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Biomedical subjects

V R McCready

Publications and source records attributed to V R McCready.

At least 19 recordsLinked to original sources
PubMed1992

Anatomically derived attenuation coefficients for use in quantitative single photon emission tomography studies of the thorax.

Elimination of errors due to poor attenuation correction is an essential part of any quantitative single photon emission tomography (SPET) technique. Attenuation coefficients (mu Tc) for use in attenuation correction of SPET data were determined using technetium 99m and cobalt 57 flood sources and using topographical information obtained from computed tomography (CT) scans and magnetic resonance (MR) images. In patients with carcinoma of the bronchus, the mean attenuation coefficient for 99mTc was 0.096 cm-1 when determined across a transverse section of the thorax at the level of the tumour by means of a 57Co flood source (13 patients) and 0.093 and 0.074 cm-1 as determined from CT scans for points in the centre of the tumour and contralateral normal lung, respectively (21 patients). In 18 patients with breast tumours, the mean attenuation coefficient for 99mTc was 0.110 and 0.076 cm-1 when determined from MRI cross-sections for points in the centre of the tumour and normal contralateral lung, respectively. This indicates significant overcorrection for attenuation when the conventional value of 0.12 cm-1 is used. A value in the range 0.08-0.09 cm-1 would be more appropriate for SPET studies of the thorax. An alternative approach to quantitative region of interest (ROI) analysis is to perform attenuation correction appropriate to the centre of each ROI (using topographical information derived from CT or MRI) on non-attenuation-corrected reconstructions.

Breast Neoplasms↗
PubMed1992

A comparison of gallium-67 single photon emission computed tomography and computed tomography in mediastinal Hodgkin's disease.

The role of gallium-67 single photon emission computed tomography (Ga-67 SPECT) in the assessment of mediastinal Hodgkin's disease was evaluated prospectively. Ga-67 SPECT and computed tomography (CT) were compared and correlated with clinical findings at initial presentation in 30 patients, 6 weeks after treatment, and 6 months later in 20 of the 30 patients. At initial presentation, active disease was detected on both imaging modalities on all occasions. 6 weeks after treatment CT showed residual mediastinal abnormality in 7 patients, whereas Ga-67 SPECT showed abnormal mediastinal tracer uptake in 3 patients. 6 months later CT showed residual mediastinal abnormality in 5 patients whereas all the Ga-67 SPECT studies were negative. Ga-67 SPECT imaging is a useful tool in assessing response to therapy in mediastinal Hodgkin's disease.

Adult↗
PubMed1991

The effect of intra-tumour heterogeneity on the distribution of phosphorus-containing metabolites within human breast tumours: an in vitro study using 31P NMR spectroscopy.

The concentration of phosphorus-containing metabolites was determined in extracts of multiple samples from six human breast tumours and in samples from normal and inflamed breast tissue. The degree of lymphoid infiltrate, necrotic fraction and tumour cell and normal tissue fraction were determined on sections taken from each of the tumour samples. In four of the tumours there was a very high degree of variation between samples in the absolute concentration of metabolites. Three of these tumours showed a high degree of intra-tumour variation in the distribution of tumour cells and of normal tissue. The other two tumours were relatively homogeneous with respect to both tumour cellularity and the distribution of phosphorus-containing metabolites. Samples from normal breast tissue was found to contain only low concentrations of phosphorus-containing metabolites. However one of the inflamed samples, which consisted predominantly of macrophages, contained high levels of such compounds. The effect of time delay between resection and freezing on the levels of metabolites in human breast tumours was also examined.

Breast↗
PubMed1991

A comparison of in vivo and in vitro 31P NMR spectra from human breast tumours: variations in phospholipid metabolism.

