Aaron Garza

All Publications

• Multi-Institutional Audit of FLASH and Conventional Dosimetry with a 3D-Printed Anatomically Realistic Mouse Phantom. International journal of radiation oncology, biology, physics Ashraf, M. R., Melemenidis, S., Liu, K., Grilj, V., Jansen, J., Velasquez, B., Connell, L., Schulz, J. B., Bailat, C., Libed, A., Manjappa, R., Dutt, S., Soto, L., Lau, B., Garza, A., Larsen, W., Skinner, L., Yu, A. S., Surucu, M., Graves, E. E., Maxim, P. G., Kry, S. F., Vozenin, M. C., Schüler, E., Loo, B. W. 2024

  Abstract

  We conducted a multi-institutional dosimetric audit between FLASH and conventional dose rate (CONV) electron irradiations by using an anatomically realistic 3D-printed mouse phantom.A CT scan of a live mouse was used to create a 3D model of bony anatomy, lungs, and soft tissue. A dual-nozzle 3D printer was used to print the mouse phantom using acrylonitrile butadiene styrene (∼1.02 g/cm3) and polylactic acid (∼1.24 g/cm3) simultaneously to simulate soft tissue and bone densities, respectively. The lungs were printed separately using lightweight polylactic acid (∼0.64 g/cm3). Hounsfield units (HU), densities and print-to-print stability of the phantoms were assessed. Three institutions were each provided a phantom, and each institution performed two replicates of irradiations at selected anatomic regions. The average dose difference between FLASH and CONV dose distributions and deviation from the prescribed dose were measured with radiochromic film.Compared to the reference CT scan, CT scans of the phantom demonstrated mass density differences of 0.10 g/cm3 for bone, 0.12 g/cm3 for lung, and 0.03 g/cm3 for soft tissue regions. Differences in HU between phantoms were <10 HU for soft tissue and bone, with lung showing the most variation (54 HU), but with minimal impact on dose distribution (<0.5%). Mean differences between FLASH and CONV decreased from the first to the second replicate (4.3% to 1.2%), while differences from the prescribed dose decreased for both CONV (3.6% to 2.5%) and FLASH (6.4% to 2.7%). Total dose accuracy suggests consistent pulse dose and pulse number, though these were not specifically assessed. Positioning variability was observed, likely due to the absence of robust positioning aids or image guidance.This study marks the first dosimetric audit for FLASH using a non-homogeneous phantom, challenging conventional calibration practices reliant on homogeneous phantoms. The comparison protocol offers a framework for credentialing multi-institutional studies in FLASH preclinical research to enhance reproducibility of biological findings.

  View details for DOI 10.1016/j.ijrobp.2024.03.017

  View details for PubMedID 38493902

• AVATAR 2.0: next level communication systems for radiotherapy through face-to-face video, biofeedback, translation, and audiovisual immersion. Frontiers in oncology Schulz, J. B., Zalavari, L., Gutkin, P., Jiang, A., Wang, Y., Gibson, C., Garza, A., Bush, K. K., Wang, L., Donaldson, S. S., Loo, B. W., Hiniker, S. M., Skinner, L. 2024; 14: 1405433

  Abstract

  Purpose: This paper discusses an advanced version of our audiovisual-assisted therapeutic ambience in radiotherapy (AVATAR) radiolucent display systems designed for pediatric radiotherapy, enabling anesthesia-free treatments, video communication, and biofeedback. The scope of the AVATAR system is expanded here in two major ways: (i) through alternative mounting systems to accommodate a broader range of radiotherapy machines (specifically to fit robotic-arm and toroidal geometry photon radiotherapy and proton radiotherapy systems) and (ii) through additional hardware to provide video-calling, optimized audio for clear communication, and combined video inputs for biofeedback, translation, and other advanced functionalities.Methods and materials: Because robustness requires strong parts and radio-transparency requires thin, light parts, three-dimensional printing was used to rapidly prototype hollow structures and to iteratively improve robustness. Two system designs were made: one that mounts superior and another that mounts inferior to the patient's head. Radiation dose measurements and calculations were conducted to assess dose perturbations at surface and depth due to the screen.Results: For 6-MV volumetric modulated arc therapy (VMAT) plans, with and without the screen, the mean and maximum dose differences inside the planning target volume were 0.2% and 2.6% of the 200 cGy prescription, respectively. For a single static beam through the screen, the maximum measured excess surface dose was 13.4 ± 0.5%, and the largest measured dose attenuation at 5-cm water-equivalent depth was 2.1 ± 0.2%. These percentages are relative to the dose without the screen at those locations.Conclusions: The radiolucent screen systems provided here are shown to give minimal dosimetric effects on megavoltage VMAT photon treatments. For static beams, however, surface dose effects should be considered when these beams pass through the thickest components of the screen. Design files are also provided.

  View details for DOI 10.3389/fonc.2024.1405433

  View details for PubMedID 39439954

• Haptic Feedback Relocation from the Fingertips to the Wrist for Two-Finger Manipulation in Virtual Reality Palmer, J. E., Sarac, M., Garza, A. A., Okamura, A. M., IEEE IEEE. 2022: 628-633

  View details for DOI 10.1109/IROS47612.2022.9981392

  View details for Web of Science ID 000908368200061