PUBLICATIONS

This page includes the titles and abstracts of the 10 most recent publications by members of the Radiation Physics Department. A full list of past publications can be found on the link below.

IPEM Topical Report: An evidence and risk assessment based analysis of the efficacy of tube and generator quality assurance tests on general x-ray units

Ian Honey, Amy Rose, Chris Baker, Paul Charnock, Jason Fazakerley, Gareth Richard Iball, Manthos Koutalonis, Mandy Price, Caroline Renaud, Daniel Shaw, Tim J Wood and Mark Worrall, Physics in Medicine & Biology, Accepted Manuscript online 15 November 2018

This work aims to assess the efficacy of current x-ray quality assurance (QA) testing regimes on tube and generator systems for general radiographic usage in the UK. 1393 sets of QA results data from 9 UK medical physics departments were collected and analysed. Test failure rates ranged from 0 % to 39% and were used to assess the likelihood of the test finding a fault. The magnitude of the recorded faults were used to assess the severity of the failure with due consideration to its impact on image quality and patient dose. The severity and likelihood of the faults were used along with a risk matrix to assess the efficacy of each test. 11 tests were graded 'orange' (indicating an effective test that should be continued), 4 tests were graded 'yellow' (indicating a less effective test that may be continued with a lower frequency considered), and 4 tests were graded green (indicating a low efficacy test that could be removed from test regimes).

Development and clinical implementation of a simple knowledgebased planning tool for prostate volumetric modulated arc therapy

Mark Lee Wilson , Nicholas Oliver Harding and William Peter Colley, Biomed. Phys. Eng. Express 4 (2018) 065019

Assessment of alternate functional parameters in sincalide cholescintigraphy and possible role in patient selection in gall bladder dyskinesia: A case-control study

Vittal SR Rao, Emmanouil Papadopoulos, Fahad Mahmood, Graham Wright and Kevin Wedgwood, Rao VSR, Papadopoulos E, Mahmood F, Wright G, Wedgwood K (2018) Assessment of alternate functional parameters in sincalide cholescintigraphy and possible role in patient selection in gall bladder dyskinesia: A case-control study. Glob Surg 4: DOI: 10.15761/ GOS.1000190

IPEM topical report: the first UK survey of dose indices from radiotherapy treatment planning computed tomography scans for adult patients

T Wood, A Davis, J Earley, S Edyvean, U Findlay, R Lindsay, R Plaistow, A Nisbet, A Palmer and M Williams, Phys. Med. Biol. 63 185008

CT scans are an integral component of modern radiotherapy treatments, enabling the accurate localisation of the treatment target and organs-at-risk, and providing the tissue density information required for the calculation of dose in the treatment planning system. For these reasons, it is important to ensure exposures are optimised to give the required clinical image quality with doses that are as low as reasonably achievable. However, there is little guidance in the literature on dose levels in radiotherapy CT imaging either within the UK or internationally. This IPEM topical report presents the results of the first UK wide survey of dose indices in radiotherapy CT planning scans. Patient dose indices were collected for prostate, gynaecological, breast, lung 3D, lung 4D, brain and head and neck scans. Median values per scanner and examination type were calculated and national dose reference levels and achievable levels of CT dose index (CTDIvol), dose-length-product (DLP) and scan length are proposed based on the third quartile and median values of these distributions, respectively. A total of 68 radiotherapy CT scanners were included in this audit. The proposed dose reference levels for CTDIvol and DLP are; prostate 16 mGy and 570 mGy cm, gynaecological 16 mGy and 610 mGy cm, breast 10 mGy and 390 mGy cm, lung 3D 14 mGy and 550 mGy cm, lung 4D 63 mGy and 1750 mGy cm, brain 50 mGy and 1500 mGy cm and head and neck 49 mGy and 2150 mGy cm. Significant variations in dose indices were noted, with head and neck and lung 4D yielding a factor of eighteen difference between the lowest and highest dose scanners. There was also evidence of some clustering in the data by scanner manufacturer, which may be indicative of a lack of local optimisation of individual systems to the clinical task. It is anticipated that providing this data to the UK and wider radiotherapy community will aid the optimisation of treatment planning CT scan protocols.

Measurement of effective detective quantum efficiency for a photon counting scanning mammography system and comparison with two flat panel full-field digital mammography systems

T J Wood, C S Moore, J R Saunderson and A W Beavis, Phys. Med. Biol. 63 025025

Effective detective quantum efficiency (eDQE) describes the resolution and noise properties of an imaging system along with scatter and primary transmission, all measured under clinically appropriate conditions. Effective dose efficiency (eDE) is the eDQE normalised to mean glandular dose and has been proposed as a useful metric for the optimisation of clinical imaging systems. The aim of this study was to develop a methodology for measuring eDQE and eDE on a Philips microdose mammography (MDM) L30 photon counting scanning system, and to compare performance with two conventional flat panel systems. A custom made lead-blocker was manufactured to enable the accurate determination of dose measurements, and modulation transfer functions were determined free-in-air at heights of 2, 4 and 6 cm above the breast support platform. eDQE were calculated for a Philips MDM L30, Hologic Dimensions and Siemens Inspiration digital mammography system for 2, 4 and 6 cm thick poly(methyl methacrylate) (PMMA). The beam qualities (target/filter and kilovoltage) assessed were those selected by the automatic exposure control, and anti-scatter grids were used where available. Measurements of eDQE demonstrate significant differences in performance between the slit- and scan-directions for the photon counting imaging system. MTF has been shown to be the limiting factor in the scan-direction, which results in a rapid fall in eDQE at mid-to-high spatial frequencies. A comparison with two flat panel mammography systems demonstrates that this may limit image quality for small details, such as micro-calcifications, which correlates with a more conventional image quality assessment with the CDMAM phantom. eDE has shown the scanning photon counting system offers superior performance for low spatial frequencies, which will be important for the detection of large low contrast masses. Both eDQE and eDE are proposed as useful metrics that should enable optimisation of the Philips MDM L30.

