Radiation Dose Reduction Research Articles

Monte Carlo Simulation of Organ Absorbed Dose of Worker's Radiation Exposure in Bone Scintigraphy

Objectives: This study examines individual organ doses and the impact of ionizing radiation sources on effective radiation doses. Methods: In the research, the ICRP-defined adult standing phantom was used as the phantom material in the Visual Monte Carlo Dose Calculation Program (VMC). Subsequently, the incurred doses were calculated by defining different doses, distances, and durations for the 99mTc radioactive source. Results: Exposure times were set at 5 minutes and 20 minutes in comparison. The results indicated that for 5 minutes and 20 minutes at 360 cm, doses remained below the ICRP recommended annual dose limit of 5.7 µSv/h for occupational exposure. Conclusion: Organ absorbed and effective doses varied with exposure time and source-phantom distance. To optimize radiation exposure, people working in radiation fields must make an increased effort to reduce radiation doses following the ALARA principles. Keywords: Effective dose, absorbed dose, VMC software, Monte Carlo

Deep learning based ultra-low dose fan-beam computed tomography image enhancement algorithm: Feasibility study in image quality for radiotherapy.

We investigated the feasibility of deep learning-based ultra-low dose kV-fan-beam computed tomography (kV-FBCT) image enhancement algorithm for clinical application in abdominal and pelvic tumor radiotherapy. A total of 76 patients of abdominal and pelvic tumors were prospectively selected. The Catphan504 was acquired with the same conditions as the standard phantom test set. We used a CycleGAN-based model for image enhancement. Normal dose CT (NDCT), ultra-low dose CT (LDCT) and deep learning enhanced CT (DLR) were evaluated by subjective and objective analyses in terms of imaging quality, HU accuracy, and image signal-to-noise ratio (SNR). The image noise of DLR was significantly reduced, and the contrast-to-noise ratio (CNR) was significantly improved compared to the LDCT. The most significant improvement was the acrylic which represented soft tissue in CNR from 1.89 to 3.37, improving by 76%, nearly approaching the NDCT, and in low-density resolution from 7.64 to 12.6, improving by 64%. The spatial frequencies of MTF10 and MTF50 in DLR were 4.28 and 2.35 cycles/mm in DLR, respectively, which are higher than LDCT 3.87 and 2.12 cycles/mm, and even slightly higher than NDCT 4.15 and 2.28 cycles/mm. The accuracy and stability of HU values of DLR were similar to NDCT. The image quality evaluation of the two doctors agreed well with DLR and NDCT. A two-by-two comparison between groups showed that the differences in image scores of LDCT compared with NDCT and DLR were all statistically significant (p<0.05), and the subjective scores of DLR were close to NDCT. The image quality of DLR was close to NDCT with reduced radiation dose, which can fully meet the needs of conventional image-guided adaptive radiotherapy (ART) and achieve the quality requirements of clinical radiotherapy. The proposed method provided a technical basis for LDCT-guided ART.

Simulation of the shielding effect of lead apron undergoing chest CT scan.

Lead aprons are used to reduce radiation dose to patients. As the distance between the lead apron and the edge of the scan range increases, organ dose is expected to decrease, but with increasing scattered radiation dose in the body. By simulation, this work aims at estimate whether the organ dose increases due to the scattered radiation in the body with lead apron. A standard-sized male and a female phantom is used to simulate organ doses of chest scans in various lead apron shielding situations. Simulations in this work considered different distance between the edge of the 0.35-mm lead apron and the edge of the scan range. For the female phantom, the dose to the gonads was significantly reduced (56% on average), but not as much as men (78% on average). However, the amount of dose reduction is small for male and female phantoms (0.0082mGy/100mAs and 0.0160mGy/100mAs).

