Evaluation Of Setup Errors Research Articles

Evaluation of Set-Up Errors and Set-Up Margin in Three-Dimensional Conformal Radiotherapy for Pelvic Tumours by Using Electronic Portal Imaging Device

The KDU Journal of Multidisciplinary Studies (KJMS) is published biannually, by the Faculty of Graduate Studies, General Sir John Kotelawala Defence University, Sri Lanka. KJMS is an international open access and peer reviewed journal which publishes high quality original research papers from multi-disciplinary and interdisciplinary approaches.

Evaluation of set-up errors and estimation of set-up margin during external beam radiation therapy of prostate cancer using electronic portal imaging device (EPID)

AbstractAim:In radiation therapy, accurate dose distribution in target volume requires accurate treatment setup. The set-up errors are unwanted and inherent in the treatment process. By achieving these errors, a set-up margin (SM) of clinical target volume (CTV) to planning target volume (PTV) can be determined. In the current study, systematic and random set-up errors that occurred during prostate cancer radiotherapy were measured by an electronic portal imaging device (EPID). The obtained values were used to propose the optimum CTV-to-PTV margin in prostate cancer radiotherapy.Materials and methods:A total of 21 patients with prostate cancer treated with external beam radiation therapy (EBRT) participated in this study. A total of 280 portal images were acquired during 12 months. Gross, population systematic (Σ) and random (σ) errors were obtained based on the portal images in Anterior–Posterior (AP), Medio-Lateral (ML) and Superior–Inferior (SI) directions. The SM of CTV to PTV were then calculated and compared by using the formulas presented by the International Commission on Radiation Units and Measurements (ICRU) 62, Stroom and Heijmen and Van Herk et al.Results:The findings showed that the population systematic errors during prostate cancer radiotherapy in AP, ML and SI directions were 1·40, 1·95 and 1·94 mm, respectively. The population random errors in AP, ML and SI directions were 2·09, 1·85 and 2·29 mm, respectively. The SM of CTV to PTV calculated in accordance with the formula of ICRU 62 in AP, ML and SI directions were 2·51, 2·68 and 3·00 mm, respectively. And according to Stroom and Heijmen, formula were 4·23, 5·19 and 5·48 mm, respectively. And Van Herk et al. formula were 4·96, 6·17 and 6·45 mm, respectively.Findings:The SM of CTV to PTV in all directions, based on the formulas of ICRU 62, Stroom and Heijmen and van Herk et al., were equal to 2·73, 4·98 and 5·86 mm, respectively; these values were obtained by averaging the margins in all directions.

Evaluation of setup errors in conformal radiotherapy for pelvic tumours: Case of the Regional Center of Oncology, Agadir

ContextThe errors made during repetitive patient placements affect significantly the accuracy of treatment and the results of radiotherapy. ObjectivesTo determine the total, systematic and random error in order to estimate the margin between the Clinical Target Volume (CTV) and the Planning Target Volume (PTV) in the pelvic region. Materials and methodsSet up errors was estimated by superimposing a digitally reconstructed radiograph (DRR) as a reference image with an electronic portal image device (EPID). The total errors in the Medio-Lateral (ML), Cranio-Caudal (CC) and Antero-Posterior (AP) directions were compared by t-test. For systematic and random errors, the ratio of variance (F statistic) was used. Margins were calculated using Van Herk formalis. Results208 images (80 DRRs and 128 EPIDs) were assessed. The systematic error ranged from 1.93 to 2.01 mm, 1.26 to 1.39 mm, and 1.20 to 2.94 mm in the x, y and z-axis, respectively. The random error ranged from 2.33 to 2.90 mm, 1.25 to 1.66 mm, and 1.04 to 1.28 mm. The PTV margin according to the Van Herk equation in the x, y and z directions was estimated to be 7.11, 4.64 and 3.90 mm for the cervix uteri and a 6.47, 4.03, and 3.70 mm for the rectum. ConclusionThe use of weekly EPID/DRR allows estimating the setup of the planning target volume (PTV) expansion according to our configuration. In this study, the evaluated set up margin was approximately 8 ​mm in the X-axis, 5 ​mm in Y and Z axis for pelvic conformal radiotherapy.

