New reconstruction algorithm allows shortened acquisition time for myocardial perfusion SPECT

Purpose

Shortening scan time and/or reducing radiation dose at maintained image quality are the main issues of the current research in radionuclide myocardial perfusion imaging (MPI). We aimed to validate a new iterative reconstruction (IR) algorithm for SPECT MPI allowing shortened acquisition time (HALF time) while maintaining image quality vs. standard full time acquisition (FULL time).

Methods

In this study, 50 patients, referred for evaluation of known or suspected coronary artery disease by SPECT MPI using 99mTc-Tetrofosmin, underwent 1-day adenosine stress 300 MBq/rest 900 MBq protocol with standard (stress 15 min/rest 15 min FULL time) immediately followed by short emission scan (stress 9 min/rest 7 min HALF time) on a Ventri SPECT camera (GE Healthcare). FULL time scans were processed with IR, short scans were additionally processed with a recently developed software algorithm for HALF time emission scans. All reconstructions were subsequently analyzed using commercially available software (QPS/QGS, Cedars Medical Sinai) with/without X-ray based attenuation correction (AC). Uptake values (percent of maximum) were compared by regression and Bland-Altman (BA) analysis in a 20-segment model.

Results

HALF scans yielded a 96% readout and 100% clinical diagnosis concordance compared to FULL. Correlation for uptake in each segment (n?=?1,000) was r?=?0.87at stress (p?<?0.001) and r?=?0.89 at rest (p?<?0.001) with respective BA limits of agreement of ?11% to 10% and ?12% to 11%. After AC similar correlation (r?=?0.82, rest; r?=?0.80, stress, both p?<?0.001) and BA limits were found (?12% to 10%; ?13% to 12%).

Conclusion

With the new IR algorithm, SPECT MPI can be acquired at half of the scan time without compromising image quality, resulting in an excellent agreement with FULL time scans regarding to uptake and clinical conclusion.     

Simultaneous dual-radionuclide myocardial perfusion imaging with a solid-state dedicated cardiac camera

Purpose

We compared simultaneous dual-radionuclide (DR) stress and rest myocardial perfusion imaging (MPI) with a novel solid-state cardiac camera and a conventional SPECT camera with separate stress and rest acquisitions.

Methods

Of 27 consecutive patients recruited, 24 (64.5±11.8 years of age, 16 men) were injected with 74 MBq of ²⁰¹Tl (rest) and 250 MBq ^99mTc-MIBI (stress). Conventional MPI acquisition times for stress and rest are 21 min and 16 min, respectively. Rest ²⁰¹Tl for 6 min and simultaneous DR 15-min list mode gated scans were performed on a D-SPECT cardiac scanner. In 11 patients DR D-SPECT was performed first and in 13 patients conventional stress ^99mTc-MIBI SPECT imaging was performed followed by DR D-SPECT. The DR D-SPECT data were processed using a spill-over and scatter correction method. DR D-SPECT images were compared with rest ²⁰¹Tl D-SPECT and with conventional SPECT images by visual analysis employing the 17-segment model and a five-point scale (0 normal, 4 absent) to calculate the summed stress and rest scores. Image quality was assessed on a four-point scale (1 poor, 4 very good) and gut activity was assessed on a four-point scale (0 none, 3 high).

Results

Conventional MPI studies were abnormal at stress in 17 patients and at rest in 9 patients. In the 17 abnormal stress studies DR D-SPECT MPI showed 113 abnormal segments and conventional MPI showed 93 abnormal segments. In the nine abnormal rest studies DR D-SPECT showed 45 abnormal segments and conventional MPI showed 48 abnormal segments. The summed stress and rest scores on conventional SPECT and DR D-SPECT were highly correlated (r=0.9790 and 0.9694, respectively). The summed scores of rest ²⁰¹Tl D-SPECT and DR-DSPECT were also highly correlated (r=0.9968, p<0.0001 for all). In six patients stress perfusion defects were significantly larger on stress DR D-SPECT images, and five of these patients were imaged earlier by D-SPECT than by conventional SPECT.

Conclusion

Fast and high-quality simultaneous DR MPI is feasible with D-SPECT in a single imaging session with comparable diagnostic performance and image quality to conventional SPECT and to a separate rest ²⁰¹Tl D-SPECT acquisition.     

