Single-photon Emission Computed Tomography Myocardial Imaging Research Articles

The Effect of an Energy Window with an Ellipsoid Phantom on the Differential Defect Contrast on Myocardial SPECT Images.

Good quality single-photon emission computed tomography (SPECT) images are required to achieve a perfect diagnosis and determine the severity of defects within the myocardial wall. There are many techniques that can support the diagnosis of defect formations in acquired images and contribute to avoiding errors before image construction. The main aim of this study was to determine the effect of energy width (15%, 20%, and 25%) on defect contrast in myocardial SPECT images correlated with the decentralization of positioning of a phantom. A phantom of polyethylene plastic was used to mimic the myocardial wall of the left ventricle. The phantom consists of two chambers, inner and outer. Two rectangular pieces of plastic were placed in anterior and inferior locations in the mid-region of the myocardial phantom to simulate myocardial infarction (defects). The average defect contrast for all phantom positions using 15% to 20% energy was (1.2, 1.6) for the anterior region and (1.1, 2) for the inferior region, respectively. Additionally, the energy window width was >25% with a large displacement of the positioning off center, leading to loss of the defect contrast in myocardial SPECT images, particularly in the inferior region. The study showed decreasing defect contrast in both locations, anterior and inferior, with increasing energy window width correlated with eccentricity positioning of the phantom on an imaging table.

Comparison of totally automated and manual processing for calculation of left ventricular volumes and ejection fraction using gated myocardial perfusion SPECT

ated single-photon emission computed tomography (SPECT) allows for the assessment of myocardial left ventricular ejection fraction and left ventricular volumes. There is conflicting data regarding the difference between automated and manual processing of gated myocardial SPECT images. The purpose of this retrospective “cross-sectional study is to compare the degree of variability between automated and manual processing of Quantitative Gated SPECT algorithms for assessing left ventricular volumes and ejection percent”. Study was carried out in the Nuclear Medicine department “at the Security Forces Hospital, Riyadh, Saudi Arabia, and comprised of 96 participants who “underwent” both stress and “rest gated” myocardial perfusion “imaging” (MPI) from February to May 2021. Data were analyzed “using SPSS for Windows (version 22; IBM Corp., Armonk, NY, USA). The mean of EF, ESV, and EDV on stress test using the automatic technique were 62.46 ± 14.62%, 45.00 ± 37.10 ml, and 107.01 ± 43.70 ml, respectively while using the manual technique were 57.21±14.80%, 44.35±35.93 ml, and 93.26±39.14 ml, respectively. The mean of EF, ESV, and EDV on rest test using the automatic technique were 62.85± 15.47%, 43.44± 36.35 ml, and 104.27±42.51 ml, respectively while using the manual technique were 57.74±15.33%, 43.30±36.42 ml, and 91.72±41.50 ml, respectively. For LVEF and EDV, the difference between automated and manual techniques is statistically significant (p<0.05). However, no “statistically significant difference” exists between automated and manual ESV techniques (p>0.05). Discrepancies were observed that exist by using the fully automated and manual technique for determining LVEF and Left ventricular volumes by gated MPI.

Added Prognostic Value of Plaque Burden to Computed Tomography Angiography and Myocardial Perfusion Imaging in Patients with Diabetes

BackgroundWe aimed to compare the added prognostic value of plaque burden to cardiac computed tomographic angiography (CCTA) anatomic assessment and single-photon emission computed tomography (SPECT) physiologic assessment in patients with diabetes undergoing both tests. MethodsConsecutive patients with diabetes who underwent clinically indicated CCTA and SPECT myocardial imaging for suspected coronary artery disease were included. Stenosis severity and segment involvement score (SIS) were determined from CCTA, and presence of ischemia was determined from SPECT. Patients were followed from date of imaging for major adverse cardiovascular events (MACE). ResultsA total of 778 patients were included (mean age 60.6 ± 14.4 years, 55% males). After a median follow-up of 31 months, 87 (11%) patients experienced a MACE. In multivariable Cox regression models, SIS significantly predicted outcomes in models including obstructive stenosis and ischemia (hazard ratio 1.17, 95% confidence interval 1.10-1.24, P < .001; hazard ratio 1.16, 95% confidence interval 1.10-1.23, P < .001, respectively), and improved discrimination (Harrel's C 0.75, P = .006; 0.76, P = .006 in models with CCTA obstructive stenosis and SPECT ischemia, respectively). Results were consistent using subgroups of summed scores by composition of plaque (calcified vs noncalcified) and alternate definitions of obstructive stenosis. ConclusionOur results suggest that in high-risk patients with diabetes and suspected coronary disease, SIS has incremental prognostic value over ischemia by SPECT or stenosis by CCTA in predicting incident cardiovascular outcomes.

