摘要:

We have investigated the reproducibility of dynamic contrast enhanced imaging techniques in nine patients with cerebral glioma. Patients were imaged twice with a 2 day interval between scans. Maps were produced of the time taken to achieve 90% enhancement (T90), the maximal intensity change per time interval ratio (MITR), the volume transfer coefficient between plasma and the extravascular extracellular space (Ktrans) and the extravascular extracellular contrast distribution volume,ve. Measurements ofKtransgreater than 1.2 min−1were used to exclude pixels where first pass perfusion effects dominated the measurement. Measures of the test–retest coefficient of variation (CoV) and intraclass correlation coefficients were used to assess reproducibility for measurements from a volume of interest containing enhancing tissue from the whole tumour. MITR showed poor reproducibility (mean CoV 17.9%, 95% confidence limits for group comparisons 20.2%). T90 showed good reproducibility (mean CoV 7.1%, 95% confidence limits for group comparisons 5.2%). Calculated values ofKtransandvealso showed good reproducibility (mean CoV 7.7% and 6.2% respectively, 95% confidence limits for group comparisons 6.2% and 4.8%, respectively). We conclude that the measurements ofKtransandvederived from pharmacokinetic analysis are sufficiently reproducible to support their use as a biological markers in therapeutic trials.

DOI:10.1259/bjr/70653746

出版商:British Institute of Radiology    

年代:2003

数据来源: WILEY

摘要:

The commissioning of a Pinnacle3treatment planning system is described. Four Elekta linear accelerators were commissioned for external beam photons. Measured data were used to derive parameter values for the Pinnacle3beam model by (1) fitting a Monte Carlo model of the accelerator head to measured data and then extracting the parameters for the Pinnacle3beam model, and by (2) using the auto-modelling facility within Pinnacle3. Both of these methods yielded dose distributions in accord with published recommendations. A separate small-field beam model, customized for an in-house compact blocking system, was also created, which satisfied appropriate acceptance criteria for stereotactically guided conformal brain treatments. Inhomogeneous, oblique, asymmetrical and irregular fields were also assessed, with calculated and measured doses agreeing to within ±3%. Dose–volume histogram calculation was found to be accurate to within ±5% dose or volume for a grid size of 4 mm × 4 mm × 4 mm, with better accuracy being achieved for finer grids. Isocentric doses were compared between Pinnacle3's collapsed cone convolution algorithm and the Bentley–Milan algorithm within the Target-2 treatment planning system. Dose differences were generally less than 3% in the dose prescribed, with larger values for breast plans, where the Pinnacle3algorithm calculated scatter more accurately. Pelvic and thoracic plans were also verified using an anthropomorphic phantom, with local dose differences between calculated and delivered dose of up to 8%, but mainly less than 3%, and with no systematic difference. Ionization chamber verifications using START and RT-01 trial procedures demonstrated differences between calculated and measured doses of less than 2%. Following satisfactory performance in the commissioning process, Pinnacle3has now been introduced into routine clinical use.

DOI:10.1259/bjr/42085182

出版商:British Institute of Radiology    

年代:2003

数据来源: WILEY

摘要:

A Monte Carlo program has been developed that incorporates a voxel phantom of an adult patient in a model of the complete X-ray imaging system, including the anti-scatter grid and screen–film receptor. This allows the realistic estimation of patient dose and the corresponding image (optical density map) for a wide range of equipment configurations. This paper focuses on the application of the program to lumbar spine anteroposterior and lateral screen–film examinations. The program has been applied to study the variation of physical image quality measures and effective dose for changing system parameters such as tube voltage, grid design and screen–film system speed. These variations form the basis for optimization of these system parameters. In our approach to optimization, the best systems are those that can match (or come close to) the calculated image quality measure of systems preferred in a recent European clinical trial, but with lower patient dose. The largest dose savings found were 21% for a 400 speed class system with a grid having a strip density of 40 cm−1and a grid ratio of 16. A further dose saving of 13% was possible when a 600 speed class system was employed. The best systems found from the optimization correspond to those recommended by the European Commission guidelines on image quality criteria for diagnostic radiographic images.

DOI:10.1259/bjr/52734084

出版商:British Institute of Radiology    

年代:2003

数据来源: WILEY

摘要:

The objective of this study was to investigate the influence of time of day on patient radiation exposure due to cardiac interventions. The elective interventional workload of one experienced cardiologist documented over the course of 4 months amounted to 325 diagnostic catheterizations and 145 percutaneous coronary interventions (PCI). All radiation parameters documented during diagnostic coronary angiography remained constant throughout the entire day. In contrast, for PCI measurements made from 7:00 a.m. to 1:00 p.m., our study revealed a mean overall dose–area product (DAP) of 11.8±6.8 Gy cm2(n=115). These radiation exposure levels increased significantly later in the afternoon (n=30) by 28% to a level of 15.0±11.1 Gy cm2(p<0.045). Cinegraphic DAP increased from 3.7±2.7 Gy cm2to 5.0±3.2 Gy cm2(p<0.033). The number of cinegraphic runs and frames rose from 7.9±2.9 to 9.1±3.1 (p<0.025), and from 136±63 to 164±70 (p<0.014), respectively. The following conclusion is warranted by our data and should now be confirmed in a wider multicentre study: radiation protection of the patients could be influenced by the fatigue of the cardiologist conducting the procedure. To enhance patient radiation safety, elective percutaneous angioplasty should be scheduled for the first 6 h of the interventionalist's occupational workload. Diagnostic interventions may be safely scheduled later.

DOI:10.1259/bjr/14780035

出版商:British Institute of Radiology    

年代:2003

数据来源: WILEY

摘要:

Diabetic mastopathy is a source of confusion with breast carcinoma. The association between mastopathy and Type I diabetes of long duration has been reported, but this clinical condition is poorly recognized since breast examination is not routinely performed in young diabetic patients. Radiologists' awareness of the constellation of findings in diabetic mastopathy may spare patients from undergoing unwarranted surgical biopsies.

DOI:10.1259/bjr/51145312

出版商:British Institute of Radiology    

年代:2003

数据来源: WILEY

摘要:

We report the use of a covered stent to successfully treat a pseudoaneurysm of the popliteal artery, which occurred following total knee arthroplasty. Percutaneous endovascular repair offers a safe alternative to surgical management of this condition.

DOI:10.1259/bjr/32510074

出版商:British Institute of Radiology    

年代:2003

数据来源: WILEY

摘要:

CT urography and virtual endoscopy images are generated from dedicated multislice helical CT data sets and various three-dimensional reconstruction techniques. These imaging techniques can provide external and endoscopic images of the urinary tract and also provide high spatial resolution images helping overcome some of the limitations of intravenous urography and ultrasound. This pictorial review presents clinical applications of CT urography and virtual endoscopy in various urinary tract abnormalities.

DOI:10.1259/bjr/26360633

出版商:British Institute of Radiology    

年代:2003

数据来源: WILEY

DOI:10.1259/bjr.76.903.760210b

出版商:British Institute of Radiology    

年代:2003

数据来源: WILEY

DOI:10.1259/bjr/64628028

出版商:British Institute of Radiology    

年代:2003

数据来源: WILEY

DOI:10.1259/bjr.76.903.760213b

出版商:British Institute of Radiology    

年代:2003

数据来源: WILEY