Evaluation of set-up errors and determination of set-up margin in pelvic radiotherapy by electronic portal imaging device (EPID)

AbstractIntroduction and purpose:The error in set-up of patients is an inherent part of treatment processes. The positioning errors can be used to determine the margins of the planning target volume (PTV) to cover the target volume, while minimising the radiation dose delivered to normal tissues. This study aimed to evaluate random and systematic errors occurring in inter-fraction set-ups of pelvic radiotherapy measured by electronic portal imaging device (EPID) and then to propose the optimum clinical target volume (CTV) to PTV margin in pelvic cancer patients.Materials and methods:This study examined 22 patients treated with pelvic radiotherapy. A total of 182 portal images were evaluated. Population random (σ) and systematic (Σ) errors were determined based on the portal images in three directions (X, Y and Z). The set-up margin for CTV to PTV was calculated by published margin formulae of International Commission on Radiation Units and measurements (ICRU) report No. 62 recommendation and formulas presented by Stroom and Heijmen and Van Herk et al.Results:Systematic set-up errors for radiotherapy to patients ranged between 2·36 and 4·99 mm, and random errors ranged between 1·51 and 2·74 mm. The margin required to cover the target volume retrospectively was calculated based on ICRU 62 and formulas presented by Stroom and Heijmen and Van Herk et al. were used to calculate the range 2·8–5·7 mm, 5·7–11·9 mm and 6·9–14·4 mm, respectively.Conclusion:According to our findings, it can be concluded that by extending the CTV margin by 6·9–14·4 mm, we can ensure that 90% of the pelvic cancer patients will receive ≥ 95% of the prescribed dose in the CTV area.

Evaluation of Setup Errors at the Skin Surface Position for Whole Breast Radiotherapy of Breast Cancer Patients.

We used image-processing software to analyze the setup errors at the skin surface position of breast cancer patients (n=66) who underwent post-operative whole breast irradiation at our hospital in 2014-2015. The sixty-six digital reconstructed radiographs (DRR) were created at the treatment planning for each patient. The lineacgraphies (n=377) were taken after the patients' setup during radiotherapy. The lineacgraphies and DRR were superimposed at the skin surface position for each patient with the image-processing software. We measured the deviations of the isocenters for the nipple-lung (X) direction and craniocaudal (Y) direction and the deviation of the rotation angle of the XY axes between the lineacgraphy and DRR on the superimposed images. The systematic error (μ, Σ) and random error (σ) were calculated from the X and Y deviations and rotation angle deviation. The μ of X, Y, and rotation angle were 0.01 mm, -1.2 mm, and 0.05°, respectively. The Σ of X, Y, and rotation angle were 1.8 mm, 1.5 mm, and 0.9°, respectively. The σ of X, Y, and rotation angle were 2.0 mm, 1.5 mm, and 1.0°, respectively. Our analyses thus revealed that evaluations using image-processing software at the skin surface position in routine breast radiotherapy result in sufficiently small setup errors.

The experience of a developing country using an electronic portal imaging device for the verification of patient positioning and dosimetry in radiotherapy for prostate cancer

AbstractPurposeThis is a retrospective study to evaluate the efficacy and safety of routine use of electronic portal imaging device (EPID) in intensity-modulated radiation therapy for localised prostate cancer.Materials and methodsData from 20 patients with localised prostate cancer treated by radical radiotherapy using intensity-modulated technique in Habib Bourguiba Hospital were analysed to define the action levels for pretreatment planer dose distribution of 100 treatment fields and the set-up errors of 418 portal imaging. Pretreatment planar dose distribution was measured with the EPID. The additional dose from repeated portal imaging was determined with treatment planning system.ResultsFor all 100 fields, the predicted and the measured planar dose distribution agrees well with mean±standard deviation value for γmax=2·31±0·57, γavg=0·36±0·07 and γ%≤1=98·94%±0·71%, respectively. For the evaluation of set-up errors, the mean total errors with 1 SD in the lateral, longitudinal and vertical directions were 0·11±0·44 cm; 0·02±0·37 cm and −0·02±0·21 cm, respectively. The imaging additional dose was evaluated as 1 cGy per monitor unit.ConclusionEPID is a useful tool to verify pretreatment dose distribution and to assess the correct field position without a significant increase in the absorbed dose due to the repetition of portal imaging.

