An Analysis of Trainee Status of the Primary Care Physician and Ambulatory Care Outcomes.

PURPOSE: Prior studies report disparities in outcomes for patients cared for by trainees versus faculty physicians at academic medical centers. This study examined the effect of having a trainee as the primary care physician versus a faculty member on routine population health outcomes after adjusting for differences in social determinants of health and primary care retention. METHOD: This cohort study assessed 38,404 patients receiving primary care at an academic hospital-affiliated practice by 60 faculty and 110 internal medicine trainees during academic year 2019. The effect of primary care practitioner trainee status on routine ambulatory care metrics was modeled using log-binomial regression with generalized estimating equation methods to account for physician-level clustering. Risk estimates before and after adjusting for social determinants of health and loss to follow-up are presented. RESULTS: Trainee and faculty cohorts had similar distributions of acute illness burden; however, patients in the trainee cohort were significantly more likely to identify as a race other than White (2,476 [52.6%] vs 14,785 [38.5%], P < .001), live in a zip code associated with poverty (1,688 [35.9%] vs 9,122 [23.8%], P < .001), use public health insurance (1,021 [21.7%] vs 6,108 [15.9%], P < .001), and have limited English proficiency (1,415 [30.1%] vs 5,203 [13.6%], P < .001). In adjusted analyses, trainee status of primary care physician was not associated with lack of breast cancer screening but was associated with missed opportunities to screen for colorectal cancer (relative risk [RR], 0.77; 95% confidence interval [CI], 0.68-0.88), control type 2 diabetes mellitus (RR, 0.78; 95% CI, 0.64-0.94), and control hypertension (RR, 0.80; 95% CI, 0.69-0.94). CONCLUSIONS: Primary care physician trainee status was associated with poorer quality of care in the ambulatory setting after adjusting for differences in socioeconomic factors and loss to follow-up, highlighting a potential ambulatory training gap.

A multi-omic analysis of MCF10A cells provides a resource for integrative assessment of ligand-mediated molecular and phenotypic responses.

The phenotype of a cell and its underlying molecular state is strongly influenced by extracellular signals, including growth factors, hormones, and extracellular matrix proteins. While these signals are normally tightly controlled, their dysregulation leads to phenotypic and molecular states associated with diverse diseases. To develop a detailed understanding of the linkage between molecular and phenotypic changes, we generated a comprehensive dataset that catalogs the transcriptional, proteomic, epigenomic and phenotypic responses of MCF10A mammary epithelial cells after exposure to the ligands EGF, HGF, OSM, IFNG, TGFB and BMP2. Systematic assessment of the molecular and cellular phenotypes induced by these ligands comprise the LINCS Microenvironment (ME) perturbation dataset, which has been curated and made publicly available for community-wide analysis and development of novel computational methods ( synapse.org/LINCS_MCF10A ). In illustrative analyses, we demonstrate how this dataset can be used to discover functionally related molecular features linked to specific cellular phenotypes. Beyond these analyses, this dataset will serve as a resource for the broader scientific community to mine for biological insights, to compare signals carried across distinct molecular modalities, and to develop new computational methods for integrative data analysis.

Trends in Urethral Suspension With Robotic Prostatectomy Procedures Following Medicare Payment Policy Changes.

