Characterization of myocardial perfusion imaging systems - an extension of quality metrics.

Purpose: The aim of this study was to evaluate the performance of myocardial perfusion imaging (MPI) systems in detecting perfusion defects (PDs). The defect perfusion index (DPI) was introduced to extend and further advance the current MPI quality metrics.

Methods: An anthropomorphic phantom simulating normal and pathological myocardial perfusion conditions was imaged by various NaI-crystal detector systems with and without corrections for scatter (SC) and attenuation (AC) (Symbia, Symbia + SC, Symbia IQ + SCAC, Symbia IQ), and cadmium-zinc-telluride detector systems without corrections (DSPECT, D530c).

Optimal Tc activity ratio in the single-day stress-rest myocardial perfusion imaging protocol: A multi-SPECT phantom study.

Background: This investigation used image data generated by an anthropomorphic phantom to determine the minimal Tc rest-stress activity concentration ratio (R) able to minimize the ghosting effect in the single-day stress-first myocardial perfusion imaging, using different positions of the perfusion defect (PD), scanners and reconstruction protocols.

Methods: A cardiac phantom with a simulated PD was imaged under different R using different gamma cameras and reconstruction algorithms. The residual activity from precedent stress administration was simulated by modeling effective half-times in each compartment of the phantom and assuming a delay of 3 hours between the stress and rest studies.

Impact of non-specific normal databases on perfusion quantification of low-dose myocardial SPECT studies.

Aim: To evaluate the impact of non-specific normal databases on the percent summed rest score (SR%) and stress score (SS%) from simulated low-dose SPECT studies by shortening the acquisition time/projection.

Methods: Forty normal-weight and 40 overweight/obese patients underwent myocardial studies with a conventional gamma-camera (BrightView, Philips) using three different acquisition times/projection: 30, 15, and 8 s (100%-counts, 50%-counts, and 25%-counts scan, respectively) and reconstructed using the iterative algorithm with resolution recovery (IRR) Astonish (Philips). Three sets of normal databases were used: (1) full-counts IRR; (2) half-counts IRR; and (3) full-counts traditional reconstruction algorithm database (TRAD).

Comparative analysis of iterative reconstruction algorithms with resolution recovery and new solid state cameras dedicated to myocardial perfusion imaging.

New technologies are available in myocardial perfusion imaging. They include new software that recovers image resolution and limits image noise, multifocal collimators and dedicated cardiac cameras in which solid-state detectors are used and all available detectors are constrained to imaging just the cardiac field of view. These innovations resulted in shortened study times or reduced administered activity to patients, while preserving image quality.

Differences in polar-map patterns using the novel technologies for myocardial perfusion imaging.

Background: New technologies are available in MPI. Our aim was to evaluate their impact on the uniformity of normal myocardial uptake in the polar-map representation, over different count statistics, with and without the attenuation (AC) and scatter corrections (SC).

Methods: A phantom study was performed using 5 Anger gamma cameras with filtered back projection or iterative reconstruction with resolution recovery (IRR), with or without SCAC; a D530c, with or without AC; and a D-SPECT.

Advances in image reconstruction software in nuclear cardiology: Is all that glitters gold?

The cornerstone results of nuclear cardiology in the last 25 years were obtained with the Filtered Back Projection as the preferred reconstruction method for tomographic studies. Recently, evolution of the OSEM iterative reconstruction algorithms was implemented by different vendors. The value and limitations of the new methods are briefly addressed.

Uncontrolled risk factors and worsening perfusion pattern on SPECT myocardial perfusion imaging in medically treated patients with stable chronic ischaemic heart disease.

Purpose: Few data exist on the correlation between the effectiveness of risk factor control and the evolution of myocardial perfusion over time in patients with stable ischaemic heart disease. The aim of the study was to evaluate the changes in stress-rest myocardial perfusion in medically treated patients with stable chronic ischaemic heart disease and the relationship with risk factor control.

