Intraperitoneal versus retromuscular mesh placement for open incisional hernias: an analysis of the Americas Hernia Society Quality Collaborative.

BACKGROUND: Incisional hernia repair with mesh improves long-term outcomes, but the ideal mesh position remains unclear. This study compared intraperitoneal versus retromuscular or preperitoneal sublay (RPS) mesh positions for open incisional hernia repairs. METHODS: All patients who had elective open incisional hernia repairs were identified retrospectively in the Americas Hernia Society Quality Collaborative database. The primary outcome was the rate of 30-day surgical-site infection (SSI). Other outcomes of interest included 30-day surgical-site occurrences requiring procedural intervention (SSOPI), hernia-related quality-of-life survey (HerQLes) scores and long-term recurrence. A logistic model was used to generate propensity scores for mesh position using several clinically relevant co-variables. Regression models adjusting for propensity score and baseline characteristics were developed to assess the effect of mesh placement. RESULTS: A total of 4211 patients were included in the study population: 587 had intraperitoneal mesh and 3624 had RPS mesh. Analysis with propensity score adjustment provided no evidence for differences in SSOPI (odds ratio (OR) 0·79, 95 per cent c.i. 0·49 to 1·26) and SSI (OR 0·91, 0·50 to 1·67) rates or HerQLes scores at 30 days (OR 1·20, 0·79 to 1·82), or recurrence rates (hazard ratio 1·28, 0·90 to 1·82). CONCLUSION: Mesh position had no effect on short- or long-term outcomes, including SSOPI and SSI rates, HerQLes scores and long-term recurrence rates.

ANTECEDENTES: La reparación de una eventración con malla mejora los resultados a largo plazo, pero sigue sin estar definida cuál es la posición ideal de colocación de la malla. Este estudio comparó los resultados de la reparación abierta de una eventración con malla en posición intraperitoneal versus retromuscular o preperitoneal (retromuscular or preperitoneal sublay, RPS). MÉTODOS: Se identificaron de forma retrospectiva todos los pacientes a los que se reparó una eventración por via abierta en el Americas Hernia Society Quality Collaborative. La variable principal fue la tasa de infección de la herida quirúrgica (surgical site infections, SSI) a los 30 días. Se analizaron también las incidencias acaecidas en la herida que hubieran precisado algún tratamiento (surgical site occurrences requiring procedural intervention, SSOPI) dentro de los 30 días postintervención, los resultados de una encuesta de calidad de vida relacionada con la hernia (HerQles) y la recidiva a largo plazo. Se utilizó un modelo logístico con diferentes covariables clínicas relevantes para generar puntajes de propensión con respecto a la posición de malla. Para analizar el efecto de la posición de la malla, se desarrollaron diferentes modelos de regresión ajustados por las características basales y el puntaje de propensión. RESULTADOS: Se incluyeron en el estudio 4.211 pacientes, 587 con malla intraperitoneal y 3.624 con malla RPS. El análisis con ajuste por puntaje de propensión no mostró diferencias en SSOPI (razón de oportunidades, odds ratio, OR 0,624, i.c. del 95% 0,364-1,07), SSI (OR 0,927, i.c. del 95% 0,475-1,81), puntuación HerQles a 30 días (OR 1,19, i.c. del 95% 0,79-1,8) o en el índice de recidivas (OR 1,28, i.c. del 95% 0,897-1,82). CONCLUSIÓN: La posición de la colocación de la malla no tuvo efecto en los resultados a corto o largo plazo, incluidas las tasas de SSOPI y SSI, las puntuaciones de HerQles y la tasa de recidiva a largo plazo.

Management of ventral hernia defect during enterocutaneous fistula takedown: practice patterns and short-term outcomes from the Abdominal Core Health Quality Collaborative.

