Computed tomography radiation dose optimisation in molecular imaging

The aim of this PhD project is to evaluate methods and technologies and generate reference data for optimising computed tomography (CT) radiation doses given during positron emission tomography (PET)-CT and single photon emission computed tomography (SPECT)-CT scans.

This project comprises:

- Two publications on national/regional CT radiation dose surveys in PET-CT and SPECT-CT for the United Kingdom and the Nordics, which are used to suggest national diagnostic reference levels (NDRLs) in molecular imaging (MI). NDRLs allow departments performing the scans to compare their radiation doses for their patients to determine how their CT doses compare with the rest of the population and therefore whether they need to be optimised.

- One publication on a phantom study showing how much dose can be saved by optimising the tube voltage according to object or patient size using a technology called CARE kV (Siemens Healthcare), for non-contrast-enhanced localisation/characterisation CT protocols, and whether these changes affect quantification in PET images.

- One publication showing whether non-attenuation-corrected (NAC) PET images provide comparable lesion detection to attenuation-corrected (AC) images in Fluorine-18 sodium fluoride (F-18 NaF) PET bone scans, which would potentially allow CT radiation dose savings since the CT scan range could be individualised (and thus reduced compared with the clinical standard whole body scan) to cover only clinically relevant areas for the individual patient.

- One publication determining the dose savings which could be made by using an individualised localisation/characterisation CT approach in NaF PET-CT bone scans in newly diagnosed breast cancer patients about to undergo neoadjuvant chemotherapy, whilst also investigating whether this approach of a reduced CT scan range would be likely to compromise the patient's diagnosis.

The aim of this PhD project is to evaluate ways in which we can reduce radiation doses to patients given in computed tomography (CT) scans, as part of positron emission tomography (PET)-CT and single photon emission computed tomography (SPECT)-CT scans.

This project comprises:

- Two publications which document the radiation doses given to patients in the United Kingdom and the Nordic countries for CT scans performed in PET-CT and SPECT-CT. This information allows departments performing these scans to see if the doses they give are low or high by comparison with the rest of the population.

- One publication which uses CT scans on test objects mimicking patients, to see how adjusting the strength (energy) of the x-rays used in the CT part of the PET-CT scan according to the size of the test object affects the radiation dose, and whether this also affects the PET images. In this study, a specific type of technology is investigated called 'CARE kV' (Siemens Healthcare), which automatically works out which is the best x-ray strength to use for the individual patient.

- One publication showing whether PET images with corrections applied for patient size give the same result as PET images without correction for size, in PET-CT scans looking for cancer spread in the bones, in newly diagnosed breast cancer patients who are about to start chemotherapy before surgery. This is important for reducing CT radiation dose, because if a correction is applied for patient size, this requires a CT scan of the whole body, whereas if the correction does not need to be applied, the CT scan length and therefore radiation dose can be reduced.

- One publication showing how much CT radiation dose could be saved in PET-CT scans looking for cancer spread in the bones in newly diagnosed breast cancer patients who are about to start chemotherapy before surgery, by only performing the CT scan over the parts of the body which the PET part of the scan shows is needed, rather than CT scanning the whole body (which is current standard practice).