An in vivo 31P NMR spectrum was obtained from each of four human breast tumours. The phosphomonoester and phosphodiester region of each spectrum consisted of a broad peak. Chemical extracts from samples of each of the tumours obtained at resection were examined on a high field strength NMR system. The phosphomonoester region in the spectrum from each extract resolved into three peaks consisting of phosphocholine, phosphoethanolamine and a nucleoside monophosphate. The phosphodiester region resolved into two components, glycerophosphorylcholine and glycerophosphorylethanolamine. Comparing the in vivo and in vitro data from each tumour showed that the contribution of phosphodiester was much lower in the in vitro spectra. We believe this to be a consequence of phospholipid, which would not appear in the aqueous extract, contributing to the phosphodiester peak in vivo.

Breast Neoplasms↗
PubMed1991

Immunoscintigraphy of colorectal cancer using a monoclonal antibody 77-1.

The monoclonal antibody (mAb) 77-1 recognizes epithelial membrane antigen (EMA) expressed by the majority of colorectal cancers. Following administration of indium-111 labelled 77-1, gamma camera imaging was carried out on 16 patients with known or suspected colorectal cancer prior to surgery or endoscopic laser therapy. Fourteen of the patients were found to have cancer, with one patient having two primary lesions. Two patients suspected of tumour recurrence were not found to have a lesion at laparotomy. Imaging before operation or laser therapy detected 10 out of 15 lesions (67%). Tumours which produced positive images were found to express the target antigen on immunocytochemical staining of the excised tumours. A mean tumour to normal colon ratio of 1.63 +/- S.D. 0.46 and a mean tumour to blood ratio of 3.60 +/- 1.48 were found at day 6 after antibody administration. A high uptake of radiolabel by the liver prevented the detection of hepatic metastases, present in three patients. Of the two patients with suspected recurrence a false positive scan was found in one owing to the presence of inflammatory tissue. Indium-111 labelled 77-1 may have a role in the imaging or targeting of colorectal cancer.

Aged↗
PubMed1979

The urinary excretion of gallium-67 citrate in patients with neoplastic disease.

The urinary excretion of gallium-67 has been studied in twenty-nine patients with considerable variation, ranging from 2.71 to 35.21 per cent of the injected dose in the first twenty-four hours. The data was analyzed to determine whether differences in excretion could be related to sex, age, plasma level, site or extent of disease but no significant relation could be found. While chemotherapy or radiotherapy has been shown to affect both the plasma clearance and protein binding they have no influence upon the urinary excretion of the isotope in this study. This study shows that all patients with high urinary excretion had bone metastasis from various types of primary tumour. Not all patients with bone metastasis have high urinary excretion of gallium-67. It would appear, however, from our limited series that patients with bone metastasis and normal urinary excretion of gallium-67 show a good response to treatment.

Adult↗
PubMed1979

The stability and distribution of Tc-HIDA in vivo and in vitro.

Tc-HIDA is a promising new agent for imaging the biliary system. In this study radiochromatography on paper or Sephadex G25 gel has been used to measure the proportions of TcHIDA, 'hydrolysed Tc' and pertechnetate in solutions from a commercial kit (CIS TCK 15) and in body fluids from patients and rats receiving this radiopharmaceutical. The tissue distribution in male and female rats has shown the radiopharmaceutical to be rapidly removed from the blood by the liver and then excreted via the intestines. There appears to be a sex difference in the uptake in the kidneys and in the urinary excretion in both rats and patients.

Animals↗
PubMed1978

Ultrasound tomography of the liver: Non-invasive method of choice for the differential diagnosis of jaundice.

Grey-scale ultrasound tomography was used to examine the liver and biliary tree of 100 consecutive unselected jaundiced patients in a prospective study. It was successful in differentiating between hepato-cellular and obstructive jaundice in 94%. It precisely localised the site of obstruction in 75% of those patients with enlargement of the head of the pancreas from either carcinoma or gall-stones impacted in the Ampulla of Vater. This figure was reduced to 60% when all cases of obstruction were considered. Cirrhosis and chronic active hepatitis were found to be associated with an abnormal pattern of echoes within the liver. These echoes were stronger and more numerous than normal. This association was not apparent with drug-induced cholestasis or acute viral hepatitis. Grey-scale ultrasound tomography is quick, safe and completely non-invasive. It should be the initial investigation of choice in the differential diagnosis of jaundice. When precise localisation of an obstruction is not possible after a repeat attempt, then percutaneous transhepatic cholangiography should be considered.