BACKGROUND: An enterocutaneous fistula (ECF) with an associated large hernia defect poses a significant challenge for the reconstructive surgeon. We aim to describe operative details and 30-day outcomes of elective hernia repair with an ECF when performed by surgeons participating in the Abdominal Core Health Quality Collaborative (ACHQC). STUDY DESIGN: Patients undergoing concomitant hernia and ECF elective repair were identified within the ACHQC. Outcomes of interest were operative details and 30-day rates of surgical site infections (SSI), surgical site occurrences requiring procedural intervention (SSOPI), medical complications, and mortality. RESULTS: 170 patients were identified (mean age 60 years, 52.4% females, mean BMI 32.3 kg/m2). 106 patients (62%) had small-bowel ECFs, mostly managed with resection without diversion. 30 patients (18%) had colonic ECFs, which were managed with resection without diversion (14%) or resection with diversion (6%). 100 (59%) had a prior mesh in place, which was removed in 90% of patients. Hernias measured 14 cm ± 7 in width, and 68 (40%) had a myofascial release performed (41 TARs). Mesh was placed in 115 cases (68%), 72% as a sublay, and more frequently of biologic (44%) or permanent synthetic (34%) material. 30-day SSI was 18% (37% superficial, 40% deep), and 30-day SSOPI was 21%. 19 patients (11%) were re-operated: 8 (8%) due to a wound complication and 4 (2%) due to a missed enterotomy. Two infected meshes were removed, one biologic and one synthetic. CONCLUSIONS: Surgeons participating in the ACHQC predominantly resect ECFs and repair the associated hernias with sublay mesh with or without a myofascial release. Morbidity remains high, most closely related to wound complications, as such, concomitant definitive repairs should be entertained with caution.

Is there an advantage to laparoscopy over open repair of primary umbilical hernias in obese patients? An analysis of the Americas Hernia Society Quality Collaborative (AHSQC).

PURPOSE: The most common techniques used to repair umbilical hernias are open and laparoscopic. As the obesity epidemic in the United States is growing, it is essential to understand how this morbidity affects umbilical hernia repairs. This study compares laparoscopic versus open umbilical hernia repairs in obese patients. METHODS: All patients with body mass index (BMI) ≥ 30 kg/m2 who underwent elective, open or laparoscopic repair of a primary umbilical hernia with mesh were identified from the Americas Hernia Society Quality Collaborative (AHSQC). A retrospective review of the prospectively collected data was conducted. Outcomes of interest included surgical site infections (SSI), surgical site occurrences requiring procedural intervention (SSOPI), hernia-related quality-of-life survey (HerQles), and long-term recurrence. A logistic regression model was used to generate propensity scores. RESULTS: Of 1507 patients who met the inclusion criteria, 322 were laparoscopic, and 1185 were open cases. The laparoscopic group had higher mean BMI (37 ± 6 vs. 35 ± 5 kg/m2 , P < 0.001 ) and mean hernia width (3 cm ± 1 vs. 2 cm ± 2, P < 0.001). Using a propensity score model, we controlled for several clinically relevant covariates. Propensity score adjustment showed no differences in the 30-day HerQles score (OR 0.93, 95% CI 0.58-1.49), SSI (OR 1.57, 95% CI 0.52-4.77), SSOPI (OR 2.85, 95% CI 0.84-9.62) or hernia recurrence (hazard ratio 0.86, 95% CI 0.50-1.49). CONCLUSION: In obese patients with primary umbilical hernias, there is likely no benefit to laparoscopy over open umbilical hernia repair with mesh with regard to wound morbidity. Although, the long-term recurrence also showed no difference between these two approaches, overall follow up was lacking.

Short-term outcomes and healthcare resource utilization following incisional hernia repair with synthetic mesh in patients with Crohn's disease.

