Study of X-ray field junction dose using an a-Si electronic portal imaging device

Field junctions between megavoltage photon beams are important in modern radiotherapy for treatments such as head and neck and breast cancer. An electronic portal imaging device (EPID) may be used to study junction dose between two megavoltage X-ray fields. In this study, the junction dose was used to determine machine characteristics such as jaw positions and their reproducibility, collimator rotation and the effect of gantry rotation. All measurements were done on Varian linear accelerators with EPID (Varian, Palo Alto, CA). The results show reproducibility in jaw positions of approximately 0.3 mm for repeated jaw placement while EPID readings were reproducible within a standard deviation of 0.4% for fixed jaw positions. Junction dose also allowed collimator rotation error of 0.1 degrees to be observed. Dependence of junction dose on gantry rotation due to gravity was observed; the gravity effect being maximum at 180 degrees gantry angle (beam pointing up). EPIDs were found to be reliable tools for checking field junctions, which in turn may be used to check jaw reproducibility and collimator rotation of linacs.

Rectal filling at planning does not predict stability of the prostate gland during a course of radical radiotherapy if patients with large rectal filling are re-imaged

AIMS

It has been suggested that large rectal filling is associated with an increased risk of prostate motion in radiotherapy. The aim of the present study was to determine if there is a correlation between rectal distension on planning computed tomography and the intrafraction and interfraction stability of the prostate gland during a course of radical radiotherapy for prostate cancer if a protocol was used to rescan patients with excessive rectal diameter during planning.

MATERIALS AND METHODS

The computed tomography planning scans of 89 patients with adenocarcinoma of the prostate treated with conformal radiotherapy were reviewed. All patients had three gold seed fiducial markers implanted into the prostate before planning computed tomography. About one in five patients had repeat computed tomography because their rectum was judged to be too large at the time of the first planning computed tomography. Rectal distension was assessed on planning computed tomography using outlines following European Organization for Research and Treatment of Cancer guidelines by measuring the rectal volume, the average cross-sectional area and the mean anterior-posterior diameter of the rectum. Daily kV images were obtained before and after treatment delivery to determine positional matching of the fiducial markers in the superior-inferior, anterior-posterior and right-left dimensions.

RESULTS

In total, 2860 pre- and post-treatment daily kV image pairs were obtained of 89 patients (average 32.1 image pairs per patient). The median rectal cross-sectional area was 7.3cm(2) (range 2.8-17.1), the median rectal volume was 54.8cm(3) (range 20.9-128.2), and the median anterior-posterior rectal diameter was 3.03cm (range 1.58-8.30). Unifactor linear regression models showed no statistically significant relationship between intra- and interfraction prostate stability and rectal volume on planning computed tomography.

CONCLUSIONS

No statistically significant relationship between rectal distension on planning computed tomography and the intra- and interfraction stability of the prostate gland was identified if patients with a large rectal volume were rescanned for planning.

Second primary cancers in patients with skin cancer: a population-based study in Northern Ireland

Among all 14,500 incident cases of basal cell carcinoma (BCC), 6405 squamous cell carcinomas (SCC) and 1839 melanomas reported to the Northern Ireland Cancer Registry between 1993 and 2002, compared with the general population, risk of new primaries after BCC or SCC was increased by 9 and 57%, respectively. The subsequent risk of cancer, overall, was more than double after melanoma.

Morphine, opioids, and the feline pulmonary vascular bed

BACKGROUND

Opioid-induced vasodepressor responses have been reported in a variety of species and laboratory models. The aim of this study was to ascertain the relative potencies of different clinically relevant opioids compared with traditional vasodepressor agents in the feline pulmonary vascular bed. A second aim was to study the effects of morphine and to identify the receptors involved in the mediation or the modulation of these effects.

METHODS

This was a prospective vehicle-controlled study involving an intact chest preparation of adult mongrel cats. The effects of various opioids, morphine, fentanyl, remifentanil, sufentanil, and meperidine were compared with other vasodepressor agents. Additionally, the effects of L-N(5)-(1-iminoethyl) ornithine hydrochloride (L-NIO) (nitric oxide synthase inhibitor), nimesulide [selective cyclooxygenase (COX)-2 inhibitor], glibenclamide (ATP-sensitive K+ channel blocker), naloxone (non-selective opioid receptor antagonist), and diphenhydramine (histamine H(1)-receptor antagonist) were investigated on pulmonary arterial responses to morphine and other selected agonists in the feline pulmonary vascular bed. The systemic pressure and lobar arterial perfusion pressure were continuously monitored, electronically averaged, and recorded.

