Fayçal Ben Bouallègue

Comparative values of gated blood-pool SPECT and CMR for ejection fraction and volume estimation.

ObjectiveGated blood-pool single-photon emission computed tomography (GBPS) was compared with cardiac magnetic resonance (CMR) for the measurement of left ventricular (LV) and right ventricular (RV) ejection fractions (EF) and volumes [end-diastolic volume (EDV) or end-systolic volume (ESV)] in a mixed population. MethodsThirty patients (70% men; mean age: 61±14 years) referred for various symptoms or heart diseases, predominantly ischemic, were included. GBPS data were analyzed using segmentation software described earlier based on the watershed algorithm. CMR images were acquired for both ventricles at the same time using a steady-state-free precession sequence and short-axis views. No compensation for papillary muscles was used. LVEF and RVEF and volumes were assessed with GBPS and CMR and were compared. ResultsLVEF and volumes were correlated (P<0.001). The difference in LVEF between GBPS and CMR was not significant (P=0.063). The limits of agreement were close for LVEF (−11 to 15%) and wider for LV volumes (−82 to 11 ml for EDV and −52 to 15 ml for ESV), with higher volume values obtained with CMR (mean differences of 36±24 ml for EDV and 19±17 ml for ESV). The RVEF and volumes assessed by GBPS and CMR were correlated (P<0.001). The difference in RVESV between GBPS or CMR was not significant (P=0.136). The limits of agreement were relatively close for all RV parameters (−15 to 8% for EF; −44 to 22 ml for EDV, and −25 to 21 ml for ESV). In 24 patients without valvulopathy or shunt, the difference between LV stroke volume and RV stroke volume was lower with GBPS than with CMR (9±14 ml and 18±13 ml, respectively, with P=0.027). ConclusionGBPS is a simple and widely available technique that can assess both LVEF and RVEF, and volumes with slight differences compared with CMR.

Association between textural and morphological tumor indices on baseline PET‐CT and early metabolic response on interim PET‐CT in bulky malignant lymphomas

Purpose We investigated whether metabolic, textural, and morphological tumoral indices evaluated on baseline PET‐CT were predictive of early metabolic response on interim PET‐CT in a cohort of patients with bulky Hodgkin and non‐Hodgkin malignant lymphomas. Methods This retrospective study included 57 patients referred for initial PET‐CT examination. In‐house dedicated software was used to delineate tumor contours using a fixed 30% threshold of SUV max and then to compute tumoral metabolic parameters (SUV max, mean, peak, standard deviation, skewness and kurtosis, metabolic tumoral volume (MTV), total lesion glycolysis, and area under the curve of the cumulative histogram), textural parameters (Morans and Gearys indices, energy, entropy, contrast, correlation derived from the gray‐level co‐occurrence matrix, area under the curve of the power spectral density, auto‐correlation distance, and granularity), and shape parameters (surface, asphericity, convexity, surfacic extension, and 2D and 3D fractal dimensions). Early metabolic response was assessed on interim PET‐CT using the Deauville 5‐point scale and patients were ranked according to the Lugano classification as complete or not complete metabolic responders. The impact of the segmentation method (alternate threshold at 41%) and image resolution (Gaussian postsmoothing of 3, 5, and 7 mm) was investigated. The association of the proposed parameters with early response was assessed in univariate and multivariate analyses. Their added predictive value was explored using supervised classification by support vector machines (SVM). We evaluated in leave‐one‐out cross‐validation three SVMs admitting as input features (a) MTV, (b) MTV + histological type, and (c) MTV + histology + relevant texture/shape indices. Results Features associated with complete metabolic response were low MTV (P = 0.01), low TLG (P = 0.003), high power spectral density AUC (P = 0.007), high surfacic extension (P = 0.006), low 2D fractal dimension (P = 0.007), and low 3D fractal dimension (P = 0.003). The prognostic value of these metrics was optimal with the 30% segmentation threshold and overall was progressively altered with decreasing image resolution. In cross‐validation, the SVM accounting for texture and shape achieved the highest predictive value with ROC AUC of 0.82 and 80% accuracy (compared with 0.68 and 61% for MTV, and 0.65 and 68% for MTV + histology). Conclusions The combination of usual prognostic factors with appropriately chosen textural and shape parameters evaluated on baseline PET‐CT improves the prediction of early metabolic response in bulky lymphoma.

