Bailing Hsu

Quantitation of myocardial blood flow and myocardial flow reserve with 99mTc-sestamibi dynamic SPECT/CT to enhance detection of coronary artery disease.

PurposeConventional dual-head single photon emission computed tomography (SPECT)/CT systems capable of fast dynamic SPECT (DySPECT) imaging have a potential for flow quantitation. This study introduced a new method to quantify myocardial blood flow (MBF) and myocardial flow reserve (MFR) with DySPECT scan and evaluated the diagnostic performance of detecting coronary artery disease (CAD) compared with perfusion using invasive coronary angiography (CAG) as the reference standard.MethodsThis study included 21 patients with suspected or known CAD who had received DySPECT, ECG-gated SPECT (GSPECT), and CAG (13 with ≥50xa0% stenosis in any vessel; non-CAD group: 8 with patent arteries or <50xa0% stenosis). DySPECT and GSPECT scans were performed on a widely used dual-head SPECT/CT scanner. The DySPECT imaging protocol utilized 12-min multiple back-and-forth gantry rotations during injections of 99mTc-sestamibi (MIBI) tracer at rest or dipyridamole-stress stages. DySPECT images were reconstructed with full physical corrections and converted to the physical unit of becquerels per milliliter. Stress MBF (SMBF), rest MBF (RMBF), and MFR were quantified by a one-tissue compartment flow model using time-activity curves derived from DySPECT images. Perfusion images were processed for GSPECT scan and interpreted to obtain summed stress score (SSS) and summed difference score (SDS). Receiver-operating characteristic (ROC) analyses were conducted to evaluate the diagnostic performance of flow and perfusion.ResultsUsing the criteria of ≥50xa0% stenosis as positive CAD, areas under the ROC curve (AUCs) of flow assessment were overall significantly greater than those of perfusion. For patient-based analysis, AUCs for MFR, SMBF, SSS, and SDS were 0.91u2009±u20090.07, 0.86u2009±u20090.09, 0.64u2009±u20090.12, and 0.59u2009±u20090.13. For vessel-based analysis, AUCs for MFR, SMBF, SSS, and SDS were 0.81u2009±u20090.05, 0.76u2009±u20090.06, 0.62u2009±u20090.07, and 0.56u2009±u20090.08, respectively.ConclusionThe preliminary data suggest that MBF quantitation with a conventional SPECT/CT system and the flow quantitation method is a clinically effective approach to enhance CAD detection.

Feasibility and operator variability of myocardial blood flow and reserve measurements with 99mTc-sestamibi quantitative dynamic SPECT/CT imaging

PurposeMyocardial blood flow (MBF) quantification with dynamic SPECT could lead to widespread utilization of MBF imaging in clinical practice with little cost increase over current standard SPECT myocardial perfusion imaging. This work evaluates the feasibility and operator-dependent variability of MBF and flow reserve measurements with 99mTc-sestamibi (MIBI) dynamic SPECT imaging using a standard dual-head SPECT camera.MethodsTwenty-eight patients underwent dipyridamole-stress and rest imaging with dynamic SPECT/CT acquisition. Quantitative images were iteratively reconstructed with all physical corrections and then myocardial and arterial blood regions of interest (ROI) were defined semi-automatically. A compartmental model was fitted to these ROI-sampled time-activity-curves, and flow-dependent MIBI extraction correction was applied to derive regional MBF values. Myocardial flow reserve (MFR) was estimated as stress/rest MBF ratio. MBF and MFR in low and high risk populations were evaluated for ability to detect disease. Images were each processed twice (≥7xa0days apart) by one expert and one novice operator to evaluate intra- and inter-operator variability of MBF and MFR measurement in the three coronary artery vascular territories.ResultsMean rest flow, stress flow, and MFR values were 0.83, 1.82xa0mL·minute−1·g−1, and 2.45, respectively. For stress/rest MFR, the inter-operator reproducibility was r2xa0=xa00.86 with RPCxa0=xa01.1. Stress MBF and MFR were significantly reduced (Pxa0<xa0.05) in high risk (nxa0=xa09) vs low risk populations (nxa0=xa019), indicating ability to detect disease. For expert and novice operators very good intra-operator correlations of r2xa0=xa00.98 and 0.95 (nxa0=xa0168, Pxa0<xa0.001) were observed for combined rest and stress regional flow values. Bland-Altman reproducibility coefficients (RPC) were 0.25 and 0.47xa0mL·minute−1·g−1 for the expert and novice operators, respectively (Pxa0<xa0.001). Inter-operator correlation was r2xa0=xa00.91 and Bland-Altman RPCxa0=xa00.58xa0mL·minute−1·g−1 (nxa0=xa0336).ConclusionsMBF and reserve measurements using 99mTc-sestamibi on a traditional, two-headed camera with fast rotation and with quantitative dynamic SPECT appears to be feasible, warranting further investigation.