RESULTS

In the cat pulmonary vascular bed of the isolated left lower lobe, morphine, remifentanil, fentanyl, sufentanil, and meperidine induced a dose-dependent moderate vasodepressor response and it appeared that sufentanil was the most potent on a nanomolar basis. The effects of morphine were not significantly altered after administration of L-NIO, nimesulide, and glibenclamide. However, the vascular responses to morphine were significantly attenuated following administration of naloxone and diphenhydramine.

CONCLUSION

The results of the present study suggest that sufentanil appears to have slightly more potency and morphine the least of the five opioid agonists studied on a nanomolar basis. Morphine-induced vasodilatory responses appeared to be mediated or modulated by both opioid receptor and histamine-receptor-sensitive pathways.

The impact of different time frames of risk communication on Type 2 diabetes patients' understanding and memory for risk of coronary heart disease and stroke

AIMS

We examined the impact of communicating risk of coronary heart disease (CHD) and stroke, using three time frames (1, 5 or 10 years), on Type 2 diabetic (T2D) patients' understanding of risk of CHD/stroke and their memory for these risks.

METHODS

Patients (N = 95) estimated their risk of developing CHD/having a stroke as a result of diabetes, in one of three time frames. Using the United Kingdom Prospective Diabetes Study Risk Engine and the same time frame, patients were then given individualized, objective risk estimates of developing CHD/stroke. Following explanation of these risks, patients' risk understanding was examined by asking them to report again their risk of developing CHD/stroke. Six weeks later we assessed patient memory for these risks by asking them to recall their actual risk estimates for CHD/stroke.

RESULTS

In all time frames, we successfully reduced participants' originally inflated risk perceptions of CHD (F(1,92) = 73.01, P < 0.001) and stroke (F(1,91) = 119.05, P < 0.001), although the 10-year risk group was the most resistant to correction for both CHD (F(1,90) = 9.32, P < 0.001) and stroke (F(2,88) = 3.97, P < 0.02). Participants' recall of their stroke risk at 6 weeks regressed towards original, inflated risk perceptions for the 10-year group only (F(4,176) = 4.73, P < 0.001).

CONCLUSION

Patients' inflated perceptions of CHD/stroke risk can be easily corrected using shorter (1- or 5-year) risk communication time frames.

Effects of the Diabetes Manual 1:1 structured education in primary care

AIMS

To determine the effects of the Diabetes Manual on glycaemic control, diabetes-related distress and confidence to self-care of patients with Type 2 diabetes.

METHODS

A cluster randomized, controlled trial of an intervention group vs. a 6-month delayed-intervention control group with a nested qualitative study. Participants were 48 urban general practices in the West Midlands, UK, with high population deprivation levels and 245 adults with Type 2 diabetes with a mean age of 62 years recruited pre-randomization. The Diabetes Manual is 1:1 structured education designed for delivery by practice nurses. Measured outcomes were HbA(1c), cardiovascular risk factors, diabetes-related distress measured by the Problem Areas in Diabetes Scale and confidence to self-care measured by the Diabetes Management Self-Efficacy Scale. Outcomes were assessed at baseline and 26 weeks.

RESULTS

There was no significant difference in HbA(1c) between the intervention group and the control group [difference -0.08%, 95% confidence interval (CI) -0.28, 0.11]. Diabetes-related distress scores were lower in the intervention group compared with the control group (difference -4.5, 95% CI -8.1, -1.0). Confidence to self-care Scores were 11.2 points higher (95% CI 4.4, 18.0) in the intervention group compared with the control group. The patient response rate was 18.5%.

CONCLUSIONS

In this population, the Diabetes Manual achieved a small improvement in patient diabetes-related distress and confidence to self-care over 26 weeks, without a change in glycaemic control. Further study is needed to optimize the intervention and characterize those for whom it is more clinically and psychologically effective to support its use in primary care.