RADT-45. INTEGRATION OF FUNCTIONAL MAGNETIC RESONANCE IMAGING INTO STEREOTACTIC RADIOSURGERY PLANNING TO REDUCE SYMPTOMATIC RADIATION NECROSIS

Abstract BACKGROUND Radiation necrosis (RN) is a common complication of stereotactic radiosurgery (SRS). Functional magnetic resonance imaging (fMRI) localizes eloquent cortical areas for neurosurgical planning but is seldom applied to SRS. We explored the relationship between symptomatic RN and functional neuroanatomy on fMRI. We evaluated the potential benefit of reducing radiation dose to functional areas. METHODS From 2011 to 2022, patients with an fMRI within 3 months of SRS for resected or unresected brain metastases (BM) were included. The BM nearest to the primary motor, language, or visual cortices was designated as the index BM. The functional area on fMRI nearest to the index BM was designated as the fOAR. Focally symptomatic RN (FSRN) was defined as radiographic RN alongside new or worsening focal neurologic symptoms consistent with the fOAR. Patients treated with 5-fraction SRS and modern planning techniques after 2013 were included in the dosimetric analysis. Associations between fOAR dose and FSRN were evaluated with logistic regression. SRS replanning was performed to determine if fOAR dose could be reduced without sacrificing target coverage. RESULTS Among 94 patients, 82% received SRS postoperatively, and 71% received 5-fraction SRS. fOARs included the primary motor (77%), language (19%), and visual (2%) cortices. Of 20 patients with radiographic RN, 20% were neurologically asymptomatic, 20% had anatomically unrelated neurologic symptoms, and 60% had FSRN. The dosimetric analysis included 39 patients. The fOAR volume receiving a single-fraction equivalent dose ≥14 Gy (V14Gy) was associated with FSRN at 18 months post-SRS (OR=6.8/mL, p=0.05). Replanning reduced fOAR V14Gy in all cases. The mean reduction was 28%. CONCLUSION Neurologic symptoms of SRS-induced RN reflect nearby functional neuroanatomy on fMRI. Dose reduction to functional areas while maintaining target coverage is consistently achievable and may mitigate symptomatic RN. Integrated fMRI-based SRS planning may protect neurologic function when treating tumors near eloquent areas.

Evaluating the Efficacy of Deep Learning Reconstruction in Reducing Radiation Dose for Computer-Aided Volumetry for Liver Tumor: A Phantom Study.

The purpose of this study was to compare radiation dose reduction capability for accurate liver tumor measurements of a computer-aided volumetry (CADv) software for filtered back projection (FBP), hybrid-type iterative reconstruction (IR), mode-based iterative reconstruction (MBIR), and deep learning reconstruction (DLR) at a phantom study. A commercially available anthropomorphic abdominal phantom was scanned five times with a 320-detector row CT at 600 mA, 400 mA, 200 mA, and 100 mA and reconstructed by four methods. Signal-to-noise ratios (SNRs) of all lesions within the arterial and portal-venous phase inserts were calculated, and SNR of the lesion phantom was compared with that of all reconstruction methods by means of Tukey's honestly significant difference (HSD) test. Then, tumor volume (V) of each nodule was automatically measured using commercially available CADv software. To compare dose reduction capability for each reconstruction method at both phases, mean differences between measured V and standard references were compared by Tukey's honestly significant difference test among the four different reconstruction methods on CT obtained at each of the four tube currents. With each of the tube currents, SNRs for MBIR and DLR were significantly higher than those for FBP and hybrid-type IR (p < 0.05). At the arterial phase, the mean difference in V for the CT protocol obtained at 600 or 100 mA and reconstructed with DLR was significantly smaller than that for others (p < 0.05). At the portal-venous phase, the mean differences in V for the CT protocol obtained at 100 mA and reconstructed with hybrid-type IR, MBIR, and DLR were significantly smaller than that for FBP (p < 0.05). Findings of our phantom study show that reconstruction method had influence on CADv merits for abdominal CT with not only standard but also reduced dose examinations and that DLR can potentially yield better image quality and CADv measurements than FBP, hybrid-type IR, or MBIR in this setting.

Purcell-enhanced x-ray scintillation.

Scintillation materials convert high-energy radiation to optical light through a complex multistage process. The last stage of the process is spontaneous light emission, which usually governs and limits the scintillator emission rate and light yield. For decades, scintillator research focused on developing faster-emitting materials or external photonic coatings for improving light yields. Here, we experimentally demonstrate a fundamentally different approach: enhancing the scintillation rate and yield via the Purcell effect, utilizing optical environment engineering to boost spontaneous emission. This enhancement is universally applicable to any scintillating material and dopant when the material's nanoscale geometry is engineered. We design a thin multilayer nanophotonic scintillator, demonstrating Purcell-enhanced scintillation with 50% enhancement in emission rate and 80% enhancement in light yield. The emission is robust to fabrication disorder, further highlighting its potential for x-ray applications. Our results show prospects for bridging nanophotonics and scintillator science toward reduced radiation dosage and increased resolution for high-energy particle detection.

