Rasika Rajapakshe

Defining a magnetic resonance scan sequence for permanent seed prostate brachytherapy postimplant assessment

PURPOSE We describe a magnetic resonance (MR) scan sequence for prostate brachytherapy postimplant assessment. METHODS AND MATERIALS One brachytherapy team at the British Columbia Cancer Agency has incorporated MR-CT fusion into their permanent seed prostate brachytherapy quality assurance procedure. Several attempts were required to ensure that the diagnostic MR scanner at the adjoining general hospital performed the desired sequence, providing many examples of suboptimal scans and underlining the pitfalls for a center trying to incorporate the use of MR scanning into their brachytherapy program. RESULTS The recommended sequence (Fast Spin Echo T2-weighted, repetition time [TR]/echo time [TE] 4500/90, echo train length [ETL] 10, 20×20 field of view [FOV], 80 bandwidth [BW]) is associated with superior edge detection when compared with those images in which a typical diagnostic sequence was used. The use of a low bandwidth sequence does not compromise edge detection or seed identification when compared with a higher bandwidth. CONCLUSIONS We have defined a magnetic resonance imaging sequence, which appears to optimize both prostate delineation and identification of seeds, lending itself to straightforward fusion with CT images and allowing for less uncertainty in permanent seed prostate brachytherapy quality assurance.

Assessing the Breast Cancer Risk Distribution for Women Undergoing Screening in British Columbia

Breast cancer risk estimations are both informative and useful at the population level, with many screening programs relying on these assessments to allocate resources such as breast MRI. This cross-sectional multicenter study attempts to quantify the breast cancer risk distribution for women between the ages of 40 to 79 years undergoing screening mammography in British Columbia (BC), Canada. The proportion of women at high breast cancer risk was estimated by surveying women enrolled in the Screening Mammography Program of British Columbia (SMPBC) for known breast cancer risk factors. Each respondents 10-year risk was computed with both the Tyrer–Cuzick and Gail risk assessment models. The resulting risk distributions were evaluated using the guidelines from the National Institute for Health and Care Excellence (United Kingdom). Of the 4,266 women surveyed, 3.5% of women between the ages of 40 to 79 years were found to have a high 10-year risk of developing breast cancer using the Tyrer–Cuzick model (1.1% using the Gail model). When extrapolated to the screening population, it was estimated that 19,414 women in the SMPBC are considered to be at high breast cancer risk. These women may benefit from additional MRI screening; preliminary analysis suggests that 4 to 5 additional MRI machines would be required to screen these high-risk women. However, the use of different models and guidelines will modify the number of women qualifying for additional screening interventions, thus impacting the MRI resources required. The results of this project can now be used to inform decision-making groups about resource allocation for breast cancer screening in BC. Cancer Prev Res; 6(10); 1084–92. ©2013 AACR.

Assessing the Effects of Participant Preference and Demographics in the Usage of Web-based Survey Questionnaires by Women Attending Screening Mammography in British Columbia

Background Increased usage of Internet applications has allowed for the collection of patient reported outcomes (PROs) and other health data through Web-based communication and questionnaires. While these Web platforms allow for increased speed and scope of communication delivery, there are certain limitations associated with this technology, as survey mode preferences vary across demographic groups. Objective To investigate the impact of demographic factors and participant preferences on the use of a Web-based questionnaire in comparison with more traditional methods (mail and phone) for women participating in screening mammography in British Columbia, Canada. Methods A sample of women attending the Screening Mammography Program of British Columbia (SMPBC) participated in a breast cancer risk assessment project. The study questionnaire was administered through one of three modes (ie, telephone, mail, or website platform). Survey mode preferences and actual methods of response were analyzed for participants recruited from Victoria General Hospital. Both univariate and multivariate analyses were used to investigate the association of demographic factors (ie, age, education level, and ethnicity) with certain survey response types. Results A total of 1192 women successfully completed the study questionnaire at Victoria General Hospital. Mail was stated as the most preferred survey mode (509/1192, 42.70%), followed by website platform (422/1192, 35.40%), and telephone (147/1192, 12.33%). Over 80% (955/1192) of participants completed the questionnaire in the mode previously specified as their most preferred; mail was the most common method of response (688/1192, 57.72%). Mail was also the most preferred type of questionnaire response method when participants responded in a mode other than their original preference. The average age of participants who responded via the Web-based platform (age 52.9, 95% confidence interval [CI] 52.1-53.7) was significantly lower than those who used mail and telephone methods (age 55.9, 95% CI 55.2-56.5; P<.001); each decade of increased age was associated with a 0.97-fold decrease in the odds of using the website platform (P<.001). Web-based participation was more likely for those who completed higher levels of education; each interval increase leading to a 1.83 increase in the odds of website platform usage (P<.001). Ethnicity was not shown to play a role in participant preference for the website platform (P=.96). Conclusions It is beneficial to consider participant survey mode preference when planning to collect PROs and other patient health data. Younger participants and those of higher education level were more likely to use the website platform questionnaire; Web-based participation failed to vary across ethnic group. Because mail questionnaires were still the most preferred survey mode, it will be important to employ strategies, such as user-friendly design and Web-based support, to ensure that the patient feedback being collected is representative of the population being served.

