摘要:

The radiation protection supervisor (RPS) is a position required by the Ionising Radiation Regulations of 1985 [1]. This position continues a role which was a requirement of the previous UK regulations prior to European directives.

DOI:10.1259/0007-1285-69-825-791

出版商:The British Institute of Radiology    

年代:1996

数据来源: WILEY

摘要:

This meeting, organized by the Radiation Protection Committee of the British Institute of Radiology, was held on 22 April, 1996. The programme gave both new recruits to diagnostic radiology and established radiologists the opportunity to learn or refresh their knowledge of radiation protection matters. To this end papers were invited from a range of speakers on diverse topics such as measurement of dose, risk, dose saving methods and hazards. Much is happening in radiation protection matters with improved understanding of the radiobiology of radiation effect and the realization that there is no safe dose threshold. This has led to significant change in radiation safety legislation and guidance. Hence it was rather disappointing that so few radiologists were prepared to spend a day learning about the dangers of the product with which they make their living.

DOI:10.1259/0007-1285-69-825-793

出版商:The British Institute of Radiology    

年代:1996

数据来源: WILEY

摘要:

AbstractThe cell kinetic responses of the epithelia of the skin, oral mucosa and intestine to photon irradiation are reviewed. One of the fundamental assumptions made in the development of mathematical models, used to predict the acute response of normal tissues to changes in fractionation protocols, is “equal effect per fraction”. There is now accumulating cell kinetic data to indicate that this assumption is unlikely to be valid. The implications of these findings are discussed.

DOI:10.1259/0007-1285-69-825-795

出版商:The British Institute of Radiology    

年代:1996

数据来源: WILEY

摘要:

AbstractThe clinical and radiological features of seven patients presenting with cholecystocolic fistulae are reviewed. The majority of the patients were elderly (age range 43–85 years, mean 70.7 years) and there was a female preponderance (6:1). The condition usually has a benign clinical course. Diarrhoea was the most common presenting symptom and the typical clinical features of gallbladder disease were absent. Cholangitis occurred in only one patient. The time between onset of symptoms and diagnosis varied from 1 week to 2 years (mean 22 weeks). In only one patient was the diagnosis of biliary–intestinal fistula suspected on the basis of the plain abdominal radiograph (Case 5). A diagnosis of cholecystocolic fistula was established by barium enema (5 cases), endoscopic retrograde cholangiopancreatography (ERCP) (1 case) and diagnostic laparotomy (1 case). The only cause identified in this series was acute or chronic cholecystitis.

DOI:10.1259/0007-1285-69-825-804

出版商:The British Institute of Radiology    

年代:1996

数据来源: WILEY

摘要:

AbstractRenal artery stenosis (RAS) is the commonest secondary cause of hypertension and may result in renal ischaemia with resultant renal failure. Recent studies have suggested that colour Doppler ultrasound, with spectral analysis of the intrarenal waveforms, can identify those patients with a significant RAS. A prospective study was performed in which colour Doppler ultrasound was compared with angiography in 73 patients (143 kidneys) presenting for renal angiography. Colour Doppler ultrasound was unsuccessful in 16% of kidneys due to a combination of technical failures and small kidney size. Accessory renal vessels were present in 14% of kidneys on angiography but none was detected by ultrasound. Of the 120 kidneys that had both examinations, no significant difference in intrarenal pulsatility or resistive index was noted between the angiographically stenosed and normal arteries. There were significant differences for intrarenal peak and end diastolic velocities, and acceleration time and index. Of these measurements, acceleration time was the best indicator of RAS. The probability of detecting a high grade RAS in an individual patient did not reach 90% until the acceleration time was prolonged to more than 0.12 s. Intrarenal colour Doppler ultrasound is not a general screening test for RAS and it should be reserved for selected patient groups where the incidence of disease is high Patients with prolonged acceleration times of more than 0.12 s have a high likelihood of at least 70% RAS and should proceed directly to angiography.