Analytic sparse-view CBCT reconstruction using a novel sinogram restoration method based on higher-order Fourier harmonic peaks

This study presents an analytic sparse-view cone-beam computed tomography (CBCT) reconstruction method using a novel sinogram restoration technique based on higher-order Fourier harmonic peaks to obtain CBCT images of reasonable quality with a reduced radiation dose. The proposed method involves four main steps: (1) acquiring sparse-view (P144) sinogram from a CBCT system, (2) upsampling (P720) the original sparse-view sinogram with equally spaced zero padding, (3) separating higher-order Fourier harmonic peaks of the upsampled sinogram using a band-pass filter, and (4) restoring the sinogram of the higher-order harmonic peaks by taking its magnitude, followed by computationally cost-efficient filtered-backprojection (FBP)-based CBCT reconstruction and denoising processes. The notation P144 indicates that the number of projections is 144. To verify the efficacy of the proposed method, an experiment was performed on a chest phantom using a prototype CBCT system comprising an X-ray tube (90 kV p and 40 mA), a large-area flat-panel detector (388 μm pixel size), and a rotational gantry. The quality of the restored sparse-view CBCT images was quantitatively evaluated in terms of the image intensity profile, universal quality index (UQI), and peak signal-to-noise ratio (PSNR). The results indicate that the proposed sinogram restoration method effectively recovered zero-padded areas in the original upsampled sinogram with image intensities nearly identical to those of the reference dense-view (P720) sinogram, which demonstrates the efficacy of the proposed sinogram restoration method. The quality of the sparse-view CBCT image restored with higher-order harmonic peaks was close to that of the reference dense-view CBCT image, maintaining the image quality. The UQI and PSNR values of the restored sparse-view CBCT image were 0.93 and 34.84, respectively, which are approximately 1.3 and 1.2 times greater than those of the original sparse-view CBCT image, respectively, improving the image quality. Consequently, the proposed method has the potential to resolve the issues caused by sparse-view sampling in FBP-based CBCT.

Development of a user-friendly calculator for a pediatric split-bolus polytrauma computed tomography protocol.

We present here a user-friendly calculator for the setting of a pediatric split-bolus polytrauma computed tomography (CT) protocol with a mixed arterial and venous phase, aiming to both reduce radiation dose and improve workflow while assuring optimal image quality. All the different parameters are calculated based on patient's weight with rapid computation of the injected contrast media and saline volumes, injection's flow rate, injection's timing, and optimal acquisition time. The designed calculator is built in a widely available Google Sheets file, accessible by a quick response (QR) code. Although polytrauma imaging represents the main goal of the technique, it can be used in a wide variety of contexts, including oncological, infectious, and vascular pathologies.

Feasibility of balloon rectal spacer implantation in HDR and LDR brachytherapy for prostate cancer treatment

PurposeThis study evaluates the use of a biodegradable balloon rectal spacer in two prostate cancer patients undergoing Low Dose Radiation (LDR) and salvage High Dose Radiation (HDR) brachytherapy. The spacer aims to reduce radiation dose to adjacent organs, particularly the rectum, in patients previously treated with radiation. MethodsThe balloon spacer was implanted transperineally under transrectal ultrasonography (TRUS) guidance in two patients. For the LDR case (73-year-old, intermediate-risk), the balloon was placed post-implant with 55 iodine-125 seeds delivering 145 Gy. For the HDR case (66-year-old, high-risk), the balloon was placed one week before treatment, which delivered 23 Gy in two weekly fractions using 16 channels. ResultsThe balloon provided a 14-15mm separation between rectum and prostate. In the LDR case, prostate D90 was 149.1Gy (102.83%), V100 was 91.95%, and rectum D30 was 23.93Gy (16.50%). For the HDR case, prostate D90 was 11.63Gy (105.79%), V100 was 93.63%, and rectum D0.5cc was 8.04Gy (73.15%). Both patients tolerated the treatment well, with no observed postoperative complications at 6-month follow-up. ConclusionsThe use of a rectal balloon spacer in both salvage HDR and LDR brachytherapy is feasible and safe, allowing for controlled placement and providing rectal protection from high radiation doses.

Dual-energy computed tomography: pediatric considerations.

