This work presents a comprehensive methodology for constructing a tissue equivalent mouse phantom using image modeling and 3D printing technology. The phantom can be used in multimodality imaging and irradiation experiments, quality control, and management. Computed tomography (CT) images of a mouse were acquired and imported into 3D modeling software. A skeleton and skin shell models were segmented in the modeling software and manufactured using 3D printing technology. The bone model was constructed with VERO-WHITE printing material with additional ingredients, including a photosensitive resin, polyurethane epoxy resin, and acrylate. Acrylonitrile butadiene styrene resin material was used to construct the skin shell. The skin shell was attached to the skeleton and filled with a specially formulated gel to act as a soft tissue substitute. The gel consisted of agarose, micro-pearl powder, sodium chloride, and magnevist solution (gadopentetate dimeglumine). A micro-container filled with 18F-fluorodeoxyglucose (18F-FDG) radioactive tracer was placed in the abdomen for micro and human positron emission tomography (PET)/CT imaging. The mouse phantom had tissue equivalency in dose attenuation with x-rays and relaxation times with magnetic resonance imaging (MRI). The CT Hounsfield Unit (HU) range for the gel soft tissue material was 31-36 HU. The 3D printed bone mimetic material had equivalent tissue/bone contrast compared with in vivo mouse measurements with a mean value of 130 ± 10 HU. At different magnetic field strengths, the T 1 relaxation time of the soft tissue was 382.75-506.48 ms, and T 2 was 51.11-70.76 ms. 18F-FDG tracer could be clearly observed in PET imaging. The 3D printed mouse phantom was successfully constructed with tissue-equivalent materials. Our model can be used for CT, MRI, and PET as a standard device for small-animal imaging and quality control.

Objectives: This retrospective study aims to develop a multiomics approach that integrates radiomics, dosiomics, and delta features to predict treatment responses in brain metastasis (BM) patients undergoing PULSAR. Methods: A retrospective study encompassing 39 BM patients with 69 lesions treated with PULSAR was undertaken. Radiomics, dosiomics, and delta features were extracted from both pre-treatment and intra-treatment MRI scans alongside dose distributions. Six individual models, alongside an ensemble feature selection (EFS) model, were evaluated. The classification task focused on distinguishing between two lesion groups based on whether they exhibited a volume reduction of more than 20% at follow-up. Performance metrics, including sensitivity, specificity, accuracy, precision, F1 score, and the area under the receiver operating characteristic (ROC) curve (AUC), were assessed. Results: The EFS model integrated the features from pre-treatment radiomics, pre-treatment dosiomics, intra-treatment radiomics, and delta radiomics. It outperformed six individual models, achieving an AUC of 0.979, accuracy of 0.917, and F1 score of 0.821. Among the top nine features of the EFS model, six features came from post-wavelet transformation and three from original images. Conclusions: The study demonstrated the feasibility of employing a data-driven multiomics approach to predict treatment outcomes in BM patients receiving PULSAR treatment. Integrating multiomics with intra-treatment decision support in PULSAR shows promise for optimizing patient management and reducing the risks of under- or over-treatment.

Introduction: SCINTIX ^® therapy, a form of biology-guided radiotherapy using real-time positron emission tomography (PET) imaging on the RefleXion ^® X1 platform, recently received FDA clearance for FDG-guided treatment of lung and bone tumors. This study evaluates the feasibility and dosimetric quality of Biology-Guided Radiotherapy (BgRT) plans for FDG-avid lesions in anatomical sites beyond current indications using processed diagnostic PET (dPET) images. Methods: Eleven previously treated FDG-avid lesions in ten patients (sites: liver, head and neck, pancreas, kidney, pelvic/abdominal nodes) were retrospectively analyzed. dPET images were processed to emulate RefleXion X1 PET characteristics. BgRT plans were generated using a non-clinical version of the RefleXion treatment planning system, delivering stereotactic body radiation therapy-level doses (48Gy/3fx for liver, 40Gy/5fx for other sites). Plan deliverability was evaluated based on normalized target signal (NTS >2.7) and activity concentration (AC > 5 kBq/ml). Plans were categorized based on the presence of dose-limiting organs at risk (OAR) constraints. Dosimetric parameters were assessed according to institutional standards. Statistical analyses examined relationships between dPET standardized uptake value (SUV), PET-derived parameters, planning target volume (PTV) characteristics, and plan complexity. Results: BgRT plans were successfully generated for all lesions. All met the NTS threshold (mean = 9.3); 72.7% met the AC goal (mean = 12.1 kBq/ml). Among cases with dPET SUV > 6, 87.5% met AC criterion, supporting this threshold as a reasonable selection criterion. Plans without dose-limiting OARs (n = 6) achieved higher PTV coverage (V100%=94.4%, conformity index (CI) = 1.08) compared to plans with OAR constraints (n = 5, V100%=78.0%, CI = 1.4). All plans were deemed clinically acceptable despite observed heterogeneity within target regions. MLC modulation intensity correlated strongly with target volume (r = 0.907) and superior-inferior extent (r = 0.896) rather than OAR proximity. Conclusion: BgRT planning using processed dPET is feasible for non-lung/bone FDG-avid lesions. SUV > 6 may serve as a reasonable threshold, though feasibility is affected by tumor location, FDG background, and nearby critical structures. Findings support clinical potential of SCINTIX expansion into new anatomical sites.

