Single-photon Emission Computed Tomography Interpretation Research Articles

Machine learning-based diagnosis and risk classification of coronary artery disease using myocardial perfusion imaging SPECT: A radiomics study

This study aimed to investigate the diagnostic performance of machine learning-based radiomics analysis to diagnose coronary artery disease status and risk from rest/stress Myocardial Perfusion Imaging (MPI) single-photon emission computed tomography (SPECT). A total of 395 patients suspicious of coronary artery disease who underwent 2-day stress-rest protocol MPI SPECT were enrolled in this study. The left ventricle myocardium, excluding the cardiac cavity, was manually delineated on rest and stress images to define a volume of interest. Added to clinical features (age, sex, family history, diabetes status, smoking, and ejection fraction), a total of 118 radiomics features, were extracted from rest and stress MPI SPECT images to establish different feature sets, including Rest-, Stress-, Delta-, and Combined-radiomics (all together) feature sets. The data were randomly divided into 80% and 20% subsets for training and testing, respectively. The performance of classifiers built from combinations of three feature selections, and nine machine learning algorithms was evaluated for two different diagnostic tasks, including 1) normal/abnormal (no CAD vs. CAD) classification, and 2) low-risk/high-risk CAD classification. Different metrics, including the area under the ROC curve (AUC), accuracy (ACC), sensitivity (SEN), and specificity (SPE), were reported for models’ evaluation. Overall, models built on the Stress feature set (compared to other feature sets), and models to diagnose the second task (compared to task 1 models) revealed better performance. The Stress-mRMR-KNN (feature set-feature selection-classifier) reached the highest performance for task 1 with AUC, ACC, SEN, and SPE equal to 0.61, 0.63, 0.64, and 0.6, respectively. The Stress-Boruta-GB model achieved the highest performance for task 2 with AUC, ACC, SEN, and SPE of 0.79, 0.76, 0.75, and 0.76, respectively. Diabetes status from the clinical feature family, and dependence count non-uniformity normalized, from the NGLDM family, which is representative of non-uniformity in the region of interest were the most frequently selected features from stress feature set for CAD risk classification. This study revealed promising results for CAD risk classification using machine learning models built on MPI SPECT radiomics. The proposed models are helpful to alleviate the labor-intensive MPI SPECT interpretation process regarding CAD status and can potentially expedite the diagnostic process.

Scintigraphie pulmonaire pour suspicion d’embolie pulmonaire aiguë : état des lieux des pratiques en France en 2014

AimThe aim of this study was to assess lung scintigraphy practices in France for the diagnosis of acute pulmonary embolism, especially regarding the proportion of centers using single photon emission computed tomography (SPECT) rather than planar ventilation/perfusion (V/Q) imaging. Materials and methodsAn online survey composed of simple multiple-choice questions was distributed to the 210 french nuclear medicine departments in April and May 2014. The survey covered image acquisition, interpretation criteria for SPECT and planar images, and use of pseudoplanar images and radiopharmaceuticals. Departments were initially solicited by 2 sets of e-mails. They were subsequently contacted by phone. A single response per department was consolidated. ResultsTwo hundred nine responses were collected (participation rate: 99.5%). Sixty-seven percent of french centers indicated use of V/Q SPECT in routine practice. The first intention acquisition protocol was SPECT/CT in 34%, SPECT in 26% and V/Q planar in 34%. The most commonly used criteria for SPECT interpretation were those of the EANM (63%). Criteria used for planar interpretation were heterogeneous (EANM criteria, 39%; no standardized criteria, 28%; PIOPED, 23%). Eighty-three percent of centers used 99mTc aerosol and 17% 81mKr. ConclusionThis survey shows that SPECT has largely replaced planar imaging for PE diagnosis with lung scintigraphy. Acquisition protocols and interpretation criteria are inconsistent (especially for planar imaging).

Semiquantitative slab view display for visual evaluation of 123I-FP-CIT SPECT.