A myocardial extraction method using deep learning for 99mTc myocardial perfusion SPECT images: A basic study to reduce the effects of extra-myocardial activity

AimThe purpose of this study was to automatically extract myocardial regions from transaxial single-photon emission computed tomography (SPECT) images using deep learning to reduce the effects of extracardiac activity, which has been problematic in cardiac nuclear imaging. Method: Myocardial region extraction was performed using two deep neural network architectures, U-Net and U-Net ++, and 694 myocardial SPECT images manually labeled with myocardial regions were used as the training data. In addition, a multi-slice input method was introduced during the learning session while taking the relationships to adjacent slices into account. Accuracy was assessed using Dice coefficients at both the slice and pixel levels, and the most effective number of input slices was determined. Results: The Dice coefficient was 0.918 at the pixel level, and there were no false positives at the slice level using U-Net++ with 9 input slices. Conclusion: The proposed system based on U-Net++ with multi-slice input provided highly accurate myocardial region extraction and reduced the effects of extracardiac activity in myocardial SPECT images.

Added prognostic value of plaque burden to computed tomography angiography anatomic assessment and myocardial perfusion imaging in patients with diabetes Mellitus

Abstract Introduction Cardiac computed tomographic angiography (CCTA)-derived measures of coronary artery disease (CAD) burden such as segment involvement score (SIS), which quantifies the number of segments with plaque, have been shown to independently predict incident cardiovascular events. Purpose We aimed to compare the added prognostic value of plaque burden to CCTA anatomic assessment and single photon emission computed tomography (SPECT) physiologic assessment in patients with diabetes undergoing both tests. Methods Consecutive patients with diabetes who underwent clinically indicated CCTA and SPECT myocardial imaging for suspected coronary artery disease at a tertiary care center were retrospectively identified from medical records. Stenosis severity and segment involvement score (SIS) were determined from CCTA, and presence of ischemia was determined from SPECT. Patients were followed from date of imaging for major adverse cardiovascular events (MACE; inclusive of all-cause death, non-fatal myocardial infarction, and percutaneous coronary intervention or coronary artery bypass grafting 90-days after imaging test.) Results A total of 778 patients were included (mean age 60.6±14.4 years, 55% males). Obstructive stenosis (left main ≥50%, all other coronary segments ≥70%) and ischemia were found in 15% and 16% of patients respectively. After a median follow-up of 31 months, 87 (11%) patients experienced a MACE. In multivariable Cox regression models, SIS significantly predicted outcomes in models including obstructive stenosis and ischemia (HR 1.17, 95% CI 1.10 - 1.24, p&amp;lt;0.001; 1.16, 95% CI 1.10 - 1.23, p&amp;lt;0.001). The addition of SIS also significantly improved discrimination (Harrel's C 0.75, p=0.006; 0.76, p=0.006 in models with CCTA obstructive stenosis and SPECT ischemia respectively). Results were consistent using subgroups of summed scores by composition of plaque (calcified vs non-calcified) and alternate definitions of obstructive stenosis. Conclusion Our results suggest that in high-risk patients with diabetes and suspected coronary disease, SIS has incremental prognostic value over ischemia by SPECT or stenosis by CCTA in predicting incident cardiovascular outcomes. Funding Acknowledgement Type of funding sources: None.

