PhD defense by Natalie Anne Bebbington

The Department of Clinical Medicine, Aalborg University and Aalborg University Hospital are pleased to invite to PhD defense by Physicist, Natalie Anne Bebbington, who will defend the thesis entitled: Computed tomography radiation dose optimisation in molecular imaging


01.10.2021 kl. 13.00 - 16.00


The PhD defense will take place

Friday, 1st of October, 2021
Time: 1 pm
In the auditorium, Aalborg University Hospital, Syd
Hobrovej 18-22, 9000 Aalborg

After the defense there will be held a reception. All are welcome.



Associate Professor Helle D Zacho
Department of Nuclear Medicine, Aalborg University Hospital and
Department of Clinical Medicine, Aalborg University, Denmark

Assessment Committee

Professor Bodil Steen Rasmussen, (chair)
Department of Anesthesiology, Aalborg University Hospital and
Department of Clinical Medicine
Aalborg University, Denmark

Dr Bal Sanghera, Research Medical Physicist
Paul Strickland Scanner Centre. Mount Vernon Hospital
London, United Kingdom

Associate Professor Lars Tolbod
Department of Nuclear Medicine & PET-centre
Aarhus University Hospital and Department of Clinical Medicine
Aarhus University, Denmark


About the PhD thesis

Computed tomography (CT) scans are undertaken as part of positron emission tomography (PET) and single photon emission computed tomography (SPECT) examinations, collectively termed as molecular imaging (MI) techniques. The CT, PET and SPECT imaging procedures all involve exposure to ionising radiation, and due to the supposition that radiation exposure can cause cancer in later life, medical imaging personnel are legally required to ensure that radiation doses are kept as low as reasonably achievable.


The CT scan can be performed for a variety of different clinical purposes in MI: attenuation correction of the PET or SPECT images, localisation/characterisation of abnormalities seen in the PET or SPECT images, and/or fully diagnostic purposes, all of which determine the required image quality and therefore the required radiation dose to the patient. European law dictates that each country must publish CT dose reference data, to enable each department to compare their own local doses (known as National Diagnostic Reference Levels, NDRLs), as a tool for radiation dose optimisation. However, prior to this project, even globally this data was extremely sparse for CT performed as part of PET-CT and SPECT-CT scans.


This PhD project provides the first proposed CT NDRLs for the United Kingdom and the Nordics, with the proposed NDRLs also being specific to the clinical purpose of the CT scan for the first time. Furthermore, this PhD project explores some specific methods of CT radiation dose optimisation in PET-CT, relating to implementation of dose-saving scanner technologies, and changes in clinical practice. This project explores both the amount of dose which can be saved with the proposed methods and evaluates whether they are feasible for clinical implementation in the PET-CT setting.


Department of Clinical Medicine, Aalborg University


Auditoriet, Sygehus Syd, Hobrovej 18-22, 9000 Aalborg

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