3D iteratively reconstructed spatial resolution map and sensitivity characterization of a dedicated cardiac SPECT camera

Background

A solid-state cadmium zinc telluride (CZT) SPECT device provides ultrafast myocardial perfusion imaging (MPI) with a spherical field-of-view (FOV). This study aims at determining the spatial resolution and sensitivity throughout this FOV as a guide for patient positioning.

Methods and Results

For this CZT camera (Discovery 570c, GE Healthcare), the iteratively reconstructed spatial resolution along 3 Cartesian axes was compared (average resolution 6.9 ± 1.0 mm full-width at half-maximum) using a 2 dimensional array of point sources in air which was aligned with a transverse plane shifted throughout the FOV. Sensitivity was plotted in the central transverse slice and axially in locations comparable to the placement of the heart in 266 rest/stress cardiac studies (M 78, age 63 ± 13 years). The average sensitivity was 0.46 ± 0.19 kc/s/MBq with a transverse gradient of 0.039 ± 0.001 kc/s/MBq/cm (8.9% of the sensitivity per cm). Reconstructed relative activity was uniform (uniformity <9%) and count rate was linear (R = 0.999) over 3 orders of magnitude.

Conclusions

The CZT SPECT camera offers good resolution, sensitivity, and uniformity, and provides linearity in count rate. A gradient of >8%/cm in sensitivity justifies the crucial role of patient positioning with the heart closest to the detector.     

Gated tomographic radionuclide angiography using cadmium-zinc-telluride detector gamma camera; comparison to traditional gamma cameras

Purpose

Estimation of left ventricular ejection fraction (LVEF) with equilibrium 99MTc-HSA equilibrium radionuclide angiography (MUGA) is frequently used for assessing cardiac function. The purpose of this study was to compare intra- and interobserver variation between three different gamma cameras.

Materials and Methods

Eighty-two patients, scanned in the same sequential order on the three cameras. Each acquisition was analyzed twice by two technologists. Inter- and intraobserver variations were calculated as the coefficient of variation and the 95% confidence interval for limits of agreement between each sequence of analyses for each of the three cameras.

Results

The lowest intraobserver variations in LVEF for the two NaI-detector cameras were 3.1% (?4.0% to 3.5%) for the planar and 3.4% (?4.2% to 4.5%) for SPECT (P ≤ 0.001-0.019), the highest result for the CZT SPECT camera was 2.6% (?2.9% to 3.1%). Similarly, interobserver variation was 4.8% (?4.8% to 6.4%) and 4.9% (?5.4% to 7.5%), respectively, for each of the NaI-detector cameras and 3.3% (?3.4% to 4.3%) for the CZT SPECT camera (P ≤ 0.001-0.008).

Discussion

The CZT detector camera was superior to both NaI detector cameras regarding intra- and interobserver variation. The CZT SPECT camera may identify changes in LVEF with greater certainty than its NaI detector-equipped counterparts.     

Factors affecting the myocardial activity acquired during exercise SPECT with a high-sensitivity cardiac CZT camera as compared with conventional Anger camera

Purpose

Injected doses are difficult to optimize for exercise SPECT since they depend on the myocardial fraction of injected activity (MFI) that is detected by the camera. The aim of this study was to analyse the factors affecting MFI determined using a cardiac CZT camera as compared with those determined using conventional Anger cameras.

Methods

Factors affecting MFI were determined and compared in patients who had consecutive exercise SPECT acquisitions with ²⁰¹Tl (84 patients) or ^99mTc-sestamibi (87 patients) with an Anger or a CZT camera. A predictive model was validated in a group of patients routinely referred for ²⁰¹Tl (78 patients) or ^99mTc-sestamibi (80 patients) exercise CZT SPECT.