Objective. This study investigates the potential of topological data analysis (TDA) in conjunction with conventional radiomics applied to longitudinal T2-weighted magnetic resonance imaging (MRI) to evaluate treatment response following neoadjuvant therapy, with or without anti-CD40 immunotherapy, in patients with locally advanced rectal cancer. Approach. Paired pre- and post-treatment MRIs from 21 patients enrolled in the INNATE trial (NCT04130854) were analyzed, including Arm1 (radiation, chemotherapy, and anti-CD40 immunotherapy; n = 12) and Arm2 (radiation and chemotherapy alone; n = 9). Patients were categorized as having a maximal response (MR) or a partial response (PR). Three complementary delta-based analyses were performed: (1) 3D radiomics, (2) 2D radiomics and sliding-windows analysis, and (3) topological feature extraction via TDA. Statistical analysis included cross-arm comparisons (Arm1 vs Arm2), response-based comparisons (MR vs PR), and detailed pairwise subgroup analyses. Main results. For 3D radiomic features, ΔVolume effectively distinguishes between treatment strategies, with Arm1 exhibiting greater tumor reduction compared to Arm2. ΔElongation differentiates between response groups, with MR showing negative values indicative of increased tumor sphericity. In 2D radiomic analysis, Gray-level-dependence -matrix texture features computed across varying sliding windows differentiate between treatment arms but not response groups. Topological analysis identified six features derived from Betti numbers and persistence lifetimes, capturing local heterogeneity in tumor texture, shape and filtration patterns. Among these, five features significantly differentiate response groups, while one distinguishes treatment arms. At a finer level of subgroup comparison, ΔBetti ₂ demonstrates significant differences, distinguishing MR-Arm1 vs PR-Arm1 and MR-Arm1 vs MR-Arm2. Significance. This exploratory study suggests potential of topological features for outcome prediction in rectal cancer. These features may complement standard radiomics to enhance predictive performance as more data becomes available. Notably, the ability of topological features to distinguish maximal responders across treatment arms—with and without immunotherapy—may offer additional biological insights, potentially related to immune-mediated tumor response.

Background and Purpose: The RefleXion X1 (RefleXion Medical, Inc., Hayward, CA) is a unique radiotherapy platform integrating kVCT and PET as on‐board imaging guidance. This study aims to evaluate the feasibility and treatment planning quality of RefleXion X1 treatment planning system (TPS) for spinal stereotactic body radiation therapy (SBRT). Methods: This retrospective study analyzed treatment plans of 10 different patient cases, including five single‐dose level SBRT cases and five simultaneously integrated boost (SIB) SBRT cases. All plans were created using the X1 TPS with a 10 mm jaw size and evaluated against institutional planning guidelines to ensure clinical acceptability. To assess planning quality, the X1‐generated plans were compared to clinically treated plans. Key metrics such as planning target volume (PTV) coverage, maximum point dose (measured as maximal dose to any volume of 0.035cc), conformity index (CI), and organs‐at‐risk (OARs) constraints were evaluated. Statistical analysis was performed using the Wilcoxon signed‐rank test, with significance defined as p < 0.05. Results: All RefleXion X1 plans met our institutional planning guidelines for spinal SBRT and were deemed clinically acceptable. No statistically significant differences were observed in all PTV metrics, including (), (), and (). Meanwhile, X1 plans demonstrated slightly higher average maximum cauda equina doses (X1: Gy, clinically treated: Gy, ), while maintaining comparable dose sparing for other OARs. The average CI values for X1 plans and clinically treated plans were and , respectively (), demonstrating similar dose conformity. Additionally, homogeneity index (HI) and gradient index (GI) values also showed no significant differences, further supporting the comparable performance of X1 plans. Conclusions: The RefleXion X1 system can generate clinically acceptable treatment plans for complex spinal SBRT, with plan quality comparable to that of clinically treated plans at our institution.