WM 9. Immunoscintigraphic studies produced the highest tumor sampling and confirmed earlier findings that F(ab')2 fragments generate better tumor images than whole antibodies.

Single-photon emission computed tomography of brain perfusion: analysis of 60 paediatric cases.

Sixty-nine brain perfusion single-photon emission computed tomography (SPECT) scans were performed on 60 paediatric patients with various neurological diagnoses. SPECT was abnormal more frequently in degenerative brain diseases (82 per cent), than in epilepsy (63 per cent), encephalitis (62 per cent), cerebrovascular disease (43 per cent), or other brain disorders (43 per cent). SPECT was more sensitive than EEG, CT and MRI results. SPECT was of considerable value for diagnosis in many cases. It was a decisive aid in two cases, but misleading in another two, so SPECT must be related to findings obtained by clinical and other laboratory methods.

Brain perfusion defect size in SPECT predicts outcome in cerebral infarction.

The results of previous reports on the usefulness of brain perfusion single photon emission computed tomography (SPECT) in predicting the outcome of patients with acute cerebral infarction are conflicting. We therefore studied brain perfusion in 64 patients with a single supratentorial infarction. Contradictory to previous results the perfusion defect volume estimated from transversal and coronal slices correlated significantly with both presenting clinical findings and outcome. Although the clinical status at admission also correlated well with outcome, there was a subgroup of patients in which the favourable outcome was predicted only by SPECT and not by physical or any other examination at admission.

Diagnosis of acute herpes simplex encephalitis by brain perfusion single photon emission computed tomography.

Brain perfusion was studied in 14 patients with acute encephalitis by use of 123I-iodoamphetamine or 99mTc-hexamethylpropyleneamine oxime and single photon emission computed tomography (SPECT), the first examination being made 4-11 days after onset of encephalitis symptoms. All 6 patients with herpes simplex virus encephalitis (HSVE) had strongly increased accumulation of radiotracer in the affected temporal lobe; in the remaining 8 results were normal. At the time of the first SPECT conventional CT images were normal in all patients. The SPECT abnormality in HSVE gradually converted over 4-10 weeks from increased tracer accumulation to greatly subnormal accumulation. Brain perfusion SPECT may be helpful in the early diagnosis of HSVE.

Comparative evaluation of [123I]14-p-iodophenyl-beta-methyltetradecanoic acid and thallium-201 in the detection of infarcted areas in the dog heart using SPECT.

The concept of using beta-methyl-branched long-chain fatty acids for assessment of myocardial fatty acid uptake and perfusion was extended to the use of radioiodinated fatty acid with stabilization of iodine on the omega-phenyl ring. Beagle dogs were injected with thallium-201 and imaged 15 min after injection. The next day the dogs were infarcted by occluding the LAD, and 2 h later they were injected with [123I]14-p-iodophenyl-beta-methyltetradecanoic acid [123I]BMTDA and imaged for 90 min using a gated SPECT procedure. Maximum uptake of BMTDA in the heart was reached 2 min post injection and the activity level remained constant in the heart during the imaging period. The activity ratio of target to nontarget areas in the tomographic slices was significantly better for the BMTDA imaging compared to 201Tl (P greater than 0.01).

Localization of melanoma with radiolabelled monoclonal antibody fragments and iodoamphetamine.

In two melanoma patients, metastases accumulated both 99mTc-labelled monoclonal anti-tumor F(ab')2 fragments and N-isopropyl-p-(123I)-iodoamphetamine. Small metastatic deposits were localized only by labelled antibody, for which a higher target-to-nontarget ratio was observed than for radioiodoamphetamine, indicating that immunoscintigraphy may be the more sensitive method. In these two patients positive immunohistochemical staining for the antibody used was observed, whereas in a third patient, with no concentration of labelled antibody, the staining result was negative showing the specificity of the immunoscintigraphy findings. It is possible that the accumulation of radio-iodoamphetamine is due to binding to melanin but this is not certain as tissue samples from one of the two patients with positive scintigrams did not contain stainable melanin.