NRE 8011/8012 Seminar


Unraveling the Mysteries of Spatially Fractionated Radiation Therapy: Harnessing the Bath and Shower Effect for Enhanced Clinical Outcomes


Zach Carter


Georgia Institute of Technology


Thursday, February 15, 2024 at 11:00:00 AM   


Boggs Building, Room 3-47


Fan Zhang


Dose-Volume effects have been shown to increase the radiation dose tolerance of critical organs-at-risk (OARs) such as the brainstem and spinal cord when the irradiated volume is small. For example, the brainstem may tolerate doses of over 45 Gray in a single fraction during radiosurgery for trigeminal neuralgia! This unexpected ability of the brainstem to tolerate such high doses can be attributed to the very small volume that is irradiated during the procedure. A related phenomenon known as the bath and shower effect states that the dose tolerance of an OAR is reduced when the high-dose shower is surrounded by a low-dose bath. Spatially Fractionated Radiation Therapy (SFRT) aims to deliver heterogeneous Peak and Valley dose regions to the tumor as opposed to homogeneous delivery techniques such as 3D-CRT and VMAT therapy. These peak and valley regions within the tumor are analogous to bath and shower regions previously studied in normal tissues. Despite its use for over a century, the mechanisms driving the impressive clinical outcomes of SFRT remain mysterious. In this talk, we will discuss our hypothesis that bath and shower effects play a role in the observed clinical success of SFRT techniques such as GRID/LATTICE therapy and minibeam radiation therapy (MBRT). By reducing the radiation beam to millimeter-scale which exploits bath and shower effects, the tolerance of normal tissues may be increased while still delivering an ablative dose to the tumor. We will discuss efforts to develop LINAC-MBRT and LATTICE therapy techniques which can provide SFRT exposure to a much larger pool of patients than can be treated with proton-based SFRT. Finally, we will discuss the development of LATTICE and mini-LATTICE therapy using a robotic LINAC-based 4-pi delivery technique. These developments of mini-SFRT techniques that exploit the bath and shower effect have the potential to increase the therapeutic ratio and patient outcomes for difficult radioresistant lesions.


Zach Carter is a PhD candidate in Medical Physics at the Georgia Tech department of Nuclear and Radiological Engineering and board certified therapeutic medical physicist at Wellstar North Fulton hospital. Zach is a native of Woodstock, graduated from the GT MSMP program in 2017 and completed his residency at the University of Louisville James Brown Cancer Center in Louisville, KY where he received training and experience in a multi-vendor environment including Truebeam, CyberKnife, Tomotherapy and high dose-rate brachytherapy. Zach’s research interests include development of new Spatially Fractionated Radiation Therapy (SFRT) techniques and technologies as well as novel treatment techniques using the CyberKnife robotic radiation therapy system.


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