An On-Board Spectral-CT/CBCT/SPECT Imaging Configuration for Small-Animal Radiation Therapy Platform: A Monte Carlo Study

Wang, Hui; Nie, Ke; Kuang, Yu

doi:10.1109/tmi.2019.2932333

Cited by 6 publications

(19 citation statements)

References 47 publications

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“…Coincidence window 20.5 ns integrated into our previously proposed SPECT/ spectral-CT/CBCT on-board imaging system using a single photon-counting CZT imager in the same gantry. 9 The PET scanner was constructed using innovative pixelated TlBr detectors with a resolution of 1.25 mm × 1.25 mm and a thickness of 10 mm. Each detector module, measuring 20 mm × 20 mm × 10 mm, contained a 16 × 16 array of detector crystals (pixels).…”

Section: Energy Resolution 4%mentioning

confidence: 99%

“…In this study, the CZT detector characteristics and imaging geometries, as well as collimator configurations, remained consistent with those used in the prior work. 9 In spectral-CT/CBCT imaging, the source-to-axis distance and the source-to-detector distance were set at 500 and 750 mm, respectively. For SPECT imaging, the CZT imager was configured at a resolution of 0.5 mm × 0.5 mm using a 5 × 5 binning.…”

Section: Energy Resolution 4%mentioning

confidence: 99%

“…2,7,8 To address these limitations, we previously explored the integration of single-photon emission computed tomography (SPECT)/spectral-CT molecular/functional imaging and CBCT into SART platforms using a single on-board cadmium zinc tellurium (CZT) imager for feasibility. 4,9 Positron emission tomography (PET) plays an increasingly important role in RT/ART, especially bio-logically guided RT/ART, as a major tool for defining the BTV for optimized treatment planning and planning adaption. 1 Many clinical trials on PET-guided RT/ART have been performed for various cancers worldwide to evaluate the clinical benefits and pitfalls of this novel technique.…”

Section: Introductionmentioning

confidence: 99%

“…Our previous studies have demonstrated that the semiconductor material CZT can effectively detect both x-ray and low-energy gamma photons for spectral-CT/CBCT imaging and SPECT imaging in the SART system. 4,9 Although TlBr offers higher detection efficiency than CZT for both types of photons, the high K-edge energy of Tl (85.5 keV) can result in substantial crosstalk between adjacent pixels in TlBr detectors. Therefore, in this study, TIBr detectors were used to build the PET subsystem, while CZT detectors were employed for SPECT/CBCT imaging within the SART platform.…”

Section: Introductionmentioning

confidence: 99%

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PET/SPECT/spectral‐CT/CBCT imaging in a small‐animal radiation therapy platform: A Monte Carlo study—Part I: Quad‐modal imaging

Wang,

Li,

et al. 2024

Medical Physics

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BackgroundIn spite of the tremendous potential of game‐changing biological image‐ and/or biologically guided radiation therapy (RT) and adaptive radiation therapy for cancer treatment, existing limited strategies for integrating molecular imaging and/or biological information with RT have impeded the translation of preclinical research findings to clinical applications. Additionally, there is an urgent need for a highly integrated small‐animal radiation therapy (SART) platform that can seamlessly combine therapeutic and diagnostic capabilities to comprehensively enhance RT for cancer treatment.PurposeWe investigated a highly integrated quad‐modal on‐board imaging configuration combining positron emission tomography (PET), single‐photon emission computed tomography (SPECT), photon‐counting spectral CT, and cone‐beam computed tomography (CBCT) in a SART platform using a Monte Carlo model as a proof‐of‐concept.MethodsThe quad‐modal on‐board imaging configuration of the SART platform was designed and evaluated by using the GATE Monte Carlo code. A partial‐ring on‐board PET imaging subsystem, utilizing advanced semiconductor thallium bromide detector technology, was designed to achieve high sensitivity and spatial resolution. On‐board SPECT, photon‐counting spectral‐CT, and CBCT imaging were performed using a single cadmium zinc telluride flat detector panel. The absolute peak sensitivity and scatter fraction of the PET subsystem were estimated by using simulated phantoms described in the NEMA NU‐4 standard. The spatial resolution of the PET image of the platform was evaluated by imaging a simulated micro‐Derenzo hot‐rod phantom. To evaluate the quantitative imaging capability of the system's spectral CT, the Bayesian eigentissue decomposition (ETD) method was utilized to quantitatively decompose the virtual noncontrast (VNC) electron densities and iodine contrast agent fractions in the Kidney1 inserts mixed with the iodine contrast agent within the simulated phantoms. The performance of the proposed quad‐model imaging in the platform was validated by imaging a simulated phantom with multiple imaging probes, including an iodine contrast agent and radioisotopes of 18F and 99mTc.ResultsThe PET subsystem demonstrated an absolute peak sensitivity of 18.5% at the scanner center, with an energy window of 175–560 KeV, and a scatter fraction of only 3.5% for the mouse phantom, with a default energy window of 480–540 KeV. The spatial resolution of PET on‐board imaging exceeded 1.2 mm. All imaging probes were identified clearly within the phantom. The PET and SPECT images agreed well with the actual spatial distributions of the tracers within the phantom. Average relative errors on electron density and iodine contrast agent fraction in the Kidney1 inserts were less than 3%. High‐quality PET images, SPECT images, spectral‐CT images (including iodine contrast agent fraction images and VNC electron density images), and CBCT images of the simulated phantom demonstrated the comprehensive multimodal imaging capability of the system.ConclusionsThe results demonstrated the feasibility of the proposed quad‐modal imaging configuration in a SART platform. The design incorporates anatomical, molecular, and functional information about tumors, thereby facilitating successful translation of preclinical studies into clinical practices.