Dopamine transporter single-photon emission computed tomography (SPECT) with I-FP-CIT is used widely in the diagnosis of clinically uncertain parkinsonian syndromes. In terms of the evaluation of FP-CIT SPECT, some practice guidelines state that visual interpretation alone is generally sufficient in clinical patient care, whereas other guidelines consider semiquantitative analysis of striatal dopamine transporter availability mandatory. This discrepancy might be because of a relative lack of widely available display tools for FP-CIT SPECT. In this study, we evaluate a semiquantitative slab view display optimized for visual evaluation of FP-CIT SPECT that might resolve the discrepancy. The reconstructed FP-CIT SPECT image was stereotactically normalized and scaled voxel by voxel to the mean uptake in the entire brain without striata. From the resulting distribution volume ratio image, a 12-mm-thick transversal slice (slab) through the striata was displayed with a standard colour table with predefined fixed thresholds on the distribution volume ratio. Visual scoring of the semiquantitative slab view was performed twice by four independent readers in 235 unselected patients. The specific binding ratio in the caudate and putamen was computed by fully automated semiquantitative analysis with predefined standard regions of interest in template space. Intrarater and inter-rater agreement of binary visual categorization as 'normal' or 'reduced' was excellent (mean Cohen's κ=0.88 and 0.83, respectively). The area under the receiver-operator characteristic curve of the specific putamen-binding ratio for differentiation between visually normal and visually reduced (majority read) was 0.96. Visual interpretation of FP-CIT SPECT on the basis of the semiquantitative slab view display provides excellent stability within and between readers as well as very high agreement with semiquantitative analysis. This suggests that the slab view display enables reliable visual interpretation of FP-CIT SPECT in clinical routine patient care.

The role of myocardial scintigraphy in the assessment of coronary artery disease

Single photon emission computed tomography (SPECT) for the assessment of myocardial perfusion was introduced in the early 1970s, following pioneer studies of Gould et al. It has rapidly become one of the most used noninvasive technique for the assessment of myocardial ischemia. Thanks to the current technetium based tracers that allow electrocardiogram gated synchronization, it is possible to assess the regional ventricular systolic function and the evaluation of myocardial perfusion as well. In the last twenty years, beyond its diagnostic role, myocardial SPECT has become also a prognostic technique. Indeed, it has acquired a role for the short-term prediction of major coronary events in a large cohort with known or suspected coronary artery disease (CAD). The aim of this review is to give an update of the correct use and interpretation of myocardial SPECT in patients with known or suspected CAD and without left ventricular dysfunction.

Additional value of combining low-dose computed tomography to V/Q SPECT on a hybrid SPECT-CT camera for pulmonary embolism diagnosis.

The aim of the study was to assess the potential interest of combining a low-dose computed tomography (ldCT) to ventilation/perfusion (V/Q) single-photon emission computed tomography (SPECT) for the diagnosis of pulmonary embolism (PE). We addressed three main questions: Could ldCT be used in substitution to ventilation SPECT? Could ldCT improve the diagnostic performance of V/Q SPECT? Could ldCT provide alternative diagnoses to PE? A total of 393 patients previously analysed in a management outcome study that aimed at assessing the safety of V/Q SPECT for PE diagnosis were assessed. All patients underwent an ldCT under the same SPECT-computed tomography camera, which was not used at the time of initial interpretation. Three retrospective analyses were performed: Q SPECT combined with ldCT, V/Q SPECT combined with ldCT and ldCT only. On the basis of initial V/Q SPECT interpretation, 110 (28%) patients were positive and 283 (72%) were negative for PE.With Q SPECT-ldCT, 139 (35%) patients were positive and 254 (65%) were negative, with 55 (19%) discrepancies when compared with V/Q SPECT. Of the 283 patients with negative V/Q SPECT, 42 were positive with V/Q SPECT-ldCT, and among the 110 patients with positive V/Q SPECT 13 were negative with V/Q SPECT-ldCT. On using V/Q SPECT-ldCT, 97 (25%) patients were positive and 296 (75%) were negative, with 13 (3%) discrepancies when compared with V/Q SPECT (all had had a positive V/Q SPECT but a negative V/Q SPECT-ldCT). Finally, 67 (24%) ldCT scans showed a potential alternative diagnosis to PE. For PE diagnosis with lung SPECT, the use of ldCT in substitution to ventilation SPECT is associated with a high risk of overdiagnosis. The diagnostic value of ldCT in addition to V/Q SPECT remains unclear. Further studies are needed to determine its potential role in PE diagnosis.

Quantification of the myocardial area at risk using coronary CT angiography and Voronoi algorithm-based myocardial segmentation