Importance: In 2016, the Centers for Medicare and Medicaid Services cut payments for robotic prostatectomy performed for Medicare beneficiaries. Although regulations mandate that billing for urethral suspension is only acceptable for preexisting urinary incontinence, reductions in reimbursement may incentivize billing for the use of this procedure in other scenarios. Objective: To assess trends and geographic variations in payments for urethral suspension with robotic prostatectomy in the context of Medicare payment policy. Design, Setting, and Participants: This US population-based retrospective cohort study analyzed data from the IBM MarketScan Commercial Claims and Encounters and Medicare Supplemental Database for men with employer-based insurance (primary commercial or Medicare supplemental coverage) who underwent robotic prostatectomy (Current Procedural Terminology [CPT] code 55866) between 2009 and 2019. Exposures: Time period and metropolitan statistical area of patient residence. Main Outcomes and Measures: Payment for urethral suspension (CPT code 51990) with robotic prostatectomy. Results: We identified 87 774 men with prostate cancer treated with robotic prostatectomy; 3352 (3.8%) had undergone urethral suspension. The mean (SD) patient age was 59.7 (6.5) years; 16 870 patients (19.2%) had Medicare supplemental coverage. From 2015 to 2016, median payments for robotic prostatectomy changed by -$358 (-17.0%) for Medicare beneficiaries vs -$9 (0%) for commercially insured patients. With urethral suspension vs without, median (IQR) episode payments for robotic prostatectomy were higher for commercially insured men ($3678 [$3090-$4503] vs $3322 [$2601-$4306]) and Medicare beneficiaries ($2927 [$2450-$3909] vs $2379 [$2014-$3512]). Compared with men treated between 2013 and 2015, those treated between 2016 and 2017 were twice as likely to undergo urethral suspension (8.5% vs 4.1%; odds ratio, 2.17 [95% CI, 1.96-2.38]). The proportion of patients who underwent urethral suspension was stable for 2018 to 2019 and 2016 to 2017 (8.5% vs 9.0%; odds ratio, 1.06 [95% CI, 0.96-1.18]). From 2015 to 2019, the proportion of patients who underwent urethral suspension was highest in Charleston, South Carolina (92.0%), Knoxville, Tennessee (66.0%), and Columbia, South Carolina (58.0%). These regions neighbored high-volume areas without patients who underwent prostatectomy with urethral suspension (eg, 146 patients in Greenville, South Carolina, and 173 in Nashville, Tennessee). Conclusions and Relevance: In this study, urethral suspension was associated with increased costs for patients with both commercial insurance and Medicare. Patients treated between 2016 and 2017 were more likely than those treated between 2013 and 2015 to undergo this procedure. Geographic variation in use exceeded what was expected for the preexisting condition for which billing is permitted for Medicare beneficiaries. Policy statements from professional societies highlighting appropriate billing for urethral suspension may have tempered, but not reversed, the broad adoption of this procedure.

Comparing a Home Vision Self-Assessment Test to Office-Based Snellen Visual Acuity.

PURPOSE: To evaluate the agreement of a home vision screening test compared to standard in-office technician-measured Snellen visual acuity to allow for remote screening and triaging of patients. PATIENTS AND METHODS: In this prospective study, English-speaking patients with in-office ophthalmology appointments from May to August 2020 and visual acuity better than 20/125 were asked to complete a home vision test one week before their scheduled in-office appointment. The home vision test was a modified ETDRS chart displayed in a PDF document that could be printed or viewed on a monitor. The primary outcome was the mean difference between office-based and home visual acuity. RESULTS: Eighty-two eyes of 45 patients were included in the study with 45 study eyes analyzed. The mean difference between office-based and home visual acuity was -0.02 logMAR (SD 0.15, P=0.28) among study eyes. Of these eyes, 91% demonstrated agreement between the two methods within 0.2 logMAR of the mean difference, and 60% had agreement within 0.1 logMAR of the mean difference. There were no significant demographic or ocular risk factors leading to a greater difference between the tests. CONCLUSION: There was good agreement between the home and in-office Snellen tests for patients with vision better than 20/125. The home vision test can be used to remotely determine if there is a significant vision change of >0.2 logMAR or approximately 2 lines of visual acuity.

Recent trends in premature mortality and health disparities attributable to ambient PM2.5 exposure in China: 2005-2017.

