Quantifying risk using FMEA: An alternate approach to AAPM TG-100 for scoring failures and evaluating clinical workflow.

PURPOSE: Renovation of the brachytherapy program at a leading cancer center utilized methods of the AAPM TG-100 report to objectively evaluate current clinical brachytherapy workflows and develop techniques for minimizing the risk of failures, increasing efficiency, and consequently providing opportunities for improved treatment quality. The TG-100 report guides evaluation of clinical workflows with recommendations for identifying potential failure modes (FM) and scoring them from the perspective of their occurrence frequency O, failure severity S, and inability to detect them D. The current study assessed the impact of differing methods to determine the risk priority number (RPN) beyond simple multiplication. METHODS AND MATERIALS: The clinical workflow for a complex brachytherapy procedure was evaluated by a team of 15 staff members, who identified discrete FM using alternate scoring scales than those presented in the TG-100 report. These scales were expanded over all clinically relevant possibilities with care to emphasize mitigation of natural bias for scoring near the median range as well as to enhance the overall scoring-system sensitivity. Based on staff member perceptions, a more realistic measure of risk was determined using weighted functions of their scores. RESULTS: This new method expanded the range of RPN possibilities by a factor of 86, improving evaluation and recognition of safe and efficient clinical workflows. Mean RPN values for each FM decreased by 44% when changing from the old to the new clinical workflow, as evaluated using the TG-100 method. This decreased by 66% when evaluated with the new method. As a measure of the total risk associated with an entire clinical workflow, the integral of RPN values increased by 15% and decreased by 31% with the TG-100 and new methods, respectively. CONCLUSIONS: This appears to be the first application of an alternate approach to the TG-100 method for evaluating the risk of clinical workflows. It exemplifies the risk analysis techniques necessary to rapidly evaluate simple clinical workflows appropriately.

Novel and programmatic improvements to the workflow associated with the AccuBoost breast brachytherapy procedure.

PURPOSE: While the noninvasive breast brachytherapy (NIBB) treatment procedure, known as AccuBoost, for breast cancer patients is well established, the treatment quality can be improved by the efficiency of the workflow delivery. A formalized approach evaluated the current workflow through failure modes and effects analysis and generated insight for developing new procedural workflow techniques to improve the clinical treatment process. METHODS AND MATERIALS: AccuBoost treatments were observed for several months while gathering details on the multidisciplinary workflow. A list of possible failure modes for each procedure step was generated and organized by timing within the treatment process. A team of medical professionals highlighted procedural steps that unnecessarily increased treatment time, as well as introduced quality deficiencies involving applicator setup, treatment planning, and quality control checks preceding brachytherapy delivery. Procedural improvements and their impact on the clinical workflow are discussed. RESULTS: The revised clinical workflow included the following key procedural enhancements. Prepatient arrival: Improvement of prearrival preparation requires advance completion of dose calculation documentation with patient-specific setup data. Patient arrival pretreatment: Physicists carry out dwell time calculations and check the plan, while the therapist concurrently performs several checks of the ensuing hardware configuration. TREATMENT: An electronic method to export the associated HDR brachytherapy paperwork to the electronic medical record system with electronic signatures and captured approvals was generated. Posttreatment: The therapist confirms the applicators were appropriately positioned, and treatment was delivered as expected. CONCLUSIONS: The procedural improvements reduced the overall treatment time, improved consistency across users, and eased performance of this special procedure for all participants.

Stereotactic radiosurgery for gynecologic cancer.