The purpose of this study was to estimate the myocardial area at risk (MAAR) using coronary computed tomography angiography (CTA) and Voronoi algorithm-based myocardial segmentation in comparison with single-photon emission computed tomography (SPECT). Thirty-four patients with coronary artery disease underwent 128-slice coronary CTA, stress/rest thallium-201 SPECT, and coronary angiography (CAG). CTA-based MAAR was defined as the sum of all CAG stenosis (>50%) related territories (the ratio of the left ventricular volume). Using automated quantification software (17-segment model, 5-point scale), SPECT-based MAAR was defined as the number of segments with a score above zero as compared to the total 17 segments by summed stress score (SSS), difference (SDS) score map, and comprehensive SPECT interpretation with either SSS or SDS best correlating CAG findings (SSS/SDS). Results were compared using Pearson's correlation coefficient. Forty-nine stenoses were observed in 102 major coronary territories. Mean value of CTA-based MAAR was 28.3 ± 14.0%. SSS-based, SDS-based, and SSS/SDS-based MAAR was 30.1 ± 6.1%, 20.1 ± 15.8%, and 26.8 ± 15.7%, respectively. CTA-based MAAR was significantly related to SPECT-based MAAR (r = 0.531 for SSS; r = 0.494 for SDS; r = 0.814 for SSS/SDS; P < 0.05 in each). CTA-based Voronoi algorithm myocardial segmentation reliably quantifies SPECT-based MAAR. • Voronoi algorithm allows for three-dimensional myocardial segmentation of coronary CT angiography • Stenosis-related CT myocardial territories correlate to SPECT based area at risk • CT angiography myocardial segmentation may assist in clinical decision-making.

Incremental diagnostic accuracy of hybrid SPECT/CT coronary angiography in a population with an intermediate to high pre-test likelihood of coronary artery disease

Hybrid myocardial perfusion imaging with single photon emission computed tomography (SPECT) and CT coronary angiography (CCTA) has the potential to play a major role in patients with non-conclusive SPECT or CCTA results. We evaluated the performance of hybrid SPECT/CCTA vs. standalone SPECT and CCTA for the diagnosis of significant coronary artery disease (CAD) in patients with an intermediate to high pre-test likelihood of CAD. In total, 98 patients (mean age 62.5 ± 10.1 years, 68.4% male) with stable anginal complaints and a median pre-test likelihood of 87% (range 22-95%) were prospectively included in this study. Hybrid SPECT/CCTA was performed prior to conventional coronary angiography (CA) including fractional flow reserve (FFR) measurements. Hybrid analysis was performed by combined interpretation of SPECT and CCTA images. The sensitivity, specificity, positive (PPV), and negative (NPV) predictive values were calculated for standalone SPECT, CCTA, and hybrid SPECT/CCTA on per patient level, using an FFR <0.80 as a reference for significant CAD. Significant CAD was demonstrated in 56 patients (57.9%). Non-conclusive SPECT or CCTA results were found in 32 (32.7%) patients. SPECT had a sensitivity of 93%, specificity 79%, PPV 85%, and NPV 89%. CCTA had a sensitivity of 98%, specificity 62%, PPV 77%, and NPV 96%. Hybrid analysis of SPECT and CCTA improved the overall performance: sensitivity, specificity, PPV, and NPV for the presence of significant CAD to 96, 95, 96, and 95%, respectively. In > 40% of the patients with a high pre-test likelihood no significant CAD was demonstrated, emphasizing the value of accurate pre-treatment cardiovascular imaging. Hybrid SPECT/CCTA was able to accurately diagnose and exclude significant CAD surpassing standalone myocardial SPECT and CCTA, vs. a reference standard of FFR measurements.

Differential diagnostic value of single-photon emission computed tomography/spiral computed tomography with Tc-99m-methylene diphosphonate in patients with spinal lesions

The objective of this study was to compare the diagnostic value obtained using single-photon emission computed tomography (SPECT)/spiral computed tomography (CT) with Tc-99m methylene-diphosphonate with that obtained using SPECT alone in patients with spinal lesions. This was a retrospective study of 56 patients who underwent planar whole-body scintigraphy because of bone pain or osseous lesions that had been detected by other imaging techniques, or for the investigation of bone metastasis in patients with extraskeletal malignancies. Only patients who had hot spots detected in their spine and who had undergone single-photon emission computed tomography/computed tomography (SPECT/CT) imaging were included. One lesion from each patient was resected or biopsied for pathological diagnosis, and lesions for which a pathological diagnosis could be made were included in this study. Single-photon emission computed tomography (SPECT) and SPECT/CT images were independently interpreted by two experienced nuclear medicine physicians who had not been involved in the selection of data for the study. The physicians were aware of patients' sex, age, history of histologically confirmed extraskeletal malignancy, and whole-body scintigraphy results, but were unaware of the results of other investigations, such as X-ray, MRI, and laboratory tests. SPECT images were analyzed first, followed by SPECT/CT images. Each lesion was graded on a 4-point diagnostic scale (1, benign; 2, likely benign; 3, likely malignant; 4, malignant), and the inter-reviewer agreement and the agreement of the SPECT and SPECT/CT diagnoses with the pathology results were evaluated by κ scores. The pathology results revealed 39 malignant bone tumors and 17 benign lesions. In the malignant cases, 20 were bone metastases and 19 were malignant tumors of another histological type. The reviewers rated 67.9% of lesions as equivocal (grade 2-3) by SPECT, but only 19.6% as equivocal by SPECT/CT. The κ scores for inter-reviewer agreement were 0.467 for SPECT and 0.905 for SPECT/CT (both P<0.0001). The κ scores for the agreement of the interpretation of SPECT and SPECT/CT with the pathology results were 0.493 and 0.689, respectively (both P<0.0001). Compared with SPECT imaging, SPECT/spiral CT hybrid imaging significantly reduced the number of lesions judged to be equivocal. This reduction allowed for a definitive diagnosis to be made by imaging in the majority of patients.

