When would you like to be treated?--A short survey of radiotherapy outpatients.

AIMS: To determine whether patients undergoing radiotherapy would choose to attend appointments for a course of treatment scheduled outside the normal working day and working week. MATERIALS AND METHODS: A survey of radiotherapy outpatients was conducted on two single days in late 2005 and early 2006. There were four departments in the first cohort and five in the second cohort. Departments were selected from across the UK and were chosen to reflect both city centre and out of town locations. Six of the nine departments were working extended hours at the time of the survey. The second cohort received a modified questionnaire that included two additional questions relating to appointments at weekends. RESULTS: In total, 471 and 332 questionnaires were returned by the first and second cohorts, respectively. For all age groups, 9.00 am to 12.00 pm was the most preferred time for treatment. Outside the normal working day, the 8.00-9.00 am interval was the most selected, being chosen by 23.4% of respondents. Overall, 32.8% (n=260) of respondents would attend a reasonable appointment time outside the normal working day and 10.7% (n=85) were unsure. On Saturdays, 39.3% (n=130) would attend and 11.5% (n=38) were unsure. For Sundays, 31.1% (n=103) would attend and 10.9% (n=36) were unsure. CONCLUSIONS: There is sufficient support from patients for attendance outside the normal working day to ensure appointment slots would not go unfilled during a moderate extension to the working day. However, the percentage of patients that would attend varied between departments. This demonstrates the need for local evaluation of patient preference before the introduction of extended working hours.

Extended hours working in radiotherapy in the UK.

AIMS: To analyse extended hours working patterns within UK cancer centres and to assess alternatives to the normal 9.00 am to 5.00 pm working day. MATERIALS AND METHODS: Questionnaires were sent to 62 radiotherapy managers in June and July 2005 to survey where extended hours working had been implemented, the objectives for using a longer working day and how departments organised their service issues, including staffing levels, costs and patients. This was followed by visits to six departments that were working extended hours. A second questionnaire sent to 60 radiotherapy physics managers in September 2005 requested information for the hours of daily, monthly and annual megavoltage machine servicing and quality assurance (QA). A third questionnaire was distributed to all radiotherapy outpatients from four departments who attended on a single day of survey in 2005. It looked at patient preference for treatment hours. RESULTS: In total, 57 (92%) radiotherapy managers responded. Thirty-one departments (55%) were working extended hours, 22 (39%) had short-term experience and three (5%) departments had no experience. Increasing capacity to reduce waiting lists was the main reason for working extended hours. The additional hours were predominantly worked by radiographers, with little or no support from the other department disciplines. The servicing and QA spreadsheet was returned by 53% (n=32) of physicists. The average amount of servicing and Quality Assurance (QA) work being scheduled out of hours in each department was 35% (0-100%). The patient questionnaire was completed by 470 patients. When asked if patients would want to come to a reasonable appointment time outside of the normal working day, 29% (n=136) said 'yes' and 12% (n=55) were unsure. CONCLUSION: It was concluded that two shifts covering an 11.5 h working day is a robust alternative to the normal working day, taking into consideration efficient use of radiographers and patient preference for out of hours appointments.

Using combined x-ray and MR imaging for prostate I-125 post-implant dosimetry: phantom validation and preliminary patient work.

Post-implantation dosimetry is an important element of permanent prostate brachytherapy. This process relies on accurate localization of implanted seeds relative to the surrounding organs. Localization is commonly achieved using CT images, which provide suboptimal prostate delineation. On MR images, conversely, prostate visualization is excellent but seed localization is imprecise due to distortion and susceptibility artefacts. This paper presents a method based on fused MR and x-ray images acquired consecutively in a combined x-ray and MRI interventional suite. The method does not rely on any explicit registration step but on a combination of system calibration and tracking. A purpose-built phantom was imaged using MRI and x-rays, and the images were successfully registered. The same protocol was applied to three patients where combining soft tissue information from MRI with stereoscopic seed identification from x-ray imaging facilitated post-implant dosimetry. This technique has the potential to improve on dosimetry using either CT or MR alone.

