The Impact of Iterative Reconstruction on Computed Tomography Radiation Dosimetry: Evaluation in a Routine Clinical Setting.

PURPOSE: To evaluate the effect of introduction of iterative reconstruction as a mandated software upgrade on radiation dosimetry in routine clinical practice over a range of computed tomography examinations. METHODS: Random samples of scanning data were extracted from a centralised Picture Archiving Communication System pertaining to 10 commonly performed computed tomography examination types undertaken at two hospitals in Western Australia, before and after the introduction of iterative reconstruction. Changes in the mean dose length product and effective dose were evaluated along with estimations of associated changes to annual cancer incidence. RESULTS: We observed statistically significant reductions in the effective radiation dose for head computed tomography (22-27%) consistent with those reported in the literature. In contrast the reductions observed for non-contrast chest (37-47%); chest pulmonary embolism study (28%), chest/abdominal/pelvic study (16%) and thoracic spine (39%) computed tomography. Statistically significant reductions in radiation dose were not identified in angiographic computed tomography. Dose reductions translated to substantial lowering of the lifetime attributable risk, especially for younger females, and estimated numbers of incident cancers. CONCLUSION: Reduction of CT dose is a priority Iterative reconstruction algorithms have the potential to significantly assist with dose reduction across a range of protocols. However, this reduction in dose is achieved via reductions in image noise. Fully realising the potential dose reduction of iterative reconstruction requires the adjustment of image factors and forgoing the noise reduction potential of the iterative algorithm. Our study has demonstrated a reduction in radiation dose for some scanning protocols, but not to the extent experimental studies had previously shown or in all protocols expected, raising questions about the extent to which iterative reconstruction achieves dose reduction in real world clinical practice.

Cohort study of Western Australia computed tomography utilisation patterns and their policy implications.

BACKGROUND: Computed tomography (CT) scanning is a relatively high radiation dose diagnostic imaging modality with increasing concerns about radiation exposure burden at the population level in scientific literature. This study examined the epidemiology of adult CT utilisation in Western Australia (WA) in both the public hospital and private practice settings, and the policy implications. METHODS: Retrospective cohort design using aggregate adult CT data from WA public hospitals and Medical Benefits Schedule (MBS) (mid-2006 to mid-2012). CT scanning trends by sex, age, provider setting and anatomical areas were explored using crude CT scanning rates, age-standardised CT scanning rates and Poisson regression modelling. RESULTS: From mid-2006 to mid-2012 the WA adult CT scanning rate was 129 scans per 1,000 person-years (PY). Females were consistently scanned at a higher rate than males. Patients over 65 years presented the highest scanning rates (over 300 scans per 1,000 PY). Private practice accounted for 73% of adult CT scans, comprising the majority in every anatomical area. In the private setting females predominately held higher age-standardised CT scanning rates than males. This trend reversed in the public hospital setting. Patients over 85 years in the public hospital setting were the most likely age group CT scanned in nine of ten anatomical areas. Patients in the private practice setting aged 85+ years were relatively less prominent across every anatomical area, and the least likely age group scanned in facial bones and multiple areas CT scans. CONCLUSION: In comparison to the public hospital setting, the MBS subsidised private sector tended to service females and relatively younger patients with a more diverse range of anatomical areas, constituting the majority of CT scans performed in WA. Patient risk and subsequent burden is greater for females, lower ages and some anatomical areas. In the context of a national health system, Australia has various avenues to monitor radiation exposure levels, improve physician training and modify funding mechanisms to ensure individual and population medical radiation exposure is as low as reasonably achievable.

The disproportionate risk burden of CT scanning on females and younger adults in Australia: a retrospective cohort study.

OBJECTIVES: To explore the interaction of computed tomography (CT) use, dose and radiation risk of Australian Medicare-funded CT scanning and the impact on cancer incidence and mortality. METHODS: This retrospective cohort study used records of Medicare subsidised CT scans in Australia (2006/07 to 2011/12) and Australian CT dosimetry. The annual number, rate and adjusted likelihood of CT were determined for gender, age and examination type. Incident cancer and cancer-related mortality attributable to CT in Australia were estimated using lifetime attributable risk coefficients, dosimetry and scan numbers. RESULTS: The number of CT scans increased by 36% from 2006/07 to 2011/12. Only patients aged 0-4 years did not present an increase in CT scanning rates. Females were 11% more likely to be scanned than males. Head, abdomen/pelvis and spine CT scans were the most likely areas scanned. Females were attributed 61% of both incident cancers and cancer-related mortality from 55% of scans performed. Patients aged 15-44 years were attributed 37% of incident cancers and 30% of cancer-related mortality from 26% of CT scans. CONCLUSIONS: CT in Australia is increasing, including in groups at higher risk from ionising radiation. This presents a complex set of risk/benefit considerations for clinicians and policy makers.

Demonstration of the effect of generic anatomical divisions versus clinical protocols on computed tomography dose estimates and risk burden.

