[Analysis of 18F-FDG uptake pattern in PET for diagnosis of aseptic loosening versus prosthesis infection after total knee arthroplasty. A prospective pilot study]. / Analyse des 18F-FDG-Speichermusters in der PET zur Differenzierung zwischen aseptischer Prothesenlockerung und Protheseninfektion - Eine prospektive Pilotstudie.

UNLABELLED: The AIM of this prospective study was to identify a typical pattern for fluorodeoxyglucose (18F-FDG) uptake in positron emission tomography (PET) to differentiate aseptic loosening (tibial and / or femoral component) from prosthesis infection in painful knee prosthesis. PATIENTS, METHODS: 20 patients with painful knee prosthesis underwent PET imaging to evaluate aseptic loosening / prosthesis infection of their knee prosthesis. The interface between bone and surrounding soft tissue or bone was divided into 3 segments each for both the femur and the tibia and in addition for 4 segments reflecting the surrounding periprosthetic soft tissue. FDG uptake in each of the segments was scored (0-3) by two independent observers. The final diagnosis was based on operative findings with subsequent microbiological culture and histological examination. RESULTS: After surgical revision 6 femoral components and 5 tibial components were found to be loose and prosthetic infection was present in 9 prostheses. In 8 of 9 infected prostheses loosening of the femoral und tibial component occurred. There was no statistically significant correlation between the standardised uptake within each of the segments and the diagnosis of aseptic loosening or prosthesis infection. A differentiated qualitative and quantitative FDG-PET result interpretation divided into five categories was developed. Specificity / sensitivity / positive predictive value / negative predictive value were 93% / 83% / 83% / 93% for aseptic loosening of the femoral component, 87% / 80% / 67% / 93% for aseptic loosening of the tibial component and 82% / 89% / 80% / 90% for infection. CONCLUSION: This pilot study shows that FDG-PET is a promising diagnostic tool for patients with painful knee prostheses. There is a good correlation between PET images and the intraoperative and pathology findings. Its clinical value, however, warrants further evaluation in a larger patient population.

Positron emission tomography study of regional cerebral blood flow and flow-metabolism coupling during general anaesthesia with xenon in humans.

BACKGROUND: The effects of xenon on regional cerebral blood flow (rCBF) are controversial. Moreover, the precise sites of action at which xenon exerts its effects in the human brain remain to be established. METHODS: rCBF was sequentially assessed by H(2)(15)O positron emission tomography in six volunteers. rCBF was determined at baseline and during general anaesthesia induced with propofol and maintained with one minimum alveolar concentration xenon. rCBF measurements were started after the calculated plasma concentration of propofol had decreased to subanaesthetic levels (<1.0 microg ml(-1)). Changes in rCBF were calculated for 13 cerebral volumes of interest by measurement of a semi-quantitative perfusion index (PI). In addition, voxel-wise changes in rCBF were analysed using statistical parametric mapping. RESULTS: Xenon had only minor effects on PI in grey matter volumes of interest. In contrast, PI was increased in white matter [from 1.01 (0.11) to 1.24 (0.15) kcnt ml(-1) MBq(-1), P=0.05, mean (SD)]. Voxel-based analysis showed an increase of rCBF in white matter and a relative decrease of rCBF during xenon anaesthesia in distinct grey matter regions, particularly the orbito- and mesiofrontal cortex, cingulate gyrus, thalamus, hippocampus and bilateral cerebellum (P<0.05 corrected). When correlating PI with cerebral metabolic rate of glucose (previously obtained in another group of six volunteers using (18)F-fluorodeoxyglucose as tracer), the flow-metabolism coupling was preserved during xenon anaesthesia. CONCLUSIONS: Xenon exerted distinct regional effects on CBF: relative decreases in several cortical, subcortical, and cerebellar areas were accompanied by an increase in white matter. Flow-metabolism coupling was not impaired during xenon anaesthesia.

[Myocardial perfusion scintigraphy in Germany. Results of the 2005 query and current status]. / Myokardszintigraphie in Deutschland. Ergebnisse der Erhebung 2005 und Standortbestimmung.