PURPOSE: While the use of synthetic mesh for incisional hernia repair reduces recurrence rates, little evidence exists regarding the impact of this practice on the disease burden of a Crohn's patient. We aimed to describe the post-operative outcomes and healthcare resource utilization following incisional hernia repair with synthetic mesh in patients with Crohn's disease. METHODS: A retrospective review of adult patients with Crohn's disease who underwent elective open incisional hernia repair with extra-peritoneal synthetic mesh from 2014 to 2018 at a single large academic hospital with surgeons specializing in hernia repair was conducted. Primary outcomes included 30-day post-operative complications and long-term rates of fistula formation and hernia recurrence. The secondary outcome compared healthcare resource utilization during a standardized fourteen-month period before and after hernia repair. RESULTS: Among the 40 patients included, six (15%) required readmission, 4 (10%) developed a surgical site occurrence, 3 (7.5%) developed a surgical site infection, and one (2.5%) required reoperation within the first 30 days. The overall median follow-up time was 42 months (IQR = 33-56), during which time one (2.5%) patient developed an enterocutaneous fistula and eight (20%) experienced hernia recurrence. Healthcare resource utilization remained unchanged or decreased across every category following repair. CONCLUSION: The use of extra-peritoneal synthetic mesh during incisional hernia repair in patients with Crohn's disease was not associated with a prohibitively high rate of post-operative complications or an increase in healthcare resource utilization to suggest worsening disease during the first 4 years after repair. Future studies exploring the long-term outcomes of this technique are needed.

Outcomes of transversus abdominis release (TAR) with permanent synthetic retromuscular reinforcement for bridged repairs in massive ventral hernias: a retrospective review.

PURPOSE: In a subset of patients with massive and multiply recurrent hernias, despite performing a transversus abdominis release (TAR), anterior fascial re-approximation is not feasible and a bridged repair is required. We aim to report on the outcomes of this patient population at our institution. METHODS: Patients that underwent a TAR-bridged repair at the Cleveland Clinic were identified retrospectively within the Americas Hernia Society Quality Collaborative (AHSQC) database. Outcomes of interest were quality-of-life metrics measured through HerQLes and PROMIS pain intensity 3a and composite recurrence measured by patient-reported outcomes, physical examination, or CT imaging. RESULTS: Ninety-six patients met inclusion criteria. The mean hernia width was 26 ± 8 cm. The majority (93%) were incisional hernias and 71% were recurrent with 21% having five prior hernia repairs. Of those eligible for recurrence and QoL analysis, 54 (70%) had data points available. HerQLes scores showed a steady improvement throughout postoperative recovery (26 ± 21 at baseline, 44 ± 26 at 30-day follow-up, and 60 ± 33 at 6 months-3 years; P < 0.001), as did the PROMIS Pain Intensity 3a scores (46 ± 11 at baseline, 45 ± 11 at 30-day follow-up, and 39 ± 11 at 6 months-3 years; P = 0.001). At a mean follow-up of 20 ± 10 months, a composite recurrence of 46% was reported, primarily from patients reporting a "bulge" at the site. CONCLUSION: Performing a bridged TAR repair with synthetic mesh in patients with complex hernias is associated with high rates of patient-reported bulge perception. Despite this, there was a significant improvement in quality-of-life metrics. When counseling these patients during preoperative evaluation, the results of our study should be shared in candor to aid in informed decision-making.

Open retromuscular versus laparoscopic ventral hernia repair for medium-sized defects: where is the value?

PURPOSE: There is increasing emphasis on value in health care, defined as quality over cost required to deliver care. We analyzed outcomes and costs of repairing medium-sized ventral hernias to identify whether an open retromuscular or laparoscopic intraperitoneal onlay approach would provide superior value to the patient and healthcare system. METHODS: A retrospective analysis of prospectively collected data from the Americas Hernia Society Quality Collaborative was performed for patients undergoing clean, elective repair of ventral hernias between 4 and 8 cm in width at our institution between 4/2013 and 12/2016 for whom at least 1-year follow-up was available. Recurrence rates, wound complications, length of stay, patient-reported outcomes, and perioperative costs were compared. RESULTS: One hundred and eighty-six patients met criteria (105 open, 81 laparoscopic) with 93.5% having ≥ 2-year follow-up. Patients undergoing laparoscopic repair had higher BMI, lower ASA classification, slightly lower prevalence of recurrent hernias and less prior mesh utilization, and slightly smaller hernias. Length of stay was shorter in the laparoscopic group (median 1 vs. 3 days, p < 0.001), without increased readmissions. Recurrence rates, wound complications, and patient-reported outcomes were similar. Laparoscopic repair had higher up-front surgical costs, yet equivalent total perioperative costs. CONCLUSION: Both laparoscopic and open approaches for elective repair of medium-sized ventral hernias offer similar clinical outcomes, patient-reported outcomes, and total perioperative costs. Laparoscopic repair appears to offer superior value based on a significantly reduced postoperative length of stay.