An Internet-Based Means of Monitoring Quality of Life in Post-Prostate Radiation Treatment: A Prospective Cohort Study

Background Widespread integration of the Internet has resulted in an increase in the feasibility of using Web-based technologies as a means of communicating with patients. It may be possible to develop secure and standardized systems that facilitate Internet-based patient-reported outcomes which could be used to improve patient care. Objective This study investigates patient interest in participating in an online post-treatment disease outcomes and quality of life monitoring program developed specifically for patients who have received radiation treatment for prostate cancer at a regional oncology center. Methods Patients treated for prostate cancer between 2007 and 2011 (N=1113) at the British Columbia Cancer Agency, Centre for the Southern Interior were invited by mail to participate in a standardized questionnaire related to their post-treatment health. Overall participation rates were calculated. In addition, demographics, access to broadband Internet services, and treatment modalities were compared between participants and nonparticipants. Results Of the 1030 eligible invitees, 358 (358/1030, 34.7%) completed the online questionnaire. Participation rates were higher in individuals younger than age 60 when compared to those age 60 or older (42% vs 31%) and also for those living in urban areas compared with rural (37% vs 29%) and in those who received brachytherapy versus external beam radiotherapy (EBRT) (41% vs 31%). Better participation rates were seen in individuals who had access to Internet connectivity based on the different types of broadband services (DSL 35% for those with DSL connectivity vs 29% for those without DSL connectivity; cable 35% vs 32%; wireless 38% vs 26%). After adjusting for age, the model indicates that lack of access to wireless broadband connectivity, living in a rural area, and receiving EBRT were significant predictors of lower participation. Conclusions This study demonstrates that participation rates vary in patient populations within the interior region of British Columbia, especially with older patients, those in rural areas, and those with limited access to quality Internet services.

A Regional Web-Based Automated Quality Control Platform

Quality control is a key factor in ensuring a high standard of care in the field of mammography. We have found that abrupt irregularities in image quality from mammography units can arise as the result of factors ranging from vendor software upgrades, having software parameters modified during unit maintenance, or even having detectors replaced. We have developed both a simple weekly quality control test performed on processed images that can quickly capture these changes in image quality, as well as a centralized software platform that automates our test across several mammography centers. Technologists acquire a phantom exposure and upload it to our regional PACS network. The images are then automatically downloaded, analysed, and the results stored by the mammoQC software. These results are instantly available to technologists via a web dashboard, where reports can be generated automatically. Our platform currently services over 25 locations in British Columbia.

Extension of CadPlan algorithm to model the dose distribution under a motorized wedge

The CadPlan treatment planning system models the dose distribution in the non-wedge direction under a wedged field by converting the wedge thickness to an equivalent water thickness. The algorithm estimates the off-axis ratio (OAR) in the non-wedged direction using the open field OAR at a depth deeper by this equivalent water thickness. This model has been shown to work well for a Siemens Mevatron KD-2 Linac. However, the motorized wedge of the Elekta (formerly Philips) accelerators is tapered off-axis to give a flat dose profile in the non-wedged direction. The CadPlan model assumes that the wedge has a uniform thickness in the non-wedged direction and so cannot model the off-axis dose for the motorized wedge. For a 4 MV beam of a SL75/5 accelerator this leads to a 7% overestimate and a 9% underestimate of the OAR under the thin and thick edge of the wedge respectively. For 6 and 18 MV beams of a SL20 accelerator and a 6 MV beam of a SL75/5 accelerator, the model underestimates the OAR in the order of 10% under the thick end of the wedge. We have shown that by appropriate modification of the effective water thickness values at off-axis distances, the algorithm models the OAR in the non-wedged direction to within 2.5% of the measured values for the 4, 6 and 18 MV beams, for the Elekta motorized wedge.