Increased Pericardial Fat Volume Measured From Noncontrast CT Predicts Myocardial Ischemia by SPECT

We evaluated the association between pericardial fat and myocardial ischemia for risk stratification. Pericardial fat volume (PFV) and thoracic fat volume (TFV) measured from noncontrast computed tomography (CT) performed for calculating coronary calcium score (CCS) are associated with increased CCS and risk for major adverse cardiovascular events. From a cohort of 1,777 consecutive patients without previously known coronary artery disease (CAD) with noncontrast CT performed within 6 months of single photon emission computed tomography (SPECT), we compared 73 patients with ischemia by SPECT (cases) with 146 patients with normal SPECT (controls) matched by age, gender, CCS category, and symptoms and risk factors for CAD. TFV was automatically measured. Pericardial contours were manually defined within which fat voxels were automatically identified to compute PFV. Computer-assisted visual interpretation of SPECT was performed using standard 17-segment and 5-point score model; perfusion defect was quantified as summed stress score (SSS) and summed rest score (SRS). Ischemia was defined by: SSS - SRS ≥4. Independent relationships of PFV and TFV to ischemia were examined. Cases had higher mean PFV (99.1 ± 42.9 cm(3) vs. 80.1 ± 31.8 cm(3), p = 0.0003) and TFV (196.1 ± 82.7 cm(3) vs. 160.8 ± 72.1 cm(3), p = 0.001) and higher frequencies of PFV >125 cm(3) (22% vs. 8%, p = 0.004) and TFV >200 cm(3) (40% vs. 19%, p = 0.001) than controls. After adjustment for CCS, PFV and TFV remained the strongest predictors of ischemia (odds ratio [OR]: 2.91, 95% confidence interval [CI]: 1.53 to 5.52, p = 0.001 for each doubling of PFV; OR: 2.64, 95% CI: 1.48 to 4.72, p = 0.001 for TFV). Receiver operating characteristic analysis showed that prediction of ischemia, as indicated by receiver-operator characteristic area under the curve, improved significantly when PFV or TFV was added to CCS (0.75 vs. 0.68, p = 0.04 for both). Pericardial fat was significantly associated with myocardial ischemia in patients without known CAD and may help improve risk assessment.

Interobserver reproducibility of the interpretation of I-123 FP-CIT single-photon emission computed tomography

I-123 ioflupane (FP-CIT) single-photon emission computed tomography is a recognized tool in the diagnosis of Parkinsonian syndromes. In practice, data interpretation relies on visual and semiquantitative analyses. Good interobserver reproducibility is a prerequisite before claiming the robustness of a technique. This study aimed at evaluating interobserver reproducibility of this approach. Thirty nuclear medicine physicians participated in the study. Data included FP-CIT images and semiquantitative measurements of 12 cases, covering a wide spectrum of scintigraphic patterns and for which a 'true' clinical diagnosis based on long-term follow-up was available. Interobserver agreement was defined, for each case, as the highest percentage reached among the three proposed answers with complete agreement arbitrarily set at 80% or more. Variability in an individual observer's sensitivity to assess data as normal, equivocal or abnormal was scored using a three-point scale. Response rate was 99.7%. Among the three possible answers,'normal' accounted for 41.2% of the total, 'abnormal' for 49.8% and 'equivocal' for 8.1%. The mean interobserver agreement was 76% (range: 37-100%), with complete agreement being reached only in five cases. The interpretation proposed by most observers accorded to clinical diagnosis in 75% of the cases. Abnormalities of the central nervous system were encountered in all the cases with disagreement between the observer's interpretation and clinical diagnoses. An important variability in the observers' sensitivity was seen. In the particular setting of this preliminary study evaluating the reproducibility of FP-CIT single-photon emission computed tomography interpretation in a group of nuclear medicine physicians with various experiences, interobserver agreement was suboptimal. Collegial discussion and standardized interpretation criteria could contribute to an improved reproducibility.