Results

The predictive model involved: (1) camera type, adjusted mean MFI being ninefold higher for CZT than for Anger SPECT, (2) tracer type, adjusted mean MFI being twofold higher for ²⁰¹Tl than for ^99mTc-sestamibi, and (3) logarithm of body weight. The CZT SPECT model led to a +1?±?26 % error in the prediction of the actual MFI from the validation group. The mean MFI values estimated for CZT SPECT were more than twofold higher in patients with a body weight of 60 kg than in patients with a body weight of 120 kg (15.9 and 6.8 ppm for ^99mTc-sestamibi and 30.5 and 13.1ppm for ²⁰¹Tl, respectively), and for a 14-min acquisition of up to one million myocardial counts, the corresponding injected activities were only 80 and 186 MBq for ^99mTc-sestamibi and 39 and 91 MBq for ²⁰¹Tl, respectively.

Conclusion

Myocardial activities acquired during exercise CZT SPECT are strongly influenced by body weight and tracer type, and are dramatically higher than those obtained using an Anger camera, allowing very low-dose protocols to be planned, especially for ^99mTc-sestamibi and in non-obese subjects.     

A model for the prediction of a successful stress-first Tc-99m SPECT MPI

Background

Stress-only Tc-99m MPI saves time, radiation exposure, and a normal study has a benign prognosis. However, a stress-first protocol is relatively labor intensive requiring pre-test screening for suitability and early post-stress image review to determine the need for rest imaging. The purpose of this study was to develop a simple clinical score used prior to a patient??s myocardial perfusion imaging (MPI) study to determine if they should undergo a stress-first protocol.

Methods

We reviewed all patients who underwent Tc-99m SPECT MPI over a 27-month period and divided them into derivation and validation cohorts. Patients were categorized as having a successful stress-first protocol based on a summed stress score ??1, with or without attenuation correction. We generated a multivariable model from the derivation cohort to identify demographic and clinical correlates of successful stress-first imaging. Two validation cohorts using a CZT and a conventional SPECT camera were then used to test the performance of the model.

Results

The derivation cohort included 1,996 patients and the validation cohort consisted of 1,005 CZT SPECT patients and 2,430 conventional SPECT patients. The following variables were associated with unsuccessful (i.e., abnormal) stress-first imaging: age >65?years (1 point), diabetes (2 points), typical chest pain (2 points), congestive heart failure (3 points), abnormal ECG (4 points), male gender (4 points), and documented CAD (5 points). Emergency Department location (?2 points) was negatively associated with an unsuccessful protocol. An increasing score showed a strong association with an unsuccessful stress-first protocol in both the derivation and the validation cohorts (P?<?.0001) and dividing the cohorts into low (<5), intermediate (??5 and <10), and high (??10) risk scores accurately stratified patients based on their frequencies of unsuccessful stress-first imaging. ROC curve analysis showed excellent prediction in both the derivation and the validation cohorts with an area under the curve of 0.82 and 0.75-0.83, respectively.

Conclusions

This pre-test scoring tool accurately identifies patients who can successfully undergo a stress-first imaging protocol without the need for rest imaging and may allow for wider adoption of stress-first imaging protocols.     

Left ventricular mass from gated SPECT myocardial perfusion imaging: Comparison with cardiac computed tomography

Background

Increased left ventricular mass (LVM) has been correlated with adverse cardiac events, such as sudden cardiac death. However, LVM quantitation with widely utilized gated SPECT myocardial perfusion imaging (MPI) software, has little validation and clinical application. Thus, we compared LVM from two commonly employed gated SPECT packages [4D-MSPECT^® (4DM) and Quantitative Perfusion SPECT^® (QPS)] with the 3-dimensional reference standard, CT angiography (CTA).

Methods

Comparisons were made in 56 patients (mean age 61.4 ± 14.6; 32% female) referred for dual-isotope or low-dose/high-dose Tc-99m-tetrofosmin rest/stress MPI and cardiac CTA (mean 1.5 ±4.5 months apart). LVM measurement was performed for both CTA and MPI by two independent observers blinded to clinical information.

Results

Correlation with CTA was best for post-stress MPI than at rest; thus, post-stress values are reported. Values obtained with each of the techniques were very highly reproducible (interobserver correlation r = 0.99 for each technique). The mean LVM values were 142 g by CTA, 145 g by 4DM, and 135 g by QPS (P = NS for CTA vs SPECT, but P < .001 for 4DM vs QPS). There was moderately good correlation between CTA and SPECT LVM data (r = 0.74 and 0.72 for 4DM and QPS, respectively; both P < .001). However, on Bland-Altman analysis there was significant overestimation of lower values and underestimation of higher CT LVM values by both QPS and 4DM (both r = 0.68 and 0.69, P < .001). The limits of agreement relative to CT LVM were wide (?52.1 g to 64.1 g for QPS; and ?60.0 g to 53.5 g for 4DM).