Use of planar kV vs. CBCT in evaluation of setup errors in oesophagus carcinoma radiotherapy

AimThe aim of this study is to evaluate differences in terms of the setup errors observed using kV planar image compared to CBCT for oesophageal cancer patients. BackgroundPlanar kV images are quick to acquire but only allow the observation of bony structures. CBCT allows the evaluation of soft tissues, which includes the oesophagus (and tumour) and OAR, giving a more accurate verification of the positioning. Materials and MethodsAll patients were imaged with both techniques between January 2012 and March 2014 were included in the study (16 patients, 212kV images and 116 CBCT images). Differences between the setup errors observed on the two images modalities were studied. A correlation study between TNM staging, tumour location and immobilization systems with setup errors was also done. Finally, the calculation of systematic and random errors allowed to determine the CTV–PTV margin. ResultsA significant discrepancy (p<0.05) between the setup errors observed with kV and CBCT was observed in the lateral direction. No statistical correlation was found between setup errors and tumour location, immobilization system or TNM staging. The CTV–PTV margin was smaller with CBCT in the vertical (0.6cm vs. 0.9cm) and longitudinal (0.7cm vs. 1cm) directions and smaller with kV for the lateral directions (0.8cm vs. 0.9cm). ConclusionsThe chosen modality influences the setup error observed which will influence the correction applied. Allowing a better observation of the volumes of interest, CBCT should be the modality of choice in this pathology. The CTV–PTV margins could be shrunk if CBCT is used.

EP-1244: Evaluation of setup errors in a randomised study using CBCT & kVkV imaging for prostate radiotherapy

EP-1244: Evaluation of setup errors in a randomised study using CBCT & kVkV imaging for prostate radiotherapy

Evaluation of set-up errors in head and neck radiotherapy using electronic portal imaging

IntroductionThe aim of this study was to evaluate three-dimensional (3D) set-up errors and propose optimum margins for planning target volume (PTV) coverage in head and neck radiotherapy. MethodsThirty-five patients were included in the study. The total number of portal images studied was 632. Population systematic (Σ) and random (σ) errors for the patients with head and neck cancer were evaluated based on the portal images in the caudocranial longitudinal (CC) and left-right lateral (LR) direction measured in the anterior-posterior (AP) field, as well as from the images in the caudocranial longitudinal (CC) and dorsoventral lateral (DV) direction measured in the lateral (LAT) field. The values for the clinical-to-planning target volume (CTV-PTV) margins were calculated using ICRU Report 62 recommendations, along with Stroom's and van Herk's formulae. ResultsThe standard deviations of systematic set-up errors (Σ) ranged from 1.51 to 1.93 mm while the standard deviations of random set-up (σ) errors fell in between 1.77 and 1.86 mm. The mean 3D vector length of displacement was 2.66 mm. PTV margins calculated according to ICRU, Stroom's and van Herk's models were comprised between 1.95 and 6.16 mm in the three acquisition directions. Discussion and conclusionsBased on our results we can conclude that a 6-mm extension of CTV to PTV margin, as the lower limit, is enough to ensure that 90% of the patients treated for head and neck cancer will receive a minimum cumulative CTV dose greater than or equal to 95% of the prescribed dose.

Evaluation of Setup Errors with Daily Image Guidance for Gynecological Cancers

The aim of this study was to assess the setup error with daily image guidance for patients with gynecological cancers treated with external beam radiation (EBRT) and to investigate the difference in setup errors based on body mass index (BMI).

Evaluation of set-up errors using electronic portal imaging in head and neck carcinoma

Evaluation of set-up errors using electronic portal imaging in head and neck carcinoma