Left ventricular function assessment using 123I/99mTc dual-isotope acquisition with two semi-conductor cadmium–zinc–telluride (CZT) cameras: a gated cardiac phantom study

BackgroundThe impact of increased energy resolution of cadmium–zinc–telluride (CZT) cameras on the assessment of left ventricular function under dual-isotope conditions (99mTc and 123I) remains unknown.The Amsterdam-gated dynamic cardiac phantom (AGATE, Vanderwilt techniques, Boxtel, The Netherlands) was successively filled with a solution of 123I alone, 99mTc alone, and a mixture of 123I and 99mTc. A total of 12 datasets was acquired with each commercially available CZT camera (DNM 530c, GE Healthcare and DSPECT, Biosensors International) using both energy windows (99mTc or 123I) with ejection fraction set to 33, 45, and 60 %. End-diastolic (EDV) and end-systolic (ESV) volumes, ejection fraction (LVEF), and regional wall motion and thickening (17-segment model) were assessed using Cedars-Sinai QGS Software. Concordance between single- and dual-isotope acquisitions was tested using Lin’s concordance correlation coefficient (CCC) and Bland–Altman plots.ResultsThere was no significant difference between single- or simultaneous dual-isotope acquisition (123I and 99mTc) for EDV, ESV, LVEF, or segmental wall motion and thickening. Myocardial volumes using single- (123I, 99mTc) and dual-isotope (reconstructed using both 123I and 99mTc energy windows) acquisitions were, respectively, the following: EDV (mL) 88 ± 27 vs. 89 ± 27 vs. 92 ± 29 vs. 90 ± 26 for DNM 530c (p = NS) and 82 ± 20 vs. 83 ± 22 vs. 79 ± 19 vs. 77 ± 20 for DSPECT (p = NS); ESV (mL) 40 ± 1 vs. 41 ± 2 vs. 41 ± 2 vs. 42 ± 1 for DNM 530c (p = NS) and 37 ± 5 vs. 37 ± 1 vs. 35 ± 3 vs. 34 ± 2 for DSPECT (p = NS); LVEF (%) 52 ± 14 vs. 51 ± 13 vs. 53 ± 13 vs. 51 ± 13 for DNM 530c (p = NS) and 52 ± 16 vs. 54 ± 13 vs. 54 ± 14 vs. 54 ± 13 for DSPECT (p = NS); regional motion (mm) 6.72 ± 2.82 vs. 6.58 ± 2.52 vs. 6.86 ± 2.99 vs. 6.59 ± 2.76 for DNM 530c (p = NS) and 6.79 ± 3.17 vs. 6.81 ± 2.75 vs. 6.71 ± 2.50 vs. 6.62 ± 2.74 for DSPECT (p = NS). The type of camera significantly impacted only on ESV (p < 0.001).ConclusionsThe new CZT cameras yielded similar results for the assessment of LVEF and regional motion using different energy windows (123I or 99mTc) and acquisition types (single vs. dual). With simultaneous dual-isotope acquisitions, the presence of 123I did not impact on LVEF assessment within the 99mTc energy window for either CZT camera.

Determination of the Heart-to-Mediastinum Ratio of 123I-MIBG Uptake Using Dual-Isotope (123I-MIBG/99mTc-Tetrofosmin) Multipinhole Cadmium-Zinc-Telluride SPECT in Patients with Heart Failure

The aim of this retrospective study was to compare the heart-to-mediastinum ratio (HMR) of 123I-metaiodobenzylguanidine (123I-MIBG) uptake obtained using a multipinhole cadmium–zinc–telluride (CZT) camera with that obtained using conventional planar imaging. Methods: Forty consecutive heart failure patients underwent planar acquisition 4 h after 123I-MIBG injection (191 ± 41 [mean ± SD] MBq). To localize the heart using the CZT camera, 99mTc-tetrofosmin (358 ± 177 MBq) was administered and dual-isotope acquisition was performed. The HMRs were calculated with conventional planar imaging (HMRplanar), with anterior reprojection images using the CZT camera (HMRreproj), and with transaxial reconstructed images using the CZT camera (HMRtransaxial). In a phantom study, we estimated a linear model fitting the CZT camera data to the planar data, and we applied it to provide corrected CZT camera–determined HMRs in patients (cHMRreproj and cHMRtransaxial). Results: Thirty-four men and 6 women (71 ± 9 y old) with ischemic (22 patients) and nonischemic (18 patients) heart failure completed the study. For 22 of the 40 patients (55%), the New York Heart Association classification was class II and the ejection fraction was 35% ± 9%. HMRreproj (1.12 ± 0.19) and HMRtransaxial (1.35 ± 0.34) were lower than HMRplanar (1.44 ± 0.14) (P < 0.0001 and P < 0.01, respectively). cHMRreproj (1.54 ± 0.09) and cHMRtransaxial (1.45 ± 0.14) were significantly different (P < 0.0001). Lin concordance correlation and Bland–Altman analysis demonstrated an almost perfect concordance and a high agreement between HMRplanar and cHMRtransaxial (P was not significant) but not between HMRplanar and cHMRreproj (P < 0.0001). Conclusion: This study demonstrated that determination of the late HMR of cardiac 123I-MIBG uptake using dual-isotope (123I and 99mTc) acquisition on a multipinhole CZT camera was feasible in patients with heart failure. However, this determination should be performed using transaxial reconstructed images and linear correction based on phantom data acquisitions.