Conclusions

SPECT and CTA give reproducible measures of LVM. Using CTA as the reference standard, the mean SPECT LVM values are similar, but lower values are overestimated and higher values are underestimated. Thus, the SPECT values are not substitutable for CTA without mathematical correction.     

Myocardial perfusion imaging with a cadmium zinc telluride-based gamma camera versus invasive fractional flow reserve

Purpose

Recently introduced ultrafast cardiac SPECT cameras with cadmium zinc telluride-based (CZT) detectors may provide superior image quality allowing faster acquisition with reduced radiation doses. Although the level of concordance between conventional SPECT and invasive fractional flow reserve (FFR) measurement has been studied, that between FFR and CZT-based SPECT is not yet known. Therefore, we aimed to assess the level of concordance between CZT SPECT and FFR in a large patient group with stable coronary artery disease.

Methods

Both invasive FFR and myocardial perfusion imaging with a CZT-based SPECT camera, using Tc-tetrofosmin as tracer, were performed in 100 patients with stable angina and intermediate grade stenosis on invasive coronary angiography. A cut-off value of <0.75 was used to define abnormal FFR.

Results

The mean age of the patients was 64?±?11 years, and 64 % were men. SPECT demonstrated ischaemia in 31 % of the patients, and 20 % had FFR <0.75. The concordance between CZT SPECT and FFR was 73 % on a per-patient basis and 79 % on a per-vessel basis. Discordant findings were more often seen in older patients and were mainly (19 %) the result of ischaemic SPECT findings in patients with FFR ≥0.75, whereas only 8 % had an abnormal FFR without ischaemia as demonstrated by CZT SPECT.

Conclusion

Only 20 – 30 % of patients with intermediate coronary stenoses had significant ischaemia as assessed by CZT SPECT or invasive FFR. CZT SPECT showed a modest degree of concordance with FFR, which is comparable with previous results with conventional SPECT. Further investigations are particularly necessary in patients with normal SPECT and abnormal FFR, especially to determine whether these patients should undergo revascularization.     

Stress-induced myocardial ischemia is associated with early post-stress left ventricular mechanical dyssynchrony as assessed by phase analysis of 201Tl gated SPECT myocardial perfusion imaging

Purpose

In ²⁰¹Tl SPECT myocardial perfusion imaging (MPI) data are acquired shortly after the stress injection to assess early post-stress left ventricle (LV) function. The purpose of this study was to use ²⁰¹Tl SPECT MPI to investigate whether stress-induced myocardial ischemia is associated with LV mechanical dyssynchrony.

Methods

Enrolled in the study were 75 patients who were referred for dipyridamole stress and rest ²⁰¹Tl gated SPECT MPI. The early post-stress scan was started 5?min after injection, and followed by the rest scan 4?h later. The patients were divided into three groups: ischemia group (N?=?25, summed stress score, SSS, ≥5, summed rest score, SRS, <5), infarct group (N?=?16, SSS ≥5, SRS ≥5) and normal group (N?=?34, SSS <5, SRS <5). LV dyssynchrony parameters were calculated by phase analysis, and compared between the stress and rest images.

Results

In the ischemia group, LV dyssynchrony was significantly larger during stress than during rest. On the contrary, LV dyssynchrony during stress was significantly smaller than during rest in the normal and infarct groups. LV dyssynchrony during rest was significantly larger in the infarct group than in the normal and ischemia groups. There were no significant differences in LV dyssynchrony during rest between the normal and ischemia groups.

Conclusion

Stress-induced myocardial ischemia caused dyssynchronous contraction in the ischemic region, leading to a deterioration in LV synchrony. Normal myocardium had more synchronous contraction during stress. The different dyssynchrony pattern between ischemic and normal myocardium early post-stress may aid the diagnosis of coronary artery disease using ²⁰¹Tl gated SPECT MPI.     

