DOI:10.1259/bjr/16754313

出版商:British Institute of Radiology    

年代:2004

数据来源: WILEY

DOI:10.1259/bjr/14928972

出版商:British Institute of Radiology    

年代:2004

数据来源: WILEY

摘要:

Since the publication of the modified Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) criteria for the diagnosis of pulmonary embolism (PE), new clinical and scintigraphic diagnostic algorithms (the McMaster clinical criteria, the PisaPED simplified scintigraphic grading and the Miettinen logistic regression analysis) have been reported although the results have not been reproduced in other sites. Ventilation–perfusion lung scintigraphy was performed in 238 consecutive patients with a provisional diagnosis of PE. Scans were reported as normal/very low, low, intermediate or high probability for PE using standardized criteria. Each patient received a clinical grading of probability of PE as low, moderate or high using the McMaster clinical criteria. Using the PisaPED criteria (an alternate simplified scintigraphic grading system using the perfusion scan alone) each scan was also graded as normal/near normal, abnormal but not PE, or abnormal and PE. Using the logistic regression algorithm of Miettinen each scan received a numerical probability of PE. Frequencies for differing levels of probability of PE varied widely between the various algorithms. Cross tabulations revealed correlation of the standardized criteria with the Miettinen grading but not with the McMaster or the PisaPED gradings. We were unable to reproduce similar results using the McMaster clinical grading or the PisaPED simplified scintigraphic grading although the Miettinen logistic regression formula gave comparable results. New algorithms are not automatically transferable to new environments.

DOI:10.1259/bjr/83624598

出版商:British Institute of Radiology    

年代:2004

数据来源: WILEY

摘要:

The purpose of this work was to develop a robust technique for planning intensity-modulated radiation therapy (IMRT) for prostate cancer patients who are to be entered into a proposed hypofractionated dose escalation study. In this study the dose escalation will be restricted to the prostate alone, which may be regarded as a concurrent boost volume within the overall planning target volume (PTV). The dose to the prostate itself is to be delivered in 3 Gy fractions, and for this phase of the study the total prostate dose will be 57 Gy in 19 fractions, with 50 Gy prescribed to the rest of the PTV. If acute toxicity results are acceptable, the next phase will escalate doses to 60 Gy in 20 × 3 Gy fractions. There will be 30 patients in each arm. This work describes the class solution which was developed to create IMRT plans for this study, and which enabled the same set of inverse planning parameters to be used during optimization for every patient with minimal planner intervention. The resulting dose distributions were compared with those that would be achieved from a 3D conformal radiotherapy (3DCRT) technique that used a multileaf collimator (MLC) but no intensity modulation to treat the PTV, followed by a sequential boost to raise the prostate to 57 Gy. The two methods were tested on anatomical data sets for a series of 10 patients who would have been eligible for this study, and the techniques were compared in terms of doses to the target volumes and the organs at risk. The IMRT method resulted in much greater sparing of the rectum and bladder than the 3DCRT technique, whilst still delivering acceptable doses to the target volumes. In particular, the volume of rectum receiving the minimum PTV dose of 47.5 Gy was reduced from a mean value of 36.9% (range 23.4% to 61.0%) to 18.6% (10.3% to 29.0%). In conclusion, it was found possible to use a class solution approach to produce IMRT dose escalated plans. This IMRT technique has since been implemented clinically for patients enrolled in the hypofractionated dose escalation study.

DOI:10.1259/bjr/66104316

出版商:British Institute of Radiology    

年代:2004

数据来源: WILEY

摘要:

