Purpose: The unstructured and scattered nature of health data, along with the lack of standardization interoperability, limits the potential of real-world research. Establishing a standardized lexicon and data structure could enhance multicenter clinical studies and communication. The goal of this study is to structure patient data relevant to radiotherapy (RT) research and create a knowledge base (KB). To achieve this, we aim to identify the essential data elements needed to encode radiomics and dosiomics information and develop an ontology.

Methods: Building on Minimal Common Oncology Data Elements (mCODE), we propose an extension to link patients' medical image data, radiomics, and dosiomics with their electronic health records. The extension adapts mCODE’s structure to include radiomics and dosiomics as cancer biomarkers, similar to genomics. We propose that each cancer patient have both a Radiomics Report and a Dosiomics Report to characterize their tumor, alongside an extension for medical images for diagnostic and RT).

Results: Our proposed extension consists of 14 data element sets with 99 attributes. The radiomics extension includes 11 sets and 54 attributes, while the dosiomics portion has 3 sets and 15 attributes. Additionally, we extended the Radiotherapy Course information to link relevant details, such as dose distribution calculations, to the Dosiomics Report. We also included an Imaging Study Profile containing attributes related to image acquisition.

Conclusions: This study represents an initial step in developing a KB for cancer patients, aiming to standardize medical information for medical physics research and improve data storage and interoperability.

Purpose: To demonstrate that relative concentrations of free fatty acids (FFAs) to triglycerides can be determined by magnetic resonance spectroscopy (MRS) of the α methylene protons (α-protons).

Methods: PRESS (Point RESolved Spectroscopy) spectra were obtained at 9.4T from phantoms containing varying amounts of FFAs (oleic acid) and triglycerides (triolein): oleic acid:triolein weight ratios of 50%:50%, 35%:65%, 25%:75%, 15%:85%, and 5%:95%. The chemical shift of the α-protons is ≈2.25ppm and ≈2.30ppm for triglycerides and FFAs, respectively. Spectra were acquired from the 50%:50% phantom with echo times (TE) of 25ms and 30ms:200ms (10ms steps; TE1=15ms) to identify one that resolves the two central α-protons resonances via J-coupling evolution. The selected TE was employed on the other phantoms. To assess reproducibility, four spectra were acquired per phantom. Integration of the α-proton central resonances was performed (triglyceride 2.25-2.28ppm; FFA 2.29-2.31ppm). The latter peak area was divided by that of the former for each spectrum to obtain FFA-to-triglyceride ratios. Means (and standard deviations) of the ratios over the four spectra were plotted against free oleic acid to triolein concentration ratios for each phantom (determined from weight ratios and molecular weights). Correlation was evaluated using a weighted-least-squares regression.

Results: A PRESS TE of 70ms (TE1/TE2=15/55) resolved the two α-proton resonances. FFA-to-triglyceride α-proton peak area ratios linearly correlate with free oleic acid to triolein concentration ratios (Rw²=1.0).

Conclusions: Quantification of relative FFA to triglyceride concentrations in phantoms at 9.4T was performed by MRS of the α-proton resonance area ratios. Future work will assess the method in vivo.

Purpose: To characterize a novel low-cost dual-robot kilovoltage adaptive therapy device KOALA for use in low-resource settings.

Methods: The KOALA 225kVp treatment beam was evaluated by energy spectrum and dosimetry measurements. Percent depth dose (PDD) and profile measurements for an open and 8.6mm collimated beam were acquired using a Farmer ionization chamber and LDV1 Gafchromic films, respectively, at various depths in Solid Water. A star-shot test was performed. The KOALA treatment workflow from CBCT to delivery was tested for a 190˚ arc. A custom 12-leaflet motorized iris collimator was designed and dosimetrically tested with EBT4 films. A Monte Carlo (MC) model of KOALA was built in TOPAS.

Results: The measured 225kVp spectrum showed good agreement with an analytical spectrum provided by SpekPy. The measured PDD curves yielded a 55% PDD at 5cm with MC agreement within 2%. Full width at half maximum (FWHM) and penumbra values were higher in MC with average offsets of 0.9mm and 0.6mm, respectively. The star-shot test resulted in a wobble diameter of 0.3mm. The workflow test showed a 5% dose difference between MC-planned and delivered doses. The iris collimator improved the penumbra from 3.3mm (8.6mm beam) to 1.2mm (5cm iris) with an average MC-film offset of 0.2mm.

Conclusions: The KOALA system shows promise as a low-cost kilovoltage adaptive therapy device with an estimated cost of $200k USD. This dual-robot device achieves excellent dose conformity at depth with sharp dose profiles. An accurate (≤5%) MC model of KOALA has been developed for simulation of planned treatments.

Purpose: To develop and validate a Monte Carlo (MC) model of a 0.5T biplanar Linac-MR, supporting commissioning, Treatment Planning System (TPS) validation, and patient-specific QA.

