From molecules to medicine: starting small, thinking big

It takes a lot of people to save a life. Hours of research are behind every new technology in hospitals across the country. Fundamental physics, chemistry and biology lend a helping hand to patients, using knowledge generated outside the operating theatre to advance medical technology.

Professor Clive Baldock, from the Institute of Medical Physics, investigates how physics impacts on the diagnosis and treatment of cancer. “Our aim is to develop new and more effective methods for administering radiotherapy, and to assist radiation oncologists in studying the medical impact of new technology. The focus is on real world problem solving,” says Baldock.

“To deliver radiation that gives the best outcome we have to be confident that it goes to the right place, known as the spatial distribution, and ensure that it is delivered using the right intensity of radiation. We’re now developing new devices and techniques that can measure the spatial distribution of the radiation and quantify the dose that is given.”

One way to achieve this is with a device called a polymer gel dosimeter, which measures a patient’s radiation exposure. “Certain polymers undergo changes when exposed to ionising radiation. We are creating three-dimensional polymer models of human tumours that record the radiation delivered during radiotherapy. This gives us valuable information about the accuracy and precision of the spatial and intensity dose distribution,” says Baldock.

Radiation doses are traditionally measured outside the body: they are calibrated under standard conditions and modified based on the individual patient. “That works up to a point, but during a series of radiation treatments, given over a number of treatment sessions, the target area can move. Sometimes even eating a meal can have an impact on the tumour’s position, such that the subsequent radiation dose may not be optimal,” says Baldock. “We want to be able to work out the ideal radiation dose and location, so that each treatment is as accurate as possible.”

Electronic portal imaging devices (EPID) are one form of radiographic imaging technique that shows promise for quantifying radiation doses. Traditionally used for patient set-up verification in radiotherapy, it was discovered that the images of the radiation treatment fields also contain information that could be used to quantify the dose received by the patient. Calibration methods have since been developed to convert EPID images into radiation dose.

“There are some technical difficulties with measuring the amount of radiation given, but by modifying existing devices we are finding new ways to improve the dose verification of radiotherapy treatments. Preliminary work shows that we can improve image localisation, and we hope this will translate to improved patient outcomes,” reveals Baldock.

If successful, these new techniques will give radiation oncologists greater confidence that the prescribed radiation treatment is on target and on dose.