Comparing 30-day outcomes between different mesh fixation techniques in minimally invasive inguinal hernia repair.

PURPOSE: The association of postoperative patient-reported outcomes and type of mesh fixation during minimally invasive inguinal hernia repair has not been well characterized. We aimed to compare the 30-day quality of life outcomes between various mesh fixation techniques utilizing the AHSQC prospective registry. METHODS: All minimally invasive inguinal hernias with completed 30-day follow-up were abstracted from the AHSQC, excluding patients with primary indication for surgery being chronic groin pain. Mesh fixation was categorized as (1) atraumatic fixation (AF) (2) traumatic non-suture (TNS), (3) traumatic suture (TS). Our outcomes of interest were pain at site at 30-day and EuraHS quality of life assessment. RESULTS: After applying inclusion and exclusion criteria, 864 patients had surgical site pain and quality of life outcomes reported; 253 (AF), 451 (TNS), and 160 (TS). After adjusting for identified confounders, there was no statistically significant difference between any fixation method when evaluating pain as a binary variable (Yes/No). However, when looking at the EuraHS evaluation for pain and quality of life outcomes, AF was associated with better scores than both TNS and TS fixation in the cosmetic, restrictions, and overall EuraHS domains. AF was only better than TS fixation in the pain domain. CONCLUSION: Our study suggests that AF had a significantly improved hernia-specific quality of life in all domains at 30-days postoperatively. We also identified that pain as a binary variable is inadequate for its states purpose. Thus, the overall well-being and morbidity should be taken into account when evaluating hernia patients postoperatively.

Hernia recurrence inventory: inguinal hernia recurrence can be accurately assessed using patient-reported outcomes.

PURPOSE: Relying solely on in-person encounters to assess long-term outcomes of hernia repair leads to substantial loss of information and patients lost-to-follow-up, hindering research and quality improvement initiatives. We aimed to determine if inguinal hernia recurrences could be assessed using the Ventral Hernia Recurrence Inventory (VHRI), a previously existing patient-reported outcome (PRO) tool that can be administered through the telephone and has already been validated for diagnosing ventral hernia recurrence. METHODS: A prospective, multicentric comparative study was conducted. Adult patients from two centers (United States and Brazil) at least 1 year after open or minimally invasive inguinal hernia repair were asked to answer the questions of the VHRI in relation to their prior repair. A physical exam was then performed by a blinded surgeon. Testing characteristics and diagnostic performance of the PRO were calculated. Patients with suspected recurrences were preferentially recruited. RESULTS: 128 patients were enrolled after 175 repairs. All patients answered the VHRI and were further examined, where a recurrence was present in 32% of the repairs. Self-reported bulge and patient perception of a recurrence were highly sensitive (84-94%) and specific (93-94%) for the diagnosis of an inguinal hernia recurrence. Test performance was similar in the American and Brazilian populations despite several baseline differences in demographic and clinical characteristics. CONCLUSION: The VHRI can be used to assess long-term inguinal hernia recurrence and should be reestablished as the Hernia Recurrence Inventory (HRI). Its implementation in registries, quality improvement efforts, and research could contribute to improving long-term follow-up rates in hernia patients.

Primary uncomplicated midline ventral hernias: factors that influence and guide the surgical approach.

BACKGROUND: Considering recently published high-level evidence on the management of primary midline ventral hernias, we set out to review current practices and reevaluate the literature surrounding this topic. METHODS: The Americas Hernia Society Quality Collaborative (AHSQC) was used to abstract all uncomplicated primary midline ventral hernias. The primary outcomes of interest were surgical approaches, including the use of mesh, the type and position of mesh, and the use of minimally invasive surgery (MIS). RESULTS: A total of 7030 met inclusion criteria; mean age of 52 ± 14, 71% male, with a median hernia width of 2 [1, 2]. A total 69% underwent mesh repair, while 31% underwent suture repair. The most commonly used mesh was permanent synthetic (98%), placed in either the intraperitoneal (46%) or preperitoneal (42%) spaces. The majority of repairs were performed through an open approach (72%). When mesh was used through an open approach (58%), the majority were patches (70%) placed in the preperitoneal space (50%). Through an MIS approach (95%), the majority were flat meshes (53%) placed in the intraperitoneal space (58%). CONCLUSION: Recent high-level literature recommends the use of mesh repair (flat mesh) in all patients with hernia width ≥ 1 cm. This evidence is limited to the use of flat mesh through an open approach. While AHSQC surgeons do offer mesh repair in the majority of cases, this is most commonly using a mesh patch, and is selective towards larger hernias and obese patients. Further research is required to evaluate the safety of mesh patches, and a mesh repair should be offered to a young non-obese healthy patient, as they benefit similarly from the use of mesh.

