Bias-Stress Free Organic Transistors for Radiation Dosimeters Used in Cancer Treatment

Radiation therapy is utilized frequently in cancer treatment given the effectiveness of the high energy ionizing radiation in destroying cancer cells. Nevertheless, even small variations in the radiation dose can be critical to the outcome of the procedure. Additionally, the risks and high incidence of malignancies induced by the incorrect dose and the peripheral radiation in healthy tissues surrounding the target volumes represents a serious concern for patients and doctors alike. Therefore, being able to measure with high accuracy the dose and position of radiation is a critical aspect of diagnostics and treatment. In this presentation I will discuss a new type of radiation dosimeter, the RAD-OFET (<b>RA</b>diation <b>D</b>etector based on <b>O</b>rganic <b>F</b>ield <b>E</b>ffect <b>T</b>ransistor), which is tissue-equivalent, conformal to the human body and can validate in real time the dose being delivered and ensure that for nearby regions an acceptable level of low dose is being received.¹<br/>The proposed mechanism of operation for RAD-OFETs is based on trap generation/annihilation in organic semiconductors, and thus we first focused on developing highly stable devices in the absence of radiation, to ensure that all observed changes originate from the interaction with radiation and not from environmental and operational degradation. For that, we monitored spectral density of traps as a function of time during device operation to identify the most probable degradation pathways, and developed new device design rules which resulted in OFETs with unparalleled operational stability, as confirmed by the constant mobility and exceptionally low threshold voltage shift of <i>ΔV_th</i> = 0.1 eV achieved under aggressive bias stress conditions for 500 min in ambient air.² These stable OFETs were then integrated into RAD-OFET arrays for which the radiation dose was monitored with high sensitivity.<br/>These results uncover new opportunities for organic circuits that will improve the quality of healthcare through better, lower cost <i>in vivo</i> dose monitoring during radiation therapy. Placement of the sensor directly onto the human body in clinical settings will facilitate the application of therapeutic radiation with high precision, a process that will increase the effectiveness on treating cancerous tissue and minimize the impact on the surrounding healthy cells.<br/>1. Andrew M. Zeidell, Tong Ren, David S. Filston, Hamna F. Iqbal, Emma Holland, J. Daniel Bourland, John E. Anthony and Oana D. Jurchescu, Organic Field-Effect Transistors as Flexible, Tissue-Equivalent Radiation Dosimeters in Medical Applications, Adv. Sci. 7 (18), 2001522 (2020).<br/>2. Hamna F. Iqbal, Qianxiang Ai, Karl J. Thorley, Hu Chen, Iain McCulloch, Chad Risko, John E. Anthony and Oana D. Jurchescu, Suppressing bias stress degradation in high performance solution processed organic transistors operating in air, Nat. Commun. 12, 2352 (2021).