Development of a Micro-Simulation Model for Breast Cancer to Evaluate the Impacts of Personalized Early Detection Strategies

Breast cancer screening with mammography has been shown to reduce breast cancer mortality. However the frequency and the age range for screening eligibility has been controversial. Individual risk based screening regimens have recently been proposed to overcome some of the weaknesses of screening mammography. However, it is not possible to evaluate the full impact of such risk based individualized screening strategies in Canadian context. Therefore a mathematical cancer control model for breast cancer using care paths and cancer control data from the province of BC is being developed to model different early detection strategies. The model will incorporate the incidence, detection, diagnosis, progression, and case fatality of breast cancer in BC as baseline to make projections of the population health and economic impacts of different early detection methods for breast cancer. Once the model is validated, it will be possible to test early detection pathways and strategies, frequencies and durations, as well as any health care costs associated with detection, diagnosis, treatment and on-going care of breast cancer patients.

Trends in Mammogram Image Quality, Dose and Screen-Detected Cancer Rates in an Organized Screening Mammography Program

BACKGROUND: The Screening Mammography Program of British Columbia (SMPBC), Canada is a population based program that regularly performs quality assurance testing and outcomes analysis.

Characterization of Varian on-board imaging systems for use in automatic exposure control software

Modern image guided radiation therapy involves the use of an isocentrically mounted on-board imager (OBI) to take kV images of a patient’s position. Orthogonal OBI images are used with 2D-2D match software to determine the treatment couch shifts required for ideal alignment based on digitally reconstructed radiographs created in treatment planning. The lack of an automatic exposure control (AEC) on Varian OBI systems requires x-ray techniques to be selected manually which may result in over or under exposed images and compromise the accuracy of the image matching. A software based AEC system is being developed in order to predict the optimal, patient specific exposure factors. This software requires that each OBI system be uniquely characterized in terms of both the x-ray tube output and the detector response for a clinical range of energies (kVp). Characteristic curves show that the detector is highly energy dependent at low energies and increasingly energy independent with increasing energy. The detector response (per unit exposure) was determined as a function of the beam quality and the level of detector saturation due to scattered radiation was modeled based on patient thickness, kVp, and field size. Using this model, the optimal exposure can be determined to produce the highest quality image.

Stratification of 5-year cancer detection rate in an organized breast screening program based on Gail model risk factors.

7 Background: The Gail model has been validated in the United States and several European countries, but to our knowledge, it has not been validated in organized breast screening programs in Canada. The Screening Mammography Program of British Columbia (SMPBC) records participant data from a questionnaire based on Gail model parameters (which include family and personal medical history). This study investigates whether the Gail model is a valid tool to predict the breast cancer risk for the population undergoing screening mammography in the province of BC. METHODS Client information of the 223,349 British Columbian women who participated in the year 2000, along with their tumor status from 2000-2004, was extracted from the provincial database. A software program was developed to rapidly calculate the absolute 5-year Gail score from questionnaire data. Participant data was separated into .5% risk intervals and also into quintiles based on increasing Gail scores, and the mean absolute risks were compared to the actual five year rate of cancer as detected by the SMPBC. RESULTS Overall, goodness of fit between Gail score and SMPBC detection (E/O) across the categories can be rejected (χ2=247.9, df=9, p value < .001). The Gail model significantly underpredicts the cancer detection for risk categories up to 2%, however it provides a sufficient fit for categories 2%-4% as the E/O ratio is not significantly different from 1.0 in these intervals. For the highest risk interval, categorized as greater than 4% risk, the model significantly overpredicts cancer detection. Additionally, when presented in quintiles, the Gail model under-predicts risk in all but the highest quintile (1.77-11.43% risk range). CONCLUSIONS Our results, based on participants of SMPBC, suggest that the Gail model significantly under-predicts cancer detection. Although this model provides a sufficient fit for women with a Gail score between 1.51-4%, it does not predict breast cancer risk accurately for low and high risk women in the Screening Mammography Program of BC.