In the past decade, particulate matter with aerodynamic diameter less than 2.5 µm (PM2.5) has reached unprecedented levels in China and posed a significant threat to public health. Exploring the long-term trajectory of the PM2.5 attributable health burden and corresponding disparities across populations in China yields insights for policymakers regarding the effectiveness of efforts to reduce air pollution exposure. Therefore, we examine how the magnitude and equity of the PM2.5-related public health burden has changed nationally, and between provinces, as economic growth and pollution levels varied during 2005-2017. We derive long-term PM2.5 exposures in China from satellite-based observations and chemical transport models, and estimate attributable premature mortality using the Global Exposure Mortality Model (GEMM). We characterize national and interprovincial inequality in health outcomes using environmental Lorenz curves and Gini coefficients over the study period. PM2.5 exposure is linked to 1.8 (95% CI: 1.6, 2.0) million premature deaths over China in 2017, increasing by 31% from 2005. Approximately 70% of PM2.5 attributable deaths were caused by stroke and IHD (ischemic heart disease), though COPD (chronic obstructive pulmonary disease) and LRI (lower respiratory infection) disproportionately affected poorer provinces. While most economic gains and PM2.5-related deaths were concentrated in a few provinces, both gains and deaths became more equitably distributed across provinces over time. As a nation, however, trends toward equality were more recent and less clear cut across causes of death. The rise in premature mortality is due primarily to population growth and baseline risks of stroke and IHD. This rising health burden could be alleviated through policies to prevent pollution, exposure, and disease. More targeted programs may be warranted for poorer provinces with a disproportionate share of PM2.5-related premature deaths due to COPD and LRI.

Pilot randomised clinical trial of an eHealth, self-management support intervention (iVERVE) for stroke: feasibility assessment in survivors 12-24 months post-event.

BACKGROUND: Electronic communication is used in various populations to achieve health goals, but evidence in stroke is lacking. We pilot tested the feasibility and potential effectiveness of a novel personalised electronic self-management intervention to support person-centred goal attainment and secondary prevention after stroke. METHODS: A phase I, prospective, randomised controlled pilot trial (1:1 allocation) with assessor blinding, intention-to-treat analysis, and a process evaluation. Community-based survivors of stroke were recruited from participants in the Australian Stroke Clinical Registry (AuSCR) who had indicated their willingness to be contacted for research studies. Inclusion criteria include 1-2 years following hospital admission for stroke and living within 50 km of Monash University (Melbourne). Person-centred goals were set with facilitation by a clinician using a standardised template. The intervention group received electronic support messages aligned to their goals over 4 weeks. The control group received only 2-3 electronic administrative messages. Primary outcomes were study retention, goal attainment (assessed using Goal Attainment Scaling method) and satisfaction. Secondary outcomes were self-management (Health Education Impact Questionnaire: 8 domains), quality of life, mood and acceptability. RESULTS: Of 340 invitations sent from AuSCR, 73 responded, 68 were eligible and 57 (84%) completed the baseline assessment. At the goal-setting stage, 54/68 (79%) were randomised (median 16 months after stroke): 25 to intervention (median age 69 years; 40% female) and 29 to control (median age 68 years; 38% female). Forty-five (83%) participants completed the outcome follow-up assessment. At follow-up, goal attainment (mean GAS-T score ≥ 50) in the intervention group was achieved for goals related to function, participation and environment (control: environment only). Most intervention participants provided positive feedback and reported that the iVERVE messages were easy to understand (92%) and assisted them in achieving their goals (77%). We found preliminary evidence of non-significant improvements between the groups for most self-management domains (e.g. social integration and support: ß coefficient 0.34; 95% CI - 0.14 to 0.83) and several quality-of-life domains in favour of the intervention group. CONCLUSION: These findings support the need for further randomised effectiveness trials of the iVERVE program to be tested in people with new stroke. TRIAL REGISTRATION: ANZCTR, ACTRN12618001519246 . Registered on 11 September 2018-retrospectively registered.

Assessment of Maternal and Neonatal SARS-CoV-2 Viral Load, Transplacental Antibody Transfer, and Placental Pathology in Pregnancies During the COVID-19 Pandemic.