Stereotactic body radiotherapy (SBRT) distinguishes itself by necessitating more rigid patient immobilization, accounting for respiratory motion, intricate treatment planning, on-board imaging, and reduced number of ablative radiation doses to cancer targets usually refractory to chemotherapy and conventional radiation. Steep SBRT radiation dose drop-off permits narrow 'pencil beam' treatment fields to be used for ablative radiation treatment condensed into 1 to 3 treatments. Treating physicians must appreciate that SBRT comes at a bigger danger of normal tissue injury and chance of geographic tumor miss. Both must be tackled by immobilization of cancer targets and by high-precision treatment delivery. Cancer target immobilization has been achieved through use of indexed customized Styrofoam casts, evacuated bean bags, or body-fix molds with patient-independent abdominal compression.(1-3) Intrafraction motion of cancer targets due to breathing now can be reduced by patient-responsive breath hold techniques,(4) patient mouthpiece active breathing coordination,(5) respiration-correlated computed tomography,(6) or image-guided tracking of fiducials implanted within and around a moving tumor.(7-9) The Cyberknife system (Accuray [Sunnyvale, CA]) utilizes a radiation linear accelerator mounted on a industrial robotic arm that accurately follows patient respiratory motion by a camera-tracked set of light-emitting diodes (LED) impregnated on a vest fitted to a patient.(10) Substantial reductions in radiation therapy margins can be achieved by motion tracking, ultimately rendering a smaller planning target volumes that are irradiated with submillimeter accuracy.(11-13) Cancer targets treated by SBRT are irradiated by converging, tightly collimated beams. Resultant radiation dose to cancer target volume histograms have a more pronounced radiation "shoulder" indicating high percentage target coverage and a small high-dose radiation "tail." Thus, increased target conformality comes at the expense of decreased dose uniformity in the SBRT cancer target. This may have implications for both subsequent tumor control in the SBRT target and normal tissue tolerance of organs at-risk. Due to the sharp dose falloff in SBRT, the possibility of occult disease escaping ablative radiation dose occurs when cancer targets are not fully recognized and inadequate SBRT dose margins are applied. Clinical target volume (CTV) expansion by 0.5 cm, resulting in a larger planning target volume (PTV), is associated with increased target control without undue normal tissue injury.(7,8) Further reduction in the probability of geographic miss may be achieved by incorporation of 2-[(18)F]fluoro-2-deoxy-D-glucose ((18)F-FDG) positron emission tomography (PET).(8) Use of (18)F-FDG PET/CT in SBRT treatment planning is only the beginning of attempts to discover new imaging target molecular signatures for gynecologic cancers.

Method for estimating skeletal spongiosa volume and active marrow mass in the adult male and adult female.

UNLABELLED: Active bone marrow is one of the more radiosensitive tissues in the human body and, hence, it is important to predict and possibly avoid myelotoxicity in radionuclide therapies. The MIRD schema currently used to calculate marrow dose generally requires knowledge of the patient's total skeletal active marrow mass -- a value that, at present, cannot be directly measured. Conceptually, the active marrow mass in a given skeletal region may be obtained given knowledge of the trabecular spongiosa volume (SV) of the bone site. A recent study has established a multiple regression model to easily calculate total skeletal SV (or TSSV) based on simple skeletal measurements obtained from a pelvic CT scan or radiograph. This model, based on data from only 20 cadavers, did not account for sex differences in TSSV. This study thus extends this work toward sex-specific models. METHODS: Twenty male and 20 female cadavers were subjected to whole-body CT. Bone sites containing active bone marrow were manually segmented to obtain SV at each site. In addition to age and height, 14 CT-based skeletal measurements were recorded for each cadaver. Multiple linear regression techniques were used to determine the best subset of measurements that allowed an accurate prediction of TSSV. RESULTS: A pooled model (R(2) = 0.76) and a sex-specific model (R(2) = 0.79) are provided. A leave-one-out analysis reveals that these models predict total SV with less than 10% error for 50%-70% of subjects, and with less than 20% error for 70%-90% of subjects. Tables were constructed that provide the percent distribution of SV in active-marrow containing bone sites for both males and females. CONCLUSION: This study provides models that can be used to simply, yet accurately, predict total SV in individuals within the clinical setting. The models require only 2 or 3 skeletal measurements that can be easily measured on a pelvic CT scan. Even though this study does not conclusively determine which model is best at predicting TSSV, the sex-specific model is most consistent at providing reasonable estimates of TSSV. This study also explains how the predictive TSSV model can be used to estimate patient-specific active bone marrow mass under the assumption of reference values of marrow volume fraction and bone marrow cellularity by skeletal site.

Linear regression model for predicting patient-specific total skeletal spongiosa volume for use in molecular radiotherapy dosimetry.

