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PURPOSE:
We aimed to (a) elucidate the concordance of visual assessment of an initial I-ioflupane scan by a human interpreter with comparison to results using a fully automatic semiquantitative method and (b) to assess the accuracy compared to follow-up (f/u) diagnosis established by movement disorder specialists.
METHODS:
An initial I-ioflupane scan was performed in 382 patients with clinically uncertain Parkinsonian syndrome. An experienced reader performed a visual evaluation of all scans independently. The findings of the visual read were compared with semiquantitative evaluation. In addition, available f/u clinical diagnosis (serving as a reference standard) was compared with results of the human read and the software.
RESULTS:
When comparing the semiquantitative method with the visual assessment, discordance could be found in 25 (6.5%) of 382 of the cases for the experienced reader (ĸ = 0.868). The human observer indicated region of interest misalignment as the main reason for discordance. With neurology f/u serving as reference, the results of the reader revealed a slightly higher accuracy rate (87.7%, ĸ = 0.75) compared to semiquantification (86.2%, ĸ = 0.719, P < 0.001, respectively). No significant difference in the diagnostic performance of the visual read versus software-based assessment was found.
CONCLUSIONS:
In comparison with a fully automatic semiquantitative method in I-ioflupane interpretation, human assessment obtained an almost perfect agreement rate. However, compared to clinical established diagnosis serving as a reference, visual read seemed to be slightly more accurate as a solely software-based quantitative assessment.
In der vorliegenden klinischen Studie untersuchten wir die diagnostische Genauigkeit zweier nicht invasiver Verfahren, nämlich des Nachweises der nativen und kontrastmittelverstärkten Stressechokardiographie sowie der Myokardszintigraphie bei visuell als mittelgradig eingeschätzten Koronarstenosen. Eingeschlossen wurden 48 Patienten mit einer angiographisch nachgewiesenen 50- 75% Lumenreduktion eines Herzkranzgefäßes. Die Untersuchungen wurden simultan mittels pharmakologischer Belastung (Dobutamin) durchgeführt und die Ergebnisse miteinander verglichen. Als Referenzmethode diente die Druckdrahtmessung, welche eine Objektivierung der hämodynamischen Relevanz besonders mittelgradiger Koronarstenosen durch die Ermittlung der fraktionellen Flussreserve als Quotienten aus post- und prästenotischem Druck direkt im betroffenen Koronargefäß ermöglicht. Der Schwerpunkt dieser Arbeit lag in der Analyse der Beurteilbarkeit und diagnostischen Wertigkeit von Dobutamin- Stressechokardiogrammen vor und nach Applikation von Kontrastmitteln der 2. Generation (Optison® bzw. Sonovue®). Die Interpretation aller Echokardiogramme erfolgte gemäß dem 16 Segmentmodell der American Society of Echocardiography. Die Endokarddelineation wurde sowohl in Ruhe als auch unter Belastung bewertet, wobei eine signifikante Verbesserung nach Injektion des Kontrastmittels erreicht wurde. Der Index steigerte sich insbesondere in den apikalen, anterioren und lateralen Segmenten, was für die klinische Praxis vor allem eine Verbesserung der Beurteilung der hämodynamischen Relevanz von Stenosen des Versorgungsgebietes von RIVA und RCX bedeutet. Die Segmente des RCA-Versorgungsgebietes waren bereits in der nativen Bildgebung ausreichend beurteilbar. Die Stressechokardiogramme wurden bezüglich der Wandbewegungsstörungen von zwei unabhängigen und erfahrenen Untersuchern ohne Kenntnis der Ergebnisse der anderen Ischämietests bzw. des Ergebnisses der Koronarangiographie und der Bestimmung der fraktionellen Flussreserve beurteilt. Die Nativuntersuchungen wurden gemäß den standardisierten Richtlinien von Hoffmann et al. interpretiert. Für die Bewertung der kontrastverstärkten Stressechokardiogramme wurde, sich an den Ergebnissen der Druckdrahtmessung orientierend, ein