Radiotherapy to patients with artificial cardiac pacemakers.

BACKGROUND: The in vitro studies show that the modern cardiac pacemakers utilising the complementary metal-oxide semi-conductor (CMOS) circuitry can be adversely affected by therapeutic radiation. However, the published clinical data are sparse regarding the safety of radiotherapy delivery to patients with artificial pacemakers. Despite the potential risk of life threatening complications, there are no national guidelines and most radiotherapy departments have no formal clinical risk management strategy in place. A literature review was performed to assess the risks involved in irradiating patients with pacemakers and to identify strategies, which minimise the risk of pacemaker malfunction. Recommendations for radiotherapy departments are made. CONCLUSION: Modern multi-programmable pacemakers are very sensitive to therapeutic megavoltage irradiation. There is no safe radiation threshold for megavoltage radiation. The low energy kilovoltage X-rays used for radiotherapy simulation cause no pacemaker malfunction. Megavoltage radiation can be safely delivered to patients with cardiac pacemakers provided direct irradiation of pacemakers is avoided, adequate monitoring is done during and after irradiation, and the dose to the pacemaker generator is kept below 2 Gy. Close liaison with cardiologists and a pacemaker clinic is essential and radiotherapy departments should have protocols in place to identify and care for cancer patients with pacemakers.

Practical methods for compensating for missed treatment days in radiotherapy, with particular reference to head and neck schedules.

Unscheduled interruption of a radiotherapy treatment can lead to significant loss in local tumour control, particularly in tumours that repopulate rapidly. General guidelines for dealing with such treatment gaps have been issued by the Royal College of Radiologists and more specific advice on the use of compensation methods has been published previously [Hendry et al., Clin Oncol 1996;8:297-307; Slevin et al., Radiother Oncol 1992;24:215-220]. This article further elaborates on the practical application of these methods. It sets out the main considerations arising in the especially critical case of head and neck treatments and simple calculations are used to illustrate the approaches which may be adapted for particular situations. Radiobiological parameter values are suggested for use in the calculations, but these may require modification in the light of further research in this important area.

Radiation carcinogenesis modelling for risk of treatment-related second tumours following radiotherapy.

Radiobiological modelling of the risk of radiation-induced tumours following high dose radiation implies a general form for the dose-response relationship. Generally, risk will rise with radiation dose at low doses, reach a maximum value and then decline with further increase in dose. The magnitude of risk and the dose at which this risk is maximum are strongly dependent on the kinetics of repopulation by surviving normal and mutant cells and on genetic factors likely to differ between tissues and between individuals. The most reliable way to reduce the risk of second tumours is to reduce radiation dose further at sites where the dose is already low. These sites are usually distant from the primary treatment volume. For illustrative purposes, we have compared the predicted relative risks of second tumours at "distant sites" for treatment plans giving similar dose distributions (dose volume histograms) at the primary site. We suggest that dose reduction to distant sites could be of significant benefit in reducing the risk of second tumours. Further improvement will require more detailed knowledge of the radiation sensitivities and mutagenicities, together with the repopulation kinetics of the various cell lineages within the treatment volume.

Variation in the probability of cardiac complications with radiation technique in early breast cancer.

Cardiac damage is recognized to be a potentially serious side effect of breast cancer radiotherapy, the risk of which may be reduced by the choice of appropriate radiotherapy technique. We have previously described variation in physical dose to the heart dependent upon radiotherapy technique. In this paper we report the calculated improvement in normal tissue complication probability (NTCP) (for cardiac damage) achievable by these methods. Cardiac doses were calculated from dose-volume histograms (DVHs) using a "Helax" planning system for 11 patients with left-sided tumours and 5 patients with right-sided tumours. The DVH reduction algorithm of Lyman and Wolbarst [1989] was applied to each DVH to produce a value for the NTCP. For left-sided tumours, mean NTCP with the standard technique was 7.4 +/- 5.6% (range 0.6-17%) and for the optimum technique mean NTCP was 0.3 +/- 0.6% (range 0-2%) (p < 0.003 for the difference between the two techniques): a predicted reduction in late cardiac complications of 23-fold, which is not clearly evident from viewing the DVH raw data.

