Left ventricular function assessment using 123I/99mTc dual-isotope acquisition with two semi-conductor cadmium-zinc-telluride (CZT) cameras: a gated cardiac phantom study

Simultaneous assessment of myocardial perfusion and adrenergic innervation in patients with heart failure by low-dose dual-isotope CZT SPECT imaging

BACKGROUND

In patients with heart failure (HF) sequential imaging studies have demonstrated a relationship between myocardial perfusion and adrenergic innervation. We evaluated the feasibility of a simultaneous low-dose dual-isotope 123I/99mTc-acquisition protocol using a cadmium-zinc-telluride (CZT) single-photon emission computed tomography (SPECT) camera.

METHODS AND RESULTS

Thirty-six patients with HF underwent simultaneous low-dose 123I-metaiodobenzylguanidine (MIBG)/99mTc-sestamibi gated CZT-SPECT cardiac imaging. Perfusion and innervation total defect sizes and perfusion/innervation mismatch size (defined by 123I-MIBG defect size minus 99mTc-sestamibi defect size) were expressed as percentages of the total left ventricular (LV) surface area. LV ejection fraction (EF) significantly correlated with perfusion defect size (P < .005), innervation defect size (P < .005), and early (P < .05) and late (P < .01) 123I-MIBG heart-to-mediastinum (H/M) ratio. In addition, late H/M ratio was independently associated with reduced LVEF (P < .05). Although there was a significant relationship (P < .001) between perfusion and innervation defect size, innervation defect size was larger than perfusion defect size (P < .001). At multivariable linear regression analysis, 123I-MIBG washout rate (WR) correlated with perfusion/innervation mismatch (P < .05).

CONCLUSIONS

In patients with HF, a simultaneous low-dose dual-isotope 123I/99mTc-acquisition protocol is feasible and could have important clinical implications.

Monte Carlo modelling of a compact CZT-based gamma camera with application to 177Lu imaging

Background

Semiconductor gamma-camera systems based on cadmium zinc telluride (CZT) detectors present new challenges due to an energy-response that includes effects of low-energy tailing. In particular, such energy tails produce effects that need to be considered when imaging radionuclides with multiple emissions such as $$^{177}{\mathrm {Lu}}$$ 177 Lu . Monte Carlo simulation can be used to investigate the behaviour of such systems and optimise their use, provided that the detector model closely reflects the real physical detector. The aim of this work is to develop a CZT model applicable for simulation of CZT-based gamma cameras.

Methods

The equations describing the charge transport and signal induction are considered in three dimensions and are solved numerically, and the CZT model is then realised by coupling the detector-response to the photon-transport handled by the SIMIND Monte Carlo program. The CZT model is tuned to reproduce experimentally measured energy spectra of a hand-held gamma camera system for multiple radionuclides ($$^{99\mathrm {m}}{\mathrm {Tc}}$$ 99 m Tc , $$^{123}{\mathrm {I}}$$ 123 I and $$^{177}{\mathrm {Lu}}$$ 177 Lu ) and parallel-hole collimators (MEGP, LEHR) as well as an uncollimated system.

Results

Overall, the model results agree well with measurements across the range of experimental conditions. The applicability of the model is demonstrated by separating energy spectra into components to investigate the interference of high-energy photons on lower energy-windows, where pronounced effects of low-energy tailing for $$^{177}{\mathrm {Lu}}$$ 177 Lu are observed.

Conclusions

The developed model provides understanding of the specifics of the camera response and is expected to be helpful for future optimisation of gamma camera applications.

Changes in quality of life 6 months after parathyroidectomy for primary hyperparathyroidism

OBJECTIVE

The extent of symptoms due to primary hyperparathyroidism (PHPT) depends on the population being studied. PHPT is mainly discovered incidentally through routine laboratory findings. Less is known about patient-experienced improvement following successful parathyroidectomy. The aim of our study was to assess the changes in the quality of life (QoL) after successful surgery using an SF-36 questionnaire.

DESIGN

This is a prospective cohort study based on questionnaires.

METHODS

Forty consecutive patients diagnosed with PHPT were prospectively administered an SF-36 questionnaire before and 6 months after successful parathyroidectomy. A subgroup of 18 patients answered the questionnaire at 1 and 3 months after surgery. Successful surgery was based on biochemistry and pathology reports as confirmed by an endocrinologist. Results of each SF-36 subcategory were compared to the results at baseline in order to detect changes in patient-reported QoL after successful surgery.

RESULTS

There were significant improvements in six of eight SF-36 subcategories: vitality (P = 0.0001), physical functioning (P = 0.04), general health perception (P = 0.004), physical role functioning (P = 0.04), social role functioning (P = 0.004), and mental health perception (P = 0.0001). Changes appeared within a month after surgery with no further significant changes at later time points.

