A national dosimetry audit of intraoperative radiotherapy

Objective:

National dosimetry audits are a fundamental part of quality assurance in radiotherapy, especially for new techniques. Intraoperative radiotherapy with a compact mobile kilovoltage X-ray source is a novel approach for the treatment of breast and other cancers. All seven current clinical sites in the UK were audited by a single visiting group and set of measurement equipment.

Methods:

Measurements of output, isotropy and depth doses were performed using an ion chamber in solid water, thermoluminescent dosemeters and radiochromic film, respectively.

Results:

The mean difference between measured and planned dose across all centres was −3.2±2.7%. Measured isotropy was within ±3% around the lateral plane of the X-ray source and +11±4% in the forward direction compared with the lateral plane. Measured depth doses were agreed within 5±2% of manufacturer-provided calibration values or a mean gamma index of 97% at a tolerance of 7%/0.5 mm.

Conclusion:

Agreement within measurement uncertainties was found for all three parameters except forward anisotropy, which is unlikely to be clinically significant. Steep dose gradients increase the sensitivity to small variations in positioning, but these tests are practical for use in interdepartmental audits and local baseline comparison.

Advances in knowledge:

The first UK interdepartmental audit of intraoperative radiotherapy builds confidence in the delivery of this treatment.Dosimetry audits have been a fundamental part of quality assurance (QA) in UK radiotherapy departments for over 20 years [1–6]. More recently, ongoing verification of established systems has been delegated to regional audit groups; however, new techniques such as intensity-modulated radiotherapy [7,8] or volumetric modulated arc therapy [9] have been assessed on a national level. This gives confidence in the accurate, safe and consistent delivery of complex treatments, regardless of location or prior experience.Intraoperative radiotherapy (IORT) has also been practised in the UK for nearly 20 years, using a compact mobile 50 kV X-ray device called PRS400 (Photoelectron Corporation, Lexington, MA) and, more recently, INTRABEAM® (PRS500; Carl Zeiss Surgical, Oberkochen, Germany). Initially, the system was used for intracranial stereotaxy [10] but found wider application in the delivery of a single fraction of radiation soon after surgical excision of breast tumours [11]. Most patients have been treated as part of the targeted intraoperative radiotherapy (TARGIT) international randomised controlled trial [12], although some other cases have also been successfully treated where external beam therapy was contraindicated [13]. Full calibration of the system is provided by the manufacturer, but recently, methods for independent dosimetry and quality assurance have been described [14,15]. The aim of this study was to audit all UK clinical centres in 2012 (

Measuring the effect of enhanced cleaning in a UK hospital: a prospective cross-over study

Background  

Increasing hospital-acquired infections have generated much attention over the last decade. There is evidence that hygienic cleaning has a role in the control of hospital-acquired infections. This study aimed to evaluate the potential impact of one additional cleaner by using microbiological standards based on aerobic colony counts and the presence of Staphylococcus aureus including meticillin-resistant S. aureus.     

Finding a benchmark for monitoring hospital cleanliness

This study evaluated three methods for monitoring hospital cleanliness. The aim was to find a benchmark that could indicate risk to patients from a contaminated environment. We performed visual monitoring, ATP bioluminescence and microbiological screening of five clinical surfaces before and after detergent-based cleaning on two wards over a four-week period. Five additional sites that were not featured in the routine domestic specification were also sampled. Measurements from all three methods were integrated and compared in order to choose appropriate levels for routine monitoring. We found that visual assessment did not reflect ATP values nor environmental contamination with microbial flora including Staphylococcus aureus and meticillin-resistant S. aureus (MRSA). There was a relationship between microbial growth categories and the proportion of ATP values exceeding a chosen benchmark but neither reliably predicted the presence of S. aureus or MRSA. ATP values were occasionally diverse. Detergent-based cleaning reduced levels of organic soil by 32% (95% confidence interval: 16-44%; P<0.001) but did not necessarily eliminate indicator staphylococci, some of which survived the cleaning process. An ATP benchmark value of 100 relative light units offered the closest correlation with microbial growth levels <2.5 cfu/cm(2) (receiver operating characteristic ROC curve sensitivity: 57%; specificity: 57%). In conclusion, microbiological and ATP monitoring confirmed environmental contamination, persistence of hospital pathogens and measured the effect on the environment from current cleaning practices. This study has provided provisional benchmarks to assist with future assessment of hospital cleanliness. Further work is required to refine practical sampling strategy and choice of benchmarks.