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Section: Energy Resolution 4%mentioning

confidence: 99%

Section: Energy Resolution 4%mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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PET/SPECT/spectral‐CT/CBCT imaging in a small‐animal radiation therapy platform: A Monte Carlo study—Part I: Quad‐modal imaging

Wang,

Li,

et al. 2024

Medical Physics

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“…Given the favorite properties of the CZT photon counting detector (PCD), including high energy resolution, high intrinsic spatial resolution, and compact detector size, this type of detector has been increasingly studied for multiple medical imaging modalities. [13][14][15][16][17] Based on the previous studies, we designed the tri-modal OBI system using a single CZT-based PCD mounted on the Linacs. The new OBI adds additional dimensions to address complicated tumor changes during the treatment course of RT for ART procedures.…”

Section: Introductionmentioning

confidence: 99%

A Monte Carlo study to investigate the feasibility of an on‐board SPECT/spectral‐CT/CBCT imager for medical linear accelerator

et al. 2020

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The on-board flat-panel cone-beam computed tomography (CBCT) lacks molecular/functional information for current online image-guided radiation therapy (IGRT). It might not be adequate for adaptive radiation therapy (ART), particularly for biologically guided tumor delineation and targeting which might be shifted and/or distorted during the course of RT. A linear accelerator (Linac) gantry-mounted on-board imager (OBI) was proposed using a single photon counting detector (PCD) panel to achieve single photon emission computed tomography (SPECT), energy-resolved spectral CT, and conventional CBCT triple on-board imaging, which might facilitate online ART with an addition of volumetric molecular/functional imaging information. Methods: The system was designed and evaluated in the GATE Monte Carlo platform. The OBI system including a kV-beam source and a pixelated cadmium zinc telluride (CZT) detector panel mounted on a medical Linac orthogonally to the MV beam direction was designed to obtain online CBCT, spectral CT, and SPECT tri-modal imaging of patients in the treatment room. The spatial resolutions of the OBI system were determined by imaging simulated phantoms. The CBCT imaging was evaluated by a simulated contrast phantom. A PMMA phantom containing gadolinium was imaged to demonstrate quantitative imaging of spectral-CT/CBCT of the system. The capability of tri-modal imaging of the OBI was demonstrated using three different spectral CT imaging methods to differentiate gadolinium, gold, calcium within simulated PMMA and the SPECT to image radioactive 99m Tc distribution. The dual-isotope SPECT imaging of the system was also evaluated by imaging a phantom containing 99m Tc and 123 I. The radiotherapy-related parameters of iodine contrast fraction and virtual non-contrast (VNC) tissue electron density in the Kidney1 inserts of a simulated phantom were decomposed using the Bayesian eigentissue decomposition method for contrastenhanced CBCT/spectral-CT of the OBI in a single scan. Results: The spatial resolutions of CBCT and SPECT of the OBI were determined to be 15.1 lp/cm at 10% MTF and 4.8-12 mm for radii of rotation of 10-40 cm, respectively. In CBCT image of the contrast phantom, most of the soft-tissue inserts were visible with sufficient spatial structure details. As compared to the CBCT image of gadolinium, the spectral CT image provided higher image contrasts. Calcium, gadolinium, and gold were separated well by using the spectral CT material imaging methods. The reconstructed distribution of 99m Tc agreed with the spatial position within the phantom. The two isotopes were separated from each other in dual-isotope SPECT imaging of the OBI. The iodine fractions and the VNC electron densities were estimated in the iodine-enhanced Kidney1 tissue inserts with reasonable RMS errors. The main procedures of the tri-modal imaging guided online ART workflow were presented with new functional features included. Conclusions: Using a single photon counting CZT detector panel, an on-board SPECT, spectral CT, and CBCT tr...