Outcomes of transversus abdominis release in non-elective incisional hernia repair: a retrospective review of the Americas Hernia Society Quality Collaborative (AHSQC).

PURPOSE: Elective repair of large incisional hernias using posterior component separation with transversus abdominis release (TAR) has acceptable wound morbidity and long-term recurrence rates. The outcomes of using this reconstructive technique in the non-elective setting remains unknown. We aim to report 30-day outcomes of TAR in non-elective settings. METHODS: All patients undergoing open TAR in non-elective settings were identified within the Americas Hernia Society Quality Collaborative (AHSQC). A retrospective review was conducted and outcomes of interest were 30-day Surgical Site Infections (SSI), Surgical Site Occurrences (SSO), SSOs requiring procedural intervention (SSOPI), medical complications, and unplanned readmissions and reoperations. RESULTS: Fifty-nine patients met inclusion criteria. Mean BMI was 36.6 ± 8.9 kg/m2 and mean hernia width was 14.4 ± 7.2 cm. Forty (67.8%) were recurrent hernias. Pain (88%) and bowel obstruction (79.7%) were the most frequent indications for surgery. Surgical field was classified as clean in 69.5% of cases, with an 88% use of permanent synthetic mesh and fascial closure achieved in 93.2% of cases. There were 15 (25.4%) total wound events, 8 (13.6%) were SSIs. There were 8 (13.6%) SSOPIs, 6 of which were wound opening, 1 wound debridement, and 1 percutaneous drainage. At least one wound or medical complication was reported for 37% of the patients. There were no mortalities. CONCLUSION: Not surprisingly, TAR in the non-elective setting is associated with increased wound morbidity requiring procedural interventions and reoperations compared to what has previously been reported for elective cases. The long-term consequences of this wound morbidity with regard to hernia recurrence are as of yet unknown.

Telescopic dissection versus balloon dissection for laparoscopic totally extraperitoneal inguinal hernia repair (TEP): a registry-based randomized controlled trial.

OBJECTIVE: Laparoscopic totally extraperitoneal inguinal hernia repair (TEP) can be performed using either telescopic (TD) or balloon dissection (BD). The use of a disposable balloon dissector increases the cost of TEP. However, it remains unclear whether BD saves enough time to justify its cost. We hypothesized that BD would consistently save 15 min in operative time. To test this hypothesis, we designed a registry-based randomized controlled trial (RB-RCT) embedded into the Americas Hernia Society Quality Collaborative. METHODS: A single-blinded, parallel, RB-RCT was conducted. Adults with inguinal hernias presenting for elective repair were screened. Patients with unilateral hernias deemed fit to undergo TEP were eligible; those with bilateral hernias (BIH) or undergoing open repair were excluded. Individuals were randomized to TD or BD with a disposable device. TEP was performed with synthetic mesh and tacks. Subjects were blinded and followed up for 30 day. Main outcome was operative time. RESULTS: 207 patients were screened: 166 were excluded and 41 were randomized (21 BD, 20 TD). One patient (TD group) was excluded due to the incidental finding of BIH. 40 patients were analyzed (median age 56, median BMI 26 kg/m2, 98% males). Hernias were 72% indirect, 17% direct, 10% pantaloon, and 8% recurrent. Other than obesity (26.5% vs. 0, p = 0.018), there were no baseline differences between the groups. Median operative times were similar (TD 43 min, IQR 33-63; BD 46 min, IQR 35-90, p = 0.490). There were 2 seromas and 2 hematomas in the BD group, and none in the TD (p = 0.108). CONCLUSIONS: BD does not consistently result in 15-min time saving during TEP. Use of a disposable balloon dissector can be deferred in the experienced hands. TRIAL REGISTRATION: ClinicalTrials.gov (NCT03276871).