82Rb PET myocardial perfusion imaging is superior to 99mTc-labelled agent SPECT in patients with known or suspected coronary artery disease

Purpose

We compared the quality, interpretive confidence and interreader agreement between SPECT and PET myocardial perfusion imaging (MPI) in the same group of patients.

Methods

The study group comprised 27 patients (age 55?±?8.5?years, 12 men) with known or suspected coronary artery disease (CAD) who had undergone gated rest/stress MPI with ^99mTc-labelled agent SPECT (with and without attenuation correction, AC), and subsequent clinical confirmation with ⁸²Rb PET. Three experienced readers blinded to the clinical information interpreted all MPI studies.

Results

Interreader agreement was significantly superior for PET studies than for SPECT studies. Following consensus interpretation, the quality of 22?% of the non-AC SPECT studies, 33?% of the AC SPECT studies and 63?% of the PET studies was assessed as excellent or good (p?=?0.016). Interpretations were definitely normal or abnormal in 7?% of non-AC SPECT studies, 30?% of AC SPECT studies and 85?% of PET studies (p?=?0.046). In 13 patients who had received either invasive coronary angiography or CT angiography with no significant CAD, the true-positive rate for significant CAD was higher for PET, and the true-negative rate was equal for PET and AC SPECT, and lower for non-AC SPECT.

Conclusion

⁸²Rb PET MPI, used as a confirmatory test after SPECT, offers improved image quality, interpretive confidence and interreader agreement.     

Comparison between stress myocardial perfusion SPECT recorded with cadmium-zinc-telluride and Anger cameras in various study protocols

Purpose

The results of stress myocardial perfusion SPECT could be enhanced by new cadmium-zinc-telluride (CZT) cameras, although differences compared to the results with conventional Anger cameras remain poorly known for most study protocols. This study was aimed at comparing the results of CZT and Anger SPECT according to various study protocols while taking into account the influence of obesity.

Methods

The study population, which was from three different institutions equipped with identical CZT cameras, comprised 276 patients referred for study using protocols involving ²⁰¹Tl (n?=?120) or ^99mTc-sestamibi injected at low dose at stress (^99mTc-Low; stress/rest 1-day protocol; n?=?110) or at high dose at stress (^99mTc-High; rest/stress 1-day or 2-day protocol; n?=?46). Each Anger SPECT scan was followed by a high-speed CZT SPECT scan (2 to 4 min).

Results

Agreement rates between CZT and Anger SPECT were good irrespective of the study protocol (for abnormal SPECT, ²⁰¹Tl 92 %, ^99mTc-Low 86 %, ^99mTc-High 98 %), although quality scores were much higher for CZT SPECT with all study protocols. Overall correlations were high for the extent of myocardial infarction (r?=?0.80) and a little lower for ischaemic areas (r?=?0.72), the latter being larger on Anger SPECT (p?<?0.001). This larger extent was mainly observed in 50 obese patients who were in the ²⁰¹Tl or ^99mTc-Low group and in whom stress myocardial counts were particularly low with Anger SPECT (228?±?101 kcounts) and dramatically enhanced with CZT SPECT (+279?±?251 %).

Conclusion

Concordance between the results of CZT and Anger SPECT is good regardless of study protocol and especially when excluding obese patients who have low-count Anger SPECT and for whom myocardial counts are dramatically enhanced on CZT SPECT.

     

Development and validation of a patient-tailored dose regime in myocardial perfusion imaging using CZT-SPECT

Background

Guidelines for SPECT myocardial perfusion imaging (MPI) traditionally recommend a fixed tracer dose. Yet, clinical practice shows degraded image quality in heavier patients. The aim was to optimize and validate the tracer dose and scan time to obtain a constant image quality less dependent on patients’ physical characteristics.

Methods

125 patients underwent Cadmium Zinc Telluride (CZT)-SPECT stress MPI using a fixed Tc-99m-tetrofosmin tracer dose. Image quality was scored by three physicians on a 4-point grading scale and related to the number of photon counts normalized to tracer dose and scan time. Counts were correlated with various patient-specific parameters dealing with patient size and weight to find the best predicting parameter. From these data, a formula to provide constant image quality was derived, and subsequently tested in 92 new patients.

