Dual Acquisitions Research Articles

Abstract 2459: Automated VIF methods improve DCE-MRI parameterization repeatability in GBM

Abstract Introduction: Analysis of Dynamic Contrast Enhanced (DCE) MRI is widely used for measuring perfusion kinetics of cancerous tissue, though its implementation and results may vary between sites. Here we study the repeatability of quantitative DCE-MRI parameterization in a publicly available Glioblastoma (GBM) double-baseline dataset and set forth percent repeatability coefficients (%RC) which constitute a level of change at which a detectable biological change in biology may be differentiated from experimental noise. Methods: Double-baseline imaging data was previously acquired for The Cancer Imaging Archive, in the Quantitative Imaging Network (QIN) GBM Treatment Response (TR) dataset. This data includes dual baseline acquisitions of DCE-MRI MRI data performed within 5 days, for 29 patients. Each acquisition is analyzed using two vascular input function (VIF) methods: a manually segmented VIF from the superior sagittal sinus, and an automatically derived VIF determined from the top 10% of rapidly enhancing voxels. Each dynamic scan is analyzed the the Extended Tofts-Kety model (eTM; Ktrans, ve, vp) pharmacokinetic (PK) model. Bland-Altman analysis is then performed on the log-transformed PK parameters to determine the percent repeatability coefficients (%RC) of the data (95% confidence), as well as bias between first and second DCE scans. This analysis was repeated for two separate observers, writing their own analysis code, both of which are validated on a digital reference object to ensure consistency between analysis methods with zero noise. Results: For bothVIF determination methods, the 25-75th percentiles of the change in PK parameters was less than +/- 25%, the standard set forth by QIBA as a detectable biological change. For most parameters, VIF methods, and model combinations, the automatic VIF method has smallest %RC, indicating that automatic VIF determination may enhance the repeatability of the measurements between timepoints. The %RC was lowest for vp when using an automatically determined VIF. Using the automatically determined VIF and eTM, the %RCs of Ktrans, ve, and vp were measured as 72%, 82%, and 53%, respectively. Using the eTM and manually segmented VIF, the %RCs of Ktrans, ve, and vp were measured as 83%, 88%, and 66%. Conclusions: Using the QIN-GBM-TR dataset, the authors have determined that the %RC of Ktrans, ve, and vp to be 72%, 82%, and 53%, respectively (eTM, auto-VIF). Because these relative changes are large, we recommend that all sites abide by QIBA guidelines to enhance DCE parameterization reproducibility. We also recommend usage of an automated AIF determination method, as opposed to manual segmentation of large blood vessels. Citation Format: Ryan T. Woodall, Prativa Sahoo, Yujie Cui, Bihong Chen, Mark Shiroishi, Cristina Lavini, Paul Frankel, Margarita Gutova, Christine Brown, Jennifer Munson, Russell Rockne. Automated VIF methods improve DCE-MRI parameterization repeatability in GBM [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2459.

Near-field artifacts reduction in coded aperture push-broom Compton scatter imaging

Recently, we have devised a novel method called coded aperture push-broom Compton scatter imaging (CAPCSI) to improve the use of backscattered X-rays. Based on a correlation algorithm, near-field artifacts are obvious in the CAPCSI, although they could be reduced partially by averaging dual acquisitions of a mask and an antimask. In this paper, we introduce a maximum-likelihood expectation–maximization (MLEM) algorithm into the CAPCSI to improve the artifacts without dual acquisitions. First, a theoretical system matrix (SM) and a simulative SM were derived from the generation of near-field artifacts. Then, simulation for ideal sources was carried out to compare different algorithms of the correlation and the MLEM. Further, a CAPCSI prototype was set up to confirm the simulation. Because of the system nonuniformity, an experimental SM was derived in advance by a ray-driven way. Finally, imaging for character phantoms was presented. Preliminary results showed the MLEM performed much better for the point source and could obtain a cleaner background for complex objects than the correlation. In the simulation, the theoretical SM and the simulative SM were no essential difference. However, in the experiment, the experimental SM performed essentially better than the theoretical SM, because it took the near-field effects and the system nonuniformity into a comprehensive consideration. This work will help enhance the application potential of the CAPCSI.