Methods: A high-fidelity Linac-MR MC-model is created in TOPAS, including custom radiation transport module and 3D magnetic field. Multileaf collimators (MLCs) are modeled via stereolithography-mesh and controlled by empirically driven algorithms. Off-axis MLC-defined fields are used for model evaluation. Additionally, a PDD in a heterogeneous phantom (Polystyrene-Lung-Polystyrene, 8x8cm²F.S.) is compared with field on/off scenarios using IBA-PPC05’s parallel-plate chamber. Surface doses using EBT3 film for 20x20cm² field relative to 5cm depth are measured and simulated. Patient plan simulation workflow is established and tested by simulating a treatment plan (with magnetic field) and comparing to RayStation11B TPS (without magnetic field).

Results: Off-axis beam profiles pass at >95.5% for gamma-test criteria 1%|2mm. Surface doses in polystyrene for an 8x8cm² field are 73.6%, 74.9% (measured/MC, field-on) and 62.8%, 61.8% (measured/MC, field-off). The PDD in phantom passes 100% for 1%|1mm gamma-test. Film surface dose (20x20cm²F.S.) relative to 5cm depth is 85.6%, 86.5% (measurement/MC). MC simulated treatment plan has a 94% pass-rate in 3%|3mm 3D-gamma analysis compared to TPS.

Conclusion: Our Linac-MR MC-model exhibits excellent agreement with measured dose distributions, achieving a 1%|1 mm gamma pass-rate of 100% in phantom. Surface dose deviation is <1% in film and <2% in polystyrene measurement/MC comparison. The treatment-plan MC has a 94% 3D-gamma-test pass-rate. This validated MC-model supports TPS (with/without magnetic field) evaluation and is a reliable platform for patient plan simulation in MR-guided radiotherapy.

Purpose: Breast cancer is the most common cancer in women, but screening and biopsy accuracy are limited, especially for dense breasts, highlighting the need for cost-effective, accessible solutions. We developed a cost-effective, wearable 3D automated breast ultrasound (ABUS) device compatible with any commercial ultrasound (US) system and showed its potential for point-of-care supplemental breast cancer screening. With US-MRI image registration, the system could enable US-guided biopsy of MRI-visible lesions, reducing the need for resource-intensive MRI-based biopsy. Our goal is to develop an US-MRI image registration process and characterize the system’s novel 3D Doppler capabilities.

 

Methods: The biopsy system’s registration capabilities were tested using a breast phantom with inclusions. Centroids of segmented inclusions were used to calculate target registration error (TRE) and fiducial localization error (FLE). 3D power Doppler (PD) and superb microvasculature imaging (SMI) images were acquired in custom flow phantoms, and system feasibility was tested in healthy volunteers.¬

 

Results: The system displayed high registration accuracy in 3D ABUS-MRI lesions (TRE = 0.45 mm, FLE 0.31 mm). The 3D PD and SMI images from vascular phantoms were able to be viewed dynamically in oblique and non-oblique planes using novel visualization software. Images acquired in healthy volunteers demonstrated clear visualization of anatomical structures.

 

Conclusion: The system was effective in registering lesions in US-MRI images and in acquiring 3D Doppler and SMI images. These developments show the potential of our system as a supplemental breast cancer screening system and cost-effective alternative to MRI-guided breast biopsy, particularly in women with dense breasts.

Purpose
The first end-to-end validation of the combined trajectory optimization technology (CODA-iABC) for generating patient-specific dynamic trajectories in cranial SRS/SRT, evaluating plan quality, delivery accuracy, and patient comfort during dynamic couch rotation.

Methods
Seven VMAT plans were replanned using CODA-iABC, incorporating dynamic gantry, couch, and collimator rotations. Plan quality metrics included OAR doses and MUs. A transition window (TW) algorithm optimized delivery, where TW represents the fraction of a CP during which requested MLC motion must be completed. TW width ranged from 0% to 100%. A variable approach was also studied. Delivery accuracy was evaluated via gamma analysis (5%/2mm), and treatment time recorded. Patient comfort during CODA-iABC delivery was assessed by measuring couch kinematics and compared to VMAT and CODA-VMAT in terms of plan quality, beam-on-time, and delivery accuracy.

Results
CODA-iABC plans reduced OAR doses by 50% and improved MU efficiency by 25% compared to VMAT. The variable TW method was effective for dynamic delivery, achieving an average gamma pass rate of 98% and an average delivery time of 9 min. Angular speed and acceleration ranged from 0.5 to 2.5°/s and 0.5 to 6°/s², respectively. CODA-VMAT plans had smoother delivery, with 76% and 79% of treatment time at lower speeds (<1.5°/s) and accelerations (<3°/s²), while CODA-iABC plans traded higher motion for potentially superior plan quality, with only 59% and 63% of time at lower speeds and accelerations.

Conclusions
CODA-iABC enhances multi-metastases treatment by significantly improving OAR sparing and MU efficiency, while maintaining good dose accuracy at a potential cost to patient comfort.