UNLABELLED: The working group Cardiovascular Nuclear Medicine of the German Society of Nuclear Medicine (DGN), in cooperation with the working group Nuclear Cardiology of the German Cardiac Society (DGK), decided to conduct a national survey on myocardial perfusion scintigraphy (MPS). METHOD: A questionnaire to evaluate MPS for the year 2005 was sent. RESULTS: 346 completed questionnaires had been returned (213 private practices, 99 hospitals and 33 university hospitals). MPS of 112 707 patients were reported with 110 747 stress and 95 878 rest studies. The majority (>75%) was performed with (99m)Tc-MIBI or tetrofosmin. (201)Tl stress-redistribution was used in 22 637 patients (20%). The types of stress were exercise in 78%, vasodilation with adenosine or dipyridamol in 21% and dobutamine in 1%. 99.97% of all MPS were SPECT studies. Gated SPECT was performed in 36% of the stress and in 32% of the rest studies. An attenuation correction was used in 21%. 29 institutions (8%) performed gated SPECT (stress and rest) and attenuation correction. 47% of all MPS were requested by ambulatory care cardiologists, 17% by internists, 12% by primary care physicians, 21% by hospital departments and 2% by others. CONCLUSION: In Germany, MPS is predominantly performed with (99m)Tc-perfusion agents. The common type of stress is ergometry. Gated SPECT and attenuation correction do not yet represent standards of MPS practice in Germany, which indicates some potential of optimization.

Neurometabolic effects of psilocybin, 3,4-methylenedioxyethylamphetamine (MDE) and d-methamphetamine in healthy volunteers. A double-blind, placebo-controlled PET study with [18F]FDG.

The neurometabolic effects of the hallucinogen psilocybin (PSI; 0.2 mg/kg), the entactogen 3,4-methylenedioxyethylamphetamine (MDE; 2 mg/kg) and the stimulant d-methamphetamine (METH; 0.2-0.4 mg/kg) and the drugs' interactions with a prefrontal activation task were investigated in a double-blind, placebo-controlled human [F-18]fluorodeoxyglucoseFDG-positron emission tomographicPET study (each group: n = 8). Subjects underwent two scans (control: word repetition; activation word association) within 2-4 weeks. Psilocybin increased rMRGlu in distinct right hemispheric frontotemporal cortical regions, particularly in the anterior cingulate and decreased rMRGlu in the thalamus. Both MDE and METH induced cortical hypometabolism and cerebellar hypermetabolism. In the MDE group, cortical hypometabolism was more pronounced in frontal regions, with the exception of the right anterior cingulate, which tended to be hyperactive. Cognitive activation-related increases in left frontocortical regions were attenuated under all three psychoactive substances, but less so under MDE. Taking into account performance data and subjective reports on task difficulty, these effects may result from different mechanisms across the three groups. Our PSI data are in line with studies on acute schizophrenic patients suggesting frontal overactivity at rest, but diminished capacity to activate prefrontal regions upon cognitive demand. The MDE data support the hypothesis that entactogens constitute a distinct psychoactive substance class, which takes an intermediate position between stimulants and hallucinogens.

Metabolic mismatch of septal beta-oxidation and glucose utilization in left bundle branch block assessed with PET.

Preserved septal uptake of the new long-chain fatty acid analog [18F]FTHA was found in a patient with three-vessel disease, a history of previous anterior myocardial infarction and left bundle branch block (LBBB), despite severely decreased septal [18F]FDG uptake that suggested scarred tissue. Nearly absent [19F]FDG uptake in the septum could not be explained by concordant reduction of septal perfusion as assessed by 99mTc-MIBI SPECT. These data may point to divergent metabolic effects of the conduction abnormality in LBBB with consecutively reduced septal exogenous glucose utilization but unaffected septal beta-oxidation.

Monosomy 1p is correlated with enhanced in vivo glucose metabolism in meningiomas.

The 2-[18F]fluoro-2-deoxy-D-glucose (FDG) uptake of 25 human meningiomas was preoperatively evaluated in vivo by positron-emission tomography (PET). After surgery, meningioma biopsies were analyzed cytogenetically. Five meningiomas showed partial monosomy for chromosome 1p additional to other typical chromosome aberrations. This aberrant karyotype was correlated with increased FDG uptake. Three of five meningiomas with monosomy 1p were classified as grade II according to WHO, while only one of 20 tumors without monosomy 1p was classified as grade II. Thus, monosomy 1p and elevated FDG uptake in PET are to be regarded as cytogenetic and metabolic parameters for the aggressiveness of meningiomas.

