S. Pavlovic

The Utility of 18F-FDG PET/CT for Diagnosis and Adjustment of Therapy in Patients with Active Chronic Sarcoidosis

The purpose of this study was to assess the utility of 18F-FDG PET/CT for detection of inflammation in granulomatous sites and management of patients with chronic sarcoidosis. The 3 specific aims were to assess differences between 18F-FDG PET/CT and multidetector CT (MDCT) findings, to compare 18F-FDG PET/CT results with serum levels of angiotensin-converting enzyme (ACE), and to determine whether 18F-FDG PET/CT findings are associated with the decision to change therapy. Methods: We studied 90 sarcoidosis patients (mean age ± SD, 47 ± 12 y; 32 men and 58 women) with persistent symptoms who were referred for 18F-FDG PET/CT evaluation to assess the extent of inflammation. They also underwent MDCT and measurement of serum ACE level. After the follow-up (12 ± 5 mo after 18F-FDG PET/CT), the clinical status and changes in therapy were analyzed. Results: 18F-FDG PET/CT detected inflammation in 74 patients (82%) (maximum standardized uptake value, 8.1 ± 3.9). MDCT was positive for sarcoidosis in 6 additional patients (80, 89%). The difference between the 2 methods was not significant (P = 0.238, McNemar test), and their agreement was fair (κ = 0.198). Although ACE levels were significantly higher in patients with positive than negative 18F-FDG PET/CT results (P = 0.002, Mann–Whitney test), 38 patients (51%) with positive 18F-FDG PET/CT results had normal ACE levels. The therapy was initiated or changed in 73 out of 90 patients (81%). Both univariate and multivariate logistic regression analyses indicated that positive 18F-FDG PET/CT results were significantly (P < 0.001) associated with changes in therapy, with no contribution from age, sex, ACE level, CT results, or previous therapy. Conclusion: Our results indicate that 18F-FDG PET/CT is a useful adjunct to other diagnostic methods for detecting active inflammatory sites in chronic sarcoidosis patients with persistent symptoms, especially those with normal ACE levels. 18F-FDG PET/CT proved advantageous for determining the spread of active disease throughout the body and influenced the decision to adjust the therapy.

Responsiveness of FDG PET/CT to treatment of patients with active chronic sarcoidosis.

Purpose This study aimed to compare baseline to follow-up 18F-FDG PET/CT findings after treatment for active chronic sarcoidosis and to correlate changes on 18F-FDG PET/CT with changes in clinical status. Patients and Methods The sample included 66 patients with chronic sarcoidosis and evidence of active inflammation on baseline 18F-FDG PET/CT for which they received therapy. Of these 66 patients, 30 returned for the follow-up 18F-FDG PET/CT after 12 (5) months to evaluate response to treatment. They were also asked to indicate changes in clinical status. Baseline characteristics of patients who did and did not return for the follow-up were compared to assess selection bias. Results SUVmax was significantly decreased at the follow-up compared with baseline 18F-FDG PET/CT (8.46 [3.52] vs 4.90 [0.96]; P = 0.006), primarily in the mediastinum. Inflammatory activity appeared absent in 9 patients, decreased in 12 patients, and increased in 9 patients, with the corresponding changes in SUVmax of −80%, −41%, and +54%, respectively. The changes on 18F-FDG PET/CT were in agreement with self-perceived changes in clinical symptoms (P = 0.019). The angiotensin-converting enzyme at the follow-up was not significantly different from baseline (49.80 [19.25] vs 46.35 [25.58], P = 0.522). There was no difference in baseline characteristics of patients who did and did not return for the follow-up. Conclusions 18F-FDG PET/CT is able to detect clinically meaningful changes in magnitude and extent of inflammatory activity in patients receiving treatment for active chronic sarcoidosis. Thus, 18F-FDG PET/CT is a valuable adjunct to clinical evaluation for monitoring the response to treatment in these patients.