Added prognostic value of plaque burden to computed tomography angiography and myocardial perfusion imaging

Background and aimsCardiac computed tomographic angiography (CCTA) - derived measures of coronary artery disease (CAD) burden have been shown to independently predict incident cardiovascular events. We aimed to compare the added prognostic value of plaque burden to CCTA anatomic assessment and single photon emission computed tomography (SPECT) physiologic assessment in a cohort with high prevalence of risk factors undergoing both tests. MethodsConsecutive patients who underwent clinically indicated CCTA and SPECT myocardial imaging for suspected CAD were included. Stenosis severity and segment involvement score (SIS - number of segments with plaque irrespective of stenosis) were determined from CCTA, and presence of ischemia was determined from SPECT. Patients were followed for major adverse cardiovascular events (MACE, inclusive of all-cause death, non-fatal myocardial infarction, and percutaneous coronary intervention or coronary artery bypass grafting 90-days after imaging test.) ResultsA total of 956 patients were included (mean age 61.1 ± 14.2 years, 54% men, 89% hypertension, 81% diabetes, 84% dyslipidemia). Obstructive stenosis (left main ≥50%, all other coronary segments ≥70%) and ischemia were observed in a similar number of patients (14%). In multivariable Cox regression models, SIS significantly predicted outcomes and improved risk discrimination in models with CCTA obstructive stenosis (HR 1.15, p ≤ 0.001; Harrel's C 0.74, p = 0.008) and SPECT ischemia (HR 1.14, p < 0.001; Harrel's C 0.76, p = 0.019). ConclusionsOur results suggest that in patients with suspected CAD and a high prevalence of risk-factors, plaque burden adds incremental prognostic value over established CCTA and SPECT measures to predict incident cardiovascular outcomes.

Incremental prognostic value of calcified vs non-calcified plaque burden on computed tomography angiography and myocardial perfusion imaging

Abstract Funding Acknowledgements Type of funding sources: None. Background Coronary computed tomography angiography (CCTA) is currently guideline-endorsed for diagnosing suspected coronary artery disease (CAD) in low-intermediate risk patients. Single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has an established role in both the accurate detection of ischemia and identification of patients at high risk of future cardiovascular events. Recent studies have shown that the burden of atherosclerotic plaque is an independent predictor of cardiovascular events, and that this effect depends on the degree of calcification. Purpose To compare the incremental prognostic value of calcified vs non-calcified plaque burden to CCTA anatomic assessment and SPECT physiologic assessment in patients evaluated with both tests. Methods Consecutive patients who underwent clinically indicated CCTA and SPECT myocardial imaging for suspected CAD were included. Ischemia on SPECT was defined as summed difference score &amp;gt; 0 using perfusion graded on a 5-point scale. Anatomically obstructive CAD by CCTA was defined as ≥50% in the left main artery and ≥70% stenosis severity in proximal, mid and distal branches of the left anterior descending, left circumflex and right coronary artery without including side branches. Segment involvement score was defined as the sum of segments with plaque irrespective of the degree of stenosis using an 18-segment coronary artery model. A Hounsfield unit threshold of &amp;gt; =130 was used to classify plaques composition as calcified/mixed (C-SIS) vs non-calcified plaque (NC-SIS). Patients were followed for major adverse cardiovascular events (MACE, inclusive of all-cause death, non-fatal myocardial infarction, and percutaneous coronary intervention or coronary artery bypass grafting 90-days after imaging test.) Results A total of 956 patients were included. (Mean age 61.1 ± 14.2 years, 54% men, 89% hypertension, 81% diabetes, 84% dyslipidemia). Obstructive stenosis (left main ≥ 50%, all other coronary segments ≥ 70%) and ischemia were observed in similar number of patients (14%). After a median follow-up of 31 months, 102 patients (11%, 29.2 events per 1000 person-year) experienced a MACE. In multivariable Cox regression models, C-SIS, but not NC-SIS significantly predicted outcomes and improved risk discrimination in models with CCTA obstructive stenosis (HR 1.14 95% CI 1.08 - 1.20 p= &amp;lt;0.001; Harrel’s C 0.74, p = 0.011) and SPECT ischemia (HR 1.14 95% CI 1.08 - 1.20, p &amp;lt; 0.001; Harrel’s C 0.76, p = 0.015). Conclusion In the current study of high-risk patients with suspected CAD, calcified plaque burden, but not non-calcified plaque incrementally added to measures in predicting incident cardiovascular outcomes

Development of a new Python-based cardiac phantom for myocardial SPECT imaging.