DOI:10.1259/0007-1285-69-825-810

出版商:The British Institute of Radiology    

年代:1996

数据来源: WILEY

摘要:

AbstractDevelopment of dual energy X-ray absorptiometry (DXA) scanners with multidetector array technology has resulted in greatly shortened scanning times. The Hologic QDR-4500 includes an ultrafast (10 s) “turbo” scan mode recommended by the manufacturer for fast screening studies or as an aid to positioning the patient prior to scanning using the normal fast (30 s), medium (1 min) or high definition (2 min) modes. The suitability of the turbo mode for use in routine clinical studies was assessed by examining the concordance of bone mineral density (BMD) measurements obtained in this mode with measurements obtained using the three normal scanning modes. Studies in 151 female patients showed statistically significant discrepancies in four out of the six scan sites studied with systematic differences of 2.9% and 3.1% being observed for the posteroantenor (PA) spine and intertrochanteric region of the hip, respectively.In vivoprecision for the 10 s scan found by performing duplicate measurements on 37 patients had a coefficient of variation of 1.3% for PA spine and 2.5% for femoral neck BMD. An investigation of the dependence of precision on body mass index (BMI) shows that the precision of spine and hip BMD was adversely affected with increasing BMI but the trend was statistically significant only in the spine. It was concluded that turbo mode scans are acceptable for routine clinical studies of the spine and hip but should not be used for longitudinal studies or patients with BMI greater than 30 kg m−2.

DOI:10.1259/0007-1285-69-825-816

出版商:The British Institute of Radiology    

年代:1996

数据来源: WILEY

摘要:

AbstractAutopsy and pathology studies have shown that the caudal portion of the prostate gland harbors tumour in 64–75% of specimens examined. Accurate localization of the prostatic apex may be important in improving local control with external beam radiation therapy. We compared the location of the apex obtained with CT based treatment planningversuslocalization using retrograde urethrography in 32 consecutive patients. The prostatic apex, localized by CT and retrograde urethrography, was compared relative to the ischial tuberosities and the symphysis pubis. Discordance between the location of the prostatic apex as defined on CT scan and retrograde urethrography was found in 50% of patients evaluated. There was 31% discordance between the location of the prostatic apex as defined on CT and retrograde urethrography when data were analysed with the location of the prostatic apex 1 cm above the narrowing on urethrography, a definition others have suggested. The urethrogram defined prostatic apex, as compared with the CT definition, necessitated the treatment of more of the surrounding normal tissues in 31% of our cases, with four-field techniques. Comparison of dose–volume histograms of the bladder, rectum and penis irradiated for target volumes defined by CTversusretrograde urethrography showed that more penis was irradiated in some patients with the urethrogram defined prostatic apex; irradiation of the base of the penis could be relatively avoided by using a six-field treatment plan instead of the standard four-field box. There is discordance between the CT and urethrogram defined prostatic apex. Dose-volume histogram information suggests that differences in apex localization can significantly affect doses to normal adjacent prostatic tissues. Combining CT localization with the urethrogram localization of the prostatic apex optimizes radiotherapy planning and dose delivery.

DOI:10.1259/0007-1285-69-825-821

出版商:The British Institute of Radiology    

年代:1996

数据来源: WILEY

摘要:

AbstractThe rate of loss of tumour control (dp/dt) with extension of treatment time is analysed to assess the relative contributions of radiobiological parameters (radiosensitivity, clonogen doubling time, clonogen numbers and fractionation schedule) on such loss. Linear quadratic modelling and Poisson statistics are used to study individual tumour responses. A heterogeneous tumour population is constructed by the use of random sampling techniques to allow for variations in intrinsic radiosensitivity and clonogen doubling times. Average tumour control probability is calculated for this population for two different fractionation schedules (60 Gy in 30 fractions and 50 Gy in 15 fractions), each given over 15–60 days. The magnitude of dp/dtwill depend upon the tumour cure probability (P): the loss of control will be most significant for tumours which have a cure of 37% when the Poisson survival model is used. The analysis suggests that compensation for short unscheduled treatment gaps (e.g.by increasing the total dose or rescheduling with use of weekend treatment sessions) may only be required for difficult tumours (i.e.radioresistant and/or with short clonogen doubling times). Where pre-treatment clonogen numbers are relatively low as in small volume tumours or after surgical debulking, the model predicts that correction for short treatment gaps is probably not required if the average effective clonogen doubling times are longer than 5 days. Different dose–time–fractionation schedules, even though producing similar overall cure rates in clinical practice, may actually be achieving cures in different subpopulations within a population of tumours, since the value of dp/dtin each individual tumour will depend upon the set of radiobiological parameters given above. For a hypothetical randomly selected heterogeneous tumour population the predicted rates of loss of tumour control produced by an extension in treatment time are 0.9 and 1.1% per day, respectively, for the above fractionation schedules. These values are close to those reported in the clinical literature for the first 2 weeks of treatment prolongation (1–2% per day for squamous cell carcinomas). The Poisson method, when combined with random sampling techniques, consequently provides realistic data. Modelling of this clinical problem provides an insight into how tumour sub-populations, each characterized by its own set of radiobiological parameters, can influence the overall rate of loss of tumour control in a heterogeneous population. Random sampling techniques should be considered as necessary precursors for the assessment of the choices of dose/fractionation in future clinical trials particularly when more precise data regarding the radiobiological parameters and their statistical variations become available.