Is computed tomography attenuation correction more efficient than gated single photon emission computed tomography analysis in improving the diagnostic performance of myocardial perfusion imaging in patients with low prevalence of ischemic heart disease

ObjectiveThe purpose of this study was to compare computed tomography (CT)-based attenuation correction (AC) using a hybrid single photon emission computed tomography (SPECT)-CT system and quantitative analysis of wall thickening using gated SPECT with regard to the diagnostic accuracy of myocardial perfusion imaging. Materials and methodsWe prospectively included 70 patients with low prevalence of acute coronary artery disease who underwent a myocardial stress–rest SPECT study. Interpretation was based on supine nongated SPECT data with (AC) or without (NC) CT-based attenuation correction, and on gated SPECT data without attenuation correction (GNC). The scintigraphic diagnosis was obtained using standard automated quantitative analysis software and compared with a 23±14 months’ clinical follow-up for 57 patients or with the results of a coronary angiography for 13 patients. ResultsThe sensitivity, specificity, and overall accuracy were, respectively, 77, 60, and 63% for NC SPECT, 67, 81, and 79% for AC SPECT, and 69, 98, and 93% for GNC SPECT. The initial diagnosis was modified in about one-third of the cases for both AC and GNC, this rate being independent of any clinical parameter (including BMI) except sex (two to four times more artifact correction in men). ConclusionIts widespread availability, cost effectiveness, safety in terms of radiation exposure, and ability to significantly improve myocardial perfusion imaging specificity and accuracy make gated SPECT a self-sufficient modality for coronary artery disease screening and follow-up, whereas CT-AC should be discussed on a case-by-case basis.

Retrospective Voxel-Based Dosimetry for Assessing the Ability of the Body-Surface-Area Model to Predict Delivered Dose and Radioembolization Outcome

The aim of this study was to quantitatively evaluate the ability of the body-surface-area (BSA) model to predict tumor-absorbed dose and treatment outcome through retrospective voxel-based dosimetry. Methods: Data from 35 hepatocellular carcinoma patients with a total of 42 90Y-resin microsphere radioembolization treatments were included. Injected activity was planned with the BSA model. Voxel dosimetry based on 99mTc-labeled macroaggregated albumin SPECT and 90Y-microsphere PET was retrospectively performed using a dedicated treatment planning system. Average dose and dose–volume histograms (DVHs) of the anatomically defined tumors were analyzed. The selected dose metrics extracted from DVHs were minimum dose to 50% and 70% of the tumor volume and percentage of the volume receiving at least 120 Gy. Treatment response was evaluated 6 mo after therapy according to the criteria of the European Association for the Study of the Liver. Results: Six-month response was evaluated in 26 treatments: 14 were considered to produce an objective response and 12 a nonresponse. Retrospective evaluation of 90Y-microsphere PET–based dosimetry showed a large interpatient variability with a median average absorbed dose of 60 Gy to the tumor. In 62% (26/42) of the cases, tumor, nontumoral liver, and lung doses would have complied with the recommended thresholds if the injected activity calculated by the BSA method had been increased. Average doses, minimum dose to 50% and 70% of the tumor volume, and percentage of the volume receiving at least 120 Gy were significantly higher in cases of objective response than in nonresponse. Conclusion: In our population, average tumor-absorbed dose and DVH metrics were associated with tumor response. However, the activity calculated by the BSA method could have been increased to reach the recommended tumor dose threshold. Tumor uptake, target and nontarget volumes, and dose distribution heterogeneity should be considered for activity planning.

