A customizable, open-source Winston-Lutz system for multi-target, single isocentre radiotherapy.

Objective. To present and share an open-source system (phantom and software) for verifying the targeting accuracy of linac-based, single-isocenter, multi-target radiotherapy. This quality assurance test extends the traditional Winston-Lutz test, which considers a single target located at isocentre.Approach. Plans for a 3D-printed phantom are provided, which can be customized to accommodate various target (BB) positions. Given BB positions and gantry/collimator/couch combinations, the software generates multi-leaf collimator positions to facilitate multi-target Winston-Lutz (MTWL) plan creation. The software determines deviations between detected and expected BB positions on MV images resulting from MTWL plan delivery. BBs are located using a Hough circle detection algorithm, which is modified to favour the detection of circles: (1) having a reasonable size, (2) that are contained within the radiation field, and (3) having reasonable pixel intensities. Validation was performed in two ways: (1) using synthetic data with zero targeting errors and (2) by measuring real linac targeting errors and comparing against results obtained using a commercial system.Main results. Validation using the synthetic data yielded a mean (maximum) absolute discrepancy of 0.11 mm (0.21 mm), which is comparable to the synthetic phantom resolution (0.2 mm). The mean (maximum) absolute discrepancy compared to the commercial system is 0.13 mm (0.43 mm). These values are similar to results obtained with repeated deliveries of the same MTWL plan with the same phantom setup. Both validation tests yield reasonable results and are therefore considered successful. The MTWL test was performed independently by three physicists on two linacs to investigate repeatability, resulting in a mean (maximum) absolute discrepancy of 0.14 mm (0.51 mm) among the various attempts.Significance. Successful completion of this quality assurance test, using our customizable and open-source system, provides confidence that multi-target, single isocentre radiotherapy treatments can be delivered with sufficient geometric accuracy according to the chosen tolerance level.

Panton-Valentine Leukocidin associated with community acquired methicillin resistant Staphylococcus aureus: a case report and review of interim guidelines.

We report a case of community acquired methicillin resistant Staphylococcus aureus pneumonia. The causative organism was positive for the toxin Panton-Valentine Leukocidin. This resulted in a severe pneumonia requiring a prolonged stay on our intensive care unit. This infection is becoming more common in the United Kingdom. It can cause a far more aggressive illness than the hospital acquired infection with a high mortality if it becomes an invasive infection. The Department of Health has recently produced interim guidelines for its treatment which we have also reviewed.

Sci-Fri AM: YIS-01: Comprehensive MR distortion correction: Phantom validation and in-vivo application.

MR images provide excellent diagnostic information; however, their treatment planning utility is limited due to geometric uncertainties from both system and patient related sources. Despite this concern, interest in developing MR-based treatment planning protocols is on the rise because of the ease with which clinically relevant structures can be identified in MR. Here we present our systematic approach to quantifying both machine (gradient non-linearity and B0 inhomogeneity) and patient (susceptibility and chemical shift) distortions. Gradient non-linearities were previously measured using a 3D grid phantom while the remaining types of distortion were measured using a double gradient echo scan to obtain a B0 distortion map specific to each object/patient. Distortion measurement and correction were validated on phantoms and then implemented on a volunteer. B0 inhomogeneity and susceptibility distortions were simulated by offsetting the x2 -y2 shims; maximum absolute distortion was reduced from 5.4 mm to 1.0 mm and mean (± standard deviation) was reduced from 1.7 ± 1.4 mm to 0.4 ± 0.2 mm. Chemical shift distortion was qualitatively evaluated using a phantom containing fat and water inserts; displacement of the fat signal was much improved following distortion correction. Intensity correction was validated using a uniformity phantom and undistorted image profiles were compared to distorted image profiles and to profiles corrected for geometric and geometric/intensity distortion; the need for intensity correction was clearly demonstrated. Once all types of distortion correction were validated on phantoms, the technique was implemented on a volunteer brain image. Both GE and multi-shot EPI images were corrected.

Fatal brown snake (Pseudonaja textilis) envenomation despite the use of antivenom.

OBJECTIVE: To report two cases of fatal brown snake envenomation in adults despite the use of appropriate antivenom. CLINICAL FEATURES: Two men, aged 42 and 39, one with a history of hypertension, suffered fatal brown snake envenomation in Queensland. One believed he had been stung by a wasp. Both developed cardiorespiratory failure within one hour of the bite, followed by coagulopathy and pulmonary oedema. One patient developed fulminant multiorgan failure. INTERVENTION: Both patients died despite the administration of large doses of appropriate antivenom and full supportive care. CONCLUSION: Brown snake bites remain extremely dangerous despite the availability of specific antivenom. In severe cases associated with myocardial depression and gross coagulopathy, death may occur rapidly despite the use of conventional doses of antivenom. In such patients the antivenom requirement may be much greater than is currently recommended.