Semiquantitative software SPECT analysis in aneurysmal subarachnoid hemorrhage-related vasospasm

Cerebral vasospasm is a major cause of morbidity and mortality among patients after subarachnoid hemorrhage (SAH) from ruptured intracranial aneurysms. Patients are often monitored using transcranial Doppler (TCD) ultrasound and single photon emission computed tomography (SPECT) techniques. Historically SPECT has been evaluated qualitatively, though quantitative analysis software is now used to evaluate other cerebral pathologies. Our aim was to evaluate the utility of semiquantitative SPECT using Hermes brain registration and analysis software (BRASS) relative to TCD ultrasound and qualitative SPECT interpretation within a cohort of patients, all with cerebral vasospasm as measured by digital subtraction angiography. Retrospective analysis of 32 nonconsecutive patients, admitted for aneurysmal SAH examining perfusion deficits in terms of anterior, middle, and posterior vascular distributions using both TCD ultrasonography and brain perfusion SPECT studies. McNemar analysis of accuracy between modalities showed a better overall performance trend for qualitative SPECT versus BRASS SPECT (Fisher exact = 0.99) and a statistically significant better performance of qualitative SPECT versus TCD in measuring anterior cerebral artery vasospasm (Fisher exact = 0.035). BRASS SPECT, however, performed better than qualitative SPECT in diagnosing posterior circulation vasospasm (Fisher exact = 0.180 vs. 0.358) and had greater specificity in determining anterior circulation vasospasm (71 vs. 57%). BRASS SPECT is a useful method for evaluating cerebral perfusion and needs further optimization, particularly as it pertains to establishing semiquantitative cerebral perfusion parameters. It can serve as an adjunct to traditional SPECT evaluation of SAH particularly in determining subtle changes in the perfusion of the anterior and posterior arterial distributions.

Impact of 111In-DTPA-octreotide SPECT/CT fusion images in the management of neuroendocrine tumours

Somatostatin receptor scintigraphy with [(111)In]-diethylene triamine pentaacetate acid (DTPA)-octreotide is an accurate method for detecting neuroendocrine tumours (NETs) but often does not provide clear anatomical localisation of lesions. The aim of this study was to assess the clinical usefulness of anatomical-functional image fusion. Fifty-four patients with known or suspected NET were included in the study. Planar and single-photon-emission computed tomography (SPECT) imaging was performed using a dual-head gamma camera equipped with an integrated X-ray transmission system, and the images were first interpreted alone by two nuclear medicine physicians and then compared with SPECT/CT fusion images together with a radiologist. The improvement provided by SPECT/CT in the interpretation of SPECT data alone and any modification in patient management were recorded. Fusion images improved SPECT interpretation in 23 cases, providing precise anatomical localisation of increased tracer uptake in 20 cases and disease exclusion in sites of physiological uptake in 5. In 10 patients, SPECT/CT allowed definition of the functional significance of lesions detected by diagnostic CT. SPECT/CT data modified clinical management in 14 cases by changing the diagnostic approach in 8 and the therapeutic modality in 6. Our study demonstrates that image fusion is clearly superior to SPECT alone, allowing precise localisation of lesions and reducing false-positive results.

Interobserver correlation in the interpretation of 99mTc-sestamibi SPECT in reperfused acute myocardial infarction

The correct interpretation of myocardial perfusion single photon emission computed tomography (SPECT) requires knowledge of the technique reproducibility. The objective was analyze the interobserver correlation of different experience in the interpretation of myocardial perfusion SPECT in patients following acute myocardial infarction (AMI) in order to improve the quality of our site. Sixty cases (56 +/- 11 years, 87 % men) with transmural AMI who had recently undergone successful thrombolysis were included. Resting perfusion with (99m)Tc-sestamibi was performed at one week post-AMI. Semiquantitative interpretation using 17 segment-model by 2 independent specialists and 5 observers, was performed blindly. Left ventricular ejection fraction (LVEF) was measured with isotopic ventriculography one month after AMI, with a mean of 38 %. Using independent and then agreed on perfusion analysis, average involved segments/patient was 9.3 +/- 4 and the sum of severity 25 +/- 13. Readings of other observers ranged from 7 +/- 3.7 to 9.4 +/- 3.9 and 16.7 +/- 9.7 to 24.6 +/- 13, respectively, consistent with the reading of the specialists of between 0.779-0.871 (kappa: 0.565-0.741). There was no significant difference when the number of segments were analyzed in 40 % of the cases and for intensity in 60 % of them in more experienced observers. Correlation with consensus reading for the number of segments ranged from 0.84 to 0.94 and for severity from 0.79 to 0.89. Identification of culprit arteries was acceptable, with r values between 0.612 and 0.683 and kappas between 0.629 and 0.656. Correlation of the number of involved segments and severity with LVEF performed one month after AMI was 0.73 and 0.74, respectively. There was good correlation in the interpretation of myocardial perfusion SPECT, with a significantly better fit in more experienced observers. This academic exercise was also helpful in improving our residents' skills in cardiology.