Multidetector computed tomography (CT) has revolutionized medicine and is now a fundamental aspect of modern radiology. Hardware and software advancements have significantly improved CT accessibility, image quality, and acquisition times. While considerable attention has been directed towards the potential risks of ionizing radiation from CT scans in children, recent concerns regarding the possible short- and long-term risks related to magnetic resonance imaging (MRI) conducted under general anesthesia have generated fresh interest in novel pediatric CT applications and techniques that allow imaging of awake patients at low radiation doses. Among these novel techniques, dual-energy CT (DECT) stands out for its ability to provide enhanced diagnostic information, reduce radiation doses further, and facilitate faster scans, making it a highly promising tool in pediatric radiology. This manuscript explores the current role of DECT in pediatric imaging, emphasizing its technical foundations, hardware configurations, and various reconstruction techniques. We discuss advanced post-processing techniques, such as material decomposition algorithms and virtual monoenergetic imaging, highlighting their clinical advantages in improving diagnostic accuracy and patient outcomes. Furthermore, the paper reviews the clinical applications of DECT in evaluating pulmonary perfusion, cardiovascular assessments, and oncologic imaging in pediatric patients.

Hybrid plug-and-play CT image restoration using nonconvex low-rank group sparsity and deep denoiser priors

Abstract Objective. Low-dose computed tomography (LDCT) is an imaging technique that can effectively help patients reduce radiation dose, which has attracted increasing interest from researchers in the field of medical imaging. Nevertheless, LDCT imaging is often affected by a large amount of noise, making it difficult to clearly display subtle abnormalities or lesions.&amp;#xD;Therefore, this paper proposes a multiple complementary priors CT image reconstruction method by simultaneously considering both the internal prior and external image information of CT images, thereby enhancing the reconstruction quality of CT images.&amp;#xD;Approach. Specifically, we propose a CT image reconstruction method based on weighted nonconvex low-rank regularized group sparse and deep image priors under hybrid plug-and-play framework by utilizing the weighted nonconvex low rankness and group sparsity of dictionary domain coefficients of each group of similar patches, and a convolutional neural network (CNN) denoiser.&amp;#xD;To make the proposed reconstruction problem easier to tackle, we utilize the Alternate Direction Method of Multipliers (ADMM) for optimization.Main results. To verify the performance of the proposed method, we conduct detailed simulation experiments on the images of the abdominal, pelvic, and thoracic at projection views of 45, 65, and 85, and at noise levels of 1×10^5 and 1×10^6, respectively. A large number of qualitative and quantitative experimental results indicate that the proposed method has achieved better results in texture preservation and noise suppression compared to several existing iterative reconstruction methods.&amp;#xD;Significance. The proposed method fully considers the internal nonlocal low rankness and sparsity, as well as the external local information of CT images, providing a more effective solution for CT image reconstruction. Consequently, this method enables doctors to diagnose and treat diseases more accurately by reconstructing high-quality CT images.

Outcomes of Radiation Dose Reduction Protocol in Electrophysiologic and Cardiac Device Procedures

Background: Exposure to radiation has been demonstrated to be associated with adverse short- and long-term health outcomes. Objective: To presented outcomes before and after the implementation of a radiation dose reduction protocol in electrophysiologic (EP) and cardiac device procedures. Materials and Methods: The present study was a retrospective comparative study, conducted at Chiang Mai University Hospital in Thailand using 2017 and 2019 data, including all patients who underwent EP and cardiac implantable electronic device (CIED) procedures. Exclusion criteria involved patients with incomplete radiation dose records. The authors compared fluoroscopic time, radiation exposure, and complication rates before and after the protocol. Results: Among the 458 cases, with 214 Eps and 244 devices, the mean age was 58 years. For device implantation procedures, there was no significant change in fluoroscopic time as median (P₂₅, P₇₅) before and after protocol implementation were 3.1 (0.4, 5.8) versus 4.4 (1.2,7.6) minutes, respectively (p=0.117). However, there was a decreasing trend in dose area product (DAP) at 242.0 (119.2, 766.0) versus 197.9 (71.5, 494.5) cGy.cm² (p=0.073). The reduction in DAP was more pronounced in cardiac resynchronization therapy (CRT) implantation when comparing 2017 to 2019 were 1,933.6 (1,039.4, 7,683.8) versus 1,074.6 (427.2, 2,890.7) cGy.cm² (p=0.020). In EP procedures, fluoroscopic time significantly decreased from 8.1 (3.0, 14.3) minutes in 2017 to 1.0 (0.0, 3.6) minute in 2019 (p&lt;0.001), accompanied by a significant reduction in exposure dose of 45.0 (10.8, 153.3) versus 1.7 (0.0, 31.6) mGy (p&lt;0.001) and DAP of 1,022.9 (247.2, 2,660.3) versus 38.5 (0.0, 566.9) cGy.cm² (p&lt;0.001). There was no difference in the complication rate between the two periods. Conclusion: The implementation of the radiation dose reduction protocol resulted in a significant decrease in radiation exposure during EP procedures and showed a trend towards reduction in CIED procedures.