optimales Bewertungsmodell gesucht. Die größte diagnostische Genauigkeit ergab sich, wenn neu induzierte, gleich bleibende oder zunehmende Wandbewegungsstörungen in mindestens 2 direkt aneinander angrenzenden Segmenten als pathologisch gewertet wurde. Bei der Myokardszintigraphie wurden alle neuen und unter Belastung zunehmenden Defekte als pathologisch bewertet. Persistierende Defekte und Inhomogenitäten galten hingegen als nicht pathologisch. Die perfusionsszintigraphische Untersuchung errreichte mit 92% Sensitivität den höchsten Wert, jedoch mit einer relativ geringen Spezifität von 60% und einer diagnostischen Genauigkeit von 69%. Die Myokardszintigraphie zeigte sich bezüglich der Sensitivität der Stressechokardiographie überlegen, was zu einem Vorteil bei der Erkennung einer koronaren Herzerkrankung führt. Nachteilig ist die große Rate an falsch positiven Befunden. Die Perfusionsszintigraphie zeigte somit im Vergleich zur Stressechokardiographie an diesem Kollektiv eine deutlich niedrigere diagnostische Genauigkeit (69% vs. 78%). Die vorliegende Studie zeigt, dass die Kontraststressechokardiographie als nichtinvasive Untersuchungsmethode bei der Diagnose der hämodynamischen Relevanz mittelgradiger Stenosen eine bedeutende Rolle spielt, da sie die nichtinvasive Beurteilung der funktionellen Auswirkung einer Koronarstenose gegenüber der nativen Untersuchung verbessert. Der limitierende Faktor dieser Arbeit ist die nur begrenzte Anzahl der Studienteilnehmer. Es bedarf weiterer Untersuchungsreihen an größeren Studienpopulationen, um die verschiedenen Beurteilungsmodelle für die Kontrastmitteluntersuchung zu bestätigen und im klinischen Alltag zu etablieren.
SPECT as a representative of molecular imaging allows visualization of metabolic processes in vivo. In clinical practice, single photon emission imaging is an established modality for myocardial perfusion imaging or the diagnosis of adrenal or neuroendocrine tumors, to name a few. With technical advances in scanner design and data processing leading to improved spatial resolution and image quality, SPECT has become a serious contender in small animal preclinical imaging. With multi-pinhole collimation, submillimeter spatial resolutions are achieved without limiting sensitivity, which has led to a significant increase of interest in SPECT for preclinical research in recent years.
In this dissertation, the potential of a two-detector system through an analysis of three dedicated mouse collimators with multi-pinhole configurations was demonstrated. For this, sensitivity, spatial resolution, and uniformity as key parameters were determined. In the second part of the present work, an evaluation of the image quality at different activity concentrations to allow prediction of the system performance related to in vivo studies was performed. Therefore, a visual evaluation, as well as a calculation of the contrastto-noise ratio, was performed using mini Derenzo phantoms for the respective three mouse collimators. To better classify the results, the study was extended by a comparison with the predecessor system.
Due to the absence of the third bottom detector, sensitivity and uniformity are slightly compromised. All three collimators were able to achieve a spatial resolution in the submillimeter range, XUHR-M offers a peak resolution of up to 0.35 mm. In terms of resolution, both evaluated systems performed on an equal level. Visual assessment of image quality indicates a slight advantage of the new two-detector system, and the contrast-to-noise ratio seems to benefit from the improved SROSEM algorithm. However, the differences between the two systems are marginal.
The U-SPECT5/CT E-Class is proven to be state-of-the-art for small animal imaging and is a powerful instrument for preclinical molecular imaging research. Improvements in system design compensate well for the reduction in the detection area, allowing excellent imaging even with low activity concentrations.