CONCLUSIONS

Parathyroidectomy significantly improves QoL as measured by a decrease in SF-36 scores as early as 1 month after successful parathyroidectomy. The SF-36 QoL questionnaire is suitable for monitoring changes in patient well-being after successful parathyroidectomy.

First comparison of performances between the new whole-body cadmium-zinc-telluride SPECT-CT camera and a dedicated cardiac CZT camera for myocardial perfusion imaging: Analysis of phantom and patients

BACKGROUND

Dedicated cardiac Cadmium-zinc-telluride (CZT) cameras show superior performances compared with Anger systems, particularly in terms of spatial resolution and count sensitivity. This study evaluated the performances of a new polyvalent whole body CZT camera (DNM 670CZT) compared with a cardiac dedicated CZT camera (DNM 530c) for myocardial perfusion SPECT.

METHODS

The spatial resolution was evaluated with three linear sources filled with 99mTc. We used a cardiac phantom to evaluate count sensitivity, sharpness index, contrast-to-noise ratio, wall thickness, non-uniformity index, perfusion scores and ventricle volumes for both cameras. The impact of matrix size, and acquisition time was investigated. Concordance between the two cameras was evaluated in patients using QPS/QGS software for quantitative segmental perfusion, motion and thickness scores.

RESULTS

The spatial resolution was identical with the two cameras. Count sensitivity of the DNM 670CZT was twofold lower compared with the DNM 530c, leading to lower sharpness index and contrast-to-noise ratio. The wall thickness and the myocardial volumes were similar. Visual and quantitative assessments of the perfusion patterns have shown a good concordance of the two cameras on phantoms and in patients.

CONCLUSION

This study demonstrated the feasibility of myocardial perfusion SPECT imaging using the new whole-body DNM 670CZT camera.

Recent advances in cardiac SPECT instrumentation and imaging methods

Cardiac SPECT continues to play a critical role in detecting and managing cardiovascular disease, in particularly coronary artery disease (CAD) (Jaarsma et al 2012 J. Am. Coll. Cardiol. 59 1719-28), (Agostini et al 2016 Eur. J. Nucl. Med. Mol. Imaging 43 2423-32). While conventional dual-head SPECT scanners using parallel-hole collimators and scintillation crystals with photomultiplier tubes are still the workhorse of cardiac SPECT, they have the limitations of low photon sensitivity (~130 count s^-1 MBq^-1), poor image resolution (~15 mm) (Imbert et al 2012 J. Nucl. Med. 53 1897-903), relatively long acquisition time, inefficient use of the detector, high radiation dose, etc. Recently our field observed an exciting growth of new developments of dedicated cardiac scanners and collimators, as well as novel imaging algorithms for quantitative cardiac SPECT. These developments have opened doors to new applications with potential clinical impact, including ultra-low-dose imaging, absolute quantification of myocardial blood flow (MBF) and coronary flow reserve (CFR), multi-radionuclide imaging, and improved image quality as a result of attenuation, scatter, motion, and partial volume corrections (PVCs). In this article, we review the recent advances in cardiac SPECT instrumentation and imaging methods. This review mainly focuses on the most recent developments published since 2012 and points to the future of cardiac SPECT from an imaging physics perspective.

Comparative Cardiac Phantom Study Using Tc-99m/I-123 and Tl-201/I-123 Tracers with Cadmium-Zinc-Telluride Detector-Based Single-Photon Emission Computed Tomography

Objective

A recently introduced single-photon emission computed tomography (SPECT), based on cadmium-zinc-telluride (CZT) detectors (D-SPECT), supports high energy resolution for cardiac imaging. Importantly, the high energy resolution may allow simultaneous dual-isotope (SDI) imaging (e.g., using Tc-99m and I-123). We quantitatively evaluated Tc-99m/I-123 SDI imaging by D-SPECT in comparison with conventional T1-201/I-123.

Materials and Methods

Energy resolution was measured as a percentage of the full width at half maximum (FWHM) for Tc-99m, I-123, and Tl-201. The impact of cross-talk and reconstructed image contrast were quantified by measuring the contrast-to-noise ratio (CNR), and the transmural defect contrast in the left ventricle wall (C _TD) induced by a difference in energy, for combinations of Tc-99m/I-123 or Tl-201/I-123, using an RH-2 cardiac phantom. Corresponding measurement was also carried out in Anger SPECT (A-SPECT).

Results

The energy resolution of the D-SPECT system was 5.4%/5.1% for Tc-99m/I-123 and 5.4%/5.3% for Tl-201/I-123, which was approximately two times higher than the A-SPECT. No notable difference was confirmed in the CNRs of the two systems, but T1-201/I-123 showed overall higher value than Tc-99m/I-123. Compared to A-SPECT, C _TD of D-SPECT significantly increased with both Tc-99m/I-123 and T1-201/I-123 (p < 0.05). In DSPECT, the combination of Tc-99m/I-123 had a slightly better C _TD than T1-201/I-123. In addition, C _TD of Tc-99m/I-123 was improved with scatter correction at both nuclides (p < 0.05), but in Tl-201/I-123, no significant improvement was confirmed in I-123 (p > 0.05).