The joint Task Group on clinical utility of labelled antibodies of the Society of Nuclear Medicine Europa (SNME) and the European Nuclear Medicine Society (ENMS).

In September 1985 a task group on the clinical utility of labelled antibodies was founded by the Society of Nuclear Medicine - Europe. This document was elaborated to report the aims and the programs of the group. In September 1986 the European Nuclear Medicine Society decided to participate in this initiative and a joint task group was created. INITIAL DOCUMENT: A. The aims to the Task Group are to monitor, co-ordinate and promote research and clinical application of techniques using radiolabelled antibodies in nuclear medicine. A.1. The Group should develop into a major point of reference, giving scientific and technical support to each member of the Society involved in this field. B. To pursue these purposes it will be necessary to develop the following: B.1. Criteria to evaluate the suitability of antigen-antibody systems for tumour detection and/or therapy. B.2. Criteria for quality control of radioimmunoreagents. B.3. Criteria for the prevention of adverse reactions or damage due to the reagent. B.4. Selection of suitable dosimetric methods for diagnostic or therapeutic applications. B.5. Elaboration of protocols for clinical experiments, including appropriate techniques to be applied in single cases. B.6. Organization of cooperative studies. C. The Task Group should promote: C.1. Informal meetings between the members of the Group. C.2. Workshops open to the members of the Society and other researchers. C.3. Publication of reports in appropriate journals.

Active and remitted schizophrenia: psychopathological and regional cerebral blood flow findings.

Single photon emission computed tomography with technetium-99m-d,l-hexamethylpropyleneamine oxime (99mTc-HMPAO) was used to assess regional cerebral blood flow (rCBF) during both florid and remitted stages of schizophrenia. Forty schizophrenic patients in an active phase of illness (diagnosis by DSM-III-R) were examined in two clinical states (ill vs. improved). At study entry, 24 patients were drug-naive, five were currently drug-free, and 11 were being treated with antipsychotic medication. Twenty medical patients who suffered from non-specific headaches but were free of neurological and psychiatric symptoms served as control subjects. At initial examination during the active phase of illness, cerebral perfusion patterns in the schizophrenic patients were characterized by both hypofrontality and hypotemporality. After remission, hypofrontality was no longer apparent in two of four frontal regions, and hypotemporality disappeared completely. As assessed with the Positive and Negative Syndrome Scale (PANSS), formal thought disorders, hallucinations, and ideas of grandiosity correlated with rCBF in the active phase of illness, but not after remission. In the remitted but not in the florid state, blunted affect, difficulties in abstract thinking, lack of spontaneity, and stereotyped thoughts correlated with rCBF. Correlations of five symptoms with rCBF changed significantly from first to second examination. The present study suggests that correlations between single psychotic symptoms and rCBF differ significantly in florid vs. remitted phases of schizophrenia.

The role of 18F-fluoro-deoxyglucose positron emission tomography (18F-FDG PET) in diagnosis of ovarian cancer.

We evaluated the clinical significance of 18F-FDG PET to detect malignant ovarian neoplasms and tumor spread. 40 patients (median age: 57.5 years) underwent laparotomy because of clinical suspicion of malignant ovarian tumors or recurrent disease. The results of the preoperatively performed PET were correlated with the postoperative histologic diagnosis and the intraoperatively assessed tumor spread. In 10 of 40 patients benign tumors were found, among which a tubo-ovarian abscess was the only one diagnosed as false positive. 4/30 malignant neoplasms did not originate from the coelomic epithelium, but all were correctly recognized as malignant tumors by PET, as was recurrent ovarian cancer in 12 patients. Out of 14 primary ovarian carcinomas, 2 borderline tumors and 1 well-differentiated adenocarcinoma FIGO stage I were not correctly identified. Considering the tumor type, sensitivity, and specificity were 90%, calculating for the positive and negative predictive value 96% and 75%, respectively, and 90% for the diagnostic accuracy. Those statistical parameters were slightly lower for PET detection of lymph node metastasis and peritoneal carcinomatosis. Although its diagnostic accuracy may vary depending on the clinical application, 18F-FDG PET is basically a suitable method for detecting ovarian malignancies, particularly in patients with relapsed ovarian carcinoma.

Non-invasive assessment of right and left ventricular volumes 11 to 24 years after corrective surgery on patients with tetralogy of Fallot.

