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.

A practical method to calibrate and optimise automatic exposure control devices for computed radiography (CR) and digital radiography (DR) imaging systems using the signal-to-noise ratio (SNR) metric

Craig S Moore, Tim J Wood, Steven Jones, John R Saunderson and Andrew W Beavis, Biomed. Phys. Eng. Express 5 (2019) 035027

Wehave established in recent virtual clinical trials that signal-to-noise ratio (SNR) is the most appropriate metric for calibrating AEC devices used with digital imaging systems for chest, abdomen, pelvis and spine radiography. However, the practical calibration of such devices is not straightforward. The purpose of this study was to expand on previous work by developing a practical method for AEC calibration using the validated SNR metric that may be used by medical physicists in the field for phosphor plate radiography (CR) and direct digital radiography (DR- wireless and integrated) imaging systems. This methodology used a uniform tissue equivalent phantom (Poly-methyl methacrylate (PMMA)) so comparison was made with an installation vendor’s method of using copper plates. System transfer properties (STP) of each system were derived to linearise all images required for analyses. All STP correction was done in real time. The relationship between detector air kerma (DAK) and STP corrected SNR was then derived at four tube voltages (60, 80, 100 and 120 kVp) and using this relationship, together with the target value of the calibration metric (SNRtarget), it was possible to calculate theDAKrequired at each tube voltage to derive a calibration curve for each system; CR systems exhibited a linear increase with kVp,DRsystems exhibited a ‘U’ shape. The curve derived using the vendor’s method was not considered optimised because it did not hold SNR constant. This work has demonstrated that a relatively simple method to calibrate AEC devices, using an easily accessible tissue equivalent phantom, can be used in the field in real time by medical physicists working with installation engineers. AEC calibration curves that produce clinically adequate image quality with acceptable patient dose have been installed in our radiology department for CR and DRsystems using the methodology described in this paper.

A patient tumour-on-a-chip system for personalised investigation of radiotherapy based treatment regimens

R. Kennedy, D. Kuvshinov, A. Sdrolia, E. Kuvshinova, K. Hilton, S. Crank, A. W. Beavis, V. Green & J. Greenman, R. Kennedy, D. Kuvshinov, A. Sdrolia, E. Kuvshinova, K. Hilton, S. Crank, A. W. Beavis, V. Green & J. Greenman, A patient tumour-on-a-chip system for personalised investigation of radiotherapy based treatment regimens. Scientific Reports, volume 9, Article number: 6327 (2019)

Development of personalised cancer models to predict response to radiation would benefit patient care; particularly in malignancies where treatment resistance is prevalent. Herein, a robust, easy to use, tumour-on-a-chip platform which maintains precision cut head and neck cancer for the purpose of ex vivo irradiation is described. The device utilises sintered discs to separate the biopsy and medium, mimicking in vivo microvascular flow and diffusion, maintaining tissue viability for 68 h. Integrity of tissues is demonstrated by the low levels of lactate dehydrogenase release and retained histology, accompanied by assessment of cell viability by trypan blue exclusion and flow cytometry; fluid dynamic modelling validates culture conditions. An irradiation jig is described for reproducible delivery of clinically-relevant doses (5 × 2 Gy) to newly-presenting primary tumours (n = 12); the addition of concurrent cisplatin is also investigated (n = 8) with response analysed by immunohistochemistry. Fractionated irradiation reduced proliferation (BrdU, p = 0.0064), increased DNA damage (ƴH2AX, p = 0.0043) and caspase-dependent apoptosis (caspase-cleaved cytokeratin-18) compared to control; caspase-dependent apoptosis was further increased by concurrent cisplatin compared to control (p = 0.0063). This is a proof of principle study showing the response of cancer tissue to irradiation ex vivo in a bespoke system. The novel platform described has the potential to personalise treatment for patients in a cost-effective manner with applicability to any solid tumour.

Ιmpact of sunitinib-induced hypothyroidism on survival of patients with metastatic renal cancer

Theofanis Vasileiadis, Michail Chrisofos, Michail Safioleas, Konstantinos Kontzoglou, Konstantinos Papazisis and Athina Sdrolia, Ιmpact of sunitinib-induced hypothyroidism on survival of patients with metastatic renal cancer, Theofanis Vasileiadis, Michail Chrisofos, Michail Safioleas, Konstantinos Kontzoglou, Konstantinos Papazisis and Athina Sdrolia BMC Cancer201919:407

Background Sunitinib plays an important role in managing the metastatic renal cell cancer (mRCC). Sunitinib-induced hypothyroidism is a common side-effect of the drug. There have been attempts to link hypothyroidism with a better clinical outcome in sunitinib-treated (mRCC) patients. Our aim was to relate the impact of hypothyroidism to the survival of these patients. Methods We have evaluated 70 patients with mRCC that received sunitinib as a first line treatment. Thyroid-stimulating hormone (TSH) was measured at baseline, after 15 days of treatment (day-15) and at the end of the second cycle (day-75). Biomarker data and correlations with response were analysed with Microsoft Excel. Comparison results from Student’s t-test with a p less than 0.05 were considered statistically significant. Kaplan-Meyer and log-rank tests were performed using GraphPad Prism 5 for Windows. Results Regarding the response to treatment, a progression-free survival (PFS) of 9.47 months and an overall survival (OS) of 22.03 months were demonstrated. Our data are consistent with published data by other authors. On day-15 from the beginning of the treatment an important number of patients exhibited a TSH elevation. On day-15 42.86% had a TSH over the upper normal limit and 50.0% at the end of the second cycle (day-75). TSH increased earlier in patients that exhibited an objective response (× 3.33 times the baseline values on day-15) than patients that exhibited disease stabilisation (× 2.18) or disease progression (× 1.59). Early increases in TSH were associated with a longer PFS (11.92 vs. 8.82 months, p = 0.0476) and a longer OS (3.10 vs. 1.08 years, p = 0.0011). Conclusions Early TSH-increase is associated with a clinical benefit. The patients that showed at least a twofold increase of their baseline TSH, responded to therapy by stabilisation or by regression of disease. This is the only study to our knowledge which shows that early increases - 2 weeks from starting the treatment - in TSH levels have a prognostic value. Both PFS and OS of the patients who demonstrated a higher than a twofold rise were significantly longer than the PFS and the OS of the patients that presented a lower or no TSH-increase.

Investigation of the bolusing effect of the Varian ExactTM IGRT couch on flattened and flattening filter-free (FFF) photon beams of a Varian TrueBeam linac

Athina Sdrolia, Nilesh Tambe, Jenny E Marsden, Mark L Wilson, William P Colley and Andrew W Beavis , 2018 Biomed. Phys. Eng. Express 5 015011

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.

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Queen's Centre for Oncology & Haematology
Castle Hill Hospital
Cottingham
East Yorkshire
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