Conclusion

D-SPECT was considered to be capable of performing high-quality SDI imaging using Tc-99m/I-123.

Relationships between left ventricular sympathetic innervation and diastolic dysfunction: the role of myocardial innervation/perfusion mismatch

BACKGROUND

A possible relationship between cardiac sympathetic denervation and left ventricular (LV) diastolic dysfunction has been suggested. However, an evaluation of the interactions between myocardial adrenergic tone and LV perfusion and diastolic function is lacking.

METHODS AND RESULTS

Seventy-two patients underwent 99mTc-tetrofosmin/123I-metaiodobenzylguanidine (123I-MIBG) cardiac Cadmium-Zinc-Telluride (CZT) imaging. The summed rest score (SRS) and summed 123I-MIBG score (SS-MIBG) were computed as measures of regional perfusion and innervation heterogeneities. LV segments showing an impaired innervation, despite a relatively preserved perfusion (99mTc-tetrofosmin-123I-MIBG tracers' uptake ≥25%), were individuated (innervation/perfusion mismatch). The peak filling rate (PFR) was computed as a measure of LV diastolic function. Nineteen of the 72 (26%) patients presented a normal LV diastolic function, while 29 (40%) and 24 (34%) had a mild and overt diastolic dysfunction. Subjects with diastolic dysfunction showed more abnormal SRS and SS-MIBG values (P < 0.001). In the global population, 502/1224 (41%) LV segments showed an innervation/perfusion mismatch. A modest correlation between the extent of cardiac innervation/perfusion mismatch and PFR values was evident (R = -0.27, P = 0.029). On multivariate analysis, the extent of regional innervation/perfusion mismatch remained an independent predictor of overt LV diastolic abnormalities (P = 0.017).

CONCLUSIONS

The burden of LV regions showing an innervation/perfusion mismatch associates with the occurrence of overt diastolic dysfunction.

Determination of the Heart-to-Mediastinum Ratio of 123I-MIBG Uptake Using Dual-Isotope (123I-MIBG/99mTc-Tetrofosmin) Multipinhole Cadmium-Zinc-Telluride SPECT in Patients with Heart Failure

The aim of this retrospective study was to compare the heart-to-mediastinum ratio (HMR) of ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG) uptake obtained using a multipinhole cadmium-zinc-telluride (CZT) camera with that obtained using conventional planar imaging. Methods: Forty consecutive heart failure patients underwent planar acquisition 4 h after ¹²³I-MIBG injection (191 ± 41 [mean ± SD] MBq). To localize the heart using the CZT camera, ^99mTc-tetrofosmin (358 ± 177 MBq) was administered and dual-isotope acquisition was performed. The HMRs were calculated with conventional planar imaging (HMR_planar), with anterior reprojection images using the CZT camera (HMR_reproj), and with transaxial reconstructed images using the CZT camera (HMR_transaxial). In a phantom study, we estimated a linear model fitting the CZT camera data to the planar data, and we applied it to provide corrected CZT camera-determined HMRs in patients (cHMR_reproj and cHMR_transaxial). Results: Thirty-four men and 6 women (71 ± 9 y old) with ischemic (22 patients) and nonischemic (18 patients) heart failure completed the study. For 22 of the 40 patients (55%), the New York Heart Association classification was class II and the ejection fraction was 35% ± 9%. HMR_reproj (1.12 ± 0.19) and HMR_transaxial (1.35 ± 0.34) were lower than HMR_planar (1.44 ± 0.14) (P < 0.0001 and P < 0.01, respectively). cHMR_reproj (1.54 ± 0.09) and cHMR_transaxial (1.45 ± 0.14) were significantly different (P < 0.0001). Lin concordance correlation and Bland-Altman analysis demonstrated an almost perfect concordance and a high agreement between HMR_planar and cHMR_transaxial (P was not significant) but not between HMR_planar and cHMR_reproj (P < 0.0001). Conclusion: This study demonstrated that determination of the late HMR of cardiac ¹²³I-MIBG uptake using dual-isotope (¹²³I and ^99mTc) acquisition on a multipinhole CZT camera was feasible in patients with heart failure. However, this determination should be performed using transaxial reconstructed images and linear correction based on phantom data acquisitions.

Cardiac metabolic imaging: current imaging modalities and future perspectives

In this review, current imaging techniques and their future perspectives in the field of cardiac metabolic imaging in humans are discussed. This includes a range of noninvasive imaging techniques, allowing a detailed investigation of cardiac metabolism in health and disease. The main imaging modalities discussed are magnetic resonance spectroscopy techniques for determination of metabolite content (triglycerides, glucose, ATP, phosphocreatine, and so on), MRI for myocardial perfusion, and single-photon emission computed tomography and positron emission tomography for quantitation of perfusion and substrate uptake.