Methods: The study cohort included 174 consecutive patients (age 60 ± 9 years, 68 % men) undergoing stress-rest myocardial perfusion imaging (MPI) (study 1), who also underwent repeat evaluation (study 2) and who were clinically stable on medical therapy.

Comparative analysis of full-time, half-time, and quarter-time myocardial ECG-gated SPECT quantification in normal-weight and overweight patients.

Background: The introduction of a camera-based dose-reduction strategy in myocardial perfusion imaging (MPI) clinical setting entails the definition of objective and reproducible criteria for establishing the amount of activity to be injected.

Aim: The aim is to evaluate the impact of count statistics on the estimation of summed-scores (SS), end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF).

Methods: Data rest/stress ECG-gated SPECT (2-day protocol and 8 MBq·kg) were acquired with Bright View gamma camera and Astonish algorithm for 40 normal-weight and 40 overweight patients.

Comparative analysis of iterative reconstruction algorithms with resolution recovery and time of flight modeling for F-FDG cardiac PET: A multi-center phantom study.

Background: The purpose of this study was to evaluate the image quality in cardiac F-FDG PET using the time of flight (TOF) and/or point spread function (PSF) modeling in the iterative reconstruction (IR).

Methods: Three scanners and an anthropomorphic cardiac phantom with an insert simulating a transmural defect (TD) were used. Two sets of scans (with/without TD) were acquired, and four reconstruction schemes were considered: (1) IR; (2) IR + PSF, (3) IR + TOF, and (4) IR + TOF + PSF.

Comparative analysis of cadmium-zincum-telluride cameras dedicated to myocardial perfusion SPECT: A phantom study.

Background: This investigation used image data generated by an anthropomorphic phantom with a cardiac insert for a comparison between two solid state cameras: D-SPECT and D530c.

Methods: For each camera, two sets (with and without a simulated transmural defect (TD)) of scans were acquired starting from the in vivo standard count statistics in the left ventricle (LV). Other two acquisitions corresponding to 150% and 50% of the reference count statistics were acquired.

The importance of a correct positioning of the heart using IQ-SPECT system with multifocal collimators in myocardial perfusion imaging: a phantom study.

Background: We have recently validated a quarter-time protocol in Myocardial Perfusion Imaging named IQ-SPECT, whose basic principle is to implement a multifocal collimator; However, in clinical practice, it may sometimes be difficult to center the heart in the region of highest magnification of the multifocal collimators (the so-called sweet spot). We therefore aimed to evaluate whether a heart mispositioning may affect results in MPI.

Methods: We simulated a rest study with an anthropomorphic phantom with an in vivo distribution of 400 MBq [(99m)Tc]tetrofosmin, with and without a transmural defect (TD).

Comparative analysis of iterative reconstruction algorithms with resolution recovery for cardiac SPECT studies. A multi-center phantom study.

Background: This investigation used image data generated by a physical phantom over a wide range of count statistics to evaluate the effectiveness of several of the newer commercially available SPECT reconstruction iterative algorithms (IRR) in improving perfusion defect contrast and spatial resolution, while controlling image noise.

Methods: A cardiac phantom was imaged using four different gamma cameras over a wide range of counts statistics (from 6 to 0.8 Mcounts).

Temporal evolution of administered activity in cardiac gated SPECT and patients' effective dose: analysis of an historical series.

Purpose: Myocardial perfusion imaging contributes >20 % of the average medical radiation exposure to the population in the USA. Imaging protocols able to achieve a radiation exposure ≤9 mSv in 50 % of the studies by 2014 have been recommended. The aim of this study was to analyse the temporal evolution of administered activities in patients scheduled for dual-day (99m)Tc tracer gated single photon emission computed tomography (SPECT) and to compare different dose administration protocols in terms of patients' effective dose.

Innovative reconstruction algorithms in cardiac SPECT scintigraphy.