Simultaneous Tc-99m and I-123 dual-radionuclide imaging with a solid-state detector-based brain-SPECT system and energy-based scatter correction.

BackgroundA brain single-photon emission computed tomography (SPECT) system using cadmium telluride (CdTe) solid-state detectors was previously developed. This CdTe-SPECT system is suitable for simultaneous dual-radionuclide imaging due to its fine energy resolution (6.6 %). However, the problems of down-scatter and low-energy tail due to the spectral characteristics of a pixelated solid-state detector should be addressed. The objective of this work was to develop a system for simultaneous Tc-99m and I-123 brain studies and evaluate its accuracy.MethodsA scatter correction method using five energy windows (FiveEWs) was developed. The windows are Tc-lower, Tc-main, shared sub-window of Tc-upper and I-lower, I-main, and I-upper. This FiveEW method uses pre-measured responses for primary gamma rays from each radionuclide to compensate for the overestimation of scatter by the triple-energy window method that is used. Two phantom experiments and a healthy volunteer experiment were conducted using the CdTe-SPECT system. A cylindrical phantom and a six-compartment phantom with five different mixtures of Tc-99m and I-123 and a cold one were scanned. The quantitative accuracy was evaluated using 18 regions of interest for each phantom. In the volunteer study, five healthy volunteers were injected with Tc-99m human serum albumin diethylene triamine pentaacetic acid (HSA-D) and scanned (single acquisition). They were then injected with I-123 N-isopropyl-4-iodoamphetamine hydrochloride (IMP) and scanned again (dual acquisition). The counts of the Tc-99m images for the single and dual acquisitions were compared.ResultsIn the cylindrical phantom experiments, the percentage difference (PD) between the single and dual acquisitions was 5.7 ± 4.0 % (mean ± standard deviation). In the six-compartment phantom experiment, the PDs between measured and injected activity for Tc-99m and I-123 were 14.4 ± 11.0 and 2.3 ± 1.8 %, respectively. In the volunteer study, the PD between the single and dual acquisitions was 4.5 ± 3.4 %.ConclusionsThis CdTe-SPECT system using the FiveEW method can provide accurate simultaneous dual-radionuclide imaging. A solid-state detector SPECT system using the FiveEW method will permit quantitative simultaneous Tc-99m and I-123 study to become clinically applicable.

POTENTIAL OF MULTITEMPORAL TANDEM-X DERIVED CROP SURFACE MODELS FOR MAIZE GROWTH MONITORING

In this study, first results of retrieving plant heights of maize fields from multitemporal TanDEM-X images are shown. Three TanDEM-X dual polarization spotlight acquisitions were taken over a rural area in Germany in the growing season 2014. By interferometric processing, digital terrain models (DTM) were derived for each date with 5m resolution. From the data of the first acquisition (June 1st) taken before planting, a DTM of the bare ground is generated. The data of the following acquisition dates (July 15th, July 26th) are used to establish crop surface models (CSM). A CSM represents the crop surface of a whole field in a high resolution. By subtracting the DTM of the ground from each CSM, the actual plant height is calculated. Within these data sets 30 maize fields in the area of interest could be detected and verified by external land use data. Besides the spaceborne measurements, one of the maize fields was intensively investigated using terrestrial laser scanning (TLS), which was carried out at the same dates as the predicted TanDEM-X acquisitions. Visual inspection of the derived plant heights, and accordance of the individually processed polarisations over the maize fields, demonstrate the feasibility of the proposed method. Unfortunately, the infield variability of the intensively monitored field could not be successfully captured in the TanDEM-X derived plant heights and merely the general trend is visible. Nevertheless, the study shows the potential of the TanDEM-X constellation for maize height monitoring on field level.

