Using an EPID for patient-specific VMAT quality assurance.

PURPOSE: A patient-specific quality assurance (QA) method was developed to verify gantry-specific individual multileaf collimator (MLC) apertures (control points) in volumetric modulated arc therapy (VMAT) plans using an electronic portal imaging device (EPID). METHODS: VMAT treatment plans were generated in an Eclipse treatment planning system (TPS). DICOM images from a Varian EPID (aS1000) acquired in continuous acquisition mode were used for pretreatment QA. Each cine image file contains the grayscale image of the MLC aperture related to its specific control point and the corresponding gantry angle information. The TPS MLC file of this RapidArc plan contains the leaf positions for all 177 control points (gantry angles). In-house software was developed that interpolates the measured images based on the gantry angle and overlays them with the MLC pattern for all control points. The 38% isointensity line was used to define the edge of the MLC leaves on the portal images. The software generates graphs and tables that provide analysis for the number of mismatched leaf positions for a chosen distance to agreement at each control point and the frequency in which each particular leaf mismatches for the entire arc. RESULTS: Seven patients plans were analyzed using this method. The leaves with the highest mismatched rate were found to be treatment plan dependent. CONCLUSIONS: This in-house software can be used to automatically verify the MLC leaf positions for all control points of VMAT plans using cine images acquired by an EPID.

Level-set segmentation of pulmonary nodules in megavolt electronic portal images using a CT prior.

PURPOSE: Pulmonary nodules present unique problems during radiation treatment due to nodule position uncertainty that is caused by respiration. The radiation field has to be enlarged to account for nodule motion during treatment. The purpose of this work is to provide a method of locating a pulmonary nodule in a megavolt portal image that can be used to reduce the internal target volume (ITV) during radiation therapy. A reduction in the ITV would result in a decrease in radiation toxicity to healthy tissue. METHODS: Eight patients with nonsmall cell lung cancer were used in this study. CT scans that include the pulmonary nodule were captured with a GE Healthcare LightSpeed RT 16 scanner. Megavolt portal images were acquired with a Varian Trilogy unit equipped with an AS1000 electronic portal imaging device. The nodule localization method uses grayscale morphological filtering and level-set segmentation with a prior. The treatment-time portion of the algorithm is implemented on a graphical processing unit. RESULTS: The method was retrospectively tested on eight cases that include a total of 151 megavolt portal image frames. The method reduced the nodule position uncertainty by an average of 40% for seven out of the eight cases. The treatment phase portion of the method has a subsecond execution time that makes it suitable for near-real-time nodule localization. CONCLUSIONS: A method was developed to localize a pulmonary nodule in a megavolt portal image. The method uses the characteristics of the nodule in a prior CT scan to enhance the nodule in the portal image and to identify the nodule region by level-set segmentation. In a retrospective study, the method reduced the nodule position uncertainty by an average of 40% for seven out of the eight cases studied.

Cardiac function after chemoradiation for esophageal cancer: comparison of heart dose-volume histogram parameters to multiple gated acquisition scan changes.

In this paper we determine if preoperative chemoradiation for locally advanced esophageal cancer leads to changes in cardiac ejection fraction. This is a retrospective review of 20 patients treated at our institution for esophageal cancer between 2000 and 2002. Multiple gated acquisition cardiac scans were obtained before and after platinum-based chemoradiation (50.4 Gy). Dose-volume histograms for heart, left ventricle and left anterior descending artery were analyzed. Outcomes assessed included pre- and postchemoradiation ejection fraction ratio and percentage change in ejection fraction postchemoradiation. A statistically significant difference was found between median prechemoradiation ejection fraction (59%) and postchemoradiation ejection fraction (54%) (P = 0.01), but the magnitude of the difference was not clinically significant. Median percentage volume of heart receiving more than 20, 30 and 40 Gy were 61.5%, 58.5% and 53.5%, respectively. Our data showed a clinically insignificant decline in ejection fraction following chemoradiation for esophageal cancer. We did not observe statistically or clinically significant associations between radiation dose to heart, left ventricle or left anterior descending artery and postchemoradiation ejection fraction.

Do the psychiatric patients reject themselves?

Five statements measuring social distance from and prejudice against the ex-mentally ill were read to 137 psychiatric patients and relatives from urban background. Their agreement and disagreement with the five statements was analysed and compared with controls from an orthopaedic clinic.Maximum social distance was found on statements about establishing marital relationship with an ex-mental patient. The social distance was found less frequently in working in a mental hospital; sharing same house, falling in love and working with an ex-mental patient respectively. The psychiatric patients and their relatives are more rejecting than the controls.

Dhat syndrome: a culture-bound sex neurosis of the orient.

The Indian Dhat syndrome is a culture-bound symptom complex. The clinical picture includes severe anxiety and hypochondriasis. The patient is preoccupied with the excessive loss of semen by nocturnal emissions. There is a fear that semen is being lost, and mixed in urine. A study was carried out to investigate the cultural basis of the Dhat syndrome. One hundred and seven respondents from the general public were interviewed. A vignette describing an individual having nocturnal emissions was read aloud to the respondents. Attitudes toward nocturnal emission, its causes, and its management were investigated. A large segment of the general public from all socioeconomic classes believed that semen loss is harmful. Seminal fluid is considered an elixir of life both in the physical and in the mystical sense. Its preservation guarantees health, longevity, and supernatural powers. This belief is more frequent in lower socioeconomic classes. The susceptible individual reacts to the prevalent belief system and to the fears of semen loss. The symptoms usually disappear if the misconceptions about semen loss are effectively dealt with. It is expected that with increasing literacy and progress in sex knowledge the syndrome will become less common.