Biomedical subjects
Publications and source records attributed to P Y Poon.
Seven normal volunteers and 69 patients with known disease in either the mediastinum or hila or both were imaged using a prototype magnetic resonance imager operating at 0.15T. Normal mediastinal and hilar structures were readily identified and mediastinal diseases were well demonstrated by magnetic resonance imaging (MRI). The value of MRI lies in the morphological demonstration of the presence and extent of disease.
Whole-tissue and homogenized samples of human liver were studied in a NMR spectrometer, T1 and T2 relaxation times were measured as a function of added inorganic or organic iron. When inorganic iron (Fe+3) was added, pronounced T1 and T2 shortening was noted. However, when organic iron, in the form of ferritin, was added, the amount of T1 and T2 relaxation enhancement was much reduced for the same amount of added iron. The in vitro ferritin results model the situation found in clinical studies of hemochromatosis. Only in cases of severe iron overload were significant decreases in relaxation times observed. The T2 relaxation time was the more reliable indicator of excessive levels of iron in the liver. The large range of T1 and T2 values encountered in normal volunteers precludes the use of MR to quantitatively measure iron levels in the liver. The T1 and T2 relaxation times measured at intervals for one individual tend to fluctuate as well, making the use of MR to follow the course of treatment of iron overload disorders unreliable.
Twenty-two normal volunteers and 32 patients with either benign prostatic hypertrophy or prostatic carcinoma were examined by magnetic resonance imaging (MRI). The images were of high quality and clearly demonstrated the prostate gland and the surrounding anatomy but were of limited value in differentiating between benign and malignant prostatic disease. Using a specific pulse sequence, the authors were able to visualize what they believed to be the periprostatic venous plexus and suggest that the demonstration of this venous plexus may be of value in showing extraglandular spread of carcinoma of the prostate.
Fourteen patients with various orbital space-occupying lesions were studied by magnetic resonance (MR) imaging with a 0.15 T imager using spin-echo and inversion-recovery pulse sequences. Computed tomographic and ultrasonographic (US) examinations were done in 13 of these patients. All 14 lesions could be demonstrated by MR. Magnetic resonance was found to be better than US but not as good as CT in providing morphological details. Regarding tissue characterization, US was the most useful among the three modalities. With the T2-weighted spin-echo pulse sequence, a possible trend in tissue characterization could be shown. From our preliminary experience, we conclude that MR imaging using a 0.15 T resistive magnet offers no distinct advantage over the combination of CT and US in the diagnosis of orbital tumors.
The knees of 11 volunteers were examined by magnetic resonance (MR) imaging. The imaging was done with a 0.15 T resistive magnet using spin-echo pulse sequences. Normal anatomy was well displayed. The visualized structures included the menisci, cruciate ligaments, articular cartilage, cortical and cancellous bone, muscles, tendons, subcutaneous and intraarticular fat, and blood vessels. To obtain optimal visualization of the anterior cruciate ligaments, various positionings of the subjects and angulation of the imaging planes were tried. Rotation of the sagittal scanning plane away from the longitudinal axis of the body was found to be most satisfactory. The results obtained so far are very promising and demonstrate the real potential of MR imaging in the knee, which we believe lies in its ability to visualize the menisci and cruciate ligaments without use of contrast agents.
An evaluation was made of 1030 computed tomography (CT) scans performed on cancer patients. Seventy percent of the scans taken were of the pelvis, abdomen, or thorax. Both referring clinicians and radiologists rated the diagnostic and management efficacy of each scan using a simple scale of values. Over 50% of the scans provided unique diagnostic information: 39% resulted in a change in diagnosis or in known extent of disease; and 14% led to a change in patient management. The fraction of abnormal results was not a reliable measure of efficacy. Specific groups of patients were identified, which demonstrated that both diagnostic and management efficacy should be measured in assessing the value of CT as a diagnostic modality.