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PET/SPECT/Spectral‐CT/CBCT imaging in a small‐animal radiation therapy platform: A Monte Carlo study—Part II: Biologically guided radiotherapy

Li,

Wang,

et al. 2024

Medical Physics

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BackgroundThis study addresses the technical gap between clinical radiation therapy (RT) and preclinical small‐animal RT, hindering the comprehensive validation of innovative clinical RT approaches in small‐animal models of cancer and the translation of preclinical RT studies into clinical practices.PurposeThe main aim was to explore the feasibility of biologically guided RT implemented within a small‐animal radiation therapy (SART) platform, with integrated quad‐modal on‐board positron emission tomography (PET), single‐photon emission computed tomography, photon‐counting spectral CT, and cone‐beam CT (CBCT) imaging, in a Monte Carlo model as a proof‐of‐concept.MethodsWe developed a SART workflow employing quad‐modal imaging guidance, integrating multimodal image‐guided RT and emission‐guided RT (EGRT). The EGRT algorithm was outlined using positron signals from a PET radiotracer, enabling near real‐time adjustments to radiation treatment beams for precise targeting in the presence of a 2‐mm setup error. Molecular image‐guided RT, incorporating a dose escalation/de‐escalation scheme, was demonstrated using a simulated phantom with a dose painting plan. The plan involved delivering a low dose to the CBCT‐delineated planning target volume (PTV) and a high dose boosted to the highly active biological target volume (hBTV) identified by the 18F‐PET image. Additionally, the Bayesian eigentissue decomposition method illustrated the quantitative decomposition of radiotherapy‐related parameters, specifically iodine uptake fraction and virtual noncontrast (VNC) electron density, using a simulated phantom with Kidney1 and Liver2 inserts mixed with an iodine contrast agent at electron fractions of 0.01–0.02.ResultsEGRT simulations generated over 4,000 beamlet responses in dose slice deliveries and illustrated superior dose coverage and distribution with significantly lower doses delivered to normal tissues, even with a 2‐mm setup error introduced, demonstrating the robustness of the novel EGRT scheme compared to conventional image‐guided RT. In the dose‐painting plan, doubling the dose to the hBTV while maintaining a low dose for the PTV resulted in an organ‐at‐risk (OAR) dose comparable to the low‐dose treatment for the PTV alone. Furthermore, the decomposition of radiotherapy‐related parameters in Kidney1 and Liver2 inserts, including iodine uptake fractions and VNC electron densities, exhibited average relative errors of less than 1.0% and 2.5%, respectively.ConclusionsThe results demonstrated the successful implementation of biologically guided RT within the proposed quad‐model image‐guided SART platform, with potential applications in preclinical RT and adaptive RT studies.

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An On-Board Spectral-CT/CBCT/SPECT Imaging Configuration for Small-Animal Radiation Therapy Platform: A Monte Carlo Study

Cited by 6 publications

References 47 publications

PET/SPECT/spectral‐CT/CBCT imaging in a small‐animal radiation therapy platform: A Monte Carlo study—Part I: Quad‐modal imaging

PET/SPECT/spectral‐CT/CBCT imaging in a small‐animal radiation therapy platform: A Monte Carlo study—Part I: Quad‐modal imaging

A Monte Carlo study to investigate the feasibility of an on‐board SPECT/spectral‐CT/CBCT imager for medical linear accelerator

PET/SPECT/Spectral‐CT/CBCT imaging in a small‐animal radiation therapy platform: A Monte Carlo study—Part II: Biologically guided radiotherapy

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