Heart failure is one of the growing causes of death especially in developed countries due to longer life expectancy. Although many pharmacological and instrumental therapeutic approaches have been introduced for prevention and treatment of heart failure, there are still limitations and challenges. Nuclear cardiology has experienced rapid growth in the last few decades, in particular the application of single photon emission computed tomography (SPECT) and positron emission tomography (PET), which allow non-invasive functional assessment of cardiac condition including neurohormonal systems involved in heart failure; its application has dramatically improved the capacity for fundamental research and clinical diagnosis. In this article, we review the current status of applying radionuclide technology in non-invasive imaging of neurohormonal system in the heart, especially focusing on the tracers that are currently available. A short discussion about disadvantages and perspectives is also included.
Background
Small-animal single-photon emission computed tomography (SPECT) systems with multi-pinhole collimation and large stationary detectors have advantages compared to systems with moving small detectors. These systems benefit from less labour-intensive maintenance and quality control as fewer prone parts are moving, higher accuracy for focused scans and maintaining high resolution with increased sensitivity due to focused pinholes on the field of view. This study aims to investigate the performance of a novel ultra-high-resolution scanner with two-detector configuration (U-SPECT5-E) and to compare its image quality to a conventional micro-SPECT system with three stationary detectors (U-SPECT\(^+\)).
Methods
The new U-SPECT5-E with two stationary detectors was used for acquiring data with \(^{99m}\)Tc-filled point source, hot-rod and uniformity phantoms to analyse sensitivity, spatial resolution, uniformity and contrast-to-noise ratio (CNR). Three dedicated multi-pinhole mouse collimators with 75 pinholes each and 0.25-, 0.60- and 1.00-mm pinholes for extra ultra-high resolution (XUHR-M), general-purpose (GP-M) and ultra-high sensitivity (UHS-M) imaging were examined. For CNR analysis, four different activity ranges representing low- and high-count settings were investigated for all three collimators. The experiments for the performance assessment were repeated with the same GP-M collimator in the three-detector U-SPECT\(^+\) for comparison.
Results
Peak sensitivity was 237 cps/MBq (XUHR-M), 847 cps/MBq (GP-M), 2054 cps/MBq (UHS-M) for U-SPECT5-E and 1710 cps/MBq (GP-M) for U-SPECT\(^+\). In the visually analysed sections of the reconstructed mini Derenzo phantoms, rods as small as 0.35 mm (XUHR-M), 0.50 mm (GP-M) for the two-detector as well as the three-detector SPECT and 0.75 mm (UHS-M) were resolved. Uniformity for maximum resolution recorded 40.7% (XUHR-M), 29.1% (GP-M, U-SPECT5-E), 16.3% (GP-M, U-SPECT\(^+\)) and 23.0% (UHS-M), respectively. UHS-M reached highest CNR values for low-count images; for rods smaller than 0.45 mm, acceptable CNR was only achieved by XUHR-M. GP-M was superior for imaging rods sized from 0.60 to 1.50 mm for intermediate activity concentrations. U-SPECT5-E and U-SPECT+ both provided comparable CNR.
Conclusions
While uniformity and sensitivity are negatively affected by the absence of a third detector, the investigated U-SPECT5-E system with two stationary detectors delivers excellent spatial resolution and CNR comparable to the performance of an established three-detector-setup.