The plasma activity of the lysosomal enzyme N-acetyl-beta, D-glucosaminidase (NAGase) has been shown to correlate with hyperglycaemia; their temporal relationships have been investigated. In 12 insulin-treated male diabetic patients, NAGase showed a slight diurnal variation with a nadir at 07.00 h (F = 9.54, p less than 0.001). The mean plasma glucose and NAGase fluctuated similarly (rs = 0.88, p less than 0.01) but did not correlate within individual patients. Normoglycaemia was induced in eight insulin-treated diabetic patients for 4 days but the mean NAGase did not fall significantly. Glycaemic improvement over 3 months was achieved by dietary therapy in 28 newly-presenting non-insulin-dependent diabetic patients: there were significant falls in mean fasting plasma glucose (mean +/- SD: 12.8 +/- 3.3 to 8.3 +/- 3.1 mmol/l; p less than 0.001), glycosylated haemoglobin levels (12.4 +/- 2.4 to 9.3 +/- 2.3%, p less than 0.001) and a corresponding decrease of NAGase (1.5 +/- 0.5 to 1.2 +/- 0.4 mumol 4-nitrophenyl-N-acetyl-beta-D-glucosamide released.h-1.ml-1; p less than 0.001). The change in NAGase correlated with the changes in plasma glucose and glycosylated haemoglobin levels (r = 0.61, p less than 0.025; r = 0.48, p less than 0.05, respectively). Plasma NAGase activity may be influenced by glycaemia in diabetes.
A collaborative study compared methods for measuring glycosylated haemoglobin in seven laboratories in the United Kingdom. No satisfactory standard for general use was found. Satisfactory internal quality control systems were in use for each assay which allowed the maintenance of a normal range in each participating laboratory. No satisfactory quality control system suitable for general use could be identified. Costs and convenience of the assays are reported. The technical problems with each type of assay and precautions for their use were identified, such as the need for standardization in incubation times, the practicability of automation of colorimetric assays, and the precision of pH needed for buffers in column separation methods. The relevance of the technical problems to interpretation of measurements is also considered. It is concluded that laboratories measuring glycosylated haemoglobin should maintain a normal range, use 'in-house' quality controls to monitor assay performance and keep clinical colleagues informed of the findings and of any changes in methodology that might affect the interpretation of results.
Four patients with intramedullary spinal cord metastases from small cell carcinoma of the lung (SCCL) are described, with emphasis on clinical presentation and treatment. All patients developed the Brown-Séquard syndrome due to intramedullary tumor in the cervical spinal cord, three within 2 mo after combined modality treatment using chemotherapy and radiotherapy. One patient presented with a Brown-Séquard syndrome and an extradural spinal cord compression from tumor. The radiological and cerebrospinal fluid findings are presented and discussed. Radiation treatment was administered to the involved segments of spinal cord in each patient. All patients responded; two for 3 and 7 mo, two for 3 and 4 wk, respectively. There was significant improvement in the quality of life for three of the four patients.
Pelvic computed tomography (CT) was done in 100 unselected patients with untreated carcinoma of the uterine cervix. The size of the primary tumor, its extension into vagina, parametria, utero-sacral ligaments, pelvic sidewalls, bladder and rectum and pelvic lymphadenopathy were determined. Independently, similar findings from pelvic examination under general anesthesia (EUA) and cystoscopy were also recorded. International Federation of Gynecology and Obstetrics (FIGO) staging was used for comparison. The staging according to CT in 69 patients (69%) agreed with that at EUA and cystoscopy. In 31 patients there was both understanding (15%) and overstaging (16%) by CT.
1. In a cross-sectional study, 32 insulin-treated diabetic patients had elevated low shear (27.1 vs 22.1 mPa s, P less than 0.05) and high shear blood compared with 10 non-diabetic controls. After correction to 45% packed cell volume, the abnormality had a tendency to be greater in patients with proliferative (mean low shear viscosity, 30.8 mPa s) than background (29.2 mPa s) or nil/minimal retinopathy (27.6 mPa s, 0.05 less than P less than 0.97, permutational trend test). 2. The fibrinogen levels were higher in the diabetic group (P less than 0.05) and correlated with the low shear blood viscosity (rs = 0.38, P less than 0.05). 3. In a prospective study, 74 insulin-treated diabetic patients with background retinopathy were randomized into two groups. Thirty-six patients were on attempted improved therapy (A group); in these the mean glycosylated haemoglobin (Hb A1c) fell within 1 year (11.6 to 10.1%, P less than 0.001). both the corrected low shear blood and plasma viscosity fell similarly (P less than 0.001). The fall was greater than in those patients who were kept on usual therapy (U group) and whose glycosylated haemoglobin did not change significantly (11.7 to 11.4% over the year. 4. The effect of diabetes on blood viscosity may not be a direct pathological factor, as the same increased viscosity would be produced by a mean increase of 1.7% in packed cell volume, compared with a population range of 14% packed cell volume.
