2 research outputs found
Quantitative cone-beam computed tomography reconstruction for radiotherapy planning
Radiotherapy planning involves the calculation of dose deposition throughout the patient,
based upon quantitative electron density images from computed tomography (CT) scans
taken before treatment. Cone beam CT (CBCT), consisting of a point source and flat panel
detector, is often built onto radiotherapy delivery machines and used during a treatment
session to ensure alignment of the patient to the plan. If the plan could be recalculated
throughout the course of treatment, then margins of uncertainty and toxicity to healthy
tissues could be reduced. CBCT reconstructions are normally too poor to be used as the
basis of planning however, due to their insufficient sampling, beam hardening and high level
of scatter. In this work, we investigate reconstruction techniques to enable dose calculation
from CBCT. Firstly, we develop an iterative method for directly inferring electron density
from the raw X-ray measurements, which is robust to both low doses and polyenergetic
artefacts from hard bone and metallic implants. Secondly, we supplement this with a
fast integrated scatter model, also able to take into account the polyenergetic nature of
the diagnostic X-ray source. Finally, we demonstrate the ability to provide accurate dose
calculation using our methodology from numerical and physical experiments. Not only
does this unlock the capability to perform CBCT radiotherapy planning, offering more
targeted and less toxic treatment, but the developed techniques are also applicable and
beneficial for many other CT applications