Quantification and Determination of Normal ¹²³I-Meta Iodobenzylguanidine Heart-to-Mediastinum Ratio (HMR) from Cardiac SPECT/CT and Correlation with Planar HMR

Abstract

Assessment of cardiac I-meta iodobenzylguanidine (I-mIBG) uptake relies on the heart-to-mediastinum ratio (HMR) derived from planar images. We have developed novel semiautomated quantitative methodologies for assessing HMR from SPECT images using a dedicated cardiac multipinhole SPECT/CT system and determined the lower limit of normal (LLN) SPECT-derived HMR and the correlation to planar-derived HMR. Twenty-one healthy volunteers were injected withI-mIBG and imaged using 2 different cameras. Planar images were acquired using a conventional SPECT camera equipped with parallel hole collimators, and hybrid SPECT/CT images were acquired using a dedicated cardiac SPECT system with 19 pinhole collimators interfaced with 64-slice CT. Planar HMR was calculated as per standard guidelines (manual traditional method) and elliptic region-of-interest (Elip-ROI) and region-growing (RG-ROI) techniques. SPECT HMR was quantified using a new method that incorporates various cardiac and mediastinal segmentation schemes in which upper and lower limits of the heart were determined from CT and the left ventricular ROI, and mean counts were calculated using Elip-ROI and RG-ROI techniques. Mean counts in mediastinal ROI were computed from a fixed volume in 3 different regions: upper mediastinum (UM), lower mediastinum (LM), and contralateral lung (CL). HMRs were processed by 2 observers, and reproducibility was assessed by intraclass correlation coefficient and Bland-Altman analysis. Planar HMR calculated using the RG-ROI method showed highest intra- and interobserver levels of agreement compared with Elip-ROI and manual traditional methods. SPECT HMR calculated on the basis of UM, LM, and CL background regions showed excellent intra- and interobserver agreement. SPECT HMR with UM resulted in highest correlation ( = 0.91) with planar HMR compared with that with LM ( = 0.74) and CL ( = 0.73). The LLN of SPECT HMR with UM and that of planar HMR was calculated as 5.5 and 1.6, respectively. The normal values of SPECT-derived HMR and planar-derived HMR were correlated linearly. We reconfirmed the previous planar HMR threshold and determined SPECT LLN HMR for SPECT. Planar HMR can be estimated from SPECT HMR via a simple linear regression equation, allowing use of the new cardiac-dedicated SPECT camera forI-mIBG imaging.

Recent advances in cardiac SPECT instrumentation and imaging methods

“…The results showed that high concordance can be obtained between the H/M ratios obtained from the CZT reconstructed SPECT images after linear correction (1.45 ± 0.14) and those obtained from the planar images (1.44 ± 0.14). Another mIBG study of 21 HVT also showed high correlation (R = 0.91) between 3D SPECT H/M ratios obtained from GE 570c scanner and 2D planar H/M ratios obtained from a dual-headed conventional SPECT scanner (Infinia with LEHR collimators) (Alvi et al 2018). The lower limit of normal H/M ratios was also calculated as 5.5 for the GE 570c scanner.…”

Novel [18F]-Labeled Meta-Bromobenzylguanidine Derivatives: Potential Positron Emission Tomography Imaging Probes for the Norepinephrine Transporter

“…High liver uptake is one of the main problems for [ 123 I]­MIBG cardiac images, as these signals may overlap with those from the inferior left ventricular walls and interfere with heart definition. ,− In this study, a small PEG chain was introduced at the para position of phenethylguanidine to improve the excretion kinetics from the nontargeted organs. Compared to [ 123 I]­MIBG, the cardiac uptake of 18 F-12 (8.88 ± 0.53 %ID/g at 30 min postinjection) was slightly higher than that of [ 123 I]­MIBG (7.50 ± 0.54 %ID/g at 30 min postinjection) in ICR mice.…”

Feasible Classified Models for Parkinson Disease from 99mTc-TRODAT-1 SPECT Imaging

“…We adopted two approaches for selecting the ROI during three-dimensional evaluation, namely, the single threshold method and the seed region growing method [24]. The single threshold method used the whole-brain as the ROI in the reconstructed 99m Tc-TRODAT-1 SPECT image to determine the intensity count value within the region.…”