Importance: Biological data are lacking with respect to risk of vertical transmission and mechanisms of fetoplacental protection in maternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Objective: To quantify SARS-CoV-2 viral load in maternal and neonatal biofluids, transplacental passage of anti-SARS-CoV-2 antibody, and incidence of fetoplacental infection. Design, Setting, and Participants: This cohort study was conducted among pregnant women presenting for care at 3 tertiary care centers in Boston, Massachusetts. Women with reverse transcription-polymerase chain reaction (RT-PCR) results positive for SARS-CoV-2 were recruited from April 2 to June 13, 2020, and follow-up occurred through July 10, 2020. Contemporaneous participants without SARS-CoV-2 infection were enrolled as a convenience sample from pregnant women with RT-PCR results negative for SARS-CoV-2. Exposures: SARS-CoV-2 infection in pregnancy, defined by nasopharyngeal swab RT-PCR. Main Outcomes and Measures: The main outcomes were SARS-CoV-2 viral load in maternal plasma or respiratory fluids and umbilical cord plasma, quantification of anti-SARS-CoV-2 antibodies in maternal and cord plasma, and presence of SARS-CoV-2 RNA in the placenta. Results: Among 127 pregnant women enrolled, 64 with RT-PCR results positive for SARS-CoV-2 (mean [SD] age, 31.6 [5.6] years) and 63 with RT-PCR results negative for SARS-CoV-2 (mean [SD] age, 33.9 [5.4] years) provided samples for analysis. Of women with SARS-CoV-2 infection, 23 (36%) were asymptomatic, 22 (34%) had mild disease, 7 (11%) had moderate disease, 10 (16%) had severe disease, and 2 (3%) had critical disease. In viral load analyses among 107 women, there was no detectable viremia in maternal or cord blood and no evidence of vertical transmission. Among 77 neonates tested in whom SARS-CoV-2 antibodies were quantified in cord blood, 1 had detectable immunoglobuilin M to nucleocapsid. Among 88 placentas tested, SARS-CoV-2 RNA was not detected in any. In antibody analyses among 37 women with SARS-CoV-2 infection, anti-receptor binding domain immunoglobin G was detected in 24 women (65%) and anti-nucleocapsid was detected in 26 women (70%). Mother-to-neonate transfer of anti-SARS-CoV-2 antibodies was significantly lower than transfer of anti-influenza hemagglutinin A antibodies (mean [SD] cord-to-maternal ratio: anti-receptor binding domain immunoglobin G, 0.72 [0.57]; anti-nucleocapsid, 0.74 [0.44]; anti-influenza, 1.44 [0.80]; P < .001). Nonoverlapping placental expression of SARS-CoV-2 receptors angiotensin-converting enzyme 2 and transmembrane serine protease 2 was noted. Conclusions and Relevance: In this cohort study, there was no evidence of placental infection or definitive vertical transmission of SARS-CoV-2. Transplacental transfer of anti-SARS-CoV-2 antibodies was inefficient. Lack of viremia and reduced coexpression and colocalization of placental angiotensin-converting enzyme 2 and transmembrane serine protease 2 may serve as protective mechanisms against vertical transmission.

Variation in Physician-Specific Episode Payments for Major Cancer Surgery and Implications for the Merit-Based Incentive Program.