The aim of this work was to develop a digital dynamic cardiac phantom able to mimic gated myocardial perfusion single photon emission computed tomography (SPECT) images. A software code package was written to construct a cardiac digital phantom based on mathematical ellipsoidal model utilizing powerful numerical and mathematic libraries of python programing language. An ellipsoidal mathematical model was adopted to create the left ventricle geometrical volume including myocardial boundaries, left ventricular cavity, with incorporation of myocardial wall thickening and motion. Realistic myocardial count density from true patient studies was used to simulate statistical intensity variation during myocardial contraction. A combination of different levels of defect extent and severity were precisely modeled taking into consideration defect size variation during cardiac contraction. Wall thickening was also modeled taking into account the effect of partial volume. It has been successful to build a python-based software code that is able to model gated myocardial perfusion SPECT images with variable left ventricular volumes and ejection fraction. The recent flexibility of python programming enabled us to manipulate the shape and control the functional parameters in addition to creating variable sized-defects, extents and severities in different locations. Furthermore, the phantom code also provides different levels of image filtration mimicking those filters used in image reconstruction and their influence on image quality. Defect extent and severity were found to impact functional parameter estimation in consistence to clinical examinations. A python-based gated myocardial perfusion SPECT phantom has been successfully developed. The phantom proved to be reliable to assess cardiac software analysis tools in terms of perfusion and functional parameters. The software code is under further development and refinement so that more functionalities and features can be added.

Single-Photon Emission Computed Tomography Myocardial Ischemia Detection in High-Risk Asymptomatic Patients: Correlation with Coronary Calcium Score and High-Sensitivity C-Reactive Protein.

Background:The association between myocardial ischemia in high-risk patients with coronary calcium score (CCS) and high-sensitivity C-reactive protein (hs-CRP) is not well established.Aims:We evaluated the correlation between hs-CRP, CCS, and myocardial ischemia in asymptomatic high-risk patients without known coronary artery disease (CAD).Materials and Methods:We prospectively assessed 68 asymptomatic high-risk outpatients without known CAD. One-day rest-stress Tc-99m single-photon emission computed tomography (SPECT) myocardial perfusion imaging and multislice computed tomography were performed. Multivariate regression analysis was performed for the assessment of predictors of myocardial ischemia. Standard risk factors and hs-CRP values were analyzed.Results:CCS >0 Agatston score was observed in 26 patients (46.4%). Seven patients had CCS between 10 and 99 AU, 8 patients between 100 and 400 AU, and 11 patients had CCS >400 AU. Mild ischemia was noted in 11 patients, moderate ischemia in 10 patients, and severe ischemia in 6 patients. Hs-CRP was >1 mg/L in 39 patients, of whom 8 patients had CCS >0, 13 patients had normal SPECT results, 6 patients had mild ischemia, and 12 patients had moderate and severe ischemia. Multivariate regression analysis showed independent predictors for increased CCS: low-density lipoprotein cholesterol (odds ratio [OR]: 2.891; P = 0.001); age >70 years (OR: 2.568; P = 0.001); and smoking (OR: 1.931; P = 0.001). We found hs-CRP to be an independent predictor of myocardial ischemia (OR: 4.145; 95% confidence interval: 1.398–7.471, P = 0.001).Conclusion:hs-CRP was an independent predictor of myocardial ischemia. hs-CRP might improve the selection of high-risk asymptomatic patients for myocardial SPECT imaging.

In vivo validation of gated myocardial SPECT imaging for quantification of small hearts: comparison with cardiac MRI.