The utility of myocardial perfusion imaging before renal transplantation: a retrospective analysis

Callan, Paul D.; Bhandari, Sunil; Clark, Andrew L.; Eadington, David; Papadopoulos, Emmanouil; Tweddel, Ann C, Nuclear Medicine Communications: January 02, 2018 - Volume Publish

Background Renal transplantation (RT) reduces morbidity and mortality in patients with end-stage renal failure. Myocardial perfusion imaging provides prognostic information in patients with renal failure, but its role before transplantation remains unclear. We performed a retrospective review assessing the prognostic value of technetium-99m sestamibi myocardial perfusion imaging at a tertiary UK centre. Patients and methods We included scans performed between 2005 and 2012. Available scans were reanalysed to calculate the semiquantitative summed scores: sum rest score (SRS), sum stress score (SSS), sum difference score and sum motion score (SMS). Kaplan–Meier survival estimates assessed all-cause mortality and cardiac events according to scan findings, transplant decision and SSS. Cox-proportional hazards tested for an association between clinical/scan variables and all-cause mortality, and combined all-cause mortality/cardiovascular (CV) events. Results One hundred and thirty-eight scans were identified with complete follow-up. During a median 40.4-month follow-up, 21 patients died, with 11 nonfatal CV events. There was no significant difference between groups according to scan findings for mortality (log-rank P=0.17) or mortality/CV events (P=0.06). An SSS greater than 8 was associated with higher mortality and CV events combined (P=0.028). An abnormal baseline ECG [hazard ratio (HR): 16.1] and higher SRS (HR: 2.3) were associated independently with higher mortality; an abnormal ECG (HR: 3.4) also predicted higher cardiac events/mortality. Conclusion Moderate to severe perfusion defects by SSS were associated with higher mortality and CV events. Higher SRS was associated independently with increased mortality on multivariable analysis, highlighting a key role for semiquantitative analysis methods for risk stratification. An abnormal ECG was associated strongly with both endpoints, and may be a useful screening tool to select patients for further investigation.

UK guidance on the management of personal dosimetry systems for healthcare staff working at multiple organisations

Andy Rogers, Claire-Louise Chapple, Maria Murray, David Platton, John Saunderson, The British Journal of Radiology : 20170363.

There has been concern expressed by the UK regulator, the Health & Safety Executive, regarding the management of occupation dose for healthcare radiation workers who work across multiple organisations. In response to this concern the British Institute of Radiology led a working group of relevant professional bodies to develop guidance in this area. The guidance addresses issues of general system management that would apply to all personal dosimetry systems, regardless of whether or not the workers within that system work across organisational boundaries, along with exploring efficient strategies to comply with legislation where those workers do indeed work across organisational boundaries. For those specific instances, the guidance discusses both system requirements to enable organisations to co-operate [Ionising radiation Regulations 1999 Regulation 15], as well as specific instances of staff exposure. This is broken down into three categories - low, medium and high risk. A suggested approach to each is given to guide employers and their radiation advisers in adopting sensible strategies for the monitoring of their staff and the subsequent sharing of dosimetry data to ensure overall compliance with both dose limits and optimisation requirements.

A method to incorporate the effect of beam quality on image noise in a digitally reconstructed radiograph (DRR) based computer simulation for optimisation of digital radiography

Craig Moore, Tim Wood, John Saunderson and Andrew Beavis , Physics in Medicine and Biology. 2017 62:7379

The use of computer simulated digital x-radiographs for optimisation purposes has become widespread in recent years. To make these optimisation investigations effective, it is vital simulated radiographs contain accurate anatomical and system noise. Computer algorithms that simulate radiographs based solely on the incident detector x-ray intensity ('dose') have been reported extensively in the literature. However, while it has been established for digital mammography that x-ray beam quality is an important factor when modelling noise in simulated images there are no such studies for diagnostic imaging of the chest, abdomen and pelvis. This study investigates the influence of beam quality on image noise in a digital radiography (DR) imaging system, and incorporates these effects into a digitally reconstructed radiograph (DRR) computer simulator. Image noise was measured on a real DR imaging system as a function of dose (absorbed energy) over a range of clinically relevant beam qualities.

Simulated 'absorbed energy' and 'beam quality' DRRs were then created for each patient and tube voltage under investigation. Simulated noise images, corrected for dose and beam quality, were subsequently produced from the absorbed energy and beam quality DRRs, using the measured noise, absorbed energy and beam quality relationships. The noise images were superimposed onto the noiseless absorbed energy DRRs to create the final images. Signal-to-noise measurements in simulated chest, abdomen and spine images were within 10% of the corresponding measurements in real images. This compares favourably to our previous algorithm where images corrected for dose only were all within 20%.

Measuring the response of human head and neck squamous cell carcinoma to irradiation in a microfluidic model allowing customized therapy

Ramsah Cheah, Rishi Srivastava, Nicholas D. Stafford, Andrew W. Beavis, Victoria Green and John Greenman , INTERNATIONAL JOURNAL OF ONCOLOGY 51: 1227-1238, 2017

Radiation therapy planning for gastroesophageal junctional carcinoma in a paraesophageal hiatal hernia

Nilesh Tambe, MSc; Mohan Hingorani, FRCR; Andrew Beavis, PhD; Sanjay Dixit, FRCR, Appl Rad Oncol. 2018;7(2):45-48

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