Patients who had corrective surgery for tetralogy of Fallot using a transannular right ventricular outflow tract (TRVOT) patch showed a higher risk of post-operative mortality and reoperation in the long-term follow-up. A total of 642 patients were operated upon for tetralogy of Fallot between 1952 and 1982. Twenty-six patients who survived for more than 10 years were selected for this study. Fifteen randomly selected patients (group 1) without outflow tract patch were compared with 11 patients (group 2) where a transannular right ventricular outflow patch had been used. Right and left ventricular volumes were assessed using combined first-pass and equilibrium radionuclide ventriculography. After administration of 25 mCi of 99mTc-pertechnetate, data were acquired with a gamma camera with a large viewing field and the patient at rest and during exercise. The patients in group 1 were able to manage a workload of 65 +/- 24 W on the bicycle ergometer while the patients in group 2 could only reach a mean maximum of 34 +/- 12 W. Right ventricular end-diastolic volume (RV-EDV) at rest was 198 +/- 67 ml in group 1 and 224 +/- 69 ml in group 2. During exercise, RV-EDV was increased to 218 +/- 75 ml in group 1 (P less than 0.01) and to 246 +/- 79 ml in group 2. Right ventricular end-systolic volumes did not change significantly during exercise. In group 1, the left ventricular (LV) volumes were comparable to the normal; in group 2, LV-EDV was diminished at rest and during the stress test.(ABSTRACT TRUNCATED AT 250 WORDS)

A computer assisted comparison of 99Tcm-methylene-diphosphonate and 99Tcm-pyrophosphate bone imaging.

A total of 350 patient studies were carried out using clinical trials' batches of the Technetium (MDP) agent for bone scintigraphy (The Radiochemical Centre), and a commercially available Technetium pyrophosphate agent (CIS). The bone seeking properties of 99Tcm Sn-methylene-diphosphonate (MDP) and 99Tcm Sn-pyrophosphate (PYP) were evaluated by their comparative uptake in compact bone, cancellous bone and soft tissue using a region-of-interest technique. From these data uptake ratios were computed in order to correlate the values with (a) the amount of 99Tcm-MDP injected, (b) the time after injection and (c) the age of patients examined. All ratios derived with 99Tcm-MDP were superior to those using 99Tcm-PYP and were not dependent on the amount of 99Tcm-MDP injected. Uptake ratios determined for 99Tcm-MDP (1.5 h to 2.5 h after injection) were found to be higher than those for 99Tcm-PYP 2.5 to 3.5 h after injection. Soft tissue accumulation of 99Tcm-MDP, visible on scintiphotos, occurred only in 26% of cases but with 99Tcm-PYP, in 75% out of all cases studied. A decrease of cancellous bone/compact bone ratios with increasing age of the patients was found with both radiopharmaceuticals. This is most probably correlated with a diminished mass and/or surface of the cancellous bone in the elderly patient.

Correlation of histology, cytogenetics and proliferation fraction (Ki-67 and PCNA) quantitated by image analysis in meningiomas.

Sixty meningiomas were classified histologically according to the WHO criteria and analyzed cytogenetically. The Ki-67 and PCNA proliferation fractions (PRFs) were assessed by immunhistochemistry. The staining results were quantified by TV-image analysis (Miamed, Leica, Germany). Within meningiomas of WHO-grade II/III and those with complete or partial deletion of # 1p, we found a significantly higher mean and maximal Ki-67 PRFs than in those of WHO-grade I and those with all other karyotypes. This was not the case for PCNA PRFs. No differences in PRFs were detectable between histological subtypes. Although these results were obtained after measurement of five high power fields (HPFs) only, the heterogeneity of PRF distribution within the tumors was high. Even after the measurement of 100 HPFs, the 95% confidence intervals were in a range of 18% to 34.3% PRF. This finding seems to be responsible for the moderate interobserver reproducibility of image analytical determination of PRF (r = 0.74). Nevertheless, there was a good correlation between subjective and objective image analytical assessment of PRF (r = 0.83). The significance of the maximum Ki-67 PRF per specimen implies the possibility of selecting those areas which show the highest fraction of positively stained nuclei for measurement, avoiding the problem of intraslide heterogeneity. Thus the time needed for image analytical quantification may be reduced.