Low-dose radiographic inspection of welding by a novel aperiodic reverse stochastic resonance method

Abstract Low-dose radiographic inspection is a growing trend in industry to minimize radiation risks to humans and the environment. However, reduction in radiation dose often introduces significant noise, which affects image quality and hinders accurate identification of subtle defects. This study addresses this issue by introducing a novel phenomenon called aperiodic reverse stochastic resonance (ARSR), observed in nonlinear systems excited by aperiodic binary signals. ARSR enables simultaneous amplitude amplification and reversal of signals under specific noise conditions. Leveraging ARSR, we propose an image denoising framework for low-dose radiographic inspections. First, a set of projection data is obtained by using Radon transform to reduce the dimensionality of X-ray images from different angles. Then, the projection data is modulated based on the ARSR system. Finally, the image is reconstructed based on the inverse Radon transform. Simulations and experimental comparison results in welding applications validate the effectiveness of the framework, demonstrating significant improvements in image quality for low-dose radiographic defect detection. Unlike advanced methods such as Gaussian filtering, BM3D, and DnCNN, which operate at the pixel level, ARSR performs denoising at the projection data stage, reducing noise impact, preserving original information, and focusing on physical data processing during imaging. This approach enhances the detection of subtle defects, highlighting the potential of stochastic resonance in image processing.

Feasibility of ultra-low activity 18F-FDG PET/CT imaging in children.

To investigate the feasibility of pediatric 18F-FDG total-body PET/CT imaging with an ultra-low activity and explore an optimized acquisition time range. A total of 38 pediatric patients were prospectively enrolled and underwent dynamic total-body PET/CT imaging using ultra-low 18F-FDG activity (0.37 MBq/kg). The 60-minute list-mode raw data were acquired and then reconstructed as static PET images by using 50-51, 50-52, 50-53, 50-54, 50-55, 50-58, 50-60, and 45-60 minutes data, which were noted as G1, G2, G3, G4, G5, G8, G10, and G15, respectively. Image qualities were subjectively evaluated using the Likert scale and were objectively evaluated by the quantitative metrics including standard uptake value (SUV), signal-to-noise ratio (SNR), target-to-background ratio (TBR), and contrast-to-noise ratio (CNR). The injected activity of FDG was 13.38 ± 5.68 MBq (4.40-28.16 MBq) and produced 0.58 ± 0.19 mSv (0.29-1.04 mSv) of effective dose. The inter-reader agreement of subjective image quality was excellent (kappa = 0.878; 95% CI, 0.845-0.910). The average scores of image quality for G1-G15 were 1.10 ± 0.20, 2.03 ± 0.26, 2.66 ± 0.35, 3.00 ± 0.27, 3.32 ± 0.34, 4.25 ± 0.30, 4.49 ± 0.36, and 4.70 ± 0.37, respectively. All image scores are above 3 and all lesions are detectable starting from G8. SNRs of backgrounds, TBRs, and CNRs were significant differences from the control group before G8 (all P < 0.05). The image quality of the 8 min acquisition for pediatric 18F-FDG total-body PET/CT with an ultra-low activity could meet the diagnostic requirements. This study confirms the feasibility of ultra-low dose PET imaging in children, and its methods and findings may guide clinical practice. pediatric patients will benefit from reduced radiation doses.

