Biomedical subjects

J W Oxtoby

Publications and source records attributed to J W Oxtoby.

6 recordsLinked to original sources

PubMed2004

Ultrasound measured renal length versus low dose CT volume in predicting single kidney glomerular filtration rate.

Ultrasound measured renal length and CT measured renal volume are potential surrogate markers for single kidney glomerular filtration rate (SKGFR). The aims of this study are to determine: (1) the repeatability of ultrasound measured length and low radiation dose spiral CT measured volume; (2) the relationship between renal length and volume; and (3) whether length and/or volume is a predictor of SKGFR. 69 patients with suspected renal artery stenosis underwent ultrasound renal length measurement, CT evaluation of renal volume and assessment of SKGFR. 40 patients had ultrasound measurement of length and CT evaluation of volume performed twice on two separate visits. 25 patients also had ultrasound measured renal parenchymal thickness and area. The region of interest was drawn around the kidneys and a threshold set to subtract renal peripelvic fat and renal pelvis. The volume from each slice was summed to obtain the total volume for each kidney. The limits of agreement for ultrasound measured renal length were -1.6 cm to 1.52 cm and that for CT renal volume were -33 ml to 32 ml. There was significant correlation between ultrasound measured length and CT volume (r=0.74, p<0.01). Volume was a better predictor of SKGFR (r(2)=0.57) than length (r(2)=0.48). The combined parameters of ultrasound measured length, area and parenchymal thickness were a better predictor of volume (r(2)=0.81) and SKGFR (r(2)=0.58) than ultrasound measured length on its own. The low dose CT technique was reasonably reproducible and renal volume measurements correlate better with SKGFR than length. Ultrasound predictions of renal volume and SKGFR can be improved by incorporating cross-sectional area and parenchymal thickness. Further investigation is required to refine our low dose CT technique.

Glomerular Filtration Rate↗

PubMed2001

3D gadolinium-enhanced MRI venography: evaluation of central chest veins and impact on patient management.

AIM: To assess the value of a simplified 3D gadolinium-enhanced magnetic resonance imaging (MRI) venography for central chest veins. MATERIALS AND METHODS: In this retrospective study of 24 patients, the MRI findings and medical records were reviewed to determine whether MRI results correlated with subsequent findings, and to determine the effect on clinical management. 3D steady state gradient-echo sequence, fast imaging with steady state precession (FISP), was used. We employed a simplified protocol not requiring bolus timing or subtraction to achieve rapid data acquisition and hence good compliance in this group of frail patients. Following intravenous administration of a bolus of gadolinium, two acquisitions were obtained in order to ensure adequate opacification of all veins. Individual partitions and maximum intensity projections were then analysed to determine whether the veins were patent, stenosed or occluded. RESULTS: The indications for MRI were to assess the patency of central veins for the purpose of cannulation or arteriovenous fistula formation in 17 patients. Out of the 12 patients who proceeded to an intervention, MRI venography successfully predicted an appropriate site in 10 patients. In the remaining seven patients, MRI venography was valuable in confirming or excluding the clinical suspicion of central venous thrombosis and directly influenced the management in five patients. CONCLUSION: 3D gadolinium-enhanced MRI venography is a valuable means of providing a global representation of the central venous system and guiding subsequent central venous cannulation.

Adolescent↗

PubMed1999

Effective dose to children and adolescents from radiopharmaceuticals.

Published values of tissue weighting factors for adolescents and children derived from the life-span study of the atomic bomb survivors have been used to calculate the effective dose to patients aged 1, 5, 10 and 15 years undergoing a common paediatric procedure requiring one of the following radiopharmaceuticals: 99Tcm-mercaptoacetyltriglycine (MAG3), 99Tcm-diethylenetriaminepentaacetic acid (DTPA), 99Tcm-dimercaptosuccinic acid (DMSA), 99Tcm-pertechnetate, 99Tcm-iminodiacetic acid (IDA) derivatives, 99Tcm-hexamethylpropyleneamineoxine (HMPAO), 99Tcm-labelled leukocytes, 99Tcm-labelled erythrocytes, 99Tcm-phosphates, 99Tcm-methyloxyisobutylisonitrile (MIBI), 201Tl-chloride, sodium 123I-iodide, 123I-metaiodobenzylguanidine (MIBG) and 67Ga-citrate. Administered activities for each age group were based on ARSAC maximum usual values for adult patients and scaling factors listed by the European Association of Nuclear Medicine for different body weights. These effective doses were compared to values derived from ICRP whole-population tissue weighting factors and found to differ by -33% to +71% of these values, and by less than +/- 20% for two-thirds of the procedures. Because these differences were considerably less than the uncertainties in the estimates of organ absorbed dose, we conclude that these published age-specific tissue weighting factors should not be used for the estimation of effective dose to children and adolescents following the administration of radiopharmaceuticals, and that whole-population factors should continue to be used for these estimations.

Adolescent↗

PubMed1996

MRI characteristics of chondroblastoma.

We report a retrospective study of MR imaging of 16 patients with histologically proven chondroblastoma, 12 at primary presentation and four clinically suspected recurrences. In all the primary cases MR imaging showed a lobulated low signal intensity (SI) rim. Low SI foci within the tumour were present in 11 out of the 12 cases and corresponded to calcification seen on radiographs or CT. Bone marrow oedema was also present in 11 out of 12 cases and an adjacent joint effusion in eight out of 12. The STIR sequence was of particular value, giving optimal delineation of marrow and soft tissue oedema. Of the suspected recurrences one showed peritumoral oedema and was subsequently proven histologically. Three showed no peritumoral oedema and subsequent histology was negative in these cases. The presence or absence of oedema may be a useful indicator of tumour activity although further study is required.

Adolescent↗

PubMed1995

Technical note: femoral angiography using the reverse shuffle technique.

We report our findings using the "reverse shuffle" technique of stepping table femoral angiography. This technique represents a simple modification of the conventional stepping table sequence entailing a reverse table movement allowing acquisition of early and late films in the distal positions. It was developed in order to minimize the number of runs required in each examination. In a retrospective study 52/53 (98%) of angiograms using the reverse shuffle technique required only a single run compared with 30/51 (58%) using the conventional technique. We believe that the reverse shuffle should be used where possible when stepping table angiography is performed. Furthermore, the incorporation of a reverse table movement may also be advantageous in angiography using automated digital subtraction angiography (DSA) stepping systems.

Aged↗

PubMedDate not supplied

Mirizzi syndrome treated by percutaneous stone removal.

We report a case of Mirizzi syndrome due to a cystic duct stone occurring in a 66-year-old man in the presence of multiple debilitating medical conditions which precluded surgery. The patient was successfully treated by percutaneous stone removal and made a swift and uneventful recovery. This is the first report of Mirizzi syndrome due to a ductal stone being treated in this manner.

Aged↗