Radiological Physics and Technology最新文献

Purpose: To investigate the dosimetric characteristics of intracavitary/interstitial brachytherapy (IC/ISBT) plans created via the hybrid inverse planning optimization (HIPO) algorithm with the dwell time Lock function.

Materials and methods: Sixteen patients with locally advanced cervical cancer treated with high-dose-rate IC/ISBT were evaluated. Based on the clinical plan data, five plans were retrospectively created: Manchester-based HIPO for needles, HIPO for all applicators, HIPO for needles after HIPO for tandem/ovoid, HIPO for ovoid after HIPO for tandem/needle, and HIPO for ovoid/needle after HIPO for tandem. The target coverage, organs at risk (OARs) doses, therapeutic ratios, and the dwell time contributions of the needles were analyzed to evaluate the plan quality. Dice similarity coefficients (DSCs) between clinical plan and each created plan were calculated to evaluate the similarity of the shape of the dose distribution.

Results: All plans created using HIPO had a sufficient target coverage, while the OAR dose for the Manchester-based HIPO plans was considerably higher than the other plans. The plan with HIPO for all applicators and with HIPO for the ovoid applicator after HIPO for tandem/needles had comparable or superior therapeutic ratios than those of the clinical plan while the dwell time contributions of the needle were much larger. For DSCs, an intermediate to low correlation was observed between the clinical plan and all HIPO plans.

Conclusions: The HIPO algorithm could create high-quality IC/ISBT plans, although the dosimetric consequences were affected by the locking function.

Purpose: The purpose of this study was to validate the accuracy of a method for determining the iodine contrast dose using effective diameter (D_eff) when performing dynamic computed tomography (CT) scans of the upper abdomen in patients with unknown body weight (BW).

Methods: D_eff was measured at the heart, at the right diaphragm upper edge, and at the right pulmonary rib diaphragm levels in the localizer radiograph and axial images. Correlation coefficients between D_eff and BW were determined for each cross section.

Results: D_{eff_axial} and BW showed the highest correlation at the right diaphragm upper edge level in men (r_S = 0.862) and at the right pulmonary rib diaphragm level in women (r_S = 0.890).

Conclusions: The BW estimated from D_eff showed a strong correlation with measured BW and may serve as a practical alternative in cases where BW is unknown.

In internal target volume (ITV)-based treatment planning, respiratory-gated four-dimensional computed tomography (4D-CT) is used to visualize the respiratory motions of lung tumors. However, in cases of irregular breathing, conventional 4D-CT cannot be synchronized with patient-specific respiratory waveforms, which poses challenges to obtaining images that accurately represent the ITV of the tumor. To address this challenge, we propose "simulated respiratory-gated 4D-CT" synchronized with the simulated waveform. This study aimed to assess the precision of ITV delineation using simulated respiratory-gated 4D-CT in patients with irregular breathing. A respiratory motion phantom was employed by inserting a simulated tumor and assessing the method under sinusoidal and irregular breathing conditions. Irregular respiratory waveforms of 20 patients were used to simulate irregular breathing. The phantom was imaged using conventional 4D-CT, slow-scan CT, and our method. For conventional 4D-CT and our method, the average and maximum intensity projections (MIP) were obtained via postprocessing. ITVs corresponding to each respiratory motion were manually contoured. Furthermore, the Dice similarity coefficient (DSC) was computed based on the ITV of conventional 4D-CT. No significant disparity was found between the ITVs obtained using our method and those obtained using conventional 4D-CT under sinusoidal motion. The DSC values of the ITVs derived from our method using MIP were the highest. In the assessment of the irregular respiratory waveforms, the ITVs obtained via MIP using our method closely approximated the ideal ITV in 20 patients. These findings demonstrate that our method can enhance the accuracy of ITV delineation in lung tumors during irregular breathing episodes.

Abdominal computed tomography (CT) is normally performed with patients raising their arms over abdominal region to prevent arm-induced artifacts that degrade image quality. This study aimed to evaluate the effects of deep learning-based image reconstruction (DLIR) on arm-induced artifacts and image quality in abdominal CT with arms-down positioning, compared to adaptive statistical iterative reconstruction-Veo (ASIR-V) and filtered-backprojection (FBP). A liver nodule phantom with arms from a PBU-60 phantom was scanned in three arms-down positions: alongside the torso, across the abdomen, and crossed over the pelvis. Abdominal CT images of 10 patients in arms-alongside-torso position were also included. Images were reconstructed using DLIRs (L-low, M-medium, and H-high), ASIR-Vs (50% and 100%), and FBP. Phantom images were assessed for artifact strength (location parameter of the Gumbel distribution and standard deviation), signal-to-noise ratio, and contrast-to-noise ratio. Two radiologists qualitatively evaluated patient images for noise, artifacts, sharpness, and overall quality. DLIR-H significantly reduced streak artifacts by 37% in location parameters and by 43% in SD, while improving SNR by 28% and CNR by 29% compared to ASIR-V50%. DLIR-M performed significantly better than ASIR-V50% in all quantitative metrics, except in the arms-alongside-torso position. FBP performed worst, although sharpness was comparable. DLIR-H received the best qualitative scores (low noise and artifacts, minimal blurring, and excellent overall image quality), although ASIR-V100% had lower subjective noise. DLIR outperformed ASIR-V and FBP in arm-induced artifact reduction and image quality and is a preferable reconstruction method for arms-down abdominal CT.