One-year follow-up of myocardial perfusion and function evaluated by gated Spect Mibi in patients with earlier myocardial infarction and chronic total occlusion

ObjectiveOptimal treatment for chronic total occlusion (CTO) in the infarct-related coronary artery is not clear. Our aim was to assess myocardial perfusion, left ventricular ejection fraction (EF), and left ventricular size using gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging with 99mTc-methoxy-isobutyl-isonitrile in patients with CTO before and 1 year after recanalization. MethodsThirty patients with earlier myocardial infarction and at least one CTO underwent percutaneous coronary intervention (PCI) as well as nitrate-enhanced gated SPECT myocardial perfusion and dobutamine stress echocardiography before and 11±1 months after recanalization. They were divided into three groups based on the outcome of the follow-up angiography: (i) successful recanalization with no evidence of in-stent restenosis (n=13); (ii) successful recanalization with in-stent restenosis (n=7) and (iii) unsuccessful recanalization (n=10). ResultsOverall success of recanalization for CTO was 74%. In group 1, myocardial viability was preserved in 11 of 13 (85%) patients at baseline. Gated SPECT at 1 year showed a significant decrease in perfusion abnormalities (29±12 to 23±14%, P<0.05) and left ventricular end-diastolic volume (EDV) (168±47 to 151±47 ml, P<0.05). Improvement in EF (51±11 to 54±13%, P>0.05) and reduction in left ventricular end-systolic volume (ESV) (84±37 to 77±40 ml, P>0.05) did not reach the level of significance. Myocardial viability was preserved in only two of seven patients (28%) in group 2. Neither mean perfusion abnormalities (37±24 to 35±22%, P>0.05) nor global left ventricular parameters (EF 41±15 vs. 42±19%, EDV 298±33 vs. 299±57 ml, ESV 197±12 vs. 195±32 ml; P>0.05) changed at the follow-up. In group 3, myocardial viability was preserved in seven of 10 patients (70%) at baseline, but no significant changes in perfusion (40±18 vs. 41±19%, P>0.05) and left ventricular function (EF 42±17 vs. 44±14%, EDV 228±101 vs. 227±81 ml, ESV 143±87 vs. 146±8ml; P>0.05) were seen at the follow-up. ConclusionMyocardial perfusion and EDV may significantly improve 1 year after PCI provided recanalization of CTO was successful. Our preliminary findings suggest that successful recanalization of CTO may have favorable outcome on left ventricular perfusion and function, particularly in patients with viable myocardium before PCI. The gated SPECT myocardial perfusion imaging with 99mTc-methoxy-isobutyl-isonitrile may be useful for monitoring long-term functional outcome of PCI in patients with CTO.

Comparative utility of gated myocardial perfusion imaging and transthoracic coronary flow reserve for the assessment of coronary artery disease in patients with left bundle branch block.

ObjectivesTo compare the diagnostic utility of gated single-photon emission computed tomography (SPECT) methoxy isobutyl isonitrile (MIBI) myocardial perfusion imaging and transthoracic Doppler echocardiography (TTDE) coronary flow reserve (CFR) to coronary angiography for detecting coronary artery disease (CAD) in patients with left bundle branch block (LBBB). MethodForty-three patients with complete LBBB and an intermediate pretest probability for CAD underwent dipyridamole stress TTDE and gated SPECT MIBI during the same session and coronary angiography within a month. The parameters of myocardial perfusion (summed stress score, summed difference scores) regional wall function (wall motion score, wall thickening score) and ejection fraction were derived using the 17-segment model and 4D-MSPECT software. TTDE variables included peak flow velocity at rest and during hyperemia in left anterior descending artery (LAD), based on which CFR was calculated (normal>2). ResultsPerfusion ischemic scores were significantly higher in group 1 with angiographic evidence of greater than 50% LAD stenosis compared with group 2 with less than 50% LAD stenosis (summed stress score 12.4±5.5 vs. 8.3±3.5, P<0.05, summed difference score 3.7±1.2 vs. 1.1±0.3, P<0.01, respectively). Left ventricular regional wall function and ejection fraction were not different between the two groups. CFR was significantly lower in group 1 than in group 2 (1.65±0.21 vs. 2.31±0.28, P<0.001). Gated SPECT MIBI and CFR had similar sensitivity (88 vs. 88%), specificity (80 vs. 84%), and accuracy (84 vs. 86%) for detecting CAD in patients with LBBB. The agreement between the two methods was 85%. ConclusionOur results show comparable diagnostic utility and high agreement between gated SPECT MIBI perfusion imaging and TTDE CFR assessment for detecting CAD in patients with LBBB. The advantage of gated SPECT MIBI over TTDE CFR measurements is the ability to assess the perfusion abnormalities in multiple vascular territories during the same procedure, which is convenient for detecting multi-vessel disease in patients with LBBB.

