DOI:10.1259/bjr.71.841.9534691

出版商:The British Institute of Radiology    

年代:1998

数据来源: WILEY

摘要:

Patients with permanent cardiac pacemakers occasionally require radiotherapy. Therapeutic irradiation may cause pacemakers to malfunction due to the effects of ionizing radiation or electromagnetic interference. Modern pacemakers, using complementary metal oxide semiconductor (CMOS) circuitry, differ from older bipolar semiconductor devices both in their sensitivity to damage and the types of malfunction observed. The mechanisms and types of radiotherapy-induced pacemaker malfunction are described and in vitro and in vivo studies of pacemaker irradiation are reviewed. Some simple precautions are recommended during the planning and administration of radiotherapy to minimize the risk of harm to patients with pacemakers.

DOI:10.1259/bjr.71.841.9534692

出版商:The British Institute of Radiology    

年代:1998

数据来源: WILEY

摘要:

Two MRI strategies which have been reported to be effective in assessing cervical exit foramina, were prospectively compared with CT myelography in 20 patients with cervical radiculopathy. The first strategy utilized 3D T2* images, the second gadolinium enhanced 2D T1 images. Gadolinium (dimeglumine gadopentetate, Schering Ltd) enhanced images did not confer any benefit in the investigation of this condition, probably due to enhancement of herniated disc material and osteophytes adjacent to the neurocentral joint. Three-dimensional (3D) T2* white cerebrospinal fluid images had an accuracy approaching 90% for the diagnosis of foraminal encroachment, compared with a gold standard. MRI including a 3D T2* sequence is thus an acceptable primary investigation for cervical radiculopathy, but when the findings are incompatible with clinical symptomatology, CT myelography is still indicated.

DOI:10.1259/bjr.71.841.9534693

出版商:The British Institute of Radiology    

年代:1998

数据来源: WILEY

摘要:

Dual phase contrast enhanced spiral computed tomography (DPSCT) has the potential to improve detection of small insulin secreting islet cell tumours of the pancreas. Seven patients with biochemically proven insulinoma, who had previously undergone a range of negative radiological procedures, were referred for DPSCT. Images of the pancreas were obtained using 3 mm collimation in the arterial and arteriovenous perfusion phase following the rapid injection of contrast medium. Six tumours were localized in seven patients. The six insulinomas identified on DPSCT ranged in size from 6 mm to 18 mm and were located in the uncinate process (2), head (1), neck (2) and body (1). All six tumours were detected in the arterial phase and four in the arteriovenous phase. The four insulinomas detected on both perfusion phases were more conspicuous in the arterial phase in three patients and more conspicuous in the arteriovenous phase in one patient. In conclusion, high resolution arterial phase acquisition of the pancreas is very valuable in the detection of small insulinomas.

DOI:10.1259/bjr.71.841.9534694

出版商:The British Institute of Radiology    

年代:1998

数据来源: WILEY

摘要:

Radiographic contrast media (RCM) cause histamine-dependent allergic-like reactions. The direct effects of diatrizoate (high osmolar ionic monomer), ioxaglate (low osmolar ionic dimer), iopromide (low osmolar non ionic monomer) and iotrolan (iso-osmolar non ionic dimer) at the concentration of 200 mgI ml-1 (60 min exposure) on the release of histamine from human basophils, human lung mast cells (HLMC), and human skin mast cells (HSMC) were investigated. Diatrizoate induced 48 +/- 4% histamine release in basophils, 15 +/- 3% in HLMC and 25 +/- 6% in HSMC. The remaining RCM were relatively ineffective activators of histamine release in both HLMC and HSMC (ioxaglate 4 +/- 1% and 4 +/- 1%, iopromide 5 +/- 1% and 7 +/- 2%, iotrolan 7 +/- 2% and 10 +/- 3%, respectively). Both iotrolan and ioxaglate were effective in basophils inducing 21 +/- 3% and 24 +/- 6% histamine release, respectively, whereas iopromide was relatively ineffective (7 +/- 4%). Diatrizoate induced histamine release from all three cell types with optimal levels of histamine release after a 2-4 h incubation although significant levels occurred within 15 min. Dose-dependent histamine release from HLMC occurred in all four types of RCM, the largest response (37 +/- 3%) being produced by diatrizoate. The effect of osmolality on histamine release was investigated using different concentrations of mannitol solutions (0.25, 0.5 and 1 M). Histamine release from HLMC, HSMC and basophils after 90 min exposure to mannitol (1 M) was 24 +/- 2% (p<0.05), 9 +/- 3% (p = 0.06) and 49 +/- 1% (p<0.05), respectively, suggesting that hyperosmolality per se can induce histamine release from basophils and mast cells. Diatrizoate-induced histamine release in all three cell types was significantly reduced by lowering the temperature to 0 degree C and partially attenuated by the metabolic inhibitors antimycin A (1 microM) and 2-deoxyglucose (5 mM), and by the omission of glucose from the buffer solution. Diatrizoate-induced histamine release was not dependent on extracellular calcium. These data suggest that diatrizoate induces histamine release at least in part by non-cytotoxic mechanisms.