The study was performed with the aim of prospectively characterizing infectious meningitis of different aetiology using magnetization transfer (MT) MRI. Spin-echo (SE)T1,T2and pre- and post-contrastT1weighted MT images in 100 patients with aetiologically proven meningitis were evaluated for the visibility and enhancement of the meninges on pre- and post-contrastT1weighted MT images, respectively. The MT ratio (MTR) was calculated from the thickened meninges in tuberculous meningitis. In addition, the percentage difference in the mean signal intensity (SI) of the meninges and adjacent brain parenchyma was calculated and compared between different groups using 2-tailed student'st-test.T1weighted MT images were highly sensitive (96%) in the detection of abnormal meningeal enhancement. Meninges were visible on pre-contrastT1weighted MT images only in patients with tuberculous meningitis. The MTR from meninges in tuberculous infection was 19.10±1.02, and the percentage difference in the mean SI of the meninges and the adjacentT2normal brain parenchyma was significantly higher (p<0.05) in the tuberculous group compared with that in the non-tuberculous group. MT MRI is an important technique for the detection and characterization of infectious meningitis of different aetiology. Visibility of the meninges on pre-contrastT1weighted MT images may be considered highly suggestive of tuberculous meningitis.

DOI:10.1259/bjr/23641059

出版商:British Institute of Radiology    

年代:2004

数据来源: WILEY

摘要:

This work describes the analysis of factors which affect the results of estimation of the electron accelerating potential (kVp) applied to an X-ray tube, through determination of the end point of the energy spectrum of the emitted radiation beam. Measurements have been performed utilizing two spectrometers each with a silicon PIN photodiode: one operating at room temperature, and the other, a high resolution spectrometer, with a Peltier cooler. Both were directly irradiated by different X-ray beams. Both systems work at low voltage and without liquid nitrogen cooling, thus avoiding the drawbacks presented by germanium detectors. Each kVp value was determined by linear regression of the end of the spectrum, so as to give, simultaneously, the best fit to the experimental data and low standard deviation for the kVp value. Detector energy resolution and calibration, counting statistics and high voltage waveform ripple have been investigated in order to establish better experimental conditions and to optimize measurement time. Results of measurements carried out with X-ray tubes connected to single-phase, three-phase or constant potential units, using additional filtration of Cu, Al or Mo (for mammographic beams), are presented. The variations resulted in kVp uncertainties up to 0.1 kV.

DOI:10.1259/bjr/32514512

出版商:British Institute of Radiology    

年代:2004

数据来源: WILEY

摘要:

In 1979, the World Health Organization (WHO) established criteria based on tumour volume change for classifying response to therapy as (i) progressive disease (PD), (ii) partial recovery (PR), and (iii) no change (NC). Typically, the tumour volume is reported from diameter measurements, using the calliper method. Alternatively, the Cavalieri method provides unbiased volume estimates of any structure without assumptions about its shape. In this study, we applied the Cavalieri method in combination with point counting to investigate the changes in tumour volume in four patients with high grade glioma, using 3D MRI. In particular, the volume of tumour within the enhancement boundary, the enhancing abnormality (EA), was estimated fromT1weighted images, and the volume of the non-enhancing abnormality, (NEA) enhancing abnormality, was estimated fromT2relaxation time and magnetic transfer ratio tissue characterization maps. We compared changes in tumour volume estimated by the Cavalieri method with those obtained using the calliper method. Absolute tumour volume differed significantly between the two methods. Analysis of relative change in tumour volume, based on the WHO criteria, provided a different classification using the calliper and Cavalieri methods. The benefit of the Cavalieri method over the calliper method in the estimation of tumour volume is justified by the following factors. First, Cavalieri volume estimates are mathematically unbiased. Second, the Cavalieri method is highly efficient under an appropriate sampling density (i.e.EA volume estimates can be obtained with a coefficient of error no higher than 5% in 2–3 min). Third, the source of variation of the volume estimates due to disagreements between observers, and within observer, is much greater in the positioning of the calliper diameters than in the identification of the tumour boundaries when applying the Cavalieri method. Additionally, the error prediction formula, available to estimate the coefficient of error of Cavalieri volume estimates from the data, allows us to establish more precise classification criteria against which to identify potentially clinical significant changes in tumour volume.