Site of myocardial infarction and severity of perfusion abnormalities impact on post-stress left ventricular function in patients with single-vessel disease: gated single-photon emission computed tomography methoxyisobutylisonitrile study.

ObjectivesWe used gated single-photon emission computed tomography methoxyisobutylisonitrile (SPECT MIBI) to (i) determine whether location of myocardial infarction (MI) and severity of perfusion abnormalities affect post-stress left ventricular function in patients with single-vessel coronary artery disease, and (ii) correlate changes between post-stress and rest ejection fraction (EF) with the severity of perfusion and regional wall motion abnormalities (RWMAs). MethodsEighty-eight patients with a history (≥3 months) of anterior MI (n=45) or inferior MI (n=43) underwent a 2-day stress–rest gated SPECT MIBI. 4D-MSPECT software was used to calculate left ventricular end-diastolic volume (EDV), end-systolic volume (ESV), EF, and the difference from post-stress to rest EF (EFs–EFr). Summed stress scores, summed rest scores, and summed difference scores (SDS) were calculated based on the 17-segment model. RWMAs were visually assessed using a 5-point score. ResultsPatients with anterior MI, compared with those with inferior MI, showed significantly greater perfusion abnormalities (summed stress score 11.0±5.5 vs. 7.5±2.4, P<0.01, summed rest score 7.4±4.7 vs. 5.2±1.9, P<0.01, SDS 3.3±1.0 vs. 1.9±1.0, P<0.05) and higher post-stress and rest RWMA (RWMSS 12.2±6.0 vs. 8.7±4.1, P<0.01, RWMRS 8.7±5.4 vs. 5.6±3.0, P<0.01). In 22 patients with anterior reversible ischemia in addition to fixed defect, post-stress and rest EDV and ESV were significantly larger and post-stress EF decreased more than in 21 patients with inferior MI (EDV 144.0±28.9 ml vs. 108.6±36.9 ml, ESV 70.6±22.2 ml vs. 53.4±20.5 ml, EFs–EFr −4.2±3.5% vs. −1.5±2.2%, P<0.01). SDS and RWMA were highly correlated with EFs–EFr. ConclusionIn patients with single-vessel coronary artery disease, the extent and severity of perfusion and RWMAs assessed by gated SPECT MIBI are greater after anterior MI than inferior MI. Global left ventricular function is significantly more affected after anterior MI only in patients with reversible ischemia in addition to fixed wall defect. Decrease in EF from post-stress to rest is closely associated with the severity of perfusion and RWMAs. Overall results suggest that the extent and severity of perfusion and RWMAs are more prominent in the myocardial region supplied by left anterior descending coronary artery than by right coronary artery, which may explain significantly worse post-stress left ventricular function after anterior MI.

Using SUV as a Guide to 18F-FDG Dose Reduction

This article explores how one can lower the injected 18F-FDG dose while maintaining validity in comparing standardized uptake values (SUVs) between studies. Variations of the SUV within each lesion were examined at different acquisition times. Methods: Our protocol was approved by either the Human Investigation Committee or the Institutional Review Board. All 120 PET datasets were acquired continuously for 180 s per bed position in list mode and were reconstructed to obtain 30-, 60-, 90-, 120-, 150-, and 180-s-per-bed-position PET images with registration to a single set of nondiagnostic CT images. Qualitative assessment of the images was performed separately for correlation. The SUV measurements of each lesion were computed and normalized to the 180-s acquisition values to create a stabilization factor. These stabilization factors were used to demonstrate a predictable trend of stabilization over time. The variances of the stabilization factors over the entire dataset, composed of several tumor types over a range of sizes, were compared for each time point with the corresponding 150-s time point using a 2-sided F test, which has similar values to the 180-s time point. Results: The variance of the data decreased with increasing acquisition time and with increasing dose but leveled off for sufficiently long acquisitions. Conclusion: Through the statistical analysis of SUVs for increasing acquisition times and visual evaluation of the plots, we developed and hereby propose an algorithm that can be used to seek the maximum reduction in administered 18F-FDG dose while preserving the validity of SUV comparisons.

