arXiv subjects

Fardous Reaz

Publications and source records attributed to Fardous Reaz.

3 recordsLinked to original sources

arXiv2026

SHARP: A compact focusing system for medical applications using a diverging plasma lens

Cancer therapy for deep-seated tumors requires precise irradiation of a small target deep within the patient while minimizing radiation exposure to surrounding tissues. This can be accomplished with a round beam sharply converging towards a single spot, requiring a large beam size in both planes at the exit of the focusing system. Achieving this over a short distance using only quadrupole lenses is challenging; but by using a linear active plasma lens (APL) in defocusing mode, the beam can be quickly and non-destructively enlarged before focusing using quadrupoles. The position of the irradiation spot can also be scanned in three dimensions by changing magnet settings. The SHARP project will develop and test this concept. Such a system can be used with very high energy electrons (hundreds of MeV), creating a Bragg-peak-like spot using novel accelerator technology. This could lead to more compact radiotherapy facilities, not requiring a bulky infrastructure typically associated with proton radiotherapy machines. If successful, SHARP will enable precision conformal radiotherapy, spatial fractionation, and potentially be useful for FLASH radiotherapy.

physics.med-ph↗

arXiv2025

The Biologically Effective Particle Number Ratio (BPNR): a new framework to quantify the therapeutic window in SFRT and other modalities

Spatially Fractionated Radiation Therapy (SFRT) produces highly heterogeneous dose distributions, for which conventional metrics such as peak, valley, or average dose can yield ambiguous or inconsistent estimates of therapeutic window changes. These dose descriptors are not uniquely linked to biological outcome, complicating comparisons between modalities. We introduce the Biologically Effective Particle Number Ratio (BPNR), a model-independent and outcome-based framework that quantifies therapeutic window changes using directly measurable delivery quantities rather than spatial dose metrics. BPNR is defined as the ratio of total particle numbers (proportional to monitor units, MU) required to reach specified levels of tumor control probability (TCP) and normal tissue complication probability (NTCP). The relative BPNR (RBPNR) compares therapeutic windows across modalities and avoids ambiguities of spatial dose averaging by relying solely on biological endpoints. As an illustration, we apply the framework to preclinical proton minibeam radiotherapy (pMBRT) versus conventional proton therapy. The absence of normal tissue complications at the highest tested MU in the pMBRT arm yields an RBPNR > 1.4, indicating a widened therapeutic window. The BPNR/RBPNR methodology provides a concise, experimentally grounded, and modality-agnostic way to quantify therapeutic window changes, with potential applications across SFRT, FLASH, high-LET radiation, and combination therapies.

physics.med-ph↗

arXiv2022

Sharp dose profiles for high precision proton therapy using focused proton beams

Proton beam therapy has been developed to irradiate the tumor with higher precision and dose conformity compared to conventional X-ray irradiation. The dose conformity of this treatment modality may be further improved if narrower proton beams are used. Still, this is limited by multiple Coulomb scattering of protons through tissue. The primary aim of this work was to develop techniques to produce narrow proton beams and investigate the resulting dose profiles. We introduced and assessed three different proton beam shaping techniques: 1) metal collimators (100/150~MeV), 2) focusing of conventional- (100/150~MeV), and 3) focusing of high-energy (350~MeV, shoot-through) proton beams. Focusing was governed by the initial value of the Twiss parameter $α$~($α_0$), and can be implemented with magnetic particle accelerator optics. The dose distributions in water were calculated by Monte Carlo simulations using Geant4, and evaluated by target to surface dose ratio (TSDR) in addition to the transverse beam size~($σ_T$) at the target. The target was defined as the location of the Bragg peak or the focal point. The different techniques showed greatly differing dose profiles, where focusing gave pronouncedly higher relative target dose and efficient use of primary protons. Metal collimators with radii < 2~mm gave low TSDRs (<~0.7) and large $σ_T$(>~3.6~mm). In contrast, a focused beam of conventional (150~MeV) energy produced a very high TSDR (>~80) with similar $σ_T$ as a collimated beam. High-energy focused beams were able to produce TSDRs > 100 and $σ_T$ around 1.5~mm. From this study, it appears very attractive to implement magnetically focused proton beams in radiotherapy of small lesions or tumors in close vicinity to healthy organs at risk. This can also lead to a paradigm change in spatially fractionated radiotherapy.

physics.med-ph↗