Posterior component separation with transversus abdominis release (TAR) for repair of complex incisional hernias after orthotopic liver transplantation.

BACKGROUND: Incisional hernias (IH) after orthotopic liver transplant (OLT) are challenging due to their concurrent midline and subcostal defects adjacent to bony prominences in the context of lifelong immunosuppression. To date, no studies evaluated the posterior component separation with transversus abdominis release (TAR) to repair complex IH after OLT. We aim to report the outcomes of TAR in this scenario. STUDY DESIGN: OLT patients who underwent open, elective IH repair with TAR performed at two centers and with a minimum of 1-year follow-up were identified in the Americas Hernia Society Quality Collaborative (AHSQC). Outcomes included 30-day surgical site infections (SSI), surgical site occurrences requiring procedural intervention (SSOPI), unplanned readmissions, reoperations, and hernia recurrence. RESULTS: Forty-four patients were identified (mean age 60 ± 8, 75% male, median BMI 30.7 kg/m2) at two centers. Median hernia width was 20 cm [IQR 15-28] and 98% (43) were clean cases. Retromuscular synthetic mesh was used in all cases, and 93% (41) achieved fascial closure with no intraoperative complications. Postoperatively, there were 5 SSIs (4 deep, 1 superficial), 6 SSOPIs (4 wound opening, 1 debridement, 1 seroma drainage), four (9%) readmissions, and 3 (7%) reoperations. One patient developed a mesh infection that did not require mesh excision. After a median follow-up of 13 months [IQR 12-17], there were 11 (25%) recurrences; 8 due to central mesh fractures (CMF). Seven recurrences have been repaired either laparoscopically or using an onlay. CONCLUSIONS: In a challenging cohort of immunosuppressed patients with large IH, TAR was shown to have acceptable medium-term results, but high recurrence rate driven by CMF. Further studies investigating the mechanism of central mesh fractures are necessary to reduce these recurrences.

Environmental radon daughters reveal pathognomonic changes in the brain proteins and lipids in patients with Alzheimer's disease and Parkinson's disease, and cigarette smokers.

This paper presents an investigation of the retention of environmental radon daughters, 210Po (alpha particle emitting radio-nuclide) and 210Bi (beta particle emitting radio-nuclide), in lipid and protein fractions of the cortical grey and subcortical white matter from the frontal and temporal brain lobes of patients who had suffered from Alzheimer's disease or Parkinson's disease, of cigarette smokers, and of control subjects. 210Po and 210Bi radioactivity increased tenfold in the cortical grey and subcortical white protein fraction in patients with Alzheimer's disease and smokers, and tenfold in the cortical grey and subcortical white lipid fraction in patients with Parkinson's disease. Free radicals generated by radon daughters may add to the severity of the radio-chemical injury to the brain astrocytes. The pathognomonic distribution of radon daughters to lipids in patients with Parkinson's disease and to proteins in patients with Alzheimer's disease was attributed to high chlorine affinity of radon daughters. The changes in the membrane protein pores, channels, and gates in patients with Alzheimer's disease and in the lipid bilayer in patients with Parkinson's disease are at the core of what the authors think are two systemic brain diseases.

SU-F-BRCD-03: Dose Calculation of Electron Therapy Using Improved Lateral Buildup Ratio Method.