Results

Degradation in image quality and photon counts was observed for heavier patients for all patients’ specific parameters (P < .01). We found body weight to be the best-predicting parameter for image quality and derived a new dose formula. After applying this new body weight-depended tracer dose and scan time in a new group, image quality was found to be constant (P > .19) in all patients.

Conclusions

Also in CZT SPECT image quality decreases with weight. The use of a tracer dose and scan time that depends linearly on patient’s body weight corrected for the varying image quality in CZT-SPECT MPI. This leads to better radiation exposure justification.     

High-efficiency SPECT MPI: Comparison of automated quantification, visual interpretation, and coronary angiography

Background

Recently introduced high-efficiency (HE) SPECT cameras with solid-state CZT detectors have been shown to decrease imaging time and reduce radiation exposure to patients. An automated, computer-derived quantification of HE MPI has been shown to correlate well with coronary angiography on one HE SPECT camera system (D-SPECT), but has not been compared to visual interpretation on any of the HE SPECT platforms.

Methods

Patients undergoing a clinically indicated Tc-99m sestamibi HE SPECT (GE Discovery 530c with supine and prone imaging) study over a 1-year period followed by a coronary angiogram within 2 months were included. Only patients with a history of CABG surgery were excluded. Both MPI studies and coronary angiograms were reinterpreted by blinded readers. One hundred and twenty two very low (risk of CAD < 5%) or low (risk of CAD < 10%) likelihood subjects with normal myocardial perfusion were used to create normal reference limits. Computer-derived quantification of the total perfusion deficit at stress and rest was obtained with QPS software. The visual and automated MPI quantification were compared to coronary angiography (≥70% luminal stenosis) by receiver operating curve (ROC) analysis.

Results

Of the 3,111 patients who underwent HE SPECT over a 1-year period, 160 patients qualified for the correlation study (66% male, 52% with a history of CAD). The ROC area under the curve (AUC) was similar for both the automated and the visual interpretations using both supine only and combined supine and prone images (0.69-0.74). Using thresholds determined from sensitivity and specificity curves, the automated reads showed higher specificity (59%-67% vs 27%-60%) and lower sensitivity (71%-72% vs 79%-93%) than the visual reads. By including prone images sensitivity decreased slightly but specificity increased for both. By excluding patients with known CAD and cardiomyopathies, AUC and specificity increased for both techniques (0.72-0.82). The use of a difference score to evaluate ischemic burden resulted in lower sensitivities but higher specificities for both automated and visual quantification. There was good agreement between the visual interpretation and automated quantification in the entire cohort of 160 unselected consecutive patients (r = 0.70-0.81, P < .0001).

Conclusions

Automated and visual quantification of high-efficiency SPECT MPI with the GE Discovery camera provides similar overall diagnostic accuracy when compared to coronary angiography. There was good correlation between the two methods of assessment. Combined supine and prone stress imaging provided the best diagnostic accuracy.     

Downstream resource utilization following hybrid cardiac imaging with an integrated cadmium-zinc-telluride/64-slice CT device

Purpose

Low yield of invasive coronary angiography and unnecessary coronary interventions have been identified as key cost drivers in cardiology for evaluation of coronary artery disease (CAD). This has fuelled the search for noninvasive techniques providing comprehensive functional and anatomical information on coronary lesions. We have evaluated the impact of implementation of a novel hybrid cadmium-zinc-telluride (CZT)/64-slice CT camera into the daily clinical routine on downstream resource utilization.

Methods

Sixty-two patients with known or suspected CAD were referred for same-day single-session hybrid evaluation with CZT myocardial perfusion imaging (MPI) and coronary CT angiography (CCTA). Hybrid MPI/CCTA images from the integrated CZT/CT camera served for decision-making towards conservative versus invasive management. Based on the hybrid images patients were classified into those with and those without matched findings. Matched findings were defined as the combination of MPI defect with a stenosis by CCTA in the coronary artery subtending the respective territory. All patients with normal MPI and CCTA as well as those with isolated MPI or CCTA finding or combined but unmatched findings were categorized as ??no match??.

Results

All 23 patients with a matched finding underwent invasive coronary angiography and 21 (91%) were revascularized. Of the 39 patients with no match, 5 (13%, p?p?Conclusion Cardiac hybrid imaging in CAD evaluation has a profound impact on patient management and may contribute to optimal downstream resource utilization.     

