Dataset Information

Retrospective evaluation of CTV to PTV margins using CyberKnife in patients with thoracic tumors.

ABSTRACT: The objectives of this study were to estimate global uncertainty for patients with thoracic tumors treated in our center using the CyberKnife VSI after placement of fiducial markers and to compare our findings with the standard CTV to PTV margins used to date. Datasets for 16 patients (54 fractions) treated with the CyberKnife and the Synchrony Respiratory Tracking System were analyzed retrospectively based on CT planning, tracking information, and movement data generated and saved in the logs files by the system. For each patient, we analyzed all the main uncertainty sources and assigned a value. We also calculated an expanded global uncertainty to ensure a robust estimation of global uncertainty and to enable us to determine the position of 95% of the CTV points with a 95% confidence level during treatment. Based on our estimation of global uncertainty and compared with our general mar- gin criterion (5 mm in all three directions: superior/inferior [SI], anterior/posterior [AP], and lateral [LAT]), 100% were adequately covered in the LAT direction, as were 94% and 94% in the SI and AP directions. We retrospectively analyzed the main sources of uncertainty in the CyberKnife process patient by patient. This individualized approach enabled us to estimate margins for patients with thoracic tumors treated in our unit and compare the results with our standard 5 mm margin.

SUBMITTER: Floriano A

PROVIDER: S-EPMC5711121 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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Retrospective evaluation of CTV to PTV margins using CyberKnife in patients with thoracic tumors.

Floriano Alejandro A García Rafael R Moreno Ramon R Sánchez-Reyes Alberto A

Journal of applied clinical medical physics 20141108 6

The objectives of this study were to estimate global uncertainty for patients with thoracic tumors treated in our center using the CyberKnife VSI after placement of fiducial markers and to compare our findings with the standard CTV to PTV margins used to date. Datasets for 16 patients (54 fractions) treated with the CyberKnife and the Synchrony Respiratory Tracking System were analyzed retrospectively based on CT planning, tracking information, and movement data generated and saved in the logs f ...[more]

PMID: 25493508

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Project description:PurposeThis study aimed to analyze the effect of body mass factors (BMFs) on setup errors in gynecologic tumors, and whether the planned tumor volumes (PTVs) are adequate for obese patients.MethodsThis was a retrospective study of 46 consecutive female patients with gynecologic tumors who were treated with volumetric modulated arc therapy. Setup accuracy was verified using daily cone beam computed tomography. Accuracy was determined for each fraction by testing 2 different PTVs (cutoff I = ≤0.7 cm; cutoff II = ≤1.0 cm). A pooled analysis was conducted to test the association between accuracy levels (within vs beyond PTV) and the mean and variance of body mass index (BMI), umbilical (UC), and hip circumference (HC). A receiver operating characteristics curve analysis was carried out to test the sensitivity of BMI, UC, and HC in predicting inaccurate setup.ResultsA significant association between BMFs and level of accuracy was observed in the lateral and vertical directions, but not in the longitudinal direction. In the lateral direction, inaccurate setups were associated with a greater BMI (mean difference: ∼3.50 kg/m2; P = .001), UC (∼10 cm), and HC (∼8 cm) compared with accurate setups (P < .001). With respect to the vertical direction, inaccurate setups (>0.7 cm margin [cutoff I]) were associated with a greater BMI (mean difference = 7.4 kg/m2; P = .001), UC (5.3 cm; P < .001), and HC (16.0 cm; P < .001) with reference to accurate setups. The receiver operating characteristics curve analysis showed that a BMI >31.4 kg/m2 was predictive for inaccurate setup in the vertical direction with 90.0% sensitivity with respect to cutoff I. Furthermore, a BMI >30.3 kg/m2 was predictive for inaccurate setup in the lateral direction with 92.5% sensitivity with respect to cutoff II.ConclusionsThe accuracy of radiation therapy setups for gynecologic tumors is highly sensitive to patients' BMI, notably in the lateral and vertical directions. We suggest that daily cone beam computed tomography should be applied on patients with a BMI >30.3 kg/m2, using customized protocols that are lower in dose and comparable in image quality.