UNLABELLED: The toxicity of red bone marrow is widely considered to be a key factor in restricting the activity administered in molecular radiotherapy to suboptimal levels. The assessment of marrow toxicity requires an assessment of the dose absorbed by red bone marrow which, in many cases, requires knowledge of the total red bone marrow mass in a given patient. Previous studies demonstrated, however, that a close surrogate-spongiosa volume (combined tissues of trabecular bone and marrow)-can be used to accurately scale reference patient red marrow dose estimates and that these dose estimates are predictive of marrow toxicity. Consequently, a predictive model of the total skeletal spongiosa volume (TSSV) would be a clinically useful tool for improving patient specificity in skeletal dosimetry. METHODS: In this study, 10 male and 10 female cadavers were subjected to whole-body CT scans. Manual image segmentation was used to estimate the TSSV in all 13 active marrow-containing skeletal sites within the adult skeleton. The age, total body height, and 14 CT-based skeletal measurements were obtained for each cadaver. Multiple regression was used with the dependent variables to develop a model to predict the TSSV. RESULTS: Os coxae height and width were the 2 skeletal measurements that proved to be the most important parameters for prediction of the TSSV. The multiple R(2) value for the statistical model with these 2 parameters was 0.87. The analysis revealed that these 2 parameters predicted the estimated the TSSV to within approximately +/-10% for 15 of the 20 cadavers and to within approximately +/-20% for all 20 cadavers in this study. CONCLUSION: Although the utility of spongiosa volume in estimating patient-specific active marrow mass has been shown, estimation of the TSSV in active marrow-containing skeletal sites via patient-specific image segmentation is not a simple endeavor. However, the alternate approach demonstrated in this study is fairly simple to implement in a clinical setting, as the 2 input measurements (os coxae height and width) can be made with either pelvic CT scanning or skeletal radiography.

CT volumetry of the skeletal tissues.

Computed tomography (CT) is an important and widely used modality in the diagnosis and treatment of various cancers. In the field of molecular radiotherapy, the use of spongiosa volume (combined tissues of the bone marrow and bone trabeculae) has been suggested as a means to improve the patient-specificity of bone marrow dose estimates. The noninvasive estimation of an organ volume comes with some degree of error or variation from the true organ volume. The present study explores the ability to obtain estimates of spongiosa volume or its surrogate via manual image segmentation. The variation among different segmentation raters was explored and found not to be statistically significant (p value >0.05). Accuracy was assessed by having several raters manually segment a polyvinyl chloride (PVC) pipe with known volumes. Segmentation of the outer region of the PVC pipe resulted in mean percent errors as great as 15% while segmentation of the pipe's inner region resulted in mean percent errors within approximately 5%. Differences between volumes estimated with the high-resolution CT data set (typical of ex vivo skeletal scans) and the low-resolution CT data set (typical of in vivo skeletal scans) were also explored using both patient CT images and a PVC pipe phantom. While a statistically significant difference (p value <0.002) between the high-resolution and low-resolution data sets was observed with excised femoral heads obtained following total hip arthroplasty, the mean difference between high-resolution and low-resolution data sets was found to be only 1.24 and 2.18 cm3 for spongiosa and cortical bone, respectively. With respect to differences observed with the PVC pipe, the variation between the high-resolution and low-resolution mean percent errors was a high as approximately 20% for the outer region volume estimates and only as high as approximately 6% for the inner region volume estimates. The findings from this study suggest that manual segmentation is a reasonably accurate and reliable means for the in vivo estimation of spongiosa volume. This work also provides a foundation for future studies where spongiosa volumes are estimated by various raters in more comprehensive CT data

Correlations of total pelvic spongiosa volume with both anthropometric parameters and computed tomography-based skeletal size measurements.

Patient-specific dosimetry within the field of molecular radiotherapy continues to pose a challenge owing to the difficulty in predicting marrow toxicity. This study examined the correlation between total pelvic spongiosa volume (TPSV) and independent variables, which include both readily measured or calculated anthropometric parameters (AP), and image-based skeletal measurements requiring computed tomography (CT) images or skeletal radiographs. Fourteen (14) patients (5 male and 9 female) undergoing total hip arthroplasty (THA) were subjected to modified pelvic CT scans. These scans were utilized to estimate TPSV, which was comprised of the volumes of spongiosa within the L5 vertebra, os coxae, sacrum, and both proximal femurs. The APs investigated included total body height (TBH), total body mass (TBM), body mass index (BMI), body surface area (BSA), maximum effective mass (MEM), lean body mass (LBM), and fat-free mass (FFM). Skeletal measurements were also obtained from the CT images of the pelvic region. Correlation coefficients (r) were obtained for TPSV and each set of APs as well as each set of skeletal measurements. Total body height (r = 0. 80) and os coxae height (r = 0.83) had the highest correlation coefficients of all the APS and skeletal measurements, respectively. FFM (r = 0.50), LBM (r = 0.42), TBM (r = 0.11), and BSA (r = 0.11) did not correlate well with TPSV, which accounts for approximately 45% of total spongiosa seen throughout the skeleton at sites associated with active bone marrow. Skeletal height measurements appear to have a much higher correlation with TPSV than either their corresponding skeletal width measurements or parameters that are a function of an individual's TBM.