SPECT myocardial blood flow quantitation toward clinical use: a comparative study with 13N-Ammonia PET myocardial blood flow quantitation

ObjectivesThe aim of this study was to evaluate the accuracy of myocardial blood flow (MBF) quantitation of 99mTc-Sestamibi (MIBI) single photon emission computed tomography (SPECT) compared with 13N-Ammonia (NH3) position emission tomography (PET) on the same cohorts.BackgroundRecent advances of SPECT technologies have been applied to develop MBF quantitation as a promising tool to diagnose coronary artery disease (CAD) for areas where PET MBF quantitation is not available. However, whether the SPECT approach can achieve the same level of accuracy as the PET approach for clinical use still needs further investigations.MethodsTwelve healthy volunteers (HVT) and 16 clinical patients with CAD received both MIBI SPECT and NH3 PET flow scans. Dynamic SPECT images acquired with high temporary resolution were fully corrected for physical factors and processed to quantify K1 using the standard compartmental modeling. Human MIBI tracer extraction fraction (EF) was determined by comparing MIBI K1 and NH3 flow on the HVT group and then used to convert flow values from K1 for all subjects. MIBI and NH3 flow values were systematically compared to validate the SPECT approach.ResultsThe human MIBI EF was determined as [1.0-0.816*exp(−0.267/MBF)]. Global and regional MBF and myocardial flow reserve (MFR) of MIBI SPECT and NH3 PET were highly correlated for all subjects (global R2: MBFu2009=u20090.92, MFRu2009=u20090.78; regional R2: MBFu2009≥u20090.88, MFRu2009≥u20090.71). No significant differences for rest flow, stress flow, and MFR between these two approaches were observed (All pu2009≥u20090.088). Bland-Altman plots overall revealed small bias between MIBI SPECT and NH3 PET (global: ΔMBFu2009=u2009−0.03Lml/min/g, ΔMFRu2009=u20090.07; regional: ΔMBFu2009=u2009−0.07u2009−u20090.06 , ΔMFRu2009= −0.02 −u20090.22).ConclusionsQuantitation with SPECT technologies can be accurate to measure myocardial blood flow as PET quantitation while comprehensive imaging factors of SPECT to derive the variability between these two approaches were fully addressed and corrected.

Avoiding full corrections in dynamic SPECT images impacts the performance of SPECT myocardial blood flow quantitation

IntroductionThis study investigated the performance of SPECT myocardial blood flow (MBF) quantitation lacking full physical corrections (All Corr) in dynamic SPECT (DySPECT) images.MethodsEleven healthy normal volunteers (HVT) and twenty-four patients with angiography-documented CAD were assessed. All Corr in 99mTc-sestamibi DySPECT encompassed noise reduction (NR), resolution recovery (RR), and corrections for scatter (SC) and attenuation (AC), otherwise no correction (NC) or only partial corrections. The performance was evaluated by quality index (R2) and blood-pool spillover index (FBV) in kinetic modeling, and by rest flow (RMBF) and stress flow (SMBF) compared with those of All Corr.ResultsIn HVT group, NC diminished 2-fold flow uniformity with the most degraded quality (15%-18% reduced R2) and elevated spillover effect (45%-50% increased FBV). Consistently higher RMBF and SMBF were discovered in both groups (HVT 1.54/2.31 higher; CAD 1.60/1.72; all Pxa0<xa0.0001). Bland-Altman analysis revealed positive flow bias (HVT 0.9-2.6xa0mL/min/g; CAD 0.7-1.3) with wide ranges of 95% CI of agreement (HVT NC −1.9-7.1; NR −0.4-4.4; NRxa0+xa0SC −1.1-4.3; NRxa0+xa0SCxa0+xa0RR −0.7-2.5) (CAD NC −1.2-3.8; NR −1.0-2.8; NRxa0+xa0SC −1.0-2.5; NRxa0+xa0SCxa0+xa0RR −1.1-2.6).ConclusionsUncorrected physical interference in DySPECT images can extensively impact the performance of MBF quantitation. Full physical corrections should be considered to warrant this tool for clinical utilization.

SPECT Myocardial Blood Flow Quantitation Concludes Equivocal Myocardial Perfusion SPECT Studies to Increase Diagnostic Benefits.

Recently, myocardial blood flow quantitation with dynamic SPECT/CT has been reported to enhance the detection of coronary artery disease in human. This advance has created important clinical applications to coronary artery disease diagnosis and management for areas where myocardial perfusion PET tracers are not available. We present 2 clinical cases that undergone a combined test of 1-day rest/dipyridamole-stress dynamic SPECT and ECG-gated myocardial perfusion SPECT scans using an integrated imaging protocol and demonstrate that flow parameters are capable to conclude equivocal myocardial perfusion SPECT studies, therefore increasing diagnostic benefits to add value in making clinical decisions.