RV function improvement following nitric oxide inhalation demonstrated by gated blood pool SPECT in a patient with primary pulmonary hypertension

A 30-year-old woman with a history of dyspnoea and recurrent syncope was diagnosed with primary pulmonary hypertension (PPH). Right cardiac catheterization demonstrated pre-capillary PH with elevated mean pulmonary arterial pressure at 52 mmHg, low occlusive pulmonary arterial pressure at 5 mmHg, and elevated pulmonary vascular resistance at 638 d.s.cm. Pulmonary arterial pressure and resistance were normalized after nitric oxide (NO) inhalation. Calcium blocker medication (nifedipine 150 mg day) was initiated. The patient was explored using gated blood pool SPECT at baseline and after NO inhalation (10 ppm). SPECT data were post-processed using in-house dedicated software (TomPool). Figure 1 shows left (LV, in red) and right ventricle (RV, in blue) time-volume curves fitted using a deformable reference curve model. Figure 2 displays bi-ventricular 3D surface rendering and polar plots of local ejection fraction (EF). Baseline acquisition showed normal LV function. Global RV EF was measured at 59%, within the normal range (56% ± 8%). There was an RV annular peri-apical area of moderate hypokinesia. After NO inhalation, LV function was globally stable, whereas global RV EF increased to 69%. Segmental contractility maps showed a clear improvement in the RV free wall contractility

Effects of the two types of anorexia nervosa (binge eating/purging and restrictive) on bone metabolism in female patients

This study compared the profiles of the two types of anorexia nervosa (AN; restrictive: AN‐R, and binge eating/purging: AN‐BP) in terms of body composition, gynaecological status, disease history and the potential effects on bone metabolism.

Area at risk can be assessed by iodine-123-meta-iodobenzylguanidine single-photon emission computed tomography after myocardial infarction: a prospective study

Background Myocardial salvage is an important surrogate endpoint to estimate the impact of treatments in patients with ST-segment elevation myocardial infarction (STEMI). Aim The aim of this study was to evaluate the correlation between cardiac sympathetic denervation area assessed by single-photon emission computed tomography (SPECT) using iodine-123-meta-iodobenzylguanidine (123I-MIBG) and myocardial area at risk (AAR) assessed by cardiac magnetic resonance (CMR) (gold standard). Patients and methods A total of 35 postprimary reperfusion STEMI patients were enrolled prospectively to undergo SPECT using 123I-MIBG (evaluates cardiac sympathetic denervation) and thallium-201 (evaluates myocardial necrosis), and to undergo CMR imaging using T2-weighted spin-echo turbo inversion recovery for AAR and postgadolinium T1-weighted phase sensitive inversion recovery for scar assessment. Results 123I-MIBG imaging showed a wider denervated area (51.1±16.0% of left ventricular area) in comparison with the necrosis area on thallium-201 imaging (16.1±14.4% of left ventricular area, P<0.0001). CMR and SPECT provided similar evaluation of the transmural necrosis (P=0.10) with a good correlation (R=0.86, P<0.0001). AAR on CMR was not different compared with the denervated area (P=0.23) and was adequately correlated (R=0.56, P=0.0002). Myocardial salvage evaluated by SPECT imaging (mismatch denervated but viable myocardium) was significantly higher than by CMR (P=0.02). Conclusion In patients with STEMI, 123I-MIBG SPECT, assessing cardiac sympathetic denervation may precisely evaluate the AAR, providing an alternative to CMR for AAR assessment.

Comparison between rebinning methods and geometric re-projection for the estimation of missing oblique data in 3D-PET

ObjectiveClassically, the missing portions in the oblique projection data acquired from cylindrical scanners are synthesized by forward projecting an estimation of the activity computed from non-oblique data. Another quick and powerful way to perform the estimation of the truncated portions consists in applying Fourier rebinning methods. This paper intends to compare the performances of 3D geometric re-projection versus two Fourier rebinning techniques (iterative FOREPROJ and extended FORE) designed for re-projection.MethodsBoth analytical and noisy 3D projection data corresponding to a phantom constituted of warm and cold ellipsoids over a uniform background are simulated numerically for the SIEMENS Hi-Rez scanner. The object is reconstructed using 3D filtered back-projection. A prior estimation of the missing oblique data is performed using the three algorithms.ResultsThe resolution properties and noise behavior of the three methods are compared and demonstrate a significant signal to noise ratio improvement using rebinning-based algorithms.ConclusionsWe show that iterative FOREPROJ provides projection data with high accuracy 60% less time than geometric re-projection.