Adapting for Adaptive Radiotherapy (ART): The need to evolve our roles as Therapeutic Radiographers.

OBJECTIVES: 4D Adaptive Radiotherapy (4D-ART) has been stated as the future baseline standard-of-care for technical radiotherapy. Its goal is to optimise radiation dose received by 'adapting' to changes 'seen' in each individual patient, for each treatment delivery (fraction), throughout each treatment delivery. The drive for technological developments to achieve this is ongoing. To enhance the potential benefits, we should consider other aspects of the processes needed: How do changes in clinical practices and processes affect the role of the Therapeutic Radiographer? The aim is to raise the need to explore questions of Therapeutic Radiographers roles and responsibilities within 4D-ART. KEY FINDINGS: Moving from using current predictive strategies (such as plan-of-the-day) to being able to dynamically adapt (real-time/4D-ART) for patient changes requires rapid clinical judgements to be made. The question becomes 'who makes these decisions'? Currently Therapeutic Radiographers maybe ideally placed for this. Dynamically adaptive radiotherapy requires Radiographers to have clinical decisions-making skills and authorities within the multi-professional team (MPT). It is not sufficient to train radiographers in the 'how' to use 4D-ART techniques and technologies; the ability to make good clinical judgments comes from understanding the principles supporting this concept by understanding the 'why'. CONCLUSION: To support future service needs and ongoing developments within ART, Radiographer's roles need to adapt and evolve, as well as the way their role is perceived within the MPT. We need to provide Radiographers with the education required, abilities and authorities to act. IMPLICATIONS FOR PRACTICE: Role revision is required to include greater responsibility for clinical decision making for implementing 4D-ART practices.

Practical aspects of implementation of helical tomotherapy for intensity-modulated and image-guided radiotherapy.

AIMS: Image-guided radiotherapy (IGRT) and intensity-modulated radiotherapy (IMRT) represent two important technical developments that will probably improve patient outcome. Helical tomotherapy, provided by the TomoTherapy HiArt system, provides an elegant integrated solution providing both technologies, although others are available. Here we report our experience of clinical implementation of daily online IGRT and IMRT using helical tomotherapy. MATERIALS AND METHODS: Methods were needed to select patients who would probably benefit. Machine-specific commissioning, a quality assurance programme and patient-specific delivery quality assurance were also needed. The planning target volume dose was prescribed as the median dose, with the added criterion that the 95% isodose should cover 99% of the target volume. Although back-up plans, for delivery on conventional linear accelerators, were initially prepared, this practice was abandoned because they were used very rarely. RESULTS: In the first 12 months, 114 patients were accepted for treatment, and 3343 fractions delivered. New starts averaged 2.6 per week, with an average of 17.5 fractions treated per day, and the total number capped at 22. This has subsequently been raised to 24. Of the first 100 patients, 96 were treated with radical intent. Five were considered to have been untreatable on our standard equipment. IGRT is radiographer led and all patients were imaged daily, with positional correction made before treatment, using an action level of 1mm. A formal training programme was developed and implemented before installation. The in-room time fell significantly during the year, reflecting increasing experience and a software upgrade. More recently, after a couch upgrade in April 2009, the mean in-room time fell to 18.6 min. CONCLUSIONS: Successful implementation of tomotherapy was the result of careful planning and effective teamwork. Treatment, including daily image guidance, positional correction and intensity-modulated delivery, is fast and efficient, and can be integrated into routine service. This should encourage the adoption of these technologies.

An assessment of action levels in imaging strategies in head and neck cancer using TomoTherapy. Are our margins adequate in the absence of image guidance?

