P.J. Nolan, J. Simpson, A.J. Boston, H.C. Boston, S. Colosimo, L.J. Harkness-Brennan, D.S. Judson, A. Patel

The ProSPECTus project is developing the technology for next generation SPECT (Single Photon Emission Computed Tomography) imaging.


The detector will utilize the Compton camera principle to revolutionise the medical imaging process. This system will accurately localise gamma-ray sources through the reconstruction of interaction sequences in position and energy sensitive detectors and is expected to be 50 times more sensitive than the existing SPECT systems that use collimated scintillator detectors. The rise in imaging efficiency holds the potential to reduce scan time thus minimising patient dose and/or increasing patient throughput.


Figure 1: Compton Camera setup.

ProSPECTus is a spin off from AGATA (Advanced GAmma Tracking Array). The Compton camera device will utilize both position sensitive semiconductor detectors and state of the art digital electronics. Pulse Shape Analysis (PSA) techniques will be used to improve the intrinsic spatial resolution of the detectors while the use of cone-beam reconstruction techniques will allow accurate, quantitative reconstruction of source distributions. Monte-Carlo simulations have been conducted in the GEANT4 environment in order to devise a detector configuration, which maximises the number of easily reconstructable gamma-ray interactions. A custom pre-clinical phantom has been designed to test the position resolution and efficiency achievable with the system.


Figure 2: Custom pre-clinical phantom designed to test the position resolution and efficiency achievable with the system.

The new SPECT technique will improve future diagnosis of cancer and the probability of successful cancer therapy whilst enabling a higher throughput of patients in hospitals. ProSPECTus is a collaborative effort between the Liverpool imaging group and the STFC Daresbury Laboratory.

Compton Electron Tracking

D.S. Judson1, L.J. Harkness-Brennan1, A. Patel1, A.J. Boston1, P.J. Nolan1, M. Wilson2, M. Labiche3, I. Lazarus3

1 University of Liverpool
2 STFC Rutherford Appleton Laboratory
3 STFC Daresbury Laboratory

CELT is an STFC project investigating the feasibility of producing an electron tracking Compton camera which could potentially be used for medical imaging and radiation monitoring applications.


Compton electron tracking (CELT) should provide the high efficiency, broad energy range and wide field of view of a traditional Compton camera but with a significant reduction in the background seen in the reconstructed images.

The project uses Geant4 based simulations and electric field models to assess the viability of building a solid-­state gamma-­ray detector capable of tracking Compton scattered electrons, generated by incident gamma rays with energies in the region of 141 – 364 keV. The target is to prove the principle using simulations before generating a larger funded project to build a functional system in the future.

Diagnostic Molecular Radiotherapy (MRT)

L.J. Harkness-Brennan, H.C. Boston, D.S. Judson, S. Colosimo, L. McAreavey

A further ongoing project is aimed towards altering the current SPECT systems to retrieve greater quantitative images in molecular radiotherapy. Construction and design of low efficiency, high resolution collimators along with CZT detectors is underway with the aim of improving diagnostic imaging performance for dosimetry.


Currently, doses administered to patients are fixed for a given procedure and then scaled for the patient’s weight. Standard imaging devices make it difficult to determine the dose delivered during procedures and hence qualify the impact of treatment.

The production of this gamma-camera, primarily aimed at identifying the 364 keV photon from I-131 during the treatment of thyroid cancer shall push the boundaries of personalised treatment plans in radiotherapy, resulting in tailored dose administrations for each patient. In all, this shall save lives, enable changes in MRT treatment planning policies, and reduce the cost of treatment.