Ampulla of Vater↗
PubMed1978

The B-scan ultrasonic appearances of gas in the biliary tree.

Gas in the biliary tree has a striking but not unique ultrasonic appearance consisting of acoustic shadows trailing behind well-defined discrete high amplitude echoes deep within the liver parenchyma, and may be mimicked by intrahepatic gall stones and calcified tumours and granulomas. It interferes with assessment of liver structure, and renders ultrasound B-scan unreliable for the detection of liver metastases. Computed tomography remains unaffected by biliary gas.

Biliary Tract Diseases↗
PubMed1977

The role of ultrasound in the assessment and treatment of abdominal metastases from testicular tumours.

The para-aortic region has been investigated with ultrasound in 95 patients with testicular teratoma seen in the testicular tumour unit between 1973 and 1976. The liver was assessed in 110 patients. The technique has provided useful and reliable information. Para-aortic ultrasound can provide more information than existing diagnostic methods and is particularly useful for defining the volume of metastatic nodal masses. Its role should be regarded as complementary to that of lymphography. Ultrasonography is particularly useful to the radiotherapist since it can define the volume and limits of the tumour and thus influence choice of therapeutic approach and radiation planning technique. Ultrasound is also valuable in the assessment of response to treatment and in monitoring the patient during the subsequent follow-up period.

Abdominal Neoplasms↗
PubMed1977

Accuracy of grey-scale ultrasonography of liver and spleen in Hodgkin's disease and the other lymphomas compared with isotope scans.

Complementary techniques to laparotomy are required to monitor patients with lymphomas both before and after treatment. Our preliminary experience with grey-scale ultrasonography is presented. Fifty-two patients, themajority with Hodgkin's disease or other lymphomas, were examined with ultrasound equipment which was custom built. The essential difference between grey-scale equipment and conventional machines is the ability to display the internal consistency of soft organs. Of 20 spleens examined prior to splenectomy, the ultrasonic scan was considered suggestive of involvement in seven of nine that showed histological evidence of Hodgkin's disease. Threeof 11 histologically negative spleens were considered to be positive preoperatively and two of nine read as negative on the scan contained histological disease. Fifty livers were examined with ultrasound. Of seven patients with histological involvement four were read as positive and three as negative and six of 43 patients with no macroscopic or microscopic evidence of liver infiltration were also considered to have a positive ultrasonic scan. Ultrasonic scanning has proved useful for demonstrating enlarged lymph nodes in the porta hepatis, upper para-aortic lymph nodes and bulky mesenteric nodes. On the basis of these preliminary observations the potential value and application of the technique is discussed.

Adolescent↗
PubMed1976

Value of gallium scanning in seminoma of the testis.

Whole-body scanning using gallium-67-citrate gave consistently accurate tumour localisation in patients with seminoma of the testis. Thirteen out of 15 scans performed in patients with disseminated seminoma in relapse gave good imaging in all disease areas. Scans in patients with teratoma of the testis were less consistently positive; of nine scans performed in patients with disseminated teratoma seven were entirely negative and two scans lightly imaged large disease masses in two patients. In eight patients with combined (seminoma and teratoma) tumours the scan seemed to reflect the dominant tumour type at the time of scanning. In one of these patients the scans changed from positive to negative, being positive when seminoma was the dominant tumour and negative when a teratoma developed. Gallium-67-citrate scanning is useful in managing seminoma of the testis, both for determining the extent of disease present at initial presentation and for routine follow-up. It may be useful in the differential diagnosis of combined tumours when tumour masses are greater than 2 cm in diameter.

Adult↗
PubMed1976

The uptake of gallium 67 in colonic macrophages.

A case is presented in which a patient with a well-differentiated adenocarcinoma showed high gallium concentration in the segment with melanosis coli proximal to the obstruction. Although in this case the Gallium was associated with an increased number of faecal pigment containing macrophages it is unlikely that macrophages are the main factor in tumour uptake of Gallium compounds.

Adenocarcinoma↗