BackgroundIn patients with small hearts, the Quantitative Gated single-photon emission computed tomography (SPECT) (QGS) program frequently underestimates the left ventricular (LV) end-systolic volume (ESV) and overestimates the ejection fraction (EF). A newly developed cardiac software program, cardioREPO/EXINI heart (cREPO), has been proposed to more accurately quantify small hearts using active shape modeling and a volume-dependent edge correction algorithm for LV delineation. The aim of this study was to validate cREPO in vivo for measuring the LV volumes and EF of both small and non-small hearts, in comparison with values obtained via cardiac MRI (CMR).MethodsWe performed stress 99mTc-MIBI SPECT and CMR within a 30-day interval for 44 patients (mean age, 66 years; 27 men). Resting EF, end-diastolic volume (EDV), and ESV with QGS and cREPO were compared with values obtained via CMR.ResultsThe subjects consisted of 17 small and 27 non-small hearts. CMR yielded EDV, ESV, and EF values of 135 ± 31 ml (mean ± SD, range 85–217 ml), 57 ± 21 ml (27–105 ml), and 60 ± 6 % (45–70 %), respectively. Compared with CMR, both QGS and cREPO systematically underestimated both EDV and ESV and overestimated EF. The magnitude of the overestimation of EF by QGS, compared with CMR, correlated strongly with the given EF values (r = 0.71, P < 0.0001). In contrast, no significant correlation was seen with cREPO (r = 0.18, P = 0.24). In addition, no significant correlation was found between the magnitude of the underestimation of ESV and heart size with cREPO (r = 0.03, P = 0.83). Thus, cREPO provided a relatively constant 9 % overestimation of EF values relative to CMR, for the studied EF range for both small and non-small hearts.ConclusionsThe use of the new algorithm of cREPO ameliorated exaggerated EF in small hearts but not resolved completely. The program provided a constant 9 % overestimation for both small and non-small hearts, which should be carefully taken into account for clinical assessment of LV function.

Adenovirus-mediated expression of human sodium-iodide symporter gene permits in vivo tracking of adipose tissue-derived stem cells in a canine myocardial infarction model

IntroductionIn vivo tracking of the transplanted stem cells is important in pre-clinical research of stem cell therapy for myocardial infarction. We examined the feasibility of adenovirus-mediated sodium iodide symporter (NIS) gene to cell tracking imaging of transplanted stem cells in a canine infarcted myocardium by clinical single photon emission computed tomography (SPECT). MethodsBeagle dogs were injected intramyocardially with NIS-expressing adenovirus-transfected canine stem cells (Ad-hNIS-canine ADSCs) a week after myocardial infarction (MI) development. 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) and 99mTc-pertechnetate (99mTcO4−) SPECT imaging were performed for assessment of infarcted myocardium and viable stem cell tracking. Transthoracic echocardiography was performed to monitor any functional cardiac changes. ResultsLeft ventricular ejection fraction (LVEF) was decreased after LAD ligation. There was no significant difference in EF between the groups with the stem cell or saline injection. 125I uptake was higher in Ad-hNIS-canine ADSCs than in non-transfected ADSCs. Cell proliferation and differentiation were not affected by hNIS-carrying adenovirus transfection. 99mTc-MIBI myocardial SPECT imaging showed decreased radiotracer uptake in the infarcted apex and mid-anterolateral regions. Ad-hNIS-canine ADSCs were identified as a region of focally increased 99mTcO4− uptake at the lateral wall and around the apex of the left ventricle, peaked at 2 days and was observed until day 9. ConclusionsCombination of adenovirus-mediated NIS gene transfection and clinical nuclear imaging modalities enables to trace the fate of transplanted stem cells in infarcted myocardium for translational in vivo cell tracking study for prolonged duration.

Association between heart rate at rest and myocardial perfusion in patients with acute myocardial infarction undergoing cardiac rehabilitation – a pilot study

