Heavy metal contamination in the paddy soils of China is a serious concern because of its health risk through transfer in food chains. A field experiment was conducted in 2014–2015 to investigate the long-term effects of different biochar amendments on cadmium (Cd) and arsenic (As) immobilisation in a contaminated paddy field in southern China. Two types of biochar, a rice-straw-derived biochar (RB) and a coconut-by-product-derived biochar (CB), were amended separately to determine their impacts on rice yield and their efficacy in reducing Cd and As in rice. The two-year field experiment showed that biochar amendments significantly improved the rice yields and that CB is superior to RB, especially in the first growth season. Using a large amount of biochar amendment (22.5tha–1) significantly increased soil pH and total organic carbon, and concomitantly decreased the Cd content in rice grains over the four growth seasons, regardless of biochar type and application rate. Arsenic levels in rice were similar to the control, and results from this study suggest that there was a sustainable effect of biochar on Cd sequestration in soil and reduction of Cd accumulation in rice for at least two years. Biochar amendment in soil could be considered as a sustainable, reliable and cost-effective option to remediate heavy metal contamination in paddy fields for long periods.

Purpose: To evaluate the accuracy of an external immobilisation system in patients receiving radiotherapy for prostate cancer.

Methods: Portal Imaging data were audited in 20 patients treated using an in-house immobilisation system and 20 patients treated using an indexed commercial immobilisation system (Combifix™). Individual and group random and systematic errors were calculated to determine the accuracy of set-up using skin marks alone and with a no-action-level protocol.

Results: The initial results showed a larger systematic error in the Combifix™ in the anterior-posterior direction (2.7 mm) compared with the in-house system (1.5 mm). The possible source of this was identified as the difficulty in accurately aligning the laser to a curved couch top prior to setting the isocentre height. A change in the process of setting the isocentre was introduced, and comparable baseline set-up accuracy was achieved. This was with a systematic error of ≤2.0 mm and a random error ≤1.5 mm of patient position set-up error with skin marks alone, and using the Combifix™. The systematic errors were further reduced to <1 mm with an off-line no-action-level protocol.

Conclusion: Using the Combifix™ system a high level of set-up accuracy was reproduced in routine daily practice.

Ensuring reproducibility in any radiotherapy technique is vital to ensure that a geometric miss does not occur. Patient position and comfort play a major part in the reproducibility of setups.

Purpose: To study the effect on accuracy of the introduction of a bellyboard to the existing prone technique used for radical radiotherapy treatment of prostate cancer.

Materials and Methods: Thirty patients were treated using the bellyboard in the standard method. Portal images were compared with those of a control group of patients who had treatment with no rigid immobilisation. Patients in both groups were males with prostate cancer, who underwent radical radiotherapy treatment. Images were analysed using anatomy matching, and deviations from the isocentre were noted.

Results: Statistical analysis of the results showed no statistical significance between the groups, though within the control group there were more deviations over 0.5 cm from the isocentre position than in the bellyboard group.

Conclusions: Introduction of the bellyboard was seen to be equivalent to the use of the control technique. When the deviations from isocentre position were evaluated for each group, the control group had more deviations over 0.5 cm than the bellyboard group.

Background: A randomised study to investigate whether bilateral arm abduction is superior to unilateral abduction with respect to stability using shifts on treatment as the main outcome measure.

Material and Methods: 50 consecutive female patients were randomised to ipsilateral or bilateral arm abduction. Central lung depth (CLD) and cranial caudal depth (CCD) on the simulator image was compared with that featured on three Electronic Portal Images (EPI) captured during treatment for each patient. Systematic and random errors were analysed with respect to the average translational displacement and standard deviation per patient and per population between the planning image and the EPI.

Results: The CLD average translational displacement in the test group was −1.7 mm (95% CI = −5 to 1.6 mm) Σ pop = 2.3 mm, σ pop = 1.6 mm, and in the control group −1.9 mm (95% CI = −6 to 3 mm) Σ pop = 4 mm, σ pop = 2.1 mm. The average translational displacement of CCD in test group was 0 mm (95% CI = − 5.3 to 5.1 mm) Σ pop = 2.2 mm, σ pop = 2.6 mm. CCD translational displacement was greater in the unilateral arm abduction group at − 1.6 mm (95% CI = −6.7 to 3.4 mm) Σ pop = 3.6 mm, σ pop = 2.4mm.

Conclusion: The reduction in systematic error and inter-patient variability observed in the test group is evidence that bilateral arm abduction is a more stable and reproducible position than unilateral arm abduction. The CCD translational data indicates that patients treated with unilateral arm abduction were moving inferiorly on the breast board. These results support the adoption of bilateral arm abduction as a standard technique.

The accuracy of a range of immobilisation systems for head and neck radiotherapy has been measured. Two types of vacuum-formed shells, and eight thermoplastic systems have been evaluated. For each system, a mask was made for the same volunteer. A non-invasive optical system, using a scanning laser digitiser, was used to measure the displacement of a fiducial marker. The volunteer was asked to move a maximum comfortable distance in each of the superior, inferior, left and right directions, and a scan was taken at each location. Standard deviations, calculated from the maximum range of movements, were in the range of 1.7–2.9mm in the right–left direction, and 0.9–3.0mm in the superior–inferior direction. The smallest movements were measured for the Medtec S-frame, with nine-point fixation. A laser-scanning camera can assess the movement potential for a subject inside an immobilisation device with good accuracy and precision. Because ionising radiation is not used as part of the imaging process, the same subject can be used for several mask systems to assess which is the best one.

Background and Purpose: The aim of this study was to determine set-up accuracy when comparing an Orfit® thermoplastic shell to a traditional acetate shell for the treatment of patients with age related macular degeneration.

Method and Materials: 20 patients with age related macular degeneration were sequentially allocated to be positioned in either an Orfit® shell or a traditional acetate shell (ten patients in each group). On each day of treatment, radiographic portal imaging was used to ascertain accuracy by comparison with the CT image and verification radiograph.

Results: 140 portal images were assessed by three independent readers. Pearson Correlation and ANOVA statistics were performed on the data to assess differences between the two types of shell. Inter- and intraobserver variations were also analysed. Results, for both Orfit® and Acetate, revealed that over 95% of error movements were 2 mm or less.

Conclusions: The study indicates that both devices are of comparable accuracy and that the Orfit® shell is an acceptable method of immobilisation for the treatment of age related macular degeneration.

this paper aims to evaluate the range of techniques available to minimise both interfraction and intrafraction errors. the main interfraction errors are due to changes in volume of the rectum and bladder. intrafraction errors are mainly due to respiration and to a lesser extent cardiac motion. there are various methods of minimising internal organ motion that attempt to permit reduction of the internal margin around the clinical target volume (ctv).

techniques such as rectal balloon insertion and breathing control are evaluated to determine their role in reduction of margins for improved conformal radiotherapy. the paper concludes that rectal balloons have been shown to permit limited reduction of internal margins and morbidity levels. breathing control has not increased reproducibility, but has allowed for reduction in lung morbidity. reduction of margins can only be recommended when using breathing control in conjunction with daily ctv relocalisation.

although these techniques do have a role to play at the moment, it appears that attempting to maintain a static environment within the highly mobile patient is fraught with difficulties and we must accept that there is always going to be motion. rather than attempting to control the position of the tumour, future developments such as adaptive radiotherapy and tomotherapy may account for the movement.