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Biomedical subjects

D Nicholas

Publications and source records attributed to D Nicholas.

14 recordsLinked to original sources
PubMed1991

Clinical application of an electronic imaging device for assisting patient set-up in radiotherapy.

As radiotherapy treatment set-ups are becoming more complicated and a greater emphasis is placed on accuracy, there is an increasing need to verify and record the actual treatments being given. A direct electronic imaging device is currently marketed by Varian (the DYNARAY ID), which uses the latest technology in detection and image processing to obtain digital images of the patient's anatomy using the actual treatment beam. At Norwich we have been using a prototype machine in a busy district radiotherapy centre and have examined over 50 patients. We have found the images easy to obtain and the technique superior to the standard practice of using verification radiographs. The role of this device lies in aiding quality assurance of treatments whilst generating a permanent record of the actual treatment given.

Evaluation Studies as Topic↗
PubMed1987

Comparison of computed tomography and conventional radiology in the assessment of treatment response of lytic bony metastases in patients with carcinoma of the breast.

Full skeletal survey, localised radiographs and computed tomography (CT) examinations were compared with clinical assessment in the evaluation of treatment response of bony metastases in 20 patients with carcinoma of the breast. Conventional radiology, skeletal survey and localised views compared poorly with clinical assessment agreeing in only 35% and 50% respectively. CT concurred with the clinical assessment in 65% of patients, particularly with respect to healing (86%). CT predicted the effect of treatment in six additional patients and this was confirmed on follow-up assessment. It is suggested that the use of skeletal surveys in monitoring treatment response is limited and that for critical evaluation of treatment CT should be the method of choice.

Adult↗
PubMed1987

Prognosis following chemotherapy for metastatic malignant teratoma.

A multiple regression analysis was performed of factors affecting the prognosis of 93 patients with metastatic malignant teratoma treated at the Royal Marsden Hospital between 1979 and 1981. In a subgroup of 53 patients, where exact tumour bulk could be calculated from sequential CT scan slices, a correlation was seen between tumour marker level and volume of metastatic disease. On analysis of the risk of relapse after initial chemotherapy, the independent adverse influence was detected of serum AFP greater than 500 micrograms/l and of bulky disease defined by clinical staging. An adverse influence of high serum HCG levels was not seen, probably due to the small number of patients in this series with this presenting feature.

Adult↗
PubMed1987

Benign thymic enlargement in adults after chemotherapy: CT demonstration.

Serial computed tomographic (CT) scans of 200 patients with malignant testicular teratomas were reviewed. Of the 200 patients, 120 were treated with chemotherapy for metastatic disease; 80 patients with no evidence of metastases (stage I disease) received no treatment and served as a control group. CT was performed at regular intervals for ongoing follow-up in both groups. Thymic enlargement occurred 3-14 months after initiation of treatment in 14 of the 120 patients (11.6%) who received chemotherapy but in only one patient in the control group. Histologic examination in one patient who received chemotherapy revealed that the thymic enlargement represented true hyperplasia. Thirteen of the 14 patients (93%) with thymic enlargement after chemotherapy were well and disease free on mean follow-up of 45 months, compared with 78% of the group that did not show thymic enlargement after chemotherapy (P less than .02). Rebound thymic hyperplasia in adults after chemotherapy for metastatic testicular teratoma may be a good prognostic feature and should be considered when an anterior mediastinal mass develops after chemotherapy for metastatic malignancy.

Adult↗
PubMed1987

Quantitative assessment of lung damage due to bleomycin using computed tomography.

Visual assessment and density measurements of the lung using computed tomography (CT) were made in 18 patients undergoing treatment with bleomycin for malignant teratoma of the testis. The results of both visual assessment and density measurements were compared with changes in gas transfer per unit lung volume (KCO). Visual assessment of severity of damage to the lungs caused by bleomycin is unrelated to changes in KCO but is characteristic of bleomycin damage and allows a confident diagnosis to be made. Quantitative density measurement by CT, however, is inversely related to changes in KCO and may therefore be used to monitor the physiological effect on the patient. Examination of the lung by CT in these patients can not only characterise and define the extent of lung damage due to bleomycin but can be used to give a quantitative measurement on which to monitor treatment.

Adult↗
PubMed1986

Tissue characterization from ultrasound B-scan data.