The role of biologically effective dose (BED) in clinical oncology.

There are many clinical situations in which radiobiological considerations can be usefully applied and all clinicians should be aware of the potential benefits of developing a quantitative radiobiological approach to their practice. The concept of biologically effective dose (BED) in particular is useful for quantifying treatment expectations, but clinical oncologists should recognize that careful interpretation of modelling results is required before clinical decisions can be made and that there is a lack of reliable human parameters for application in some situations. Correct use of the BED concept will, in more complex treatment situations, sometimes involve the use of multiple parameters and BED calculations. Examples include: 1. Where the dose per fraction is being altered and it is possible that normal tissue tolerance may be compromised, calculations should include two or more alpha/beta ratio values, some being less than 3 Gy, in order to estimate the 'worst case scenario'. 2. A single one-point BED calculation will not be representative of the biological effect throughout a large planning target volume where there are significant 'hot spots'. Multiple BED evaluations are then indicated. 3. Where there are combinations of radiotherapy treatments or phases of treatments, these can be quantitatively assessed by the addition of BEDs, although the volume of tissue is not inherently included in the BED calculation and any high-dose region needs to be separately assessed as in point 2. 4. Allowance for tumour clonogen repopulation during therapy is required for some tumour types. 5. Different histological classes of cancers require the use of different alpha/beta ratios. Where there is reasonable doubt regarding this parameter, a suitable range should be used. The principles involved are illustrated by worked examples. Attention to detail and the examination of ranges of possible results should offer a safer guide to alternative dose fractionation schedules, although the ultimate choice will be tempered by clinical circumstances.

Quantifying effects of lead shielding in electron beams: a Monte Carlo study.

Lead shielding in contact with the patient's skin is often encountered in radiotherapy with electron beams. The influence of the lead shielding on dose distributions in the patient cannot fully be assessed using modern treatment planning systems. In this work the problem of quantifying the effect of lead shielding on dose distributions is addressed. Monte Carlo dose calculations were performed in a half-blocked water phantom shielded by lead, using a realistic model for the fluence of an electron linear accelerator. Electron beam energies of 6-20 MeV and lead thicknesses of 1-7 mm are used for 10 x 10 cm2 and 5 x 5 cm2 fields. The perturbation of the particle fluence and dose distributions in water introduced by the lead shielding is quantified. The effect of oblique electron beams on the dose perturbation is shown. A fictitious clinical example, the shielding of an eye in electron beam treatment, is used to demonstrate the usefulness of Monte Carlo based treatment planning algorithms that can incorporate the effects of lead shielding.

Interstitial iridium-192 implantation for recurrent and/or locally advanced head and neck cancer.

We report our experience with the use of interstitial iridium-192 implantation in the management of patients with recurrent and locally advanced squamous cell carcinoma of the head and neck. Between June 1992 and July 1998 this technique was employed in the management of two groups of patients: (1) a primary group, comprising 42 patients who had presented for the first time with advanced head and neck disease, and had therefore not undergone any previous treatment; and (2) a salvage group of 16 patients with recurrent disease previously treated with external beam radiotherapy (four received therapy to the neck, one to the cheek, eight to the tongue and three to the floor of the mouth). The follow-up in each group was short, ranging from 3 to 56 months. The overall response in the primary group was 38/42 (90%). A complete response was achieved in 35/42 (83%). In the salvage group, the overall response was 13/16 (81%); 4/16 (25%) showed a complete response and 9/16 (56%) a partial response. The estimated percentage surviving at 1 year for patients with primary disease is 70% (95% confidence interval (CI) 54-86). For those receiving salvage therapy the estimated percentage surviving at 1 year is 45% (95% CI 19-71).

Reducing cardiac dose in post-operative irradiation of breast cancer patients: the relative importance of patient positioning and CT scan planning.

