During the planning computed tomography (CT) scan, patients experience the position and any immobilisation technique required for radiotherapy.

Patient’s stress and anxiety can cause muscle tension that can introduce systematic set-up errors if not recognised and corrected.

We discuss two clinical cases that highlight the importance of time dedicated to communication and revision of the first CT acquisition during a virtual simulation procedure.

Previous researches on analysis of stability of haptic simulation largely assume that the virtual environment is passive. But the virtual environment can become non-passive due to various reasons including discretization errors and interaction dynamics between virtual tools and objects. This paper provides an analysis of the stability and performance of the haptic simulation involving non-passive virtual environment. The dynamic interaction between the virtual tools and the objects is modeled using the two-port networks. The analysis is carried out using a velocity and force mapping matrix for six-DOF simulation. New stability condition resulting from the analysis is applied to an example simulation of a one-DOF virtual wall. Maximum stiffness satisfying the stability condition established in the previous literature, and the proposed condition is compared with the maximum stiffness experimentally determined with various time steps. The newly proposed stability condition manifests less standard deviation of errors than the widely applied absolute stability condition.

Background: The rapid changes in practice of radiotherapy have taken place over the past 5 years in Pakistan. With advent of computed tomography simulator, and multileaf collimators–assisted linear accelerators and electronic portal imaging system, few centres in Pakistan have switched from conventional radiotherapy to modern computer-based technology. Our hospital is first centre in Pakistan which is using virtual simulation since March 2006. We present our experience with list of merits and demerits.

Design: Retrospective study.

Patient collection: Medical records of all patients who received radiotherapy in our centre were reviewed. Parameters included were type of malignancy, type radiotherapy (curative/palliative), simulation and planning process time and the displacement of the beam-axis from the planning isocentre in clinical situations during three-dimensional conformal radiotherapy using electronic portal imaging device (EPID). Data were collected on written proforma. Percentages, frequencies, measures of central tendency and dispersion were calculated using SPSS version 17.0.

Results: A total of 289 patients were treated from March 2006 to November 2008. Transitional cell carcinoma of urinary bladder was most common malignancy seen (42.4%) followed by prostate (28.62%) and renal cell carcinoma (14.14%). Of these 34.26% patients were treated on curative basis. The virtual simulation process could be completed in an average time of 5 min (SD 3.5). Under many cases, the treatment portals could be designed and the patient marked in one session. The displacements were recorded for 43 portals for early prostate cancer using an EPID system. The mean displacement was found 2.44 ± 0.8 mm in x (transverse), y (craniocaudal), and z (anteroposterior) directions during treatment. Standard deviation (SD) was 0.87 (90% CI 2.21–2.66). Average number of portals taken was 10 (6–27) per treatment session.

Conclusion: Computer-based simulation and treatment over conventional methods is appropriate for curative patients, achieving more accurate tumour localisation, sparing normal organs at risk, reduced field sizes and a film free environment; however efforts are required to achieve maximum immobilisation during treatment.

Background and purpose: Currently, optimal use of virtual simulation for all treatment sites is not entirely clear. This study presents data to identify specific patient groups for whom conventional simulation may be completely eliminated and replaced by virtual simulation.

Sampling and method: Two hundred and sixty patients were recruited from four treatment sites (head and neck, breast, pelvis, and thorax). Patients were randomly assigned to be treated using the usual treatment process involving conventional simulation, or a treatment process differing only in the replacement of conventional plan verification with virtual verification. Data were collected on set-up accuracy at verification, and the number of unsatisfactory verifications requiring a return to the conventional simulator. A micro-economic costing analysis was also undertaken, whereby data for each treatment process episode were also collected: number and grade of staff present, and the time for each treatment episode.

Results: The study shows no statistically significant difference in the number of returns to the conventional simulator for each site and study arm. Image registration data show similar quality of verification for each study arm. The micro-costing data show no statistical difference between the virtual and conventional simulation processes.

Conclusions: At our institution, virtual simulation including virtual verification for the sites investigated presents no disadvantage compared to conventional simulation.