DOI:10.1259/bjr.71.841.9534695

出版商:The British Institute of Radiology    

年代:1998

数据来源: WILEY

摘要:

Increased signal intensity on magnetic resonance (MR) imaging of tendons arising from the magic angle phenomenon is well recognized. This study aimed to evaluate the effect of varying the echo time (TE) upon tendon signal intensity, and to determine if a modified TE value produces acceptable T1 and proton density (PD) weighted images. Fresh bovine tendons were imaged in a 1.5 T MR scanner using spin echo (SE) T1 and PD weighted sequences and utilizing a number of different coils. For each set of sequences, the tendon was orientated at 55 degrees to the main magnetic field (B0) and imaged using constant TR and incremental TE values. Signal intensity was measured on images at each TR/TE value and compared with the signal intensities of tendons orientated at 0 degree to B0, obtained using minimum TE values. This experiment was repeated with a 1.0 T MR scanner and utilizing a spine coil. The Achilles tendon of a human volunteer was similarly imaged using a general purpose flex coil. For bovine and human tendons orientated at 55 degrees to B0, the signal intensities decreased exponentially with increasing TE. A critical TE value exceeding 37 ms, for each sequence, reduced the signal intensities to the levels obtained with the tendons orientated at 0 degree to B0, such that the magic angle phenomenon could be avoided. Although there was variability of the signal intensities with different coils, the critical TE value remained constant and the anatomical clarity was not degraded. The critical TE value was unaltered using two MR scanners of different field strengths.

DOI:10.1259/bjr.71.841.9534696

出版商:The British Institute of Radiology    

年代:1998

数据来源: WILEY

摘要:

The purpose of this paper is to evaluate the significance of two CT findings: evidence of an exophytic component of part of a hydatid cyst and dilated ducts in the vicinity of a cyst. The CT scans and clinical records of 63 patients were reviewed. There was evidence that cysts with an exophytic component are probably unstable and unsuitable for treatment by percutaneous drainage or prolonged medical treatment. Dilated pericystic ducts are a relative contraindication to nonsurgical treatment because of the danger of complicating biliary obstruction. Surgery should not be delayed unduly when either sign is encountered.

DOI:10.1259/bjr.71.841.9534697

出版商:The British Institute of Radiology    

年代:1998

数据来源: WILEY

摘要:

In general, effective dose values for similar interventional vascular radiology (IVR) procedures are different. This is due to problems with the classification of radiological procedures, which make comparisons difficult. Patient size, examination technique and clinical condition as well as the skill of the medical radiologists also affect effective dose. Currently, there is a broad agreement on the classification of similar procedures so that effective dose estimates can be made from measurements of the dose area product (DAP). Thus, reference dose values may be established and comparative studies between different services and hospitals can be made. The objective of this study is to provide dose data for some digital angiographic and interventional procedures. Values of measured DAP for 143 patients for five types of procedures are presented. Procedures investigated were abdominal angiography, arteriography of lower limbs, biliary drainage, embolization of spermatic vein and nephrostomy. All the procedures were performed using digital equipment. Values of DAP and effective dose were 30 Gy cm2 and 6.2 mSv for arteriography of lower limbs and 150 Gy cm2 and 38.2 mSv for biliary drainage. In each one of these procedures, effective dose values per minute of fluoroscopy and per radiography film have been calculated. It is possible to use this information for the rapid estimation of effective dose.

DOI:10.1259/bjr.71.841.9534698

出版商:The British Institute of Radiology    

年代:1998

数据来源: WILEY

摘要:

The need for test objects in mammography quality control programmes to provide an objective measure of image quality pertinent to clinical problems is well documented. However, interobserver variations may be greater than the fluctuations in image quality that the quality control programme is seeking to detect. We have developed a computer algorithm to score a number of features in the Leeds TOR(MAX) mammography phantom. Threshold scoring techniques have been applied in the first instance; scoring schemes which utilize measures such as signal-to-noise ratio and modulation have also been formulated. This fully automatic algorithm has been applied to a set of 10 films which have been digitized at 25 microns resolution using a Joyce-Loebl scanning microdensitometer. The films were chosen retrospectively from quality control test films to demonstrate: (a) a range of optimized imaging systems, and (b) variation from the optimum. The performance of the algorithm has been compared with that of five experienced observers, and has been shown to be as consistent as individual observers, but more consistent than a pool of observers. Problems have been encountered with the detection of small details, indicating that a more sophisticated localization technique is desirable. The computer performs more successfully with the scoring scheme which utilizes the full imaging information available, rather than with the threshold-determined one. However, both the observers and the computer algorithm failed to identify the non-optimum films, suggesting that the sensitivity of the TOR(MAX) test object may not be adequate for modern mammography imaging systems.

DOI:10.1259/bjr.71.841.9534699

出版商:The British Institute of Radiology    

年代:1998

数据来源: WILEY

摘要:

Inhomogeneity of the transmitted or received B1 field leads to intensity variations in MR images and spatial dependence in apparent concentration in MR spectra. We describe a simple method for investigating such variations. The transmitted B1 field can be measured both in vivo and in vitro which allows investigation of sample dependent effects that can not be measured on phantoms. For homogeneous regions the method also allows the received B1 field to be measured both in vivo and in vitro. Our method uses only a standard spin echo pulse sequence and simple region of interest analysis and should be implementable on any commercial scanner. The method is demonstrated using a variety of transmission and reception radiofrequency coils both in vivo and in vitro.

DOI:10.1259/bjr.71.841.9534700

出版商:The British Institute of Radiology    

年代:1998

数据来源: WILEY