The utility of two somatostatin analog radiopharmaceuticals in assessment of radiologically indeterminate pulmonary lesions.

Purpose: The aim of our study was to assess diagnostic accuracy of Tc-99m depreotide and Tc-99m-EDDA/HYNIC-TOC scintigraphy for evaluation of pulmonary lesions that appeared ambiguous on computed tomography (CT). Material and Methods: Forty-nine consecutive patients (37 men and 12 women; mean age, 60 ± 11 years) with 60 pulmonary lesions on chest radiography and CT were referred for nuclear imaging. They were prospectively allocated to undergo whole-body scintigraphy (WBS) and single photon emission computed tomography (SPECT) using either Tc-99m depreotide (26 patients, group 1) or Tc-99m-EDDA/HYNIC-TOC imaging (23 patients, group 2). Histologic findings after tissue biopsy served as a gold standard for determining diagnostic accuracy of the 2 somatostatin analogs. Visual assessment was complemented by semiquantitative analysis based on target to background ratio. Results: Among the 32 pulmonary lesions scanned with Tc-99m depreotide, focal uptake was increased in 22 of 25 malignancies, whereas no uptake was found in 6 of 7 benign lesions (88% sensitivity, 85% specificity, and 88% accuracy) on both WBS and SPECT. Imaging of 28 pulmonary lesions with Tc-99m-EDDA/HYNIC-TOC had a similar diagnostic yield (sensitivity 87%, specificity 84%, and accuracy 86%). Overall, target to background ratios were higher on SPECT than WBS but not significantly different between groups 1 and 2 (SPECT 2.72 ± 0.70 vs. 2.71 ± 0.50, WBS 1.61 ± 0.32 vs. 1.62 ± 0.28, respectively). Conclusion: This study demonstrates that Tc-99m depreotide and Tc-99m-EDDA/HYNIC-TOC have similar diagnostic value for characterizing pulmonary lesions that appear ambiguous on CT.

A new radionuclide approach for the quantification of left ventricular volumes: the 'geometric count based' method

Summary A new radionuclide method, called the ‘geometric count based’ (GCB) method, has been developed for the quantification of absolute left ventricular volume. As the method is based on planar radionuclide ventriculography, it is non‐invasive and simple, and avoids the relatively cumbersome and longer lasting, dynamic procedure using single photon computed emission tomography, which can be used for achieving the same goal. The purpose of this study was to describe the exactness of the theoretical approach to the method and validate its accuracy both by physical experiments and the initial clinical trial, as compared to contrast ventriculography. Count based data were combined with the geometric based data assuming an ellipsoid left ventricular shape with identical short axes. The following equation for computing left ventricular end diastolic volume, EDV (in ml) was developed: EDV = 2cMCtot/Cmax, where c is the manually drawn short axis (one row pixel ROI) of the prolate ellipsoid in LAO 45° (cm), M is the calibrated pixel size (in cm2), Ctot is the total counts in LV ROI, and Cmax is the maximum pixel counts in the LV ROI. Physical experiments with two different ‘heart shaped’ phantoms were used to compare the results obtained by the GCB method with the true phantom volumes and with the method assuming LV ball shape (BLV), developed by other authors. The true volumes of cylindrical and ellipsoid phantoms of 112.5 ml and 190.5 ml were computed to be 114 ml and 196 ml by the GCB and 168 ml and 180 ml by the BLV methods, respectively. In a clinical study, GCB volumes were compared to volumes measured by using single plane contrast ventriculography in 38 coronary patients. A good correlation between the GCB method and contrast ventriculography was obtained both for EDV and end systolic ventricular volumes (r = 0.94, r = 0.90). Both phantom and initial clinical studies indicate that the GCB method is an accurate, non‐invasive and simple radionuclide method for measuring left ventricular volumes. Additionally, it could be used even in the smallest nuclear medicine units, for example in intensive care units where there are mobile cameras. (© 2003 Lippincott Williams & Wilkins)

Diagnostic and prognostic value of gated SPECT MIBI early post-stress imaging in patients with intermediate Duke Treadmill Score.

