Nouveautés en cardiologie nucléaire : une gamma caméra à semi-conducteurs dédiée à l’imagerie cardiaque

During the last few years, cardiac imaging made important breakthroughs thanks to the development of various techniques allowing the risk stratification of patients with coronary artery disease. The well-established single photon emission computed tomography (SPECT) as a myocardial imaging technique made an important progress with the recent improvement of high-speed volumic acquisition, using dedicated semi-conductor gamma camera. These cameras bring significant improvement to the image quality and the image acquisition time, which is now seven times lower. New type of artefacts is expected because of the geometry of detection, thus studies are still needed to assess the exact performance of this revolutionary technology.     

Facteurs influençant la détectabilité de l’activité myocardique en caméra à semi-conducteurs

Body weight was already shown to be a major factor for the detectability of myocardial activity with conventional cameras and thus, for the optimization of injected activities and or recording times. This study was aimed to identify the factors affecting this detectability on a new solid-state camera showing a high sensitivity of detection (D.SPECT camera Cyclopharma^®).Patients and methodsThe study population involved 101 patients, who underwent myocardial SPECT with Sestamibi on a one-day stress/rest protocol. Each conventional acquisition (DST-XL General Electric Healthcare^® USA) was immediately followed by a D-SPECT^® one. Myocardial activity was determined on each acquisition in counts per seconds and expressed in fraction of the injected activity for assessing the detectability of myocardial activity.ResultsMyocardial activity was on average 12 ± 3 fold higher when recorded with the D-SPECT^® camera than with the DST-XL^® one. Body weight and especially body mass index (BMI) were the most significant correlates of the detectability of myocardial activity for both cameras. According to these correlations, an increase in the BMI from 25 to 35 kg/m was associated with a 47% decrease in the detectability of myocardial activity at stress with the DST-XL^® and of only 30% with the D-SPECT.ConclusionThe detectability of myocardial activity provided by the D.SPECT camera is dramatically higher than that documented for conventional cameras of the DST-XL^® type and is affected by the increase in body weight and in body mass index but at a lower rate than for the Anger camera.     

Ventriculographie isotopique : comparaison de l’acquisition sur gamma caméra CZT cardio dédiée à l’acquisition planaire

IntroductionGated equilibrium radionuclide venticulography is often used to determine left ventricule ejection fraction (LVEF), especially in case of follow up when cardio-toxic drugs are administred. During the last decade, the use of cardiac specific (CZT) gamma cameras has spread. They directly acquire 3D data. We wanted to determine the agreement between three nuclear medicine LVEF measurement techniques. We also wanted to determine the repeatability of these techniques.MethodsBetween April 16, 2016 and February 4, 2017 we consecutively included 77 patients who were adressed to the nuclear medicine department of CHU Martinique for LVEF measurement. Patients were injected with 99*Technetium labelled albumin. Usual planar scintigraphy was performed to serve as reference and 3D data was acquired with a CZT cardiac gamma camera. 3D data was analyzed directly with BPGS software, and also reprojected to planar data which was analyzed like the conventional planar acquisition.ResultsSeventy patients had acquisitions with both gamma cameras. The LVEF values from the CZT camera data were significantly higher than the reference planar LVEF measurements (+6.2 for 3D analysis, P < 0.01, concordance interval [?8.0; 20.3] and +1.7 for planar reprojection, P = 0.01, concordance interval [?8.9; 12.2]. For all three methods, the intra-method concordance intervals were within [?5; 5].ConclusionOur results indicate the same measurement method must be used in case of LVEF follow up. The variation between theses methods could lead to the false conclusion of impairment of LVEF (which is suspected in case of a 10% LVEF drop). Our secondary outcome show a good repeatability for all three techniques. Further studies should be initiated to determine which method is the most accurate and to determine the reproductibility of the CZT data acquisition process.     

Impact d’une réduction d’activité sur la mesure de la fraction d’éjection du ventricule gauche sur caméra D-SPECT

IntroductionRadionuclide ventriculography provides a reproducible measurement of the left ventricular fraction ejection (LVEF) but with a significant body radiation (effective dose of 5,9 mSv for the injection of 850 Mbq of ^99mTc). The highly sensitive semi-conductor (CZT) cameras could allow decreasing the injected activity by a factor 3, similarly to that of myocardial perfusion imaging. Our study was aimed to determine whether the LVEF measurement provided by radionuclide ventriculography on the CZT D-SPECT camera is impacted by a 70% reduction in recorded counts.Materials and methodsAfter the in vivo labeling of red blood cells with 850 MBq of ^99mTc, 49 patients completed a conventional 2D recording (Conv-2D) on Anger camera followed by a 3D recording on the D-SPECT camera (3D-100%). The CZT recordings of all projections were subsequently shortened to 30% of their initial durations (3D-30%) in order to assess the LVEF measured with a 70% reduction in recorded counts.ResultsMean LVEF values were 62.7 ± 11.1% on Conv-2D and higher on both 3D-100% (66.8 ± 14.8%, P < 0.001) and 3D-30% (66.3 ± 15.7%, P < 0.001). The correlation coefficients with the LVEF determined with the reference Conv-2D method were equivalents for 3D-100% (r² = 0.73) and 3D-30% (r² = 0.70) and with a similar level of overestimation for the highest LEVF values.ConclusionA 70% reduction in recorded counts does not significantly impact the LVEF measured with radionuclide ventriculography on the CZT D-SPECT camera. These values are coherent with those obtained with the reference 2D method but with a clear overestimation for the highest LVEF values.     