[Modern nuclear medical diagnosis as applied pathophysiology. Basis and outlook]. / Moderne nuklearmedizinische Diagnostik als angewandte Pathophysiologie. Basis und Ausblick.

In their capacity as "image-assisted functional diagnostics", methods of nuclear medicine link morphological patterns of radiology with clinical presentation. Based on pathophysiology they supply an insight into both global and regional parameters, present as basal values or as reserves. Both, single photon emission computed tomography (SPECT) or highly defined positron ECT (PET), enabled computer-assisted topographical overlay and thus an exact comparative evaluation of regional function versus morphology. In addition, PET gives access to a true physiological, absolute quantification employing process specific, carrier-free substrates. Novel tracers (markers of metabolism or perfusion, receptors or transmitter substances, monoclonal antibodies), an intraluminal transport model and the concept of buffer or working reserves aim at conducting early diagnosis, determination of disease severity and parameters that are relevant for therapy, on a level that is pathophysiologically oriented.

[The role of cerebral serial scintigraphy within the noninvasive diagnosis of cerebral diseases (author's transl)]. / Die Stellung der zerebralen Serienszintigraphie in der nicht-invasiven Diagnostik von Hirnerkrankungen.

Based on findings obtained from 442 patients with various cerebral diseases by comparative evaluation of cerebral serial scintigraphy (cSS) and cranial axial compouted transmission tomography (T-CAT), a scheme is introduced which illustrates reasonable employment of cSS in combination with T-CAT in patients presumed to have (a) "intracranial tumor", (b) "cerebrovascular disease" or (c) "unspecific symptoms". Concerning group (a), T-CAT should primarily be employed; as to groups (b) and (c), cSS is recommended to be the first study.

[The multimodal integration, correlation and fusion of morphology and function: the methods and initial clinical applications]. / Multimodale Integration, Korrelation und Fusion von Morphologie und Funktion: Methodik und erste klinische Anwendungen.

Besides the pure visual diagnosis of morphology in comparison with function, digital multimodal image analysis is steadily gaining in importance. Digital image processing is used in integration, correlation and fusion of topographically identical image data. After defining these terms and describing the acquisition techniques and influence parameters, this article reviews the methods of multimodal image processing, with emphasis on correlation methods. It also gives a short description of special methods in nuclear medicine. The clinical part briefly reviews the clinical use as well as the progress achieved and the benefits expected for diagnostic applications.

[Single photon emission computed tomography (SPECT). Principles, results, outlook]. / Die Single-Photon-Emissions-Computertomographie (SPECT). Prinzipien, Ergebnisse, Ausblick.

Methods, instrumentation, performance data, clinical use and results of SPECT are presented. Since SPECT is yielding functional tomograms, morphological data are not the major concern with this method. Essentially 99mTc labeled radiopharmaceuticals, 201Tl chloride or 133Xe gas are in current use. SPECT may be considered as a supplement to ultrasound in detecting space-occupying lesions of the liver (combined accuracy 95%). Cranial SPECT already allows quantification of regional cerebral blood flow following inhalation of 133Xe gas. The sensitivity of myocardial SPECT with 201Tl (three-dimensional reconstruction) at rest in patients with severe coronary artery disease was higher than 90%. To further develop SPECT as a functionally oriented supplementary method to other radiodiagnostic procedures, further improvements are required as to performance, reconstruction algorithms and radiopharmaceuticals.

[Radionuclide angiography (RNA) with 99mTc-DTPA to follow palliative embolization of renal cell carcinoma (author's transl)]. / Erfolgsbeurteilung der palliativen transfemoralen Nierentumorembolisation durch die Radionuklidangiographie (RNA) mit 99mTc-DTPA.

In 14 patients with renal cell carcinoma, not to be treated by nephrectomy, radionuclide angiography with 99mTc-DTPA (RNA) was employed before and after palliative tumor embolization. If RNA revealed remaining perfusion of the tumor, functional scintigraphy with 131J-hippurate was performed to detect and quantify residual function. Up to 16 months after embolization, 7 patients (50%) revealed neither residual perfusion nor function. In 5 patients (36%) remaining perfusion without functioning renal parenchyma and in 2 patients (14%) residual perfusion with additional function were found. In 4 cases (28%) a nuclear "tumor-halo" was imaged, describing a stripe of high radioactivity caused by capsular arteries surrounding the avascular tumor. RNA has proven to be a suitable non-invasive procedure for to blow-up of embolized renal cell carcinomas.