Unusual Extracardiac Findings Detected on Myocardial Perfusion Single Photon Emission Computed Tomography Studies With Tc-99m Sestamibi

The authors describe the incidence and various uptake patterns of Tc-99m sestamibi (MIBI) in the extracardiac area due to unusual causes on myocardial perfusion single photon emission computed tomography (SPECT) studies. Seven patients are presented in whom incidental extracardiac findings were observed during the interpretation of the raw data besides the routine evaluation of myocardial reconstructed SPECT slices. These 7 patients were detected out of 582 consecutive patients (1.2%) who had myocardial perfusion SPECT with Tc-99m MIBI. The findings on the raw data led to additional reconstruction of thoracic SPECT images and eventually detailed examination of the extracardiac area. Two of the patients underwent surgery because of incidental extracardiac findings (thymoma and multinodular goiter) on cardiac scintigraphy. Other causes of increased extracardiac activity were the intestine protruded through the left hemithorax, uptake in the pulmonary arterial wall, and pulmonary interstitial fibrosis due to sarcoidosis. The reasons for decreased Tc-99m MIBI accumulation in the extracardiac area in the 2 other patients were significantly dilated pulmonary arteries and hydatic cyst, which were not defined before to our knowledge. Familiarity with the normal biodistribution and variable uptake patterns in the raw images becomes necessary during the interpretation of myocardial SPECT in order not to miss very unusual incidental extracardiac uptake or information that could lead to alteration in patient management. Potential underlying mechanisms of extracardiac Tc-99m MIBI accumulation are discussed, and the literature about noncardiac Tc-99m MIBI findings detected on myocardial perfusion SPECT studies was reviewed.

Diagnostic impact of SPECT image display on assessment of obstructive coronary artery disease

Diagnostic assessment of myocardial perfusion impacts the management of patients with suspected coronary artery disease (CAD). Although various image displays are available for single photon emission computed tomography (SPECT) interpretation, the effects of display differences on SPECT interpretation remain undetermined. We studied 183 patients undergoing SPECT, including 131 consecutive patients referred for angiography and 52 at low CAD risk. Studies were visually interpreted by use of color and gray images, with readers blinded to the results of the other display. In accordance with established criteria, a summed stress score (SSS) of 4 or greater was considered abnormal. The prevalence of abnormal SPECT findings was higher with gray images than with color images (54% vs 48%, P < .001) based on a uniform criterion (SSS > or =4). However, color images yielded equivalent sensitivity (79% vs 82%, P = .7) and improved specificity for global (50% vs 33%, P = .02) and vessel-specific CAD involving the right coronary artery (P < .01) and left anterior descending artery (P < .05). When the criterion for gray images was adjusted upward (SSS > or =5) to reflect increased mean defect severity (SSS of 5.1 vs 4.4, P = .01), gray and color images provided equivalent sensitivity and specificity for global and vessel-specific CAD. SPECT interpretation can vary according to image display as a result of differences in perfusion defect severity. Adjustment of abnormality criteria for gray images to reflect minor increases in defect severity provides equivalent diagnostic performance of gray and color displays for CAD assessment.

Ictal Brain Hyperperfusion Contralateral to Seizure Onset: The SPECT Mirror Image

Ictal single-photon emission computed tomography (SPECT) may help localize the seizure-onset zone (SOZ) by detecting changes in regional cerebral blood flow induced by epileptic discharges. This imaging method also reveals hyperperfusions in areas of seizure propagation, including the hemisphere contralateral to the SOZ. We have studied the occurrence, the topography, and the clinical value of such contralateral ictal hyperperfusion areas (HPAs). We examined data from presurgical evaluations of 36 consecutive patients with pharmacoresistant partial epilepsy of various localizations. Ictal and interictal SPECT examinations were made with 99mTc-ECD, and the scans were processed for coregistration, normalization, subtraction, and merging with MRI images. Contralateral HPAs were observed in 72% of the patients: 50% of mesiotemporal epilepsy cases with hippocampal sclerosis, 85.7% of the other mesiotemporal epilepsies, 85.7% of neocortical lateral temporal epilepsies, and 87.5% of extratemporal epilepsies. Contralateral HPAs were usually symmetrical to the SOZ, forming a mirror image, observed in 57.1% of the patients. They could be slightly asymmetrical in mesiotemporal epilepsies, perhaps because of the particular anatomic pathways linking temporal lobes. In neocortical epilepsies, they were located in the cortex homotopic to the SOZ. We show that the symmetrical nature of the mirror image usually does not disturb SPECT interpretation. It can confirm the location of the SOZ (11 patients) and even occasionally improve the precision of its definition (nine patients) by restraining several potential SOZ-related HPAs to a single one or by permitting a restricted localization of the SOZ in a large HPA.