Diagnostic performance of low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT using the 530c CZT camera: Quantitative vs visual analysis

Background

We set out to develop normal databases and prospectively validate abnormality criteria for a low-dose Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera.

Methods

All patients received 6 mCi rest/20 mCi stress doses of Tc-99m tetrofosmin. Rest and stress images were obtained over 7-9 and 5-7 minutes according to the chest size. Low-dose CT of the chest was obtained on a standalone CT scanner. Forty patients with very low likelihood (LLK) of coronary artery disease (CAD) were used to define the normal count distributions. The abnormality criteria were prospectively validated in 55 patients who had coronary angiography and in 40 patients with LLK of CAD.

Results

The results for quantitative non-attenuation-corrected (AC) and AC analysis and visual analysis were as follows: sensitivity of 79%, 85%, and 92% (P = NS) and specificity of 44%, 75%, and 56% (P = NS), respectively. The normalcy rates for quantitative non-AC and AC analyses and visual analysis were 95%, 98%, and 98% (P = NS).

Conclusions

We have developed non-AC and AC normal databases for low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera. The per-patient diagnostic performance of quantitative analyses is not significantly different from visual analysis by an experienced reader.     

Impact of a new ultrafast CZT SPECT camera for myocardial perfusion imaging: fewer equivocal results and lower radiation dose

Purpose  

The new ultrafast cardiac single photon emission computed tomography (SPECT) cameras with cadmium-zinc-telluride (CZT)-based detectors are faster and produce higher quality images as compared to conventional SPECT cameras. We assessed the need for additional imaging, total imaging time, tracer dose and 1-year outcome between patients scanned with the CZT camera and a conventional SPECT camera.     

Myocardial perfusion imaging and coronary calcium scoring with a two-slice SPECT/CT system: can the attenuation map be calculated from the calcium scoring CT scan?

Purpose

Coronary artery calcium scoring can complement myocardial perfusion imaging (MPI). The purpose of this study was to evaluate the feasibility and accuracy of using the CalciumScore-CT derived from a combined SPECT/CT device also for SPECT attenuation correction (AC).

Methods

The study group comprised 99 patients who underwent both post-stress and rest MPI using a two-slice SPECT/CT system. For AC, one of the two scans was accompanied by a CalciumScore-CT scan (CalciumScore-CTAC) and the other by a conventional spiral CT (AttenCorr-CT) scan (AttenCorr-CTAC). In 48 patients the CalciumScore-CT scan was acquired with the post-stress scan and the AttenCorr-CT scan with the rest scan, and in 51 patients the order was reversed. The accuracy of the images based on AC was determined qualitatively by consensus reading with respect to the clinical diagnoses as well as quantitatively by comparing the perfusion summed stress scores (SSS) and the summed rest scores (SRS) between attenuation-corrected and uncorrected images.

Results

In comparison to the uncorrected images CalciumScore-CTAC led to regional inaccuracies in 14 of 51 of studies (27.5 %) versus 12 of 48 studies (25 %) with AttenCorr-CTAC for the stress studies and in 5 of 48 (10 %) versus 1 of 51 (2 %) for the rest studies, respectively. This led to intermediate and definite changes in the final diagnosis (ischaemia and/or scarring) in 12 % of the studies (12 of 99) and in 7 % of the studies (7 of 99) with CalciumScore-CTAC and in 9 % of the studies (9 of 99) and 4 % of the studies (4 of 99) with AttenCorr-CTAC. Differences in SSS and SRS with respect to the uncorrected images were greater for the CalciumScore-CTAC images than for the AttenCorr-CTAC images (ΔSSS 4.5?±?5.6 and 2.1?±?4.4, p?=?0.023; ΔSRS 4.2?±?4.9 and 1.6?±?3.2, p?=?0.004, respectively).

Conclusion

Using the same CT scan for calcium scoring and SPECT AC is feasible. Image interpretation must, however, include uncorrected images since CT-based AC relatively often introduces artefacts into the myocardial perfusion images. This effect is somewhat more pronounced with CalciumScore-CTAC than with AttenCorr-CTAC.     