PURPOSE: To calculate the percentage depth dose of any irregular shape electron beam using modified lateral build-up-ratio method. METHOD AND MATERIALS: Percentage depth dose (PDD) curves were measured using 6, 9, 12, and 15MeV electron beam energies for applicator cone sizes of 6×6, 10×10, 14×14, and 14×14cm2 . Circular cutouts for each cone were prepared from 2.0cm diameter to the maximum possible size for each cone. In addition, three irregular cutouts were prepared. The scanning was done using a water tank and two diodes - one for the signal and the other a stationary reference outside the tank. The water surface was determined by scanning the signal diode slowly from water to air and by noting the sharp change of the percentage depth dose curve at the water/air interface. RESULTS: The lateral build-up-ratio (LBR) for each circular cutout was calculated from the measured PDD curve using the open field of the 14×14 cm2 cone as the reference field. Using the LBR values and the radius of the circular cutouts, the corresponding lateral spread parameter (sigma) of the electron shower was calculated. Unlike the commonly accepted assumption that sigma is independent of cutout size, it is shown that the sigma value increases linearly with circular cutout size. Using this characteristic of sigma, the PDD curves of irregularly shaped cutouts were calculated. Finally, the calculated PDD curves were compared with measured PDD curves. CONCLUSIONS: In this research, it is shown that sigma increases with cutout size. For radius of circular cutout sizes up to the equilibrium range of the electron beam, the increase of sigma with the cutout size is linear. The percentage difference of the calculated PDD from the measured PDD for irregularly shaped cutouts was under 1.0%. Similar Result was obtained for four electron beam energies (6, 9, 12, and 15MeV).

SU-E-T-382: An Analysis of VMAT Monthly Quality Assurance.

PURPOSE: The purpose of this study is to quantify the change in monthly VMAT quality assurance (QA) and determine the tests to maintain consistent delivery with a baseline. METHODS: VMAT monthly QA has been performed for over 14 months on two Elekta Synergy LINACs. A baseline was established at acceptance and the monthly QA results were compared to those initial values. Films were used to test the dependence on varying dose rate, gantry speed, rotational direction, and MLC speed. These parameters were tested independently and then together in a test called the synchronicity test. Ion chamber readings test a DMLC field with a varying dose rate and MLC speed. Introducing intentional errors into the tested fields allowed the detectable limits of the QA to be determined. RESULTS: The monthly QA has consistently matched the baseline within a 3% dose limit on film. Analyzing the synchronicity film with a gamma test using a 5%/0.5mm tolerance showed a monthly pass rate of over 99%. The DMLC test has been identical for the entire course of VMAT QA. Furthermore, intentional changes in the MLC speed were noticed on the synchronicity test in the form of a smaller gamma pass rate as the MLC error was increased. CONCLUSIONS: There is a monthly agreement with all films testing individual parameters, ion chamber DMLC readings, as well as agreement with the synchronicity test. This collection of data has lead to the conclusion that only the synchronicity test and DMLC readings need to be performed on a monthly basis. If those tests fail, then individual parameters need to be tested to determine the singular cause of the error. Having a single test used as a red flag increases the efficiency of the monthly QA and is being implemented with an EPID to eliminate the use of film.

SU-E-T-389: Accuracy of a VMAT Planning System for Head and Neck Radiotherapy.

PURPOSE: To determine the accuracy of VMAT treatment planning and delivery for patients undergoing radiotherapy in the head and neck. METHOD AND MATERIALS: A dosimetric study of a typical head and neck treatment plan has been carried out using Chamber, film and TLD's placed inside an anthropomorphic phantom. Lateral and AP port films were taken to verify the isocenter prior to treatment. Multiple treatments were performed to assess the reproducibility and uncertainty in the TLD measurements. Gafchromatic film was used between the phantom slices and then analyzed as an independent check on the TLD results. The two data sets, from TLDs and films, were then compared with the treatment planning system dose calculations. RESULTS: The measured dose to the primary planning tumor volume agrees with the planning system within 2%. The comparison of the measured dose to the secondary tumor volume ranges from 3-6% and the spinal cord comparison ranges from 3-10%. CONCLUSION: This new Smart Arc treatment, VMAT, has great benefits to the patient in that patient motion and internal motion of the tumor is dramatically reduced. Challenges arise in predicting the dose near heterogeneities between the treatment planning system and actual measurement.

SU-E-J-06: A Time Dependence Analysis of CBCT Image Quality and Mechanical Stability.