DOI:10.1259/bjr/85294528

出版商:British Institute of Radiology    

年代:2004

数据来源: WILEY

摘要:

A method of estimating the shape and position of the lung in tangential breast fields is presented for patients who have not been CT scanned. Using the Osiris system, the external contour is obtained optically, and an estimated lung structure superimposed on the transverse outlines based on the measured lung depth in the tangential fields and an analysis of the typical lung shapes obtained from CT images. The accuracy of this fit was determined by comparison with a set of 64 CT images imported into the Osiris system. Dose distributions were calculated by two treatment planning systems: ADAC Pinnacle and GE Target2. The computed dose distributions for 6 MV photons were compared against measured doses in a specialized breast phantom. For the worst case of lung fit compared with CT, the dosimetric error (based upon ADAC Pinnacle calculations) was 2.0% in the shadow of the lung. For the complete patient data set, the relative dose errors to these points were reduced from a mean value of 8.4% and standard deviation (SD)=1.8% (no lung correction) to a mean of 0.2% and SD=1.0% (lung correction using fitted lung). It was also found that for every 1 cm of lung path length the dose to the breast along that path length increased by approximately 1%. The results of these investigations indicated that the lung fit model was satisfactory for routine clinical use, so that good dosimetric results can be obtained using lung correction without the need for CT imaging.

DOI:10.1259/bjr/51786246

出版商:British Institute of Radiology    

年代:2004

数据来源: WILEY

摘要:

Foreword. While being dimly aware that X-rays are used in far more applications than I would ever be familiar with, I was, in my ignorance, startled when I first saw some of the beautiful fossil images obtained by Peter Hohenstein. Here certainly was a field of “radiology” of which I did not even know the existence. The images are certainly arresting but, other than in the pursuit of something aesthetically pleasing, the reasons why they were ever taken eluded me. My ignorance went deeper than this. How could successful fossil X-rays be taken at all, even of a vertebrate creature? The calcium of the bones would surely have been leached away; and might not slate itself be a good enough absorber of X-rays to “hide” almost anything within? What is “slate” precisely anyway, in chemical terms, and of course, what energy X-rays had been used? Peter Hohenstein explained these things patiently and I thought his beautiful work deserved a wider audience. There are, after all, precedents for the publication of non-clinical material. In a recent issue ofRadiology, for example, readers were treated to a CT study of bowed stringed instruments [1]. Peter Hohenstein's work offers us an opportunity to step back some 400 million years and examine some of our ancestors.P DawsonDepartment of RadiologyUniversity College London HospitalsMortimer StreetLondon WIT 3AAAbstract. Few may be aware that X-ray imaging is used in palaeontology and has been used since as early as 1896. The X-raying, preparation and exposure of Hunsrück slate fossils are described. Hospital X-ray machines are used by the author in his work. An X-ray is vital to provide evidence that preparation of a slate is worthwhile as well as to facilitate preparation even if there is little external sign of what lies within. The beauty of the X-ray exposure is an added bonus.

DOI:10.1259/bjr/27832269

出版商:British Institute of Radiology    

年代:2004

数据来源: WILEY

摘要:

While phantoms are used for quality control assessment of the mammography unit,in vivodose measurements are necessary to account for the variation in size and composition of the female breast. The use of thermoluminescent dosimeters (TLDs) in mammography has been limited due to TLD visibility. The aim of this current investigation was to access the suitability of a paper-thin LiF:Mg,Cu,P TLD (GR-200F) forin vivodosimetric mammography measurements. The visibility of GR-200F has been directly compared with LiF:Mg,Cu,P TLDs (GR-200A) using a number of commercially available phantoms. The phantoms of thickness 2–5 cm were imaged over the range of tube potentials (24–28 kVp) used clinically. Both types of TLD were placed on the surface of the phantoms allowing assessment of visibility, entrance surface dose (ESD) and field homogeneity.In vivoassessment of ESD and visibility was also carried out on a volunteer undergoing a routine mammography examination. The positions of the GR-200F TLDs were not identified either on the image of the Leeds TOR(MAM) phantom or the patient mammograms. The average ESD for the Leeds phantom was 8.8 mGy, while the patient ESD was 13 mGy. It is now possible to performin vivomeasurements with the potential of increasing the accuracy of the doses measured for women that do not conform to a standard breast thickness or density.

DOI:10.1259/bjr/91138314

出版商:British Institute of Radiology    

年代:2004

数据来源: WILEY