IntroductionThis study was conducted to determine if there was a link among heart rate at rest (rHR), muscle volume changes, and single photon emission computed tomography (SPECT) parameters after 6-month cardiac rehabilitation in patients with acute myocardial infarction (AMI).Material and methodsTwenty-nine consecutive AMI patients (mean age: 63.0 ±9.1 years) who received appropriate percutaneous coronary intervention on admission were enrolled. 99mTc-Sestamibi myocardial SPECT images were obtained at the early (30 min) and delayed (4 h) phases after tracer injection at 2 weeks (0M) and 6 months (6M) after the onset of AMI. Within a few days of SPECT, all patients underwent cardiopulmonary exercise test for evaluation of cardiac rehabilitation effects. Before the initiation of exercise test, leg muscle volume was measured. All patients were stratified into the ≥ 70 beats per minute (bpm) (n = 15) or < 70 bpm (n = 14) group based on rHR at 6M.ResultsThere were no significant differences in the recanalization time, peak cardiac enzyme, or initial left ventricular ejection fraction between the two groups. After the 6-month training, the muscle volume changes in the lower limbs (< 70 bpm, 0.23 ±0.22; ≥ 70 bpm, –0.07 ±0.26, p < 0.05) were significantly greater in the < 70 bpm group than the ≥ 70 bpm group. The decreased rate of rHR had a significant correlation with the improved global severity (r = 0.62, p = 0.001) and extent (r = 0.48, p = 0.017) of left ventricle evaluated by 99mTc-Sestamibi myocardial SPECT delayed phase.ConclusionsThe result of this preliminary study demonstrated that improved myocardial perfusion was closely related to decreased rHR after cardiac rehabilitation.

Metalloprobes for functional monitoring of tumour multidrug resistance by nuclear imaging

Cancer chemotherapy has been used since the early 1950s and still remains one the major therapeutic options for many malignant tumours. A major obstacle to successful cancer chemotherapy is drug resistance. Frequently resistance is intrinsic to the cancer, but as therapy becomes more effective, acquired resistance has also become more frequent. One form of resistance, named multidrug resistance (MDR), is responsible for the failure of tumours to respond to a wide spectrum of chemotherapeutic agents. The in vivo monitoring of MDR could assist in the selection of patients for therapy and can avoid ineffective and potentially toxic treatments. Therefore, methods for functionally interrogating MDR transport activity have been sought, namely single photon emission computed tomography (SPECT) and positron emission tomography (PET). Cationic radiotracers originally developed as SPECT myocardial imaging agents, such as [(99m)Tc(MIBI)(6)](+) and [(99m)Tc(tetrofosmin)(2)O(2)](+), are used for both early cancer detection and non-invasive monitoring of the tumour MDR transport function. With the ultimate goal of obtaining better performing radioprobes for MDR imaging, other metal-based complexes and/or small molecules have also been synthesized and biologically evaluated. In this perspective we will report on the chemical efforts made to find metalloprobes for in vivo monitoring of MDR by nuclear imaging techniques. The current knowledge on the biological mechanisms and proteins involved in tumour MDR will be also briefly presented, as its understanding is invaluable for the rational design and biological evaluation of new radioprobes.

Clinical usefulness of a collimator distance dependent resolution recovery in myocardial perfusion SPECT: a clinical report from a single institute

Imperfect image resolution because of finite-sized collimator channels often causes a decrease in diagnostic performance in myocardial perfusion single-photon emission computed tomography (SPECT). This prompted us to evaluate the clinical usefulness of collimator distance dependent resolution recovery (RR) in myocardial perfusion SPECT. We retrospectively reviewed myocardial SPECT images of 60 consecutive patients (26 men, 34 women; mean age 68 years). They consisted of 25 with coronary artery disease (CAD) and 35 without, as confirmed by the coronary angiography (CAG). The patients had undergone myocardial perfusion SPECT imaging with thallium-201 (111 MBq) under an exercise or pharmacological stress protocol. Two readers reviewed the myocardial SPECT images for the presence of CAD on a 4-point scale where 0 = normal, 1 = probably normal, 2 = probably abnormal, and 3 = abnormal. Three reading sessions were held: first, ordered subsets expectation maximization (OSEM) SPECT images, second, OSEM with RR images, and third, both OSEM and RR images. Diagnostic performance for accuracy of coronary arterial stenoses was compared for OSEM, RR and both the images. The sensitivity increased using RR images, but specificity decreased, and thus overall diagnostic accuracy was decreased, as compared with using OSEM images. The overall accuracy of using both the images showed the highest diagnostic performance among the three sets of image interpretations. The sensitivity, specificity and accuracy were 33, 92, 77% for OSEM, 53, 79, 72% for RR and 51, 90, 80% for both the images. These results suggest that RR for myocardial perfusion SPECT imaging has some potential to improve diagnostic accuracy, but both OSEM and RR image sets may have to be employed for the best diagnosis of CAD.

