# Technology 1

Thick, segmented scintillator converters – for external-beam, radiotherapy imaging and non-destructive testing.

### Purpose

To develop new forms of x-ray scintillators for imaging the megavoltage beam used to treat cancer in external-beam radiation therapy. The goal is to improve visualization of soft tissues in tomographic x-ray images acquired at low, clinically practical x-ray doses.  Our lab is developing detectors based on thick segmented crystalline scintillators to replace the relatively thin phosphor scintillators presently used in active matrix, flat-panel imagers (AMFPIs) designed for radiotherapy.  Such devices can also be adapted to the needs of various forms of non-destructive testing.

### Background

Following pioneering research conducted by our lab, AMFPIs have become the gold standard for creating projection images of the patient using the high-energy, x-ray treatment beams employed in radiation therapy.  However, the low x-ray detection efficiencies (~2%) of present megavoltage imagers strongly limit their clinical utility.

### Impact

The significant improvements in x-ray detection efficiency sought in our research will make it possible to achieve soft-tissue contrast, even at the lowest doses delivered by radiotherapy treatment machines.  Moreover, such improvements will make it possible to acquire tomographic imaging information (requiring ~100 projection images) at the same dose presently required for a single projection image. Such improvements are expected to significantly assist the basic medical objective of maximizing the dose to the tumor while minimizing dose to surrounding normal tissue.

### Approach

In partnership with industrial and national lab collaborators, we design, fabricate and/or evaluate prototype segmented scintillating converters providing x-ray detection efficiencies ranging from ~7% to 50%. The performance of these prototypes is extensively investigated and can include demonstrations of computed tomography using experimental set-ups such as that depicted in the adjacent illustration.

### Project Funding

This research has been funded by the National Institutes of Health / National Cancer Institute, and by Alamos National Lab as well as by our department.

### Publications

Liu et al., Med. Phys. 42(4), 2072-2084, 2015
Liu et al., Med. Phys. 41(6), 061916, 2014. PMCID: PMC4039737
El-Mohri et al., Phys. Med. Biol. 59(4), 797-818, 2014. PMCID: PMC4061715
Liu et al. Phys. Med. Biol. 57(16), 5343-5358, 2012. PMCID: PMC3429122
El-Mohri et al., Phys. Med. Biol. 56(6), 1509-1527, 2011. PMCID: PMC3062516
Wang et al., Phys. Med. Biol. 55(13), 3659-3673, 2010. PMCID: PMC2909124
Wang et al., Med. Phys. 36(12), 5707-5718, 2009. PMCID: PMC2797046
Wang et al., Med. Phys. 36(7), 3227-3238, 2009. PMCID: PMC2805354
Wang et al., Med. Phys. 35(1), 145-158, 2008. PMCID: PMC2920060