POTENTIAL OF MULTITEMPORAL TANDEM-X DERIVED CROP SURFACE MODELS FOR MAIZE GROWTH MONITORING

Abstract. In this study, first results of retrieving plant heights of maize fields from multitemporal TanDEM-X images are shown. Three TanDEM-X dual polarization spotlight acquisitions were taken over a rural area in Germany in the growing season 2014. By interferometric processing, digital terrain models (DTM) were derived for each date with 5m resolution. From the data of the first acquisition (June 1st) taken before planting, a DTM of the bare ground is generated. The data of the following acquisition dates (July 15th, July 26th) are used to establish crop surface models (CSM). A CSM represents the crop surface of a whole field in a high resolution. By subtracting the DTM of the ground from each CSM, the actual plant height is calculated. Within these data sets 30 maize fields in the area of interest could be detected and verified by external land use data. Besides the spaceborne measurements, one of the maize fields was intensively investigated using terrestrial laser scanning (TLS), which was carried out at the same dates as the predicted TanDEM-X acquisitions. Visual inspection of the derived plant heights, and accordance of the individually processed polarisations over the maize fields, demonstrate the feasibility of the proposed method. Unfortunately, the infield variability of the intensively monitored field could not be successfully captured in the TanDEM-X derived plant heights and merely the general trend is visible. Nevertheless, the study shows the potential of the TanDEM-X constellation for maize height monitoring on field level.

Radiation dose reduction using a neck detection algorithm for single spiral brain and cervical spine CT acquisition in the trauma setting

Cervical spine injuries occur in 4-8% of adults with head trauma. Dual acquisition technique has been traditionally used for the CT scanning of brain and cervical spine. The purpose of this study was to determine the efficacy of radiation dose reduction by using a single acquisition technique that incorporated both anatomical regions with a dedicated neck detection algorithm. Thirty trauma patients for brain and cervical spine CT were included and were scanned with the single acquisition technique. The radiation doses from the single CT acquisition technique with the neck detection algorithm, which allowed appropriate independent dose administration relevant to brain and cervical spine regions, were recorded. Comparison was made both to the doses calculated from the simulation of the traditional dual acquisitions with matching parameters, and to the doses of retrospective dual acquisition legacy technique with the same sample size. The mean simulated dose for the traditional dual acquisition technique was 3.99mSv, comparable to the average dose of 4.2mSv from 30 previous patients who had CT of brain and cervical spine as dual acquisitions. The mean dose from the single acquisition technique was 3.35mSv, resulting in a 16% overall dose reduction. The images from the single acquisition technique were of excellent diagnostic quality. The new single acquisition CT technique incorporating the neck detection algorithm for brain and cervical spine significantly reduces the overall radiation dose by eliminating the unavoidable overlapping range between 2 anatomical regions which occurs with the traditional dual acquisition technique.

Aperture collimation correction and maximum-likelihood image reconstruction for near-field coded aperture imaging of single photon emission computerized tomography

Coded aperture (CA) imaging originally developed in X-ray astronomy has not been widely used in nuclear medicine due to the decoding complexity of near-field CA images. In this paper, we present a near-field CA imaging technique and image reconstruction method for high sensitivity and high resolution single photon emission computerized tomography (SPECT). Our approach makes three contributions. First, a correction method for the aperture collimation effect is used to eliminate the near-field artifacts without dual acquisitions of mask and anti-mask images. Second, a maximum-likelihood expectation-maximization (MLEM) deconvolution method is used to restore CA images. Finally, a new MLEM-based algorithm is used to partially reconstruct three-dimensional (3-D) objects from a single projection of CA images. Experiments conducted using a dual-head SPECT system equipped with a parallel-hole collimator and a CA module show a tenfold increase in count sensitivity and significant improvement in image resolution with CA collimation as compared to parallel-hole collimation. Experiments conducted using the same dual-head SPECT system equipped with a pinhole collimator show that when the object is closer to the pinhole collimator the CA image resolution is only slightly inferior to the pinhole collimated image. We found that the MLEM deconvolution method provides an inherent nonnegativity constraint on pixel values and remarkably reduces background activities of CA images. The MLEM reconstruction algorithm for CA images is capable of reconstructing 3-D objects from a single projection and can be potentially extended to full 3-D SPECT reconstruction for CA images.