AIMS: To assess the effectiveness of different on-treatment correction strategies on set-up accuracy in patients with head and neck cancer (HNC) treated on a TomoTherapy HiArt system. To assess the adequacy of clinical target volume (CTV) to planning target volume (PTV) treatment planning margins when treating with intensity-modulated radiotherapy without daily image guidance. MATERIALS AND METHODS: The set-up accuracy measured by daily online volumetric imaging was retrospectively reviewed for the first 15 patients with HNC treated on the TomoTherapy unit at Addenbrooke's Hospital. For each fraction, megavoltage computed tomography was carried out, any discrepancy from the planning scan was noted, and corrected, before treatment. These data were used to evaluate imaging correction protocols using three different action levels. The first three fractions were imaged and used to correct for systematic error, using a 5 mm action level (5 mmAL), a 3 mm action level (3 mmAL), and no action level (NAL). All imaging strategies were applied, to assess the number of fractions that would potentially have exceeded a 5 and 3 mm margin. Systematic and random errors were calculated for the population, assuming the NAL protocol had been applied, and minimum CTV-PTV margins, required to allow for errors attributable only to set-up, were calculated using van Herk's formula. RESULTS: In total, 490 fractions were analysed. Using a 5 mmAL imaging protocol, potentially 198/490 fractions (40%) were outside a 5 mm CTV-PTV margin and 400/490 (82%) were outside a 3 mm margin. Using a 3 mmAL imaging protocol, potentially 67/490 fractions (14%) were outside a 5 mm CTV-PTV margin and 253/490 (52%) were outside a 3 mm margin. A small systematic error was identified in the system; once corrected this would improve these results. Using the NAL imaging protocol, potentially 31/490 fractions (6%) were outside a 5 mm CTV-PTV margin and 143/490 fractions (29%) were outside a 3 mm margin. Estimated minimum CTV-PTV margins to account only for set-up errors, with three-fraction image-guided radiotherapy and a NAL protocol, were 2.8, 3.1 and 4.1 mm in the mediolateral, superior-inferior and anterior-posterior directions, respectively. CONCLUSION: Reducing the action level at which the systematic error is corrected improves the probability of treatment delivery accuracy. Using the NAL correction protocol reduces the number of fractions that have set-up displacements outside a 5 mm CTV-PTV margin. Although a 5 mm margin is probably sufficient for standard HNC radiotherapy, change to a 3 mm margin is not favoured at our centre without access to daily image-guided radiotherapy.

Practical issues in the implementation of image-guided radiotherapy for the treatment of prostate cancer within a UK department.

AIMS: To study the feasibility of using implanted gold seeds in combination with a commercial software system for daily localisation of the prostate gland during conformal radiotherapy, and to assess the effect this may have on departmental workload. MATERIALS AND METHODS: Six patients had three gold radio-opaque seeds implanted into the prostate gland before starting a course of radiotherapy. The seeds were identified on daily portal images and an automated online system provided immediate vector analysis of discrepancies between the planned and actual daily position of the intraprostatic seeds. In total, 138 interfractional displacements were analysed. The workload impact for the department was assessed using the basic treatment equivalence model, by comparing measurements of daily treatment session durations with a control group of patients receiving standard conformal radiotherapy, matched for treatment complexity. RESULTS: No acute complications of seed insertion were observed. A number of developmental issues required solutions to be identified before clinical implementation was possible. The standard deviations of the set-up and organ motion systematic errors in the left-right, superior-inferior and anterior-posterior directions were 2.4, 3.0 and 2.5 mm, respectively. The standard deviations of the set-up and organ motion random errors calculated were 2.5, 2.9 and 3.7 mm. The mean treatment session duration with this daily prostate localisation system was increased by 3 min compared with matched controls using standard imaging practice. If all radical prostate patients in our department were to receive image-guided radiotherapy in this way, this would increase machine workload time by 2.2 h/day. CONCLUSIONS: The implementation of this image-guided system is feasible. No additional linear accelerator modification is required and standard imaging devices can be used. It would be a useful addition to any department's image-guided radiotherapy developmental strategy.

Accuracy of a relocatable stereotactic radiotherapy head frame evaluated by use of a depth helmet.