Purpose of the ReportThe aims of this study were to compare perfusion and functional parameters between early (ES) and standard (SS) post-stress gated SPECT MIBI, to validate ES against coronary angiography, and to determine whether ES parameters can predict future cardiac events. Patients and MethodsThe sample included 63 patients with normal or mildly impaired left ventricular function and intermediate Duke Treadmill Score. They underwent a 2-day stress-rest gated SPECT MIBI with the post-stress data acquired at 15 minutes (ES) and 60 minutes (SS) after i.v. injection of 740 MBq of 99mTc-MIBI. The ES findings were compared to SS and against coronary angiography to determine their sensitivity/specificity for detecting >70% stenosis. The information about new-onset cardiac events was collected 26 ± 6 months later. ResultsPerfusion parameters did not significantly differ between ES and SS. Ejection fraction was significantly lower and regional wall motion abnormalities were significantly higher on ES than SS. The corresponding perfusion and functional parameters were strongly related (linear regression slope 0.65–1.00, intercept −0.36–8.5, R2 0.98–0.75). ES parameters had high sensitivity (96%) and specificity (83%) for detecting >70% stenosis. Lower early stress than rest EF (>5%), higher early stress than rest EDV, and early SSS >8 emerged as significant predictors of new-onset cardiac events. ConclusionsEarly post-stress gated SPECT MIBI yields comparable perfusion and functional parameters as the standard post-stress protocol. ES parameters are useful for detecting the existing coronary disease and for predicting future cardiac events. ES protocol is recommended for improving patient compliance and efficiency of nuclear cardiology services.

Evaluation of myocardial perfusion and function by gated single-photon emission computed tomography technetium-99m methoxyisobutylisonitrile in children and adolescents with severe congenital heart disease.

ObjectivesThe value of gated single-photon emission computed tomography technetium-99m methoxyisobutylisonitrile (gated SPECT 99mTc-MIBI) in children is not yet established probably because gated SPECT 99mTc-MIBI has rarely been used in pediatric clinical and research studies. The purpose of this study was to evaluate perfusion abnormalities and left ventricular (LV) function by gated SPECT 99mTc-MIBI in children and adolescents with severe congenital heart disease (CHD). MethodsSeventeen children and adolescents with severe CHD (11 boys and six girls, mean age 11±4 years) underwent 2-day rest–stress (11 boys) or 1-day rest (six girls) gated SPECT 99mTc-MIBI. Myocardial perfusion was evaluated by a 17-segment model with a 5-point score to derive the summed stress score, the summed rest score (SRS), and the summed difference score based on the 4D-MSPECT software results. The extent of myocardial perfusion abnormalities was also expressed as a percentage of the LV size. The 4D-MSPECT software was used to calculate LV end-diastolic volume, end-systolic volume (ESV), and ejection fraction (EF). ResultsReversible myocardial perfusion defect was found in 7 of 11 children (64%) who underwent rest–stress gated SPECT 99mTc-MIBI. The LV segments involved were anterior, anteroseptal, anterolateral, apical and inferior. These seven children showed significantly larger perfusion abnormalities on stress compared with rest study (18±5 vs. 7±4%, P<0.01) and higher summed stress score compared to SRS (11±4 vs. 4±2, P<0.01). Children and adolescents with myocardial ischemia had significantly lower poststress EF than rest EF (53±12 vs. 59±11%, P<0.05) and significantly higher poststress ESV than rest ESV (81±24 vs. 61±25 ml, P<0.05). In six children evaluated only at rest, perfusion defects involved anterior, anteroseptal and apical, or inferolateral segments, accounting for 31±12% of LV and with SRS of 12±5. Their global LV parameters were: end-diastolic volume 118±23 ml, ESV 56±16 ml, EF 51±10%. ConclusionPoststress and rest-gated SPECT 99mTc-MIBI results indicate that children and adolescents with severe CHD show a range of abnormalities in myocardial perfusion and LV function, which is useful for determining functional importance of morphological malformations. Thus, gated SPECT 99mTc-MIBI provides complementary information that may guide clinical decision making in children and adolescents with severe CHD.