Left-sided post-operative radiotherapy fields for the treatment of breast cancer inevitably encompass the heart within the treatment volume, resulting in late mortality which may negate the cause-specific survival advantage of the therapy. The effect of positioning was studied in 11 patients with left-sided tumours and five with right-sided tumours receiving routine post-operative radiotherapy to the breast or chest wall as part of primary therapy for breast cancer. Using the same arrangement of glancing fields for each patient treatment position, the optimum patient positioning resulted in a reduction in cardiac dose compared to our standard patient treatment position. On the left side the reduction in mean cardiac dose was 60% (p < 0.001) and the reduction in maximum dose was 32% (p < 0.001); on the right it was 17% and 31%, respectively. The volume of cardiac tissue irradiated was also reduced for all patients. Using this optimum treatment position, cardiac dose was investigated in a further 10 patients with left-sided tumours and our standard glancing field set-up was compared with 3-dimensional planning. A further reduction of 12% in the mean cardiac dose was achieved. 5 of 10 patients had a further small reduction of 4.6% in the maximum dose and one patient had a further reduction in maximum dose of 58%. In conclusion, sophisticated radiotherapy planning can reduce cardiac doses, but optimum patient positioning is of greater importance. The general application of such relatively simple measures could have a significant positive effect on overall survival from breast cancer.

The linear-quadratic transformation of dose-volume histograms in fractionated radiotherapy.

BACKGROUND AND PURPOSE: Dose-volume histograms (DVHs) are often used in radiotherapy to provide representations of treatment dose distributions. DVHs are computed from physical dose and do not include radiobiological factors; therefore, the same DVH will be computed for a treatment plan whatever fractionation regimen is used. However, dose heterogeneity resulting from variation of daily treatment dose within the volume will have biological effects due to spatial heterogeneity of fraction size as well as total dose. The purpose of the paper is to present a radiobiological (LQ) transformation of the physical dose distribution which incorporates fraction size effects and may be better suited to the prediction of biological effects. METHODS: An analytic formula is derived for the linear-quadratic transformation of a normal distribution of dose to give the corresponding distribution of biologically equivalent dose given as 2 Gy fractions. This allows LQ-transformed DVHs to be computed from physical DVHs. The resultant LQ-DVH depends on the assumed value of the relevant alpha/beta ratio. It is a modified dose distribution (corrected for spatial heterogeneity of fraction size) but does not incorporate time factors or volume effects. RESULTS: The analysis shows that the LQ-transformed distribution is always broader than the distribution of physical dose. Radiobiological 'hot spots' and 'cold spots' are further from the mean than physical distributions would indicate. The difference between conventional DVHs and LQ-transformed DVHs is dependent on the fractionation regimen used. LQ-DVHs for a single dose distribution (treatment plan) can be computed for different fractionation regimens with some simplifying assumptions (e.g. no time-factor-dependence of late effects). Regimens calculated to be radiobiologically equivalent at a single point nevertheless result in non-equivalent LQ-DVHs when spatial variation of daily treatment dose is included. The difference is especially important for tumour sites (such as breast and head and neck) for which considerable dose heterogeneity may occur and for which different treatment regimens are in use. CONCLUSIONS: LQ-DVHs should be computed in parallel with conventional DVHs and used in the evaluation of treatment plans and fractionation regimens and in the analysis of high-dose side-effects in patients.

Calculation of integrated biological response in brachytherapy.