Gated SPECT evaluation of left ventricular function using a CZT camera and a fast low-dose clinical protocol: comparison to cardiac magnetic resonance imaging

Purpose

CZT technology allows ultrafast low-dose myocardial scintigraphy but its accuracy in assessing left ventricular function is still to be defined.

Methods

The study group comprised 55 patients (23 women, mean age 63?±?9 years) referred for myocardial perfusion scintigraphy. The patients were studied at rest using a CZT camera (Discovery NM530c; GE Healthcare) and a low-dose ^99mTc-tetrofosmin clinical protocol (mean dose 264?±?38 MBq). Gated SPECT imaging was performed as a 6-min list-mode acquisition, 15 min after radiotracer injection. Images were reformatted (8-frame to 16-frame) using Lister software on a Xeleris workstation (GE Healthcare) and then reconstructed with a dedicated iterative algorithm. Analysis was performed using Quantitative Gated SPECT (QGS) software. Within 2 weeks patients underwent cardiac magnetic resonance imaging (cMRI, 1.5-T unit CVi; GE Healthcare) using a 30-frame acquisition protocol and dedicated software for analysis (MASS 6.1; Medis).

Results

The ventricular volumes obtained with 8-frame QGS showed excellent correlations with the cMRI volumes (end-diastolic volume (EDV), r?=?0.90; end-systolic volume (ESV), r?=?0.94; p?<?0.001). However, QGS significantly underestimated the ventricular volumes (mean differences: EDV, ?39.5?±?29 mL; ESV, ?15.4?±?22 mL; p?<?0.001). Similarly, the ventricular volumes obtained with 16-frame QGS showed an excellent correlations with the cMRI volumes (EDV, r?=?0.92; ESV, r?=?0.95; p?<?0.001) but with significant underestimations (mean differences: EDV, ?33.2?±?26 mL; ESV, ?17.9?±?20 mL; p?<?0.001). Despite significantly lower values (47.9?±?16 % vs. 51.2?±?15 %, p?<?0.008), 8-frame QGS mean ejection fraction (EF) was closely correlated with the cMRI values (r?=?0.84, p?<?0.001). The mean EF with 16-frame QGS showed the best correlation with the cMRI values (r?=?0.91, p?<?0.001) and was similar to the mean cMRI value (49.6?±?16 %, p not significant). Regional analysis showed a good correlation between both 8-frame and 16-frame QGS and cMRI wall motion score indexes (8-frame WMSI, r?=?0.85; 16-frame WMSI, r?=?0.89; p?<?0.01).

Conclusion

Low-dose gated SPECT with a CZT camera provides ventricular volumes that correlate well with cMRI results despite significant underestimation in the measure values. EF estimation appeared to be more accurate with 16-frame reformatted images than with 8-frame images.     

Comparison of CTAC and prone imaging for the detection of coronary artery disease using CZT SPECT

Background

Cadmium-zinc-telluride (CZT) cameras have improved the evaluation of patients with chest pain. However, inferior/inferolateral attenuation artifacts similar to those seen with conventional Anger cameras persist. We added prone acquisitions and CT attenuation correction (CTAC) to the standard supine image acquisition and analyzed the resulting examinations.

Methods and results

Seventy-two patients referred for invasive coronary angiography (CAG), and who also underwent rest/stress myocardial perfusion imaging (MPI) on a CZT camera in the supine and prone positions plus CTAC imaging, to examine known or suspected CAD between April 2013 and March 2014 were included. A sixteen-slice CT scan acquired on a SPECT/CT scanner between rest and stress imaging provided data for iterative reconstruction. Sensitivity, specificity, accuracy, and positive and negative likelihood ratios (LRs) were calculated to compare MPI with CAG on a per-patient basis. Per-patient sensitivity, specificity, and accuracy of supine images to predict coronary abnormalities on CAG were 35% [95% confidence interval (CI) 19–52], 86% (95% CI 80–92), and 74% (95% CI 66–82); those of prone imaging were 65% (95% CI 45–81), 82% (95% CI 76–87), and 78% (95% CI 68–85); and those of CTAC were 59% (95% CI 41–71), 93% (95% CI 87–97), and 85% (95% CI 76–91), respectively.

Conclusions

Prone acquisition and CTAC images improve the ability to assess the inferior/inferolateral area.