Dosimetry of ionising radiation in modern radiation oncology

Abstract

Dosimetry of ionising radiation is a well-established and mature branch of physical sciences with many applications in medicine and biology. In particular radiotherapy relies on dosimetry for optimisation of cancer treatment and avoidance of severe toxicity for patients. Several novel developments in radiotherapy have introduced new challenges for dosimetry with small and dynamically changing radiation fields being central to many of these applications such as stereotactic ablative body radiotherapy and intensity modulated radiation therapy. There is also an increasing awareness of low doses given to structures not in the target region and the associated risk of secondary cancer induction. Here accurate dosimetry is important not only for treatment optimisation but also for the generation of data that can inform radiation protection approaches in the future. The article introduces some of the challenges and highlights the interdependence of dosimetric calculations and measurements. Dosimetric concepts are explored in the context of six application fields: reference dosimetry, small fields, low dose out of field, in vivo dosimetry, brachytherapy and auditing of radiotherapy practice. Recent developments of dosimeters that can be used for these purposes are discussed using spatial resolution and number of dimensions for measurement as sorting criteria. While dosimetry is ever evolving to address the needs of advancing applications of radiation in medicine two fundamental issues remain: the accuracy of the measurement from a scientific perspective and the importance to link the measurement to a clinically relevant question. This review aims to provide an update on both of these.

Ionizing radiation‐induced acoustics for radiotherapy and diagnostic radiology applications

“…Due to the stochastic nature of energy deposition, Monte Carlo (MC) techniques are considered to be the most accurate way of calculating radiation dose . MC techniques simulate particle trajectories using random numbers to sample the probability density functions of potential interactions a particle may undergo as it traverses a medium.…”

“…Reference or relative dosimetry measurements in a phantom are used for beam characterization, treatment planning and quality assurance, while in vivo dosimetry measurements are made during treatment to directly measure the dose received by the patient. Due to the increasing complexity of linac treatment delivery techniques, such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), there is an increased need for volumetric dosimetry techniques to accurately measure the dose delivered to a phantom and to verify that treatment delivery matches the planning objectives . Additionally, the International Atomic Energy Agency (IAEA) suggests that in vivo dosimetry should be used for patients that are receiving treatment via novel delivery techniques, after software or equipment changes, in hypofractionated treatments, and curative treatments where the dose received is potentially close to surrounding normal tissue tolerance .…”

“…Due to the increasing complexity of linac treatment delivery techniques, such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), there is an increased need for volumetric dosimetry techniques to accurately measure the dose delivered to a phantom and to verify that treatment delivery matches the planning objectives. 6 Additionally, the International Atomic Energy Agency (IAEA) suggests that in vivo dosimetry should be used for patients that are receiving treatment via novel delivery techniques, after software or equipment changes, in hypofractionated treatments, and curative treatments where the dose received is potentially close to surrounding normal tissue tolerance. 32 These advancements and recommendations have necessitated the development of novel efficient and volumetric dosimetry techniques.…”

Investigating the electronic portal imaging device for small radiation field measurements

“…[6] Improper selection of radiation detector for the commissioning of small radiation fields resulted in wrong radiation therapy treatment to 145 patients in Toulouse, France[7] and to 152 patients in Springfield, Missouri. [8] This highlights the importance and continuing challenges of small radiation field measurements.…”

Characterization of Yb-doped silica optical fiber as real-time dosimeter

“…In fact, instruments and procedures that were suitable up to few years ago now may fail or provide results not sufficiently accurate 9) .…”