PURPOSE: To present analytical methods for calculating or estimating the integrated biological response in brachytherapy applications, and which allow for the presence of dose gradients. METHODS AND MATERIALS: The approach uses linear-quadratic (LQ) formulations to identify an equivalent biologically effective dose (BEDeq) which, if applied to a specified tissue volume, would produce the same biological effect as that achieved by a given brachytherapy application. For simple geometrical cases, BED multiplying factors have been derived which allow the equivalent BED for tumors to be estimated from a single BED value calculated at a dose reference point. For more complex brachytherapy applications a voxel-by-voxel determination of the equivalent BED will be more accurate. Equations are derived which when incorporated into brachytherapy software would facilitate such a process. RESULTS: At both high and low dose rates, the BEDs calculated at the dose reference point are shown to be lower than the true values by an amount which depends primarily on the magnitude of the prescribed dose; the BED multiplying factors are higher for smaller prescribed doses. The multiplying factors are less dependent on the assumed radiobiological parameters. In most clinical applications involving multiple sources, particularly those in multiplanar arrays, the multiplying factors are likely to be smaller than those derived here for single sources. The overall suggestion is that the radiobiological consequences of dose gradients in well-designed brachytherapy treatments, although important, may be less significant than is sometimes supposed. The modeling exercise also demonstrates that the integrated biological effect associated with fractionated high-dose-rate (FHDR) brachytherapy will usually be different from that for an "equivalent" continuous low-dose-rate (CLDR) regime. For practical FHDR regimes involving relatively small numbers of fractions, the integrated biological effect to tissues close to the treatment sources will be higher with HDR than for LDR. Conversely, the integrated biological effect on structures more distant from the sources will be less with HDR. This provides quantitative confirmation of an idea proposed elsewhere, and suggests the existence of a potentially useful biological advantage for HDR brachytherapy delivered in relatively small fraction numbers and which is not apparent when considering radiobiological effect only at discrete reference points. CONCLUSION: The estimation and direct calculation of integrated biological response in brachytherapy are both relatively straightforward. Although the tabular data presented here result from considering only simple geometrical cases, and may thus overestimate the consequences of dose gradients in multiplanar clinical applications, the methods described may open the way to the development of more realistic radiobiological software, and to more systematic approaches for correlating physical dose and biological effect in brachytherapy.

A linear quadratic analysis of gynaecological brachytherapy.

Four hundred and fourteen patients were treated by radical radiotherapy alone for cervical carcinoma at the Western Infirmary and the Royal Beatson Memorial Hospital between April 1982 and December 1987. All patients received external beam radiotherapy in addition to brachytherapy, using either manually inserted caesium (n = 107) or the Selectron afterloading machine (n = 307). Three mean Selectron dose rates were used: 0.91 Gy/h, 1.195 Gy/h and 1.74 Gy/h. During this period of time, the cumulative radiation effect formula was used to calculate an overall brachytherapy dose reduction to compensate for the increase in point 'A' dose rate. We have compared the local control rates and the incidence of late effects seen in these patients with theoretical parameters calculated using the linear quadratic (LQ) model. This model predicts a small rise in late effects as the dose rate increases, which is also seen in clinical practice; it also predicts a reduction in local control, partially offset by the addition of external beam radiotherapy, which would be most marked for early stage disease. There was a small fall in local control associated with Selectron treatment, but of a smaller size than predicted by the LQ model.

A system for the quality audit of treatment dose delivery in radiotherapy.

Treatment planning is a process requiring the cooperation of a number of different staff groups. The possibility for error is well recognised and quality control procedures are necessary to ensure that the chances of errors in planning leading to incorrect treatments are as low as possible. An audit system is described which is based on the calculation of the dose delivered to the patient using the parameters set for treatment as input data. The calculated dose is compared with the prescribed dose and errors greater than a defined limit are flagged. During a period of 19 months during which this audit procedure has been operating a total of 14 errors in excess of 5% were discovered and corrected, this is approximately 0.5% of the total number of plans checked.

Detection of urine loss using the Exeter recording nappy and other similar devices.

A technical evaluation of the Exeter recording nappy has been carried out with particular reference to (a) linearity, (b) reproducibility of calibration, (c) the effect of variation in the position of moistened zones produced by consecutive leakages and (d) the effect of variation in the electrical conductivity of the liquid detected. The clinical use of the nappy is also discussed. A miniature alarm coupled to a similar pad arrangement has been developed as a training system for the geriatric incontinent patient and patients with neurogenic bladders. A 'pad and pant' version of an enuresis alarm has also been designed which had advantages over the conventional under-sheet type.