OBJECTIVE: Choosing to undertake a CT scan relies on balancing risk versus benefit, however risks associated with CT scanning have generally been limited to broad anatomical locations, which do not provided adequate information to evaluate risk against benefit. Our study aimed to determine differences in radiation dose and risk estimates associated with modern CT scanning examinations when computed for clinical protocols compared with those using anatomical area. METHODS: Technical data were extracted from a tertiary hospital Picture Archiving Communication System for random samples of 20-40 CT examinations per adult clinical CT protocol. Organ and whole body radiation dose were calculated using ImPACT Monte Carlo simulation software and cancer incidence and mortality estimated using BEIR VII age and gender specific lifetime attributable risk weights. RESULTS: Thirty four unique CT protocols were identified by our study. When grouped according to anatomic area the radiation dose varied substantially, particularly for abdominal protocols. The total estimated number of incident cancers and cancer related deaths using the mean dose of anatomical area were 86 and 69 respectively. Using more specific protocol doses the estimates rose to 214 and 138 incident cancers and cancer related deaths, at least doubling the burden estimated. CONCLUSIONS: Modern CT scanning produces a greater diversity of effective doses than much of the literature describes; where a lack of focus on actual scanning protocols has produced estimates that do not reflect the range and complexity of modern CT practice. To allow clinicians, patients and policy makers to make informed risk versus benefit decisions the individual and population level risks associated with modern CT practices are essential.

Evaluating data capture methods for the establishment of diagnostic reference levels in CT scanning.

OBJECTIVE: Concerns about the radiation dose associated with CT scanning have led to a call for establishment of diagnostic reference levels. Self-complete surveys have been used extensively to gather this information, however, departmental Radiological Information System's/Picture Archive Communication Systems (RIS/PACS) also hold this information. We compared dosimetry derived from survey with that using RIS/PACSs. METHODS: Technical data were collected from a large metropolitan tertiary hospital in WA using both data collection methods for a range of adult CT scanning examinations. Radiation dose was calculated from both datasets and the results evaluated for several indexes of inter-rater agreement. RESULTS: Radiation dose calculated using self-report survey data differed both systematically and proportionally from that calculated using RIS/PACS data. Differences were not consistent across CT examination type and thus not amenable to simple correction. The disparity was greater and more variable for organ dose than effective dose due to reliance of survey data on "generic" anatomical start and stop limits compared with actual data available on RIS/PACS. CONCLUSIONS: The bias observed in our study indicates that care should be taken when interpreting the results of studies measuring radiation dose using self-complete surveys. The availability of electronic databases that include information required for the evaluation and monitoring of CT radiation dose provides the opportunity to capture better quality data in a cost-effective manner. We recommend that national and local databases are established that routinely capture these data so as to facilitate the development and monitoring of radiation dose associated with CT scanning.

Enhanced primary care improves GP service regularity in older patients without impacting on service frequency.

The objective ofthis study was to assess the impact of Enhanced Primary Care service utilisation on subsequent GP service regularity and frequency. The study involved a retrospective population-based longitudinal cohort using linked administrative health records of hospital and primary care services for people over the age of 65 years. Multinomial logistic regression modelling was used to evaluate changes in the relative likelihood of increased primary care service regularity and frequency in exposed and unexposed individuals adjusting for age, sex and recent chronic disease hospitalisation history. Enhanced Primary Care services significantly and substantially increased the relative likelihood of increased regularity with no corresponding higher likelihood of increased frequency of GP contact. Increased regularity was more likely with increasing age except for the oldest age group (90+ years). Some chronic disease histories (e.g. diabetes) showed a higher likelihood of improved regularity while others were less likely to produce an increased regularity (e.g. hypertension). The study suggests a capacity for modification of physician and patient behaviour using incentivised services within the current fee-for-service system in Australia.

Effects of the Medicare enhanced primary care program on primary care physician contact in the population of older Western Australians with chronic diseases.

OBJECTIVE: Assess uptake of Medicare's enhanced primary care (EPC) services in Western Australia (WA) in 2001 to 2006, evaluating effect of EPC services on the regularity of contact with general practitioners (GPs) in patients aged 65+ years. METHOD: Whole-population cohort study using linked routinely collected health service data from State and Federal health databases. Analyses include age-standardised rate of EPC services, odds of EPC utilisation relative to other GP services using logistic regression, and total GP service regularity pre- and post-implementation of the EPC program. RESULTS: EPC services provided to WA seniors increased 345% 2001 to 2006, comprising an increasing proportion of the total GP services (1.1 to 3.6%). Uptake of EPC services accelerated abruptly after 2004 due to greater use of 'care plans'. EPC services were associated with a history of chronic disease, especially type 2 diabetes (OR=1.74, 95% CI 1.66-1.82). Regularity of total GP services was improved with any EPC service exposure, with greater improvement occurring in the presence of annual EPC service exposure. CONCLUSIONS: EPC item uptake responded favourably to item changes from Medicare Australia. Prior exposure to EPC items increased the regularity of GP services, an outcome inversely associated with chronic disease progression.