Very pronounced bowel sparing during radiation therapy for anal carcinoma using a natural spacer (Myoma) – a case report

BackgroundUsing dose-painted intensity-modulated radiation therapy, specific dose volume constraints or implantation of tissue expanders prior to radiotherapy are validated options for reducing radiation dose on the bowel and therefore minimizing acute gastrointestinal toxicity during chemoradiation for anorectal malignancies. We describe the rare case of a female patient with a locally advanced anal carcinoma where a large myomatous uterus served as a natural spacer to protect the bowel during radiation therapy.Case presentationInitially the patient presented with anal pain, proctoscopy followed by an excisional biopsy confirmed the diagnosis of a squamous cell carcinoma of the anus. Imaging examination showed a locally advanced tumor and in addition a large uterus with typical leiomyomas up to 11.5 cm in diameter. The patient underwent chemoradiation; because of the large leiomyomas there was almost no dose burden for the small intestine and therefore practically no gastrointestinal toxicity.ConclusionAs we know, this report describes the situation that a large myomatous uterus served as a natural spacer during radiation therapy in a way that is unique to date.

Abdominal Applications of Photon-Counting CT.

Photon-counting computed tomography (PCCT) has shown promising advancements in abdominal imaging in clinical use. Though more peer-reviewed primary literature is needed, this commentary explores PCCT's potential applications, focusing on enhancing diagnostic accuracy, optimizing radiation dose management, and improving patient care. PCCT offers improved spatial and contrast resolution, lower image noise, and reduced radiation dose. Increased spatial resolution provides better detail in abdominal imaging, aiding in the detection of small lesions and subtle pathological changes. However, this generates more images per scan, raising concerns about "image overload" in PACS, potentially leading to longer reading times and increased stress for radiologists. PCCT's improved contrast resolution enhances tissue differentiation, reducing the need for intravenous contrast agents. The technology's advanced tissue characterization provides several advantages, such as non-invasive and opportunistic liver disease evaluation and improved differentiation of renal and adrenal masses. PCCT's optimized radiation dose management is crucial for patients requiring frequent scans. Enhanced diagnostic accuracy through spectral information aids in tissue differentiation, improving confidence in diagnoses. Streamlined workflows, particularly in emergency settings, and oncologic imaging, are potential benefits, reducing the need for additional imaging studies. Future integration of PCCT into clinical practice requires collaboration, education, and research to fully harness its potential, ensuring optimized abdominal imaging and improved patient care.

Development, validation, and application of a generic image-based noise addition method for simulating reduced dose computed tomography images.

Major efforts in computed tomography (CT) have been focused on reducing radiation dose to patients while maintaining adequate diagnostic quality. To that end, research tools have been developed to simulate reduced-dose images via either image-based or projection-based methods. The former is limited to fully capturing realistic texture, streak, and non-stationary characteristics of reduced dose, while the latter is impractical clinically. To develop and validate an image-based noise addition method that accounts for such attributes while being practical in clinical settings. A noise addition method was developed to add realistic noise in the image domain. The method first estimates the noise power spectrum (NPS) of CT images, which are also forward-projected to form synthetic projections. The projection data are supplemented with random white noise proportional to their attenuation values. The noise sinogram is then back-projected onto the image, filtered by the NPS, and scaled according to the desired dose reduction level. The tool was evaluated using both phantom images and patient data. The phantom images were acquired using a multi-sized image quality phantom (Mercury Phantom 3.0, Duke University), and a thorax anthropomorphic phantom (Lungman Phantom, Kyoto Kagaku) at different dose levels and reconstruction settings. The patient images consisted of two dose levels of various CT examinations and reconstruction settings. The simulated and real reduced-dose images were compared in terms of the noise magnitude and texture (i.e., NPS average frequency, NPS-fav). The utility of this methodology was also assessed for routine clinical use for CT protocol review. For the phantom images, the percent errors in the noise magnitude between the simulated images and the actual images of the Mercury Phantom and anthropomorphic phantom images were 3.34% and 3.50%, respectively. The difference in fav was 0.07mm-1 for the Mercury Phantom and 0.06mm-1 for the anthropomorphic phantom between the simulated and actual images. The average noise magnitude percent error between the simulated and actual patient images was 4.61% with noise texture judged to be visually comparable with some kernel dependencies. When implemented clinically, the tool proved practical to simplify the process of estimating radiation dose reduction for CT protocols, resulting in a 50% dose reduction of our multiple myeloma protocol. The method generated simulated CT images with realistic noise properties similar to images acquired at the same radiation exposure without needing access to raw projection data.

Geometry-Aware Attenuation Learning for Sparse-View CBCT Reconstruction.