[Regional ejection fractions to determine left ventricular function. Comparison of first-radionuclide-pass and equilibrium-radionuclide-ventriculography with the results of cineventriculography]. / Die regionalen Auswurffraktionen zur Beurteilung der linksventrikulären Funktion. Ein Vergleich von Erster-Radionuklid-Passage und Aquilibrium-Radionuklid-Ventrikulographie mit den Ergebnissen der Kineventrikulographie.

An analysis of regional left ventricular pump function by regional ejection fractions (rAF) may be done employing First Pass techniques or Equilibrium Radionuclide Ventriculography (MUGA). The ventricle was intersected orthogonally into 5 divisions. This technique was applied to 15 hearts with regular wall motion and to 26 hearts with wall motion abnormalities. The discrimination for wall motion abnormalities of the anterior wall by MUGA was better than using steps of asynergy (normo-, hypo-, dys- and asynergy). With rAF, decrease of regional pump function could be detected (10% of the investigated hearts) even when there was a regular global ejection fraction. Due to the different projection angles for First Pass and MUGA (app. 70 degrees difference), correlation coefficients for anatomically similar divisions of the left ventricle, assessed with both techniques (n = 41) were rather low with the exception of the section belonging to the apex. Assessing the wall motion of the posterior wall, with MUGA isolated wall motion abnormalities could be detected only in 2 out of 6 cases. With First Pass, wall motion abnormalities could be detected in all cases. Therefore, to determine motion and function of the posterior wall, First Pass or even better First Pass and MUGA should be employed since the latter case, the ventricle may be evaluated from two projections in one examination only.

[133Xe-DSPECT (Dynamic Single Photon Emission CT). Results of a new noninvasive method for measuring regional cerebral blood flow (rCBF). Comparison with cranial angiography and transmission CT]. / 133Xe-DSPECT (Dynamische Single Photon Emissions CT). Ergebnisse einer neuen nicht-invasiven Methode zur Messung der regionalen Hirndurchblutung (rCBF). Ein Vergleich mit kranialer Angiographie und Transmissions-CT.

133Xenon-DSPECT provides measurement of regional cerebral blood flow (rCBF in ml/100 g/min) during and after inhalation of 133Xe gas. The result is displayed as a flow map of three transaxial slices. ROI divide a slice into 12 areas (SA) computing flow values (FSA). The results in 36 patients with cranial vascular disease are presented in comparison to 12 "normals". In all patients, FSA in the diseased hemisphere were found to be below the standard range of normals. Related to number of SA, this was true in completed stroke (bilateral) in 55% or (unilateral) in 14%, in PRIND in 5% of SA and in TIA in 7%. The absolute flow values did not decrease with the severeness of the disease, presumably depending on patient's age. There were more (p less than 0,005) SA found with decreased rCBF (21%) than areas with low density in T-CT (10%). Since unilateral cerebrovascular findings presented also bilateral reduced FSA, the validity of the method lies in the calculation of flow values, which significantly adds to the results of imaging.

[201Thalium scintimetry of the heart as a new method for functional assessment in coronary heart disease (author's transl)]. / Die 201-Thallium-Szintimetrie des Herzens als neues Verfahren zur funktionellen Differenzierung der koronaren Herzkrankheit

201Tl scintimetry of the heart was used for a statistical comparison between normal people (10 individuals) and those with acute anterior wall infarcts (5 patients), anterior wall hypokinesia (5 patients) and dyskinesia (8 patients). Numerical results were obtained by a computer and depended on the relative 201tl storage in the left ventricular myocardium (64 mm2 area) related to mediastinal background uptake. It was found that maximal myocardial uptake, compared with mediastinal activity (about 290%) did not differ between normals and patients with coronary heart disease. Aneurysms of the anterior ventricular wall showed a reduction (with the ventricle perpendicular to the collimator) of 45.8%; in hypokinesia and acute myocardial infarcts, it was 64.2% and 64.6% respectively (normal 82.6%). 201Tl uptake in aneurysms (42.4%) approached background activity (36%) if a projection parallel to the collimator was used. 201Tl scintimetry provides a means of defining functional ability of the myocardium (depdending on myocardial perfusion and mass). Aneurysms and hypokinetic portions of the myocardium can be differentiated statistically from normal 201Tl uptake.