BACKGROUND: Nearly 1.5 million clinicians in the United States will be affected by Centers for Medicare and Medicaid Services' (CMS) new payment program, the Merit-based Incentive Program (MIPS), where clinicians will be penalized or rewarded based on the health care expenditures of their patients. We therefore examined expenditures for major cancer surgery to understand physician-specific variation in episode payments. METHODS: We used Surveillance, Epidemiology and End Results-Medicare data to identify patients aged 66-99 y who underwent a prostatectomy, nephrectomy, lung, or colorectal resection for cancer from 2008 to 2012. We calculated 90-d episode payments, attributed each episode to a physician, and evaluated physician-level payment variation. Next, we determined which component (index admission, readmission, physician services, postacute care, hospice) drove differences in payments. Finally, we evaluated payments by geographic region, number of comorbidities, and cancer stage. RESULTS: We identified 39,109 patients who underwent surgery by 1 of 7182 providers. There was wide variation in payments for each procedure (prostatectomy: $7046-$40,687; nephrectomy: $8855-$82,489; lung resection: $11,167-$223,467; colorectal resection: $9711-$199,480). The largest component difference in episode payments varied by condition: physician payments for prostatectomy (29%), postacute care for nephrectomy (38%) and colorectal resections (38%), and index hospital admission for lung resections (43%) but were fairly stable across region, comorbidity number, and cancer stage. CONCLUSIONS: For patients undergoing major cancer surgery, 90-d episode payments vary widely across surgeons. The components driving such variation differ by condition but remain stable across region, number of comorbidities, and cancer stage. These data suggest that programs to reduce specific component payments may have advantages over those targeting individual physicians for decreasing health care expenditures.

The Stability of Physician-Specific Episode Costs for Urologic Cancer Surgery: Implications for Urologists Under the Merit-Based Incentive Program.

OBJECTIVE: To evaluate the stability of physician-specific episode payments for prostatectomy, nephrectomy, and cystectomy in the context of value-based purchasing programs, such as the merit-based incentive payment system. METHODS: We utilized Surveillance, Epidemiology and End Results-Medicare data to identify patients aged 66-99 who underwent a prostatectomy, nephrectomy, or cystectomy from 2008 to 2012. We calculated each surgeon's average 90-day episode payment by procedure. Next, we examined payment differences between the most and least expensive quartile providers. For the most expensive quartile of physicians in 2010, we examined their spending quartile in 2011. Finally, we evaluated the correlation in spending over time and across procedures. RESULTS: We identified 14,585 patients who underwent surgery by one of 1895 unique clinicians. Differences in payments between the highest and lowest quartiles were $5881, $17,714, and $40,288 for prostatectomy, nephrectomy, and cystectomy, respectively. Only 39%, 16%, and 13% of physicians that were in the highest spending quartile for prostatectomy, nephrectomy, and cystectomy in 2010 were also in the most expensive quartile in 2011. Although we observed weak correlation in year-to-year spending for prostatectomy (0.108, P = .033 to .270, P < .001), annual payments for nephrectomy and cystectomy were not significantly correlated. Finally, there was minimal correlation in surgeon spending across procedures. CONCLUSION: There is wide variation in physician-specific episode payments for prostatectomy, nephrectomy, and cystectomy. However, physician spending patterns are not stable over time or across procedures, raising concerns about the ability of the cost-based measures in merit-based incentive payment system to change physician behavior and reliably distinguish those providing less efficient or lower quality care.

System-Level Health-Care Integration and the Costs of Cancer Care Across the Disease Continuum.

PURPOSE: Policy reforms in the Affordable Care Act encourage health care integration to improve quality and lower costs. We examined the association between system-level integration and longitudinal costs of cancer care. METHODS: We used linked SEER-Medicare data to identify patients age 66 to 99 years diagnosed with prostate, bladder, esophageal, pancreatic, lung, liver, kidney, colorectal, breast, or ovarian cancer from 2007 to 2012. We attributed each patient to one or more phases of care (ie, initial, continuing, and end of life) according to time from diagnosis until death or end of study interval. For each phase, we aggregated all claims with the primary cancer diagnosis and identified patients treated in an integrated delivery network (IDN), as defined by the Becker Hospital Review list of the top 100 most integrated health delivery systems. We then determined if care provided in an IDN was associated with decreased payments across cancers and for each individual cancer by phase and across phases. RESULTS: We identified 428,300 patients diagnosed with one of 10 common cancers. Overall, there were no differences in phase-based payments between IDNs and non-IDNs. Average adjusted annual payments by phase for IDN versus non-IDNs were as follows: initial, $14,194 versus $14,421, respectively ( P = .672); continuing, $2,051 versus $2,099 ( P = .566); and end of life, $16,257 versus $16,232 ( P = .948). However, in select cancers, we observed lower payments in IDNs. For bladder cancer, payments at the end of life were lower for IDNs ($11,041 v $12,331; P = .008). Of the four cancers with the lowest 5-year survival rates (ie, pancreatic, lung, esophageal, and liver), average expenditures during the initial and continuing-care phases were lower for patients with liver cancer treated in IDNs. CONCLUSION: For patients with one of 10 common malignancies, treatment in an IDN generally is not associated with lower costs during any phase of cancer care.