Does levodopa slow or hasten the rate of progression of Parkinson’s disease?

Levodopa therapy, as originally established by George Cotzias [2, 3], is the most powerful treatment for Parkinson's disease (PD). Levodopa's toxicity to neurons in vitro has raised concerns if it might hasten the progression of PD, although in vivo animal studies suggest it may be neuroprotective. To discuss the results of the ELLDOPA trial that was carried out to determine if levodopa therapy influences the rate of progression of Parkinson's disease (PD). ELLDOPA was a multicenter, parallel-group, double-blind, dosage-ranging, randomized, controlled clinical trial. Academic movement disorders clinics at 38 sites in the United States and Canada. Three hundred and sixty-one patients with early PD of less than 2 years' duration who did not require symptomatic therapy. Subjects were randomly assigned to one of four treatment groups: carbidopa/levodopa 12.5/50 mg t. i. d. (N=92), 25/100 mg t. i. d. (N=88), 50/200 mg t. i. d. (N=91), or matching placebo (N=90). The dosage was gradually escalated over 9 weeks and then maintained until Week 40, at which time active treatment was withdrawn over 3 days. After 2 weeks without active treatment (Week 42), a final assessment of PD severity was obtained. The prespecified primary clinical outcome was the change in the total Unified Parkinson's Disease Rating Scale (UPDRS) between baseline and Week 42, comparing the four treatment groups. The primary neuroimaging component of the study in a subgroup of 142 subjects was the percent change in striatal (123)iodine 2-beta-carboxymethoxy-3-beta-(4-iodophe nyl)tropane (beta-CIT) uptake between baseline and Week 40 visits. The neuroimaging substudy utilized single photon emission computed tomography (SPECT) of the dopamine transporter. All dosages of levodopa exerted clinical benefit compared to placebo on the UPDRS scores throughout the study, including 2 weeks after discontinuing levodopa. The UPDRS scores at Week 42 failed to reach the level encountered in the placebo group (change of 7.8+/-9.0, 1.9+/-6.0, 1.9+/-6.9, and -1.4+/-7.8, for placebo, 150 mg/day, 300 mg/ day, and 600 mg/day, respectively, p<0.0001). Nausea (p=0.001) and dyskinesias (p=0.0001) were more common in the levodopa groups, especially with the higher dosages. Freezing appeared around the same time, but was more common in the placebo (14 %) and 150 mg/day group (10 %). The percent decline of beta-CIT uptake in the striatum was significantly more pronounced in the levodopa groups than the placebo group (-7.2%, -4%, -6%, and -1.4% in 600 mg/day, 300 mg/day, 150 mg/day, and placebo, respectively; p=0.035). The clinical outcomes not only indicate that levodopa is effective in a dose-dependent manner in overcoming the signs and symptoms of PD, they also support the concept that the drug does not hasten the disease progression, but rather may slow down the rate of the disease. The clinical study failed to demonstrate any evidence of levodopa worsening early PD. However, the beta-CIT SPECT substudy indicates the opposite effect, namely that levodopa causes a more rapid decline in the integrity of the dopamine transporter located in the nigrostriatal nerve terminals in the striatum. These contradictory findings warrant further investigation into the effect of levodopa on PD. OTHER OBSERVATIONS: The ELLDOPA study was the first levodopa dose-response study ever conducted. It showed that dose is a factor in the cause of producing motor complications of dyskinesias and wearing-off, and that these can develop as early as 5 to 6 months. On the other hand, freezing of gait could be delayed or its occurrence reduced by high dosage levodopa, compared to placebo or low-dose levodopa. Withdrawal of levodopa over a 3-day step-down can be safely carried out without inducing the neuroleptic-like syndrome. The UPDRS was shown to be a reliable linear marker for disease progression. The ELLDOPA study also called into question the interpretation of beta-CIT SPECT in the presence of dopaminergic agents. Neuroimaging in ELLDOPA also showed that some people diagnosed with early PD do not have a dopaminergic deficit, calling into question how difficult the correct diagnosis may be in people with early symptoms of PD.