This study presents a novel 2D scintillation dosimeter using long scintillating fibers coupled with optical fibers for quality assurance (QA) in radiotherapy. The system provides real-time, high-resolution dose measurements by optimizing parameters such as the number of projections, fiber count, pitch, and tomographic reconstruction algorithms. The dosimeter was tested using a 6 MV photon beam from a linear accelerator, with 21 scintillating fibers (0.1 cm diameter, 13 cm length) spaced 0.5 cm apart. Scintillation light was transmitted via optical fibers to an Atik CCD camera, capturing intensity data at 37 angles (0° to 180° in 5° increments).

Dose distributions were reconstructed using various tomographic algorithms, including Filtered Back Projection (FBP), Algebraic Reconstruction Technique (ART), Simultaneous Iterative Reconstruction Technique (SIRT), and SIRT with Total Variation (TV) regularization. The SIRT+TV algorithm demonstrated the best balance of sharpness, contrast, and noise suppression, achieving a superior contrast-to-noise ratio (CNR) of 48.03. Additionally, the signal-to-noise ratio (SNR) of the reconstructed dose distributions reached 146, confirming high signal quality with minimal noise artifacts. Comparisons with EBT3 radiochromic films validated the dosimeter’s accuracy, particularly for complex and asymmetrical field shapes.

The findings highlight the potential of this system to replace multiple QA devices, improving precision in radiotherapy dosimetry. Future research will focus on enhancing spatial resolution by refining fiber arrangements, increasing projection counts, and optimizing reconstruction techniques, ultimately improving clinical applicability for advanced radiotherapy techniques such as Intensity Modulated Radiotherapy (IMRT) and Stereotactic Body Radiotherapy (SBRT).

Purpose:
To measure multi-leaf collimator (MLC) tracking latency for the Alberta Linac-MR across various gantry angles, maximum leaf velocities, and breathing patterns. Minimizing and accurately measuring latency are crucial for predicting target motion in non-invasive intrafractional tumour-tracked radiotherapy (nifteRT) and enabling real-time MRI-guided MLC tracking, which has demonstrated potential to reduce treatment margins.

 

Methods:
A QUASAR MRI motion phantom was programed to emulate 1-D tumour motions. Phantom position was sent to custom software which sets the MLC position every 40 ms. Reached MLC positions were recorded by the MLC motor driver boards every 40 ms. The set and reached MLC positions were plotted as a function of time, and the time lag between the two positions was taken as the latency. Measurements were taken at gantry angles (0°, 90°, 180°, 270°), maximum leaf velocities at the MLC (1–30 mm/s), and across artificial and patient-derived breathing patterns.

 

Results:
Measured latencies for all gantry angles were between 160 and 162 ms. Measured latencies for maximum leaf velocities at 1, 10, and 30 mm/s were 256, 155, and 270 ms respectively. Similar latencies were observed across breathing patterns, though patient-derived patterns resulted in greater tracking error.

 

Conclusions:
This work measured the latency of MLC motion in Alberta Linac-MR at ~160 ms for a variety of breathing patterns. It was found that the gantry angle has no significant impact on the measured latency. Choosing an optimal maximum leaf velocity (~10 mm/s) can minimize latency while maintaining low tracking error.

Purpose
Gold nanoparticles (GNPs) are promising radiosensitizers, but their efficacy is often evaluated in immunodeficient models. While useful, these models overlook complex interactions that could influence GNP biodistribution, potentially leading to therapeutic effects being overstated. This study aims to verify the therapeutic efficacy of GNPs in the presence of a functioning immune system by comparing the GNP-mediated radiosensitization in both immunodeficient and immunocompetent mouse tumor models.

 

Methods
MIA PaCa-2 (human) and KPCY (murine) pancreatic cancer cells were incubated with GNPs (7.5 µg/mL, 24h). Cells were irradiated (2Gy, 6MV LINAC), and the DNA double-strand breaks (DSBs) and proliferation were assessed. For in vivo biodistribution studies, tumor-bearing immunodeficient (NRG) and immunocompetent (C57BL/6) mice received intravenous injections of GNPs (2 µg/g). 24h post-injection, GNP accumulation in tumors, plasma, livers and spleens was measured.

 

Results
GNP-treated MIA PaCa-2 and KPCY demonstrated similar radiosensitization effects, exhibiting a 51% and 48% increase in DNA DSBs, respectively. This corresponded with a 19% and 14% reduction in cell proliferation for MIA PaCa-2 and KPCY cells, respectively. In vivo biodistribution studies revealed GNP tumor accumulation was 57% lower in KPCY tumors (immunocompetent) relative to MIA PaCa-2 tumors (immunodeficient), corresponding with increased GNP systemic clearance via the liver and spleen.

 

Conclusions
While both tumor models exhibited similar radiosensitization effects in vitro, immune system interactions significantly reduced GNP tumor accumulation in vivo. Ongoing radiation studies will determine if this leads to diminished radiosensitization in immunocompetent models, emphasizing the importance of physiologically relevant preclinical models to assess nanoparticle-based radiotherapy.