DOI:10.1259/0007-1285-69-825-830

出版商:The British Institute of Radiology    

年代:1996

数据来源: WILEY

摘要:

AbstractEffects on the heart constitute a potentially significant and serious clinical problem in primary radiation therapy of early breast cancer. Increased cardiac mortality among irradiated patients may offset the potential benefit in terms of a reduced risk of recurrence or of death from breast cancer. Clinical data on long-term cardiac mortality among breast cancer patients included in two randomized trials (the Stockholm and Oslo studies) of radiation therapy as an adjunct to primary surgery were analysed using the relative seriality model of radiation response. Five different radiation therapy techniques were used in the trials. The original treatment plans were recalculated on a group of model patients using a three-dimensional treatment planning system. A mean dose–volume histogram (DVH) was calculated for each treatment technique. Both heart and myocardium,i.e.excluding circulating blood within the heart, were separately investigated as risk organs. Model parameters (D50,i.e.the dose giving 50% complication probability, γ,i.e.the maximum relative slope of the dose–response curve;s, describing the organ relative seriality) were determined by a χ2fitting of the calculated probability of excess cardiac mortality, based on the DVHs, to the incidence data. Computed complication probabilities for each treatment technique were modelled within the 95% confidence interval (CI) of the clinical incidence data. It was shown that the relative seriality model, assuming a homogeneous radiation sensitivity within the volume of the heart/myocardium can be used to describe the incidence data. A small dependence on the volume was found. The results do not, however, exclude the possibility that more sensitive structures within the myocardium are the main target for radiation.

DOI:10.1259/0007-1285-69-825-839

出版商:The British Institute of Radiology    

年代:1996

数据来源: WILEY

摘要:

AbstractA high frequency of osteoradionecrosis after hyperfractionated radiotherapy (RT) of head and neck tumours led to a detailed analysis of risk factors in the dental, surgical, and radiotherapeutic areas 168 patients with oral cancer were analysed retrospectively. 19% of them had been irradiated primarily and 81% post-operatively. 116 patients received a total dose mostly ranging from 60 Gy to 70 Gy to the ICRU 29 reference point (daily single dose 2 Gy). 52 patients were treated hyperfractionally with two daily fractions of 1.2 Gy per day, 4 h minimum apart and a total dose 82.8 Gy. Dental findings could be evaluated in 126 patients. Factors were checked for prognostic significance for osteoradionecrosis (ORN). Dose dependency was computed using a PROBIT analysis. Dental status before radiotherapy was generally poor (mean 11/32 teeth present, of these 1 was dead, 2.4 carious, 2.4 loose, 0.3 destroyed). On average, six teeth (range 0–27 teeth) had to be extracted. In one-third of the patients bone surgery was necessary. ORN occurred in 8.6% of the patients treated conventionally but in 22.9% of those treated hyperfractionally (p= 0.029). Biologically effective dose (p= 0.032) and deep paradontitis (p= 0.034) proved to be significant risk factors for ORN. PROBIT analysis showed a steadily rising dose dependency of the ORN frequency after conventional radiotherapy. Using total doses up to 70 Gy the frequency of ORN was 8.6%. Dose escalation using hyperfractionation led to an intolerable ORN frequency (22.9%) where a short interfraction interval was a significant factor. The use of this dose fractionation was therefore discontinued in 1992.

DOI:10.1259/0007-1285-69-825-847

出版商:The British Institute of Radiology    

年代:1996

数据来源: WILEY