An evaluation of MR based deep learning auto-contouring for planning head and neck radiotherapy.

INTRODUCTION: Auto contouring models help consistently define volumes and reduce clinical workload. This study aimed to evaluate the cross acquisition of a Magnetic Resonance (MR) deep learning auto contouring model for organ at risk (OAR) delineation in head and neck radiotherapy. METHODS: Two auto contouring models were evaluated using deep learning contouring expert (DLCExpert) for OAR delineation: a CT model (modelCT) and an MR model (modelMRI). Models were trained to generate auto contours for the bilateral parotid glands and submandibular glands. Auto-contours for modelMRI were trained on diagnostic images and tested on 10 diagnostic, 10 MR radiotherapy planning (RTP), eight MR-Linac (MRL) scans and, by modelCT, on 10 CT planning scans. Goodness of fit scores, dice similarity coefficient (DSC) and distance to agreement (DTA) were calculated for comparison. RESULTS: ModelMRI contours improved the mean DSC and DTA compared with manual contours for the bilateral parotid glands and submandibular glands on the diagnostic and RTP MRs compared with the MRL sequence. There were statistically significant differences seen for modelMRI compared to modelCT for the left parotid (mean DTA 2.3 v 2.8 mm), right parotid (mean DTA 1.9 v 2.7 mm), left submandibular gland (mean DTA 2.2 v 2.4 mm) and right submandibular gland (mean DTA 1.6 v 3.2 mm). CONCLUSION: A deep learning MR auto-contouring model shows promise for OAR auto-contouring with statistically improved performance vs a CT based model. Performance is affected by the method of MR acquisition and further work is needed to improve its use with MRL images.

Carotid dosimetry for T1 glottic cancer radiotherapy.

OBJECTIVE: Radiotherapy for T1 glottic cancer is commonly delivered using a lateral parallel opposed pair of megavoltage photon fields. There is increasing reported evidence of cerebrovascular events due to radiation-induced carotid stenosis. An alternative field arrangement is to use an anterior oblique technique. This study compares the carotid dosimetry between the two techniques and reviews the evidence for the risk of radiation-induced vascular events. METHODS: The radiotherapy plans of 10 patients with T1 glottic cancer treated with an anterior oblique technique were examined for carotid dose. Alternative plans were then created using a parallel opposed pair of fields and the dose to the carotids compared. All patients received 50 Gy in 16 fractions treating once daily, for 5 days in a week. RESULTS: The average of the mean dose to the carotids with the anterior oblique technique was 21 Gy compared with 37 Gy using the lateral parallel opposed pair arrangement (p < 0.0001). CONCLUSION: An anterior oblique field arrangement for the treatment of T1 glottic cancer results in a significantly lower radiation dose to the carotid arteries, which may be clinically important in terms of reducing the risk of cerebrovascular events in long-term survivors. ADVANCES IN KNOWLEDGE: Although the anterior oblique technique for treating early glottic cancers is well described, and it is predictable that the dose received by the carotid arteries should be lower with this technique, to our knowledge this is the first study to quantify that reduction in dose with a series of patients.

A comparison of cyclizine, ondansetron and placebo as prophylaxis against postoperative nausea and vomiting in children.

Nausea and vomiting is a relevant and common problem with unfavourable sequelae in children undergoing some plastic surgery procedures. There is a lack of anti-emetic trials performed in children, with only a few investigating the roles of the older anti-emetic agents such as cyclizine compared with newer ones such as ondansetron. This randomised, controlled, double-blind study examined the effectiveness of a single dose of ondansetron (0.1 mg x kg-1), cyclizine (20 mg) and placebo (normal saline) in the prevention of postoperative nausea and vomiting in 150 children (mean age 3.6 years) undergoing plastic genitourinary procedures. Rates of previous postoperative nausea and vomiting and motion sickness were comparable across the groups. Postoperative vomiting was significantly reduced with ondansetron prophylaxis (p = 0.006) but there was no detectable anti-emetic effect with cyclizine. Furthermore, cyclizine caused pain on injection (p < 0.001).

The effect of carbon fiber couch inserts on surface dose with beam size variation.

There is little evidence in the literature regarding the effects of a carbon fiber insert on beam parameters with beam size variations. We demonstrated this effect and noted the magnitude of the change of surface dose induced. It was shown that use of the carbon fiber insert panel, despite providing minimal attenuation of the primary radiation, significantly decreased the skin-sparing effect. The magnitude of this decrease was relatively larger for smaller beam sizes. The surface dose was nearly 4 times as large when carbon was added to a 10 x 10-cm beam, and nearly double for a 40 x 40-cm beam.

The measurement of kappach factors for application with the IPEMB very low energy dosimetry protocol.

In 1996. the IPEMB issued a new code of practice detailing the procedures by which the output of therapeutic kilovoltage x-ray devices are to be determined. For x-ray beam qualities in the range 0.035-1.0 mm Al half-value thickness (HVL), the equation for converting the instrument reading into absorbed dose to water contained a factor named kch. This was included to account for the change in response of the parallel plate chamber from its calibration conditions free in air to those in the user's measurement phantom. As no data were available with which to quantify this factor at very low energies, the code advised that the user take a value of unity until sufficient data became available upon which to base an addendum. In this work, kch values have been determined for four chambers: two PTW 23344 large volume soft x-ray chambers, one PTW 23342 small volume soft x-ray chamber and a Markus electron chamber. Variations in the value of kch were investigated for changes in FSD, applicator size and beam quality. The water equivalence of the Mix-D phantom used for these measurements was also verified. A comparison of the results for the two PTW 23344 chambers showed no significant differences for any experimental situation, indicating that kch is a factor of chamber design rather than variations in construction. No variation in kch was identified with changes in FSD. A small dependence on applicator size was identified for larger applicators, and this was found to be dependent upon chamber design. The measured values of kch were found to increase with energy and again differences were seen between chamber designs. Overall, the values of kch recorded during these measurements ranged from 1.01 to 1.08. These results highlight a significant underestimation of doses calculated using the very low energy code of practice. This supports the need for further work to confirm these results. and the production of an addendum to the code in its present form.

Idiopathic pulmonary haemosiderosis. The peri-operative anaesthetic management of a patient for open lung biopsy.

The peri-operative anaesthetic management and hazards of a patient with idiopathic pulmonary haemosiderosis are described in association with the relevant known clinical and pathological data.

Temperature alarm and cut-out system for use with heated water humidifiers.

The temperature of the inspired humidified gases of an intubated patient may be monitored accurately, close to the airway, by a commercially available thermistor probe and alarm/cut-out device for use with heated water humidifiers. The apparatus is designed to alarm when the inspired gas temperature exceeds the pre-set temperature and when the thermistor probe is in open or short circuit. When the temperature alarm is activated, the humidifier heater is switched off automatically, thus preventing prolonged transmission of excessively hot gases to the airway. The apparatus has been used successfully in this hospital for several months, requiring minimal observer attention and maintenance.