Episode-based Payment Variation for Urologic Cancer Surgery.

OBJECTIVE: To investigate payment variation for 3 common urologic cancer surgeries and evaluate the potential for applying bundled payment programs to these procedures. METHODS: Using 2008-2011 Surveillance, Epidemiology, and End Results-Medicare linked data, we identified all beneficiaries aged greater than 65 years who underwent cystectomy, prostatectomy, or nephrectomy for cancer. Total episode payments were determined by aggregating hospital, professional, and post-acute care claims from the index surgical hospitalization through 90 days post discharge. Total episode payments were then compared to examine hospital level-variation within each procedure type and the specific payment components (ie, index hospitalization, professional, readmission, and post-acute care) driving spending variation. RESULTS: Ninety-day episodes of care were identified for 1849 cystectomies, 8770 prostatectomies, and 4304 nephrectomies. We observed wide variation in mean episode payments for all 3 conditions (cystectomy mean $35,102: range $24,112-$57,238, prostatectomy mean $10,803: range $8,816-$17,877, nephrectomy mean $17,475: range $11,681-$26,711). Majority of payment variation was attributable to index hospitalization and post-acute care for cystectomy and nephrectomy and professional payments for prostatectomy. The most expensive hospitals by procedure each demonstrated a unique opportunity for spending reduction due to individual differences in component payment patterns between hospitals. CONCLUSION: Ninety-day episode payments for urologic cancer surgery vary widely across hospitals in the United States. The key drivers of this payment variation differ for individual procedures and hospitals. Accordingly, hospitals will need individualized data and clinical re-design strategies to succeed with implementation of episode-based payment models for urologic cancer care.

Diffusion tensor imaging tensor shape analysis for assessment of regional white matter differences.

Purpose The purpose of this study was to investigate a novel tensor shape plot analysis technique of diffusion tensor imaging data as a means to assess microstructural differences in brain tissue. We hypothesized that this technique could distinguish white matter regions with different microstructural compositions. Methods Three normal canines were euthanized at seven weeks old. Their brains were imaged using identical diffusion tensor imaging protocols on a 7T small-animal magnetic resonance imaging system. We examined two white matter regions, the internal capsule and the centrum semiovale, each subdivided into an anterior and posterior region. We placed 100 regions of interest in each of the four brain regions. Eigenvalues for each region of interest triangulated onto tensor shape plots as the weighted average of three shape metrics at the plot's vertices: CS, CL, and CP. Results The distribution of data on the plots for the internal capsule differed markedly from the centrum semiovale data, thus confirming our hypothesis. Furthermore, data for the internal capsule were distributed in a relatively tight cluster, possibly reflecting the compact and parallel nature of its fibers, while data for the centrum semiovale were more widely distributed, consistent with the less compact and often crossing pattern of its fibers. This indicates that the tensor shape plot technique can depict data in similar regions as being alike. Conclusion Tensor shape plots successfully depicted differences in tissue microstructure and reflected the microstructure of individual brain regions. This proof of principle study suggests that if our findings are reproduced in larger samples, including abnormal white matter states, the technique may be useful in assessment of white matter diseases.