Intérêt d’une semi-quantification et d’une analyse statistique automatique pour l’interprétation de la tomoscintigraphie cérébrale de perfusion dans la maladie d’Alzheimer

IntroductionAs the visual interpretation of the brain perfusion SPECT for the diagnosis of Alzheimer's disease might be difficult, it is wished to benefit from techniques allowing to improve the diagnostic accuracy especially for the inexperienced readers.Materials and methodsThree readers retrospectively interpreted 77 ^99mTc-ECD SPECT studies within the context of suspected neurodegenerative disease. The probability of Alzheimer's disease was quoted from 1 to 5, and the optimum sensitivity and specificity values were determined from ROC curves. The readers also attributed a hypoperfusion score to 13 brain regions; a diagnosis was obtained from this semi-quantification using a simple logic rule. The SPECT scans were also analyzed using the Planet Neuro software and a diagnosis was reached from a threshold for 2 of the 90 analyzed regions. The gold standard was established by a comprehensive neurological evaluation with at least 5 years of follow-up.ResultsThe sensitivities and specificities of the three readers were 50 %, 56 %, 28 % and 76 %, 83 % and 90 %, respectively. Using the semi-quantification they were 50 %, 67 %, 61 % and 54 %, 85 %, 69 %. The results of two readers were more in agreement. Using the automatic quantification, sensitivity was 78 % and specificity 81 %.ConclusionThe semi-quantification seems to ameliorate the results of and the agreement between certain readers. However, the automatic quantification seems to be the only way of assisting all of the readers to improve their diagnostic performances.     

Performances diagnostiques des tomoscintigraphies myocardiques de stress,réalisées avec une caméra à semi-conducteurs et un protocole très faible dose

IntroductionThis retrospective study aimed to assess the performances in the detection of coronary artery disease patients of the stress myocardial perfusion imaging (MPI) performed with a semiconductor camera, a very low dose stress-rest protocol and short recording times.Material and methodsWe analyzed consecutive MPI exams, which has been routinely planed with the “D-SPECT” semiconductor camera, a 1-day stress-rest protocol, very low doses of Sestamibi-^99mTc (120 MBq at stress and 360 MBq at rest for a 75 kg body weight patient) and short acquisition-times targeting the recording of 500 myocardial kcounts (on average, 8 min for stress and 3 min for rest). The ability to detect coronary artery stenosis (> 50% diameter reduction) was assessed in a group of 118 patients, who had coronary angiography at ≤ 3 months from MPI, and normalcy rate was assessed in a group of 74 patients showing a low pretest probability of coronary artery disease (< 10%).ResultsSensitivity, positive predictive value and global accuracy for identifying the 81 patients with ≥ 1 coronary artery stenosis were 85%, 83% and 78%, respectively; and normalcy rate was 96%. Mean effective doses were: (1) 4.9 ± 1.4 mSv in the group with coronary angiography and where most exams (90%) comprised both stress and rest MPI; and (2) 1.9 ± 1.5 mSv in the low probability group and where most exams (70%) comprised only stress MPI.ConclusionWhen performed with a sensitive semiconductor camera and a very low dose stress-rest protocol, MPI provides high diagnostic performances, equivalent to those documented with conventional cameras in the same study setting, but with dramatic reduction of patients’ radiation.     

Apport des ostracodes à l’interprétation séquentielle du Crétacé inférieur (Berriasien–Valanginien) du bassin d’Essaouira–Agadir (Maroc)

Contribution of the ostracods to the sequential interpretation of the Lower Cretaceous (Berriasian–Valanginian) of the Essaouira–Agadir Basin (Morocco). The analysis of the ostracod fauna from the Berriasian–Valanginian of the Essaouira–Agadir Basin (Morocco) allows us to make a narrow relationship between the sequential evolution (established on sedimentary, biostratigraphical and geochemical data) and the evolution of statistical parameters of ostracods. So, the number of individuals and the number of species present comparable fluctuations and follow perfectly the sequential evolution; classes of dominant and fortuitous frequency are the most meaningful, the specific renewal rate shows extremes values at the limits of sequences and at the basis of transgressive systems tracts. To cite this article: A. Rossi et al., C. R. Palevol 2 (2003) 133–141.     

Fusion d’images en médecine nucléaire : des concepts à l’application clinique

In this paper, the authors propose a short overview of image fusion techniques in nuclear medicine. First, the methodological concepts of image fusion are discussed. Then, a sample of applications in nuclear medicine is presented. These applications ranging from diagnosis to guided therapy and monitoring clearly exemplify the challenges of image fusion in nuclear medicine.