In high precision radiotherapy, the more accurately the patient can be relocated, the smaller the clinical to planning target volume margin can be, with reduction in the volume of normal tissue irradiated. The Gill-Thomas-Cosman (GTC) relocatable stereotactic head frame provides immobilization of the patient which is highly reproducible. A depth helmet and measuring probe were used to confirm the accuracy of relocation of 31 patients treated in the GTC frame. The measurements were processed in a spreadsheet developed to calculate the size of the patient's displacement as a vector. Twenty-seven patients received fractionated stereotactically-guided conformal radiotherapy, and 4 single fraction stereotactic radiosurgery, amounting to 564 measurement episodes. The accuracy was extremely good, and considerably more accurate than standard thermoplastic head shells. Ninety-two percent of the displacement vectors were less than 2 mm, and 97% less than 2.5 mm. Considering each dimension separately, the largest mean displacement was 0.4 mm in the superior-inferior direction. Accuracy was constant through a fractionated course for most patients, but prediction based on measurements from the first few fractions was not reliable. Results were dependent on patient selection, with worse reproducibility in patients with neurological deficits, or difficulty cooperating. The depth helmet measurements detected a loosened mouth bite in one patient and allowed repositioning to be verified without the need for the simulator. Total treatment time, including use of the depth helmet to verify treatment position, is quicker (mean 15.7 min) than using portal films. The depth helmet, used in conjunction with the vector displacement spreadsheet, provides a simple way to define the CTV-PTV margin. For fractionated stereotactic radiotherapy we use a 3 mm CTV-PTV margin. This system could assist technology transfer to centres starting stereotactic radiotherapy using the GTC frame.

Total body irradiation using a modified standing technique: a single institution 7 year experience.

We describe a simple standing technique for delivering total body irradiation (TBI) using large horizontal fields, made possible by the off-centre installation of a non-dedicated treatment unit in a pre-existing bunker. Patients are treated using anterior and posterior fields with customized lung compensators. This technique enables the dose to the lung to be accurately calculated and modified to avoid overdose and to minimize the risk of pneumonitis. From February 1991 to December 1997, 94 patients with a variety of haematological malignancies were given fractionated TBI using this technique prior to allogenic or autologous bone marrow transplantation. Patients received a total dose of 14.4 Gy given in eight fractions over 4 days, with at least 6 h between fractions. The prescribed dose to the lungs was reduced to 12 Gy in eight fractions. The technique was well tolerated, took less than 10 min to set up and did not disrupt the daily routine use of the machine. Doses to all measured points on the trunk and head were within +/-6% of the prescribed dose. Doses to the lungs were within +/-5% of the prescribed dose. There were no early respiratory deaths in the 37 autologous transplant patients. There were 10 (17%) respiratory deaths in the 57 allogeneic transplant patients, 3 of confirmed infectious aetiology.

A tool to measure radiotherapy complexity and workload: derivation from the basic treatment equivalent (BTE) concept.

Radiotherapy workload is poorly represented by simple parameters of patients, fractions or fields treated because these do not contain any measure of treatment complexity. However, complexity is increasing and there is an urgent need to quantify this. We have evaluated the basic treatment equivalent (BTE) model as a measure of radiotherapy workload and complexity. Radiotherapy treatment times, from the patient entering to exiting the treatment room maze, were measured for 1298 treatment sessions on 269 patients. The data were used to assess the original model and derive three new models for predicting treatment duration. The most complicated, the 'Addenbrooke's complex model', contained two additional predictor variables, including 'site/technique', in a linear additive form. Before the study, the department used a standard treatment appointment time of 10 minutes. However, 50% of the measured treatments took longer than 10 minutes, (mean 10.9). Summed over the working day, this discrepancy indicates that a standard 10-minute appointment is a poor basis for scheduling radiotherapy. The original BTE model was effective in predicting treatment times, although this was improved by refinement of the model. The Addenbrooke's complex model correctly predicted 70% of treatment times to within 2 minutes (55% for the original BTE model), 80% to within 2.5 minutes and 95% to within 4.7 minutes. The percentage of the variation in observed times accounted for by the model is 59.4%. The models can represent radiotherapy complexity, can improve scheduling on linear accelerators, and are likely to be applicable to other departments. They are thus tools to assess the impact of changes in complexity from new techniques, trial protocols (e.g. the Medical Research Council prostate radiotherapy trial RTO1), and possible time saving from advanced technology such as multileaf collimators (MLCs) or automated machine set-up. The replacement of manually-lifted shielding blocks by MLCs should save 1.1-1.5 minutes for a three- or four-field pelvic plan (i.e. 12%-13%). The models could also be used to aid planning for future linear accelerator provision and for costing radiotherapy treatment.