PURPOSE: To quantify the change, if any, in flexmap correction factors and image quality with the XVI system over a course of several years and from these results, assess their clinical impact. METHODS: Flexmap, a calibration procedure which corrects for imperfect gantry rotation for cone-beam CT reconstruction, and image quality tests were performed on three Elekta Synergy linacs equipped with XVI. Data was collected per month over three years. U and V values, corresponding to lateral and longitudinal shifts respectively, were acquired through the XVI software. Image quality parameters were obtained through CT imaging of the Catphan 500®. For each reconstruction, pixel values for low density polyethylene (LDPE) and polystyrene materials were recorded. RESULTS: For all three linacs, analysis of the flexmap showed a significant change in the U factor for both month-to-month comparisons and comparisons between machines. The V correction factor exhibited a small variation month to month, and showed a slight, gradual increase over time (0.2 +/-0.08 mm). Image quality analysis showed a near consistent decrease (5-10%) in LDPE and polystyrene. Despite this decrease in pixel values, the ratio of the two pixel values remained constant, thus a similar decreasing trend in contrast was not observed. CONCLUSIONS: Analysis of monthly flexmap calibration showed the general monthly change in correction shifts and their general trend over several years. For image quality, our research exhibited roughly 0.5% per month decrease in pixel values of the Catphan®. Our results imply that CBCT images obtained from XVI are not appropriate for treatment planning and despite the decrease in panel response over time, image quality with respect to contrast will remain within acceptable clinical standards. Future studies may be carried out to assess any correlation between image quality and XVI source strength.

WE-G-BRB-02: MU-EPID an EPID Based Tool for IMRT Quality Assurance.

PURPOSE: A software program (MU-EPID) has been developed to perform patient specific IMRT pre-treatment QA verification using an electronic portal imaging device. METHODS: The software converts measured images of intensity modulated beams delivered to an EPID, into fluence maps that can be imported in the treatment planning system. The dose can then be calculated in the patient anatomy and compared against the patient's treatment plan for QA purposes. We first benchmarked the software using as a patient a cylindrical phantom. An aSi-1000 EPID mounted on a Varian Novalis linear accelerator was used for the image acquisition. Finally, IMRT plans from different treatment sites were used to further validate this in- house software. QA analysis was performed by evaluation of isodose distributions, DVH comparison and 2D gamma analysis. RESULTS: The validation study with the cylindrical phantom showed that the dose to the ion chamber measurement point was in good agreement with both the original treatment plan and the MU-EPID reconstructed dose. Similar results were found for the clinical cases that we studied. A gamma analysis of the dose to the isocenter plane was performed for each plan. Using 3% and 3 mm as the evaluation criteria, resulted in an average of 97.44% of pixels passing the analysis (gamma<1). Good agreement was also observed for the DVH, isodose and profile comparisons between the clinically delivered IMRT plan and the MU-EPID derived dose calculation. CONCLUSIONS: The results of the present investigation suggest that MU-EPID can be used in a clinical environment and can be used for patient specific QA for IMRT plans. This work has been supported by the SCOA.

In vivo characterization of the poly(ADP-ribosylation) of SV40 chromatin and large T antigen by immunofractionation.

We have confirmed the poly(ADP-ribosylation) of large T antigen of SV40 by using antibodies to both large T antigen and poly(ADP-ribose) and consequently have begun to characterize how this post-translational nuclear modification of the viral protein modulates its biological functions. SV40 minichromosomal subpopulation containing replicative intermediate DNA was shown to have a significantly higher affinity for anti-poly(ADP-Rib)-Sepharose than viral chromatin fractions containing mature minichromosomal DNA. An anti-large T-Sepharose column was used to isolate T antigen from crude extracts by two different approaches: (1) large T antigen was labeled with [35S]methionine in vivo and the infected cell extract was immunofractionated to isolate large T antigen and (2) large T antigen from infected cell extracts was immunofractionated followed by immunostaining. Using these techniques, 1-10% of the total T antigen from infected cells was found to be poly(ADP-ribosylated). Minichromosome preparations per se were also subjected to immunofractionation on anti-large T-Sepharose. The high level of retention of poly(ADP-ribosylated) species of minichromosomes on this matrix suggested that this post-translational modification of viral chromatin may be related to those steps in viral replication and transcription under regulation by large T antigen.