3-D Surface Rendering of Myocardial SPECT Images Segmented by Level Set Technique

SPECT(single photon emission computed tomography) myocardial imaging is a diagnosis technique that images the region of interest and examines any change induced by disease using a computer after injects intravenously a radiopharmaceutical drug emitting gamma ray and the drug has dispersed evenly in the heart . Myocardial perfusion imaging, which contains functional information, is useful for non-invasive diagnosis of myocardial disease but noises caused by physical factors and low resolution give difficulty in reading the images. In order to help reading myocardial images, this study proposed a method that segments myocardial images and reconstructs the segmented region into a 3D image. To resolve difficulty in reading, we segmented the left ventricle, the region of interest, using a level set and modeled the segmented region into a 3D image.

WE‐D‐201B‐04: Advances in Instrumentation and Techniques for Quantitative Myocardial Perfusion SPECT

Myocardial perfusion (MP) SPECT (single‐photon emission computed tomography) is a leading diagnostic tool for cardiovascular disease. Its continued importance and popularity have been fueled by new advances in instrumentation and image reconstruction and processing methods. Quantitative three‐dimensional (3D) image reconstruction methods that model the counting statistics in the acquired data and the physics of the imaging process have been widely adopted in clinical practice. They provide improved reconstructed image noise and accurate compensation of image degrading factors including collimator‐detector blur, and photon attenuation and scatter in the patient resulting in significant improvement in both the quality and quantitative accuracy of MP SPECT images. Extension of the quantitative 3D image reconstruction method to four‐dimensional (4D) has been shown to benefit 4D gated MP SPECT. Special collimators designed to provide both improved spatial resolution and increased detection efficiency have been developed and implemented on conventional SPECT systems for application to MP SPECT. The need to provide accurate attenuation compensation and anatomical correlation with MP information for individual patient has resulted in the development of multimodality SPECT/CT systems which have become standard system configuration. More recently, dedicated cardiac SPECT and SPECT/CT systems have emerged in the market place that hold great promise to advance MP SPECT a big step forward. The presentation will describe the basic principles of quantitative 3D and 4D image reconstruction methods. Advances in special collimation and SPECT/CT system designs for MP SPECT will be presented. The improvement in image quality and quantitative accuracy will be demonstrated by simulated, experimental phantom and clinical images.Learning Objectives:1. Describe the basic principles of quantitative 3D and 4D image reconstruction methods that have led to significant improved quality and quantitative accuracy of 3D and 4D gated myocardial perfusion and SPECT images.2. Describe the recent advances in instrumentation for improve myocardial perfusion SPECT.3. Demonstrate the advances using simulated, experimental phantom and clinical MP SPECT images.

Evaluating image denoising methods in myocardial perfusion single photon emission computed tomography (SPECT) imaging

The statistical nature of single photon emission computed tomography (SPECT) imaging, due to the Poisson noise effect, results in the degradation of image quality, especially in the case of lesions of low signal-to-noise ratio (SNR). A variety of well-established single-scale denoising methods applied on projection raw images have been incorporated in SPECT imaging applications, while multi-scale denoising methods with promising performance have been proposed. In this paper, a comparative evaluation study is performed between a multi-scale platelet denoising method and the well-established Butterworth filter applied as a pre- and post-processing step on images reconstructed without and/or with attenuation correction. Quantitative evaluation was carried out employing (i) a cardiac phantom containing two different size cold defects, utilized in two experiments conducted to simulate conditions without and with photon attenuation from myocardial surrounding tissue and (ii) a pilot-verified clinical dataset of 15 patients with ischemic defects. Image noise, defect contrast, SNR and defect contrast-to-noise ratio (CNR) metrics were computed for both phantom and patient defects. In addition, an observer preference study was carried out for the clinical dataset, based on rankings from two nuclear medicine clinicians. Without photon attenuation conditions, denoising by platelet and Butterworth post-processing methods outperformed Butterworth pre-processing for large size defects, while for small size defects, as well as with photon attenuation conditions, all methods have demonstrated similar denoising performance. Under both attenuation conditions, the platelet method showed improved performance with respect to defect contrast, SNR and defect CNR in the case of images reconstructed without attenuation correction, however not statistically significant (p > 0.05). Quantitative as well as preference results obtained from clinical data showed similar performance of the denoising methods studied. In conclusion, the multi-scale platelet denoising method applied on raw projection images provides more efficient noise reduction while preserving image quality in a myocardial phantom SPECT imaging as compared to the Butterworth filter applied either on projection or reconstructed images.However, this trend in favour of the platelet denoising method was not observed on clinical data reconstructed either without or with attenuation correction.