Cone Beam Computed Tomography (CBCT) plays a vital role in clinical imaging. Traditional methods typically require hundreds of 2D X-ray projections to reconstruct a high-quality 3D CBCT image, leading to considerable radiation exposure. This has led to a growing interest in sparse-view CBCT reconstruction to reduce radiation doses. While recent advances, including deep learning and neural rendering algorithms, have made strides in this area, these methods either produce unsatisfactory results or suffer from time inefficiency of individual optimization. In this paper, we introduce a novel geometry-aware encoder-decoder framework to solve this problem. Our framework starts by encoding multi-view 2D features from various 2D X-ray projections with a 2D CNN encoder. Leveraging the geometry of CBCT scanning, it then back-projects the multi-view 2D features into the 3D space to formulate a comprehensive volumetric feature map, followed by a 3D CNN decoder to recover 3D CBCT image. Importantly, our approach respects the geometric relationship between 3D CBCT image and its 2D X-ray projections during feature back projection stage, and enjoys the prior knowledge learned from the data population. This ensures its adaptability in dealing with extremely sparse view inputs without individual training, such as scenarios with only 5 or 10 X-ray projections. Extensive evaluations on two simulated datasets and one real-world dataset demonstrate exceptional reconstruction quality and time efficiency of our method.

(G4-SEOPTIM): A GEANT4 application for shielded enclosure, designing and shielding optimizing: The case of a new Moroccan shielded enclosure

PurposeThis study aims to develop and validate a Geant4 simulation application using the latest G4RadioactiveDecayPhysics v5.1 library to optimize the shielding design of a Moroccan shielded enclosure. The goal is to ensure effective radiation protection by comparing simulation results with initial geometric calculations based on the attenuation law (Beer-Lambert Law) and implementing design optimizations to enhance safety and reduce costs. MethodsThe study began with a prototype design based on linear attenuation calculations, which were costly and offered limited patient safety. Using the Geant4 Monte Carlo toolkit, we simulated the decay of a Fluorine-18 source within the shielded enclosure to evaluate dose rate distributions. The simulation's accuracy was validated through comparison with experimental measurements, and the results informed the geometric optimization of the shielding enclosure. ResultsThe Geant4 simulations demonstrated that the current shielding design effectively reduces radiation doses to acceptable levels. However, the simulations also identified opportunities for further optimization of the enclosure's geometry, allowing for more precise and efficient use of shielding materials while maintaining safety standards. ConclusionThe study confirms the utility of Geant4 for optimizing radiation shielding designs. While the initial dimensions provided adequate protection, the simulation enabled more precise geometric optimization. This approach not only enhances radiation protection but also informs the design and construction of more efficient and cost-effective shielding enclosures. The adjustments made to the enclosure's faces significantly improved radiation protection, reducing the dose rate surrounding the shielded enclosure to acceptable levels.

The Role of Nuclear Medicine in the Diagnostic Work-Up of Athletes: An Essential Guide for the Sports Cardiologist.

Athletes with heart disease are at increased risk of malignant ventricular arrhythmias and sudden cardiac death compared to their sedentary counterparts. When athletes have symptoms or abnormal findings at preparticipation screenings, a precise diagnosis by differentiating physiological features of the athlete's heart from pathological signs of cardiac disease is as important as it is challenging. While traditional imaging methods such as echocardiography, cardiac magnetic resonance, and computed tomography are commonly employed, nuclear medicine offers unique advantages, especially in scenarios requiring stress-based functional evaluation. This article reviews the use of nuclear medicine techniques in the diagnostic work-up of athletes with suspected cardiac diseases by highlighting their ability to investigate myocardial perfusion, metabolism, and innervation. The article discusses the application of single photon emission computed tomography (SPECT) and positron emission tomography (PET) using radiotracers such as [99mTc]MIBI, [99mTc]HDP, [18F]FDG, and [123I]MIBG. Several clinical scenarios are explored, including athletes with coronary atherosclerosis, congenital coronary anomalies, ventricular arrhythmias, and non-ischemic myocardial scars. Radiation concerns are addressed, highlighting that modern SPECT and PET equipment significantly reduces radiation doses, making these techniques safer for young athletes. We conclude that, despite being underutilized, nuclear medicine provides unique opportunities for accurate diagnosis and effective management of cardiac diseases in athletes.