Simplified quantification of 13N-ammonia PET myocardial blood flow: A comparative study with the standard compartment model to facilitate clinical use

BackgroundShort imaging protocol to quantify myocardial blood flow (MBF) and myocardial flow reserve (MFR) may enhance the clinical application of 13N-ammonia cardiac PET. We assessed the flow quantitation of 13N-ammonia PET implementing simple retention model and two-compartment model.MethodsFourteen healthy volunteers (HVT) and twenty-three clinical patients received 13N-ammonia PET/CT. The simple retention model used the first 7-minute image to quantify MBF. Global and regional MBF and MFR of the two models were compared.ResultsGlobal and regional MBF and MFR of these two models were highly correlated with mildly inferior correlation in RCA territory (global R2: rest MBFxa0=xa00.79, stress MBFxa0=xa00.65, MFRxa0=xa00.77; regional R2: rest MBFxa0≥xa00.72, stress MBFxa0≥xa00.52, MFRxa0≥xa00.68). There were significant differences for MFR (4.04xa0±xa00.72, 3.66xa0±xa00.48, pxa0=xa0.02) and rest MBF (0.69xa0±xa00.12, 0.78xa0±xa00.12, pxa0=xa0.02) between the two models in the HVT group.Conclusions13N-ammonia global and regional MBF and MFR from the simple retention model demonstrate strong correlations with that from the two-compartment model. Significant differences of MFR and rest MBF are noted in the HVT group, with a proposed normal reference value for the 13N-ammonia short simple retention protocol.

Noninvasive Nuclear SPECT Myocardial Blood Flow Quantitation to Guide Management for Coronary Artery Disease

Recently, myocardial blood flow quantitation with dynamic SPECT has been validated to enhance the detection of multivessel coronary artery disease (CAD) and conclude equivocal SPECT myocardial perfusion study. This advance opened an important clinical application to utilize the tool in guiding CAD management for area where myocardial perfusion tracers for PET are unavailable or unaffordable. We present a clinical patient with ongoing recursive angina who underwent multiple nuclear stress tests for a sequence of CAD evaluation in 26 months and demonstrated that SPECT myocardial blood flow quantitation properly guided CAD management to warrant patient outcome.

Quantitation of Myocardial Blood Flow with Quantitative Dynamic SPECT/CT

Background: Myocardial blood flow quantitation (MBFQ) with PET currently is not practical in Taiwan, China and other Asian countries due to the accessibility of PET imaging tracers. MBFQ with SPECT tracers, such as Tc-99m Sestamibi(MIBI) or Tc99m Tetrofosmin instead becomes clinically feasible when quantitative dynamic SPECT/CT (dSPECT/CT) imaging method has been developed. In this article, we depict the technical detail of dSPECT/CT imaging and demonstrate its feasibility to measure MBF in normal subjects with MIBI tracer.Methods: Dynamic SPECT images were acquired using Symbia T SPECT/CT system and reconstructed with 3D-OSEM with correction for attenuation, scatter, resolution, isotope decay and image noise. A coke bottle experiment was performed to obtain the calibration factor for converting pixel value to the unit of Bq/ml. A cardiac phantom experiment was performed to test the accuracy of activity measurement in myocardial wall, left ventricle cavity and torso regions. Five consecutive patients with low likelihood of coronary artery disease ＜5%) were recruited for rest/dipyridamole-stress fast MIBI dSPECT/CT scan. A net-retention flow model was employed to calculate Kl for MBF value with correction for partial volume in myocardium and MIBI extraction fraction adopted from animal data. Coronary flow reserve (CFR) was then computed as the ratio of stress and rest MBF values.Results: The calibration factor was 60264 Bq/ml. In cardiac phantom, the accuracy of activity prediction in torso region was 99.3% for 600 sec and remained 91.1% with reduced acquisition duration to 10 sec. Due to spillover and partial volume effects, the accuracy for left ventricle cavity was 87% and 54% for myocardium, likely independent to duration. The partial volume correction was 1.83. Mean MBF at rest for normal subjects was 0.57±0.14 (ml/g/min) and increased to 2.69±0.57 with DS. Mean CFR value was 4.67±0.61 which matched closely with the known CFR value of N13Ammonia PET (4.3±1.3).Conclusion: Quantitative imaging with dynamic SPECT is an effective method to measure myocardial blood flow with Tc-99m labeled tracers. Its clinical utilization can also be extended to other applications which require fast dynamic imaging to study physiological parameters with SPECT tracers.

Iterative Energy Spectrum Deconvolution (IESD): a new technique for significantly improving the effective energy resolution of gamma camera

Energy windows used clinically in nuclear medicine (20-30%) accept a significant proportion of Compton scattered photons to highly degrade image contrast. We developed an Iterative Energy Spectrum Deconvolution (IESD) algorithm for improving the energy resolution of gamma camera to reduce the impact of photon scatter on radionuclide images. Using only those deconvoluted energy components near the photopeak, we exclude scattered photons to form scatter corrected projections. All phantom studies reconstructed with attenuation correction and IESD correction were shown significant improved contrast as cardiac and hepatic activity separation. Contrast of presenting defect region was also significantly enhanced in the phantom and patient studies. Computational times for energy deconvolution times were within clinically acceptable norms (/spl sim/14 minutes/64 projections, 2 GHz, 100 iters). The computational requirements of this technique make it feasible for routine clinical use.