New protocol of myocardial SPECT imaging with technetium-99m sestamibi for reducing the time interval between rest and adenosine stress phases

We have developed a new protocol of myocardial perfusion-gated single-photon emission computed tomography (SPECT), by use of technetium-99m sestamibi (MIBI), in which SPECT imaging at rest followed by SPECT imaging after adenosine with low level ergometer stress can be conducted by use of the Monzen position within a shortened total testing time of 1 h or less. The study group consisted of 137 patients who underwent this new imaging protocol. The diagnostic quality of the images was as good as that of images obtained with the conventional method (30-60 min after the injection of MIBI). The SPECT image quality for the 137 patients was evaluated, and the percentages of images rated as excellent, good, fair, and poor were 65.3, 27.4, 5.8, and 1.5% for the rest image, and 68.2, 21.9, 8.4, and 1.5% for the stress image, respectively. The shortened total testing time reduced the physical and mental burden on the patient compared with that of conventional myocardial perfusion imaging. Because this technique allows us to perform rest and stress myocardial imaging within a short period, it is expected to be very useful in the clinical setting.

Effect of Caffeine on Myocardial Perfusion Imaging Using Single Photon Emission Computed Tomography During Adenosine Pharmacologic Stress

Approximately 6 million cardiac stress tests are performed annually in the United States, of which 2.4 million are pharmacologic stress tests using agents such as adenosine. Adenosine induces differential coronary hyperemia in normal coronary arteries versus coronary arteries with atherosclerosis, allowing single photon emission computed tomography (SPECT) imaging to identify reduced coronary flow in segments subtended by diseased coronary arteries. The potential attenuation of pharmacologic effects of adenosine in the presence of caffeine is why patients are routinely instructed to abstain from caffeine for 12 to 24 hours prior to administration of an adenosine stress test. Failure to abstain from caffeine results in cancellation or delaying of cardiac stress testing, resulting in procedural delays and its impact on patient throughput. Recent studies have evaluated such interaction and suggested a lack of clinically significant effect of caffeine on adenosine-induced hyperemia during myocardial SPECT imaging. This article reviews the clinical pharmacology of caffeine, adenosine, and dipyridamole and effect of caffeine on myocardial stress testing using adenosine and dipyridamole in clinical cardiovascular medicine. The limited published data are conflicting, but some recent publications suggest that myocardial perfusion SPECT imaging using adenosine may not be clinically significantly altered by routine consumption of caffeine, such as a cup of coffee. Although prospective randomized studies would be required to obtain a definitive answer to this question, it appears on the basis of some of the studies reviewed in this article that caffeine consumption prior to myocardial perfusion imaging may not necessitate cancellation or rescheduling of adenosine stress testing.

Attenuation Artifact During Myocardial SPECT Imaging Secondary to Saline and Silicone Breast Implants

Breast attenuation artifacts are a major cause of false-positive results in gated single photon emission computed tomography (SPECT) studies in women. The presence of a saline or silicone breast implant as a foreign object anterior to the heart will increase the likelihood of these attenuation artifacts. Recently, the US Food and Drug Administration approved silicone implants for cosmetic use again in the United States. This brief report highlights the impact of breast implants on the accuracy of diagnostic cardiac SPECT imaging.