The recent entry into the market of some advanced iterative reconstruction algorithms (IA) optimized for bone and cardiac studies has raised a great interest among specialists in nuclear medicine. In particular, myocardial perfusion studies have received a significant boost thanks to the superior quality of images obtained with these new reconstruction methods. Differently from the filtered back-projection (FBP), the basic principles of the iterative reconstruction techniques are less known; unclear is the way by which the iterative methods are able to include compensations for the main degradation phenomena in SPECT imaging.

Wide beam reconstruction for half-dose or half-time cardiac gated SPECT acquisitions: optimization of resources and reduction in radiation exposure.

Purpose: A new iterative reconstruction algorithm (WBR™) has been recently proposed for cardiac single photon emission computed tomography (SPECT). The WBR™ technology is designed to reduce noise, improving lesion identification without affecting the image resolution, allowing SPECT studies with reduced count statistic. This allows for either half-time (HT) or half-dose (HD) cardiac SPECT, with image quality and quantitative data comparable to standard-time (ST) or standard-dose (SD) SPECT.

Decreased [99mTc]Sestamibi uptake with dobutamine versus dipyridamole stress.

Aim: Animal studies suggest an interference of dobutamine on [99mTc]sestamibi uptake. In this study dobutamine was compared to dipyridamole rest-stress [99mTc]sestamibi uptake ratio (UR).

Methods: Twenty-five patients with suspect coronary artery disease (CAD) underwent rest, dobutamine, and dipyridamole [99mTc]sestamibi SPECT at 24-h intervals and coronary angiography.

ECG-manifest and ECG-silent dipyridamole technetium-99m sestamibi SPET perfusion defects in patients with ischaemic heart disease.

At dipyridamole myocardial scintigraphy, perfusion defects are seldom backed up by significant ECG changes. This would suggest myocardial blood flow heterogeneity, rather than true ischaemia, as the cause of the scintigraphic abnormalities. Electrocardiographic surface mapping has been documented to be more accurate than standard 12-lead ECG in the detection of provoked ischaemia.

Technetium-99m-sestamibi SPECT to detect restenosis after successful percutaneous coronary angioplasty.

Unlabelled: This study evaluated the accuracy of 99mTc SPECT in predicting restenosis after primary successful PTCA.

Methods: Thirty-seven patients with equivocal symptom-limited exercise stress testing were evaluated. All patients underwent separate day exercise-rest 99mTc-sestamibi SPECT.

Influence of the assessment of defect severity and intravenous nitrate administration during tracer injection on the detection of viable hibernating myocardium with data-based quantitative technetium 99m-labeled sestamibi single-photon emission computed tomography.

Background: This study aimed to verify whether the assessment of defect severity and the infusion of nitrates during tracer injection improve the capability of data-based 99mTc-labeled sestamibi single-photon emission computed tomography (SPECT) to recognize hibernating myocardium.

Methods And Results: Of 66 asynergic coronary territories in 40 patients with left ventricular dysfunction, 28 had postrevascularization functional recovery (hibernating) and 38 had unchanged dysfunction (fibrotic). Defect severity was lower in the hibernating than in the fibrotic territories on both baseline (p < 0.

Technetium-99m sestamibi tomographic evaluation of residual ischemia after anterior myocardial infarction.

Objectives: This study investigated the value of sestamibi scintigraphy in assessing residual ischemia after anterior myocardial infarction.

Background: Serial imaging with sestamibi, the uptake and retention of which correlate with regional myocardial blood flow and viability, has been used to estimate salvaged myocardium and risk area after acute infarction. We recently documented that recovery of perfusion and contraction in the infarcted area may continue well after the subacute phase, suggesting myocardial hibernation.

Evaluation of technetium-99m-sestamibi lung uptake: correlation with left ventricular function.

Unlabelled: Lung uptake of 201Tl is a reliable marker of left ventricular dysfunction. The goal of our study was to establish whether the evaluation of lung-to-heart uptake ratios (LHR) with 99mTc-sestamibi imaging may provide valuable information.

Methods: We studied 72 male subjects with recent anterior myocardial infarction undergoing 99mTc-sestamibi first-pass ventriculography and SPECT perfusion imaging.