Prognostic validation of a 17-segment score derived from a 20-segment score for myocardial perfusion SPECT interpretation

Background Recently, a 17-segment model of the left ventricle has been recommended as an optimally weighted approach for interpreting myocardial perfusion single photon emission computed tomography (SPECT). Methods to convert databases from previous 20- to new 17-segment data and criteria for abnormality for the 17-segment scores are needed. Methods and results Initially, for derivation of the conversion algorithm, 65 patients were studied (algorithm population) (pilot group, n = 28; validation group, n = 37). Three conversion algorithms were derived: algorithm 1, which used mid, distal, and apical scores; algorithm 2, which used distal and apical scores alone; and algorithm 3, which used maximal scores of the distal septal, lateral, and apical segments in the 20-segment model for 3 corresponding segments of the 17-segment model. The prognosis population comprised 16,020 consecutive patients (mean age, 65 ± 12 years; 41% women) who had exercise or vasodilator stress technetium 99m sestamibi myocardial perfusion SPECT and were followed up for 2.1 ± 0.8 years. In this population, 17-segment scores were derived from 20-segment scores by use of algorithm 2, which demonstrated the best agreement with expert 17-segment reading in the algorithm population. The prognostic value of the 20- and 17-segment scores was compared by converting the respective summed scores into percent myocardium abnormal. Conversion algorithm 2 was found to be highly concordant with expert visual analysis by the 17-segment model ( r = 0.982; κ = 0.866) in the algorithm population. In the prognosis population, 456 cardiac deaths occurred during follow-up. When the conversion algorithm was applied, extent and severity of perfusion defects were nearly identical by 20- and derived 17-segment scores. The receiver operating characteristic curve areas by 20- and 17-segment perfusion scores were identical for predicting cardiac death (both 0.77 ± 0.02, P = not significant). The optimal prognostic cutoff value for either 20- or derived 17-segment models was confirmed to be 5% myocardium abnormal, corresponding to a summed stress score greater than 3. Of note, the 17-segment model demonstrated a trend toward fewer mildly abnormal scans and more normal and severely abnormal scans. Conclusion An algorithm for conversion of 20-segment perfusion scores to 17-segment scores has been developed that is highly concordant with expert visual analysis by the 17-segment model and provides nearly identical prognostic information. This conversion model may provide a mechanism for comparison of studies analyzed by the 17-segment system with previous studies analyzed by the 20-segment approach.

Functional-anatomical image fusion in neuroendocrine tumors.

Nuclear medicine provides physiologic and functional data for normal and pathologic organs but often the clear definition of the sites of radiotracers' uptake are difficult. Radiological methods are able to identify structural changes in a detailed way, but do not give precise information on function of organs or pathologic lesions. The registration and fusion of nuclear medicine studies with structural information obtained by radiological exams allows the precise correlation of functional and anatomical data. Software-based fusion of independently performed nuclear medicine and morphologic studies is uncertain of success and the alignment procedures are labor intensive. Recently, a new imaging device combining a dual-head, variable angle gamma camera with a low-dose x-ray tube has been introduced; the acquired single-photon emission computed tomography (SPECT) and x-ray computed tomography (CT) images are coregistered by means of the hardware in the same session. This new technology can be particularly useful when applied to scintigraphic procedures in neuroendocrine tumors. In-111 pentetreotide and radiolabeled MIBG play an important role in the study of patients with these tumors; the addition of anatomical maps provides a precise localization of SPECT findings and allows the exclusion of disease in sites of physiologic tracer uptake. SPECT/CT fused images are able to provide additional information that improves the accuracy of SPECT interpretation and leads to changes in therapeutic options, so enhancing the clinical role of nuclear medicine in evaluating patients with neuroendocrine tumors.

Spectral analysis: principle and clinical applications.

This review article describes the principle and clinical applications of spectral analysis. Spectral analysis provides a spectrum of the kinetic components which are involved in the regional uptake and partitioning of tracer from the blood to the tissue. This technique allows the tissue impulse response function to be derived with minimal modeling assumptions. Spectral analysis makes no a priori assumptions regarding the number of compartments or components required to describe the time course of tracer in the tissue. Spectral analysis can be applied to various dynamic data acquired by planar scintigraphy, single photon emission computed tomography (SPECT) or positron emission tomography (PET) as an alternative approach to compartment analysis. This analysis appears to be clinically useful, because it not only facilitates the interpretation of dynamic scintigraphic, SPECT or PET data, but also simplifies comparisons between regions and between subjects.