An approach to ultrasonic tissue characterization, using textural features of the B-scan image, is described. Portions of a B-scan image, 64 X 64 pixels spatially by 8 bits deep, are acquired from regions of interest and subjected to computer analysis. A systematic approach to defining a set of 93 textural features of a B-scan is described and methods and criteria for selecting optimum combinations of these are discussed. As a test of its power, the approach has been applied to the discrimination between the B-scan textures corresponding to livers and spleens of normal humans and various measures of "success" have been quantified both on a "training set only" and on a "training set plus test set" basis. The overall test probability of success of 82% on a single image and 94% on a subject yielding multiple images indicates the potential of the techniques for conditions where a subtle but uniform change in parenchymal texture may be present.

Computers↗
PubMed1986

Lung damage after hemithoracic irradiation: dependence on mouse strain.

A comparative study was performed on CBA, C57Bl mice and their F1 hybrid cross (CBBF1) after right hemithorax irradiation using doses ranging from 15 to 35 Gy. A dose-dependent increase in breathing rate was observed, corresponding to the expression of radiation pneumonitis in the irradiated lung. The use of hemithoracic irradiation enabled this to be observed without any lethality. Results obtained from X-ray computerized tomography (CT), lung weight and histology complemented the breathing rate studies. CBA mice showed a peak response at 16 weeks followed by a decline in breathing rate coincident with a compensatory hypertrophy of the shielded left lung. The manifestation of radiation pneumonitis in C57Bl mice was considerably delayed, supporting previous findings on whole-thorax irradiated animals. The latent period in CBBF1 hybrid mice was intermediate between the parent strains.

Animals↗
PubMed1985

The assessment of early and late radiation injury to the mouse lung using X-ray computerised tomography.

X-ray computerised tomography (CT) was performed on the lungs of CBA and C57Bl mice at varying time intervals after 13 and 16 Gy irradiation to the whole thorax. With careful consideration of artefacts associated with lung cross-sectional area and breathing rate, the mean density of the lung was evaluated in Hounsfield units (CT number). In CBA mice, this parameter showed a biphasic increase in lung density with time from irradiation, corresponding to an early phase of radiation pneumonitis and a late phase dominated by pleural effusions. Reduced lung volumes were also seen during the late response and lung compression due to accumulations of pleural fluid is considered a major factor in these observations. C57Bl mice did not develop radiation pneumonitis but appeared to be equally responsive to later radiation-induced increases in lung density. The results obtained from CT-derived densitometry compared well with measurements gained from functional and survival endpoints. X-ray CT provides a sensitive and informative technique for assessing the extent of radiation injury to the mouse lung and is potentially useful for quantifying the counterpart in patients.

Animals↗
PubMed1979

Attenuation of ultrasound in skeletal muscle.

Ultrasonic attenuation in fresh and 5% formalin fixed beef skeletal muscle has been measured, as a continuous function of frequency, in the range 1-8 MHz, for muscle fibre orientations both parallel and normal to the direction of propagation. Good agreement was found in all cases between two independent sets of measurements employing transmission and reflection techniques respectively. The data are consistent with a power law dependence of attenuation coefficient on frequency, with an exponent that is not significantly different from unity. For propagation normal to the fibres attenuation values are found as 1.1 +/- 0.15 and 1.6 +/- 0.15 dB cm-1 MHz-1 for fresh and fixed tissue respectively, the corresponding values for parallel propagation being 2.9 +/- 0.23 and 4.1 +/- 0.25 dB cm-1 MHz-1.

Animals↗
PubMed1979

Ultrasonic diffraction analysis in the investigation of liver disease.

An ultrasonic analytical method has been developed which is capable of remote, in vivo differentiation between various types of soft tissue on the basis of differences in their gross histological structure. The method is analogous to that employed in X-ray crystallography and is referred to as ultrasonic diffraction analysis. A clinical trial of this method in the investigation of liver disease in 70 patients is reported, in which a total of 416 ultrasonic diffraction patterns associated with various liver conditions have been analysed and related to independent follow-up information. The existance of a malignant condition of the liver has been identified in 95% of the cases involving focal metastatic deposits and in all of the 11 cases studied where the livers had diffuse malignant involvement. Cirrhosis and secondary involvement of the liver due to Hodgkin's disease have also been shown to exhibit specific tissue signatures which enable them to be differentiated from other hepatic disorders.

Humans↗