Adapting a Low-Cost Selective Compliant Articulated Robotic Arm for Spillage Avoidance.

Flexible automation systems provide the needed adaptability to serve shorter-term projects and specialty applications in biochemical analysis. A low-cost selective compliant articulated robotic arm designed for liquid spillage avoidance is developed here. In the vertical-plane robotic arm movement test, the signals from an inertial measurement unit (IMU) and accelerometer were able to sense collisions. In the horizontal movement test, however, only the signals from the IMU enabled collision to be detected. Using a calculation method developed, it was possible to chart the regions where the obstacle was likely to be located when a collision occurred. The low cost of the IMU and its easy incorporation into the robotic arm offer the potential to meet the pressures of lowering operating costs, apply laboratory automation in resource-limited venues, and obviate human intervention in response to sudden disease outbreaks.

Quality assessment of frameless fractionated stereotactic radiotherapy using cone beam computed tomography.

PURPOSE: A quality assessment of intracranial stereotactic radiotherapy was performed using cone beam computed tomography (CBCT). Setup errors were analyzed for two groups of patients: (1) those who were positioned using a frameless SonArray (FSA) system and immobilized with a bite plate and thermoplastic (TP) mask (the bFSA group); and (2) those who were positioned by room laser and immobilized using a TP mask (the mLAS group). METHODS AND MATERIALS: A quality assurance phantom was used to study the system differences between FSA and CBCT. The quality assessment was performed using an Elekta Synergy imager (XVI) (Elekta Oncology Systems, Norcross, GA) and an On-Board Imager (OBI) (Varian Medical Systems, Palo Alto, CA) for 25 patients. For the first three fractions, and weekly thereafter, the FSA system was used for patient positioning, after which CBCT was performed to obtain setup errors. RESULTS: (1) Phantom tests: The mean differences in the isocenter displacements for the two systems was 1.2 ± 0.7 mm. No significant variances were seen between the XVI and OBI units (p~0.208). (2)Patient tests: The mean of the displacements between FSA and CBCT were independent of the CBCT system used; mean setup errors for the bFSA group were smaller (1.2 mm) than those of the mLAS group (3.2 mm) (p < 0.005). For the mLAS patients, the 90th percentile and the maximum rotational displacements were 3° and 5°, respectively. A 4-mm drift in setup accuracy occurred over the treatment course for 1 bFSA patient. CONCLUSIONS: System differences of less than 1 mm between CBCT and FSA were seen. Error regression was observed for the bFSA patients, using CBCT (up to 4 mm) during the treatment course. For the mLAS group, daily CBCT imaging was needed to obtain acceptable setup accuracies.

Comparison of analytic source models for head scatter factor calculation and planar dose calculation for IMRT.

The purpose of this study was to choose an appropriate head scatter source model for the fast and accurate independent planar dose calculation for intensity-modulated radiation therapy (IMRT) with MLC. The performance of three different head scatter source models regarding their ability to model head scatter and facilitate planar dose calculation was evaluated. A three-source model, a two-source model and a single-source model were compared in this study. In the planar dose calculation algorithm, in-air fluence distribution was derived from each of the head scatter source models while considering the combination of Jaw and MLC opening. Fluence perturbations due to tongue-and-groove effect, rounded leaf end and leaf transmission were taken into account explicitly. The dose distribution was calculated by convolving the in-air fluence distribution with an experimentally determined pencil-beam kernel. The results were compared with measurements using a diode array and passing rates with 2%/2 mm and 3%/3 mm criteria were reported. It was found that the two-source model achieved the best agreement on head scatter factor calculation. The three-source model and single-source model underestimated head scatter factors for certain symmetric rectangular fields and asymmetric fields, but similar good agreement could be achieved when monitor back scatter effect was incorporated explicitly. All the three source models resulted in comparable average passing rates (>97%) when the 3%/3 mm criterion was selected. The calculation with the single-source model and two-source model was slightly faster than the three-source model due to their simplicity.