Senior Research Scientist,
The Christie NHS Foundation Trust, Manchester
Title & Abstract:
The use of 3D Printed phantoms for improving the accuracy of Molecular Radiotherapy Dosimetry
Performing patient-specific dosimetry in molecular radiotherapy (MRT) requires accurate activity quantification. Activity is typically derived from SPECT images, acquired at different time points, by converting the image counts using a calibration factor. This calibration factor has previously been calculated by scanning a spherical insert filled with a known activity distribution. Recent work by our group has shown that the calibration factor varies with size and shape of the insert, due to partial volume effects, rendering a single calibration factor insufficient for accurate activity quantification. The use of 3D printing for MRT has been accelerating as the equipment becomes more accessible and affordable. Our group uses 3D printing to manufacture a range of fillable phantoms, ranging from standard geometric shapes, e.g. spheres and ellipsoids, to patient-specific organs and lesions generated from CT scans. I will present how these phantoms were developed and how we use them to investigate how calibration factors vary with shape and size, and the effects this has on the dosimetry. I will finish by showing how we are building up a 3D printed ‘tumour library’ consisting of standard ellipsoids and patient tumours taken from CT images, and how these inserts have been used to measure the accuracy of voxel-based dosimetry and optimise the use of partial volume correction algorithms to improve SPECT image quantification and MRT dosimetry.