Computed tomography (CT) examinations of the brain, liver, and upper abdomen were obtained in 60 previously untreated patients with histologically proven small cell carcinoma of the lung (SCCL). These results, together with clinical findings and laboratory investigations including radionuclide scans, determined the final staging of the patients. Computed tomography changed the stage from limited to extensive disease in three patients and from extensive to limited disease in seven patients. Overall, 10 of 60 patients (16%) had their final stage altered by CT. This study indicates that CT examinations may yield valuable information in some cases of small cell lung cancer but that it is of limited value in the routine staging of these patients.
Plasma N-acetyl-beta-D-glucosaminidase activities are raised in maturity-onset insulin-dependent diabetic patients. Continuous gradient DEAE-cellulose column chromatography and assay of heat-stable enzyme activity both show that the activities of all isoenzymes are equally increased rather than a previously described increase of specific isoenzymes. Plasma enzyme activities are similarly increased in patients with and without diabetic retinopathy, and correlate with simultaneous plasma glucose concentrations.
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Antero-posterior linear tomography was used in conjunction with a xeroradiographic lateral view of the neck to study 35 cases of carcinoma of larynx previously treated by irradiation. Although false negatives and false positives did occur, this method is reasonably reliable in the diagnosis or exclusion of recurrent malignancy.
The hypothesis that two of four mammographic patterns show a marked predisposition to develop breast cancer was examined in a retrospective study. Four hundred patients with breast carcinoma were randomly chosen. The xeromammograms of the opposite breasts in these patients had been done and were studied. The conclusion of Wolfe was not supported by our findings.
The accuracy of magnetic resonance (MR) imaging in the detection of metastatic compression of the spinal cord and the cauda equina (MCCE) in 75 patients with known primary malignancy outside the central nervous system is determined retrospectively by comparing the MR results with findings of myelography, surgery, clinical follow-up and autopsy. The sensitivity is 93%, the specificity 97% and the overall accuracy 95%. The signal intensity measured in the sagittal MR images of a collapsed vertebral body is divided by that of an average of three adjacent normal vertebrae to form a signal intensity ratio (SIR). The SIRs of 41 metastatic and 15 post-traumatic collapsed vertebrae are calculated. A ratio of 0.8 has the most differentiating power. All benign and one malignant compressed vertebrae have SIRs greater than 0.8.
In a prospective study of acute radiation-induced pulmonary changes, CT scans of 54 patients were performed before and at preselected times during the 6 months following fractionated radiation therapy of the thorax. The CT films were evaluated independently by three diagnostic radiologists and 36 patients were scored as having postirradiation pulmonary findings. The average interobserver agreement for this scoring was approximately 85%. The end point was observed as an increase in lung density within the irradiated volume on a follow-up CT examination. All 36 patients demonstrated lung opacities in an irregular, homogeneous, or nonhomogeneous pattern within the radiation beam boundaries. In addition, the following characteristics were observed at various frequencies in these 36 patients: extension of the changes across anatomic tissue boundaries (50%), air bronchograms (25%), loss of lung volume (15%), and pleural thickening (15%). Confinement of the findings within the irradiated volume was the only specific characteristic of postirradiation changes. In two patients the changes appeared as sharply defined, nodular opacities and were considered to be atypical of radiation damage. These were subsequently confirmed to be metastases. Prospective assessment of an adequate number of patients has helped to establish the CT appearance of acute radiation-induced pulmonary effects and, hence, to minimize its confusion with malignancies and other abnormalities.