Project description:ObjectivesTo measure the unit-level variation in Acute Kidney Injury (AKI) incidence post-thoracic surgery over a contemporary 1-year period. Secondary aims include examining the associations with sex, age group, operation type, length of stay and mortality.DesignA multicentre, observational, retrospective study in thoracic surgery.Setting17 of 35 Society for Cardiothoracic Surgery of Great Britain and Ireland (SCTS) units participated. The student wing, known as SCTS STUDENTS, supported data collection.ParticipantsOverall, 15 229 patients were collected of which 15 154 were included for analysis after exclusions. All patients (age≥18 years) undergoing any thoracic surgery from 1 April 2016 to 31 March 2017 were included. For analysis, we excluded patients with preoperative end-stage renal failure and those with incomplete data.Main outcome measuresThe primary outcome is the incidence of AKI within 7 days of the procedure or discharge date if earlier. Secondary outcomes include assessing associations with patient demographics (age, sex), type of procedure (open and minimally invasive), length of stay and mortality.ResultsOut of 15 154 patients AKI was diagnosed in 1090 patients (7.2%) within 7 days of surgery with AKI stage 1 (4.8%), stage 2 (1.7%) and stage 3 (0.7%). There was a statistically significant variation in AKI incidence between units from 3.1 to 16.1% (p<0.05). Significant differences between AKI and non-AKI were found in post-operative length of stay (7 vs 3 days, p<0.001), 30-day mortality (9 vs 1.6%, p<0.001), 90-day mortality (14.7 vs 4.4%, p<0.001) and 1-year mortality (23.1 vs 12.2 %, p<0.001).ConclusionsFollowing thoracic surgery, AKI incidence ranged from 3.1% to 16.1% between units (p<0.05) with associations between AKI and both length of stay and mortality. We propose AKI as a suitable comparative and absolute quality measure in thoracic surgery. Reducing rates of AKI may improve patient outcomes, length of stay and reduce costs.

Project description:We examined the adequacy of existing shielding guidelines using five-year clinical data from a busy CyberKnife center. From June 2006 through July 2011, 1,370 patients were treated with a total of 4,900 fractions and 680,691 radiation beams using a G4 CyberKnife. Prescription dose and total monitor units (MU) were analyzed to estimate the shielding workload and modulation factor. In addition, based on the beam's radiation source position, targeting position, MU, and beam collimator size, the MATLAB program was used to project each beam toward the shielding barrier. The summation of the projections evaluates the distribution of the shielding load. On average, each patient received 3.6 fractions, with an average 9.1 Gy per fraction prescribed at the 71.1% isodose line, using 133.7 beams and 6,200 MU. Intracranial patients received an average of 2.7 fractions, with 8.6 Gy per fraction prescribed at the 71.4% isodose line, using 133 beams and 5,083 MU. Extracranial patients received an average of 3.94 fractions, with 9.2 Gy per frac- tion prescribed at the 71% isodose line, using 134 beams and 6,514 MU. Most- used collimator sizes for intracranial patients were smaller (7.5 to 20 mm) than for extracranial patients (20 to 40 mm). Eighty-five percent of the beams exited through the floor, and about 40% of the surrounding wall area received no direct beam. For the rest of the wall, we found "hot" areas that received above-average MU. The locations of these areas were correlated with the projection of the nodes for extracranial treatments. In comparison, the beam projections on the wall were more spread for intracranial treatments. The maximum MU any area received from intracranial treatment was less than 0.25% of total MU used for intracranial treatments, and was less than 1.2% of total MU used for extracranial treatments. The combination of workload, modulation factor, and use factor in our practice are about tenfold less than recommendations in the existing CyberKnife shielding guidelines. The current guidelines were found to be adequate for shielding, even in a busy center. There may be a potential to reduce shielding in areas with no or few direct beams in the current G4 model. Since a newer model CyberKnife (M6) has recently been introduced, the patterns of usage reported here may be changed in the future. The uneven distribution of use factor we have found may, however, be considered in the vault design.

Dataset Information

Retrospective evaluation of CTV to PTV margins using CyberKnife in patients with thoracic tumors.

Publications

Retrospective evaluation of CTV to PTV margins using CyberKnife in patients with thoracic tumors.

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