The heart failure (HF) epidemic continues to rise with coronary artery disease (CAD) as one of its main causes. Novel concepts for risk stratification to guide the referring cardiologist towards revascularization procedures are of significant value. Myocardial perfusion imaging (MPI) using single-photon emission computed tomography (SPECT) agents has demonstrated high accuracy for the detection of clinically relevant stenoses. With positron emission tomography (PET) becoming more widely available, mainly due to its diagnostic performance in oncology, perfusion imaging with that modality is more practical than in the past and overcomes existing limitations of SPECT MPI. Advantages of PET include more reliable quantification of absolute myocardial blood flow, the routine use of computed tomography for attenuation correction, a higher spatiotemporal resolution and a higher count sensitivity. Current PET radiotracers such as rubidium-82 (half-life, 76 sec), oxygen-15 water (2 min) or nitrogen-13 ammonia (10 min) are labeled with radionuclides with very short half-lives, necessitating that stress imaging is performed under pharmacological vasodilator stress instead of exercise testing. However, with the introduction of novel 18F-labeled MPI PET radiotracers (half-life, 110 min), the intrinsic advantages of PET can be combined with exercise testing. Additional advantages of those radiotracers include, but are not limited to: potentially improved cost-effectiveness due to the use of pre-existing delivery systems and superior imaging qualities, mainly due to the shortest positron range among available PET MPI probes. In the present review, widely used PET MPI radiotracers will be reviewed and potential novel 18F-labeled perfusion radiotracers will be discussed.
The EANM 2015 Annual Congress, held from October 10th to 14th in Hamburg, Germany, was outstanding in many respects. With 5550 participants, this was by far the largest European congress concerning nuclear medicine. More than 1750 scientific presentations were submitted, with more than 250 abstracts from young scientists, indicating that the future success of our discipline is fuelled by a high number of young individuals becoming involved in a multitude of scientific activities. Significant improvements have been made in molecular imaging of cancer, particularly in prostate cancer. PSMA-directed PET/CT appears to become a new gold standard for staging and restaging purposes. Novel tumour specific compounds have shown their potential for target identification also in other solid neoplasms and further our understanding of tumour biology and heterogeneity. In addition, a variety of nuclear imaging techniques guiding surgical interventions have been introduced. A particular focus of the congress was put on targeted, radionuclide based therapies. Novel theranostic concepts addressing also tumour entities with high incidence rates such as prostate cancer, melanoma, and lymphoma, have shown effective anti-tumour activity. Strategies have been presented to improve further already established therapeutic regimens such as somatostatin receptor based radio receptor therapy for treating advanced neuroendocrine tumours. Significant contributions were presented also in the neurosciences track. An increasing number of target structures of high interest in neurology and psychiatry are now available for PET and SPECT imaging, facilitating specific imaging of different subtypes of dementia and movement disorders as well as neuroinflammation. Major contributions in the cardiovascular track focused on further optimization of cardiac perfusion imaging by reducing radiation exposure, reducing scanning time, and improving motion correction. Besides coronary artery disease, many contributions focused on cardiac inflammation, cardiac sarcoidosis, and specific imaging of large vessel vasculitis. The physics and instrumentation track included many highlights such as novel, high resolution scanners. The most noteworthy news and developments of this meeting were summarized in the highlights lecture. Only 55 scientific contributions were mentioned, and hence they represent only a brief summary, which is outlined in this article. For a more detailed view, all presentations can be accessed by the online version of the European Journal of Nuclear Medicine and Molecular Imaging (Volume 42, Supplement 1).
As a scintigraphic approach evaluating cardiac nerve integrity, \(^{123}\)I-metaiodobenzylguanidine (123I-mIBG) has been recently Food and Drug Administration approved. A great deal of progress has been made by the prospective ADMIRE-HF trial, which primarily demonstrated the association of denervated myocardium assessed by \(^{123}\)I-mIBG and cardiac events. However, apart from risk stratification, myocardial nerve function evaluated by molecular imaging should also be expanded to other clinical contexts, in particular to guide the referring cardiologist in selecting appropriate candidates for specific therapeutic interventions. In the present issue of the Journal of Nuclear Cardiology, the use of 123I-mIBG for identifying cardiomyopathy patients, which would most likely not benefit from ICD due low risk of arrhythmias, is described. If we aim to deliver on the promise of cardiac innervation imaging as a powerful tool for risk stratification in a manner similar to nuclear oncology, studies such as the one reviewed here may imply an important step to lay the proper groundwork for a more widespread adoption in clinical practice.