Phantoms for studying the acceleration and turbulence of liquids using magnetic resonance imaging.

Magnetic resonance angiography is a relatively new method used to image vascular structure. However, a limitation manifested through signal loss due to non-stable flow makes this technique unreliable for directly visualizing occlusions and estimating the degree of stenosis. In this study, a quantitative approach is developed to understand further the situations where signal loss occurs and a phase mapping technique is used quantitatively to study acceleration in test objects designed to generate flow disturbance. In regions of acceleration the correlation coefficient between magnetic resonance imaging velocity and the inverse of area was r > 0.999 (p < 0.001). The range of acceleration calculated was 6514-63,053 mm s-2 and at maximum acceleration the measured velocity had a systematic error of 4.0(+/- 2.0)% and coefficient of variation of 3.1%. Test objects were devised and utilized for demonstrating non-stable flow and jet formation with comparison being made to predictions from fluid dynamics theory.

The quantitative distribution of nebulized antibiotic in the lung in cystic fibrosis.

Nebulized antibiotic therapy in cystic fibrosis is an established procedure. The present study was designed to quantitate deposition, and assess its relation to the disease state. Twenty seven children and young adults with cystic fibrosis (mean 11.6 years, range 4-23 years, 12 females) were studied to establish the quantity and pattern of deposition of nebulized tobramycin in the respiratory tract. A single (120 mg) dose of nebulized 99 m technetium-labelled tobramycin was administered, and imaged with a gamma-camera. The mean penetration index (which compares the distribution of 81 m-Krypton gas with Tc-radioaerosol) was also used to measure peripheral deposition efficiency. The aerosol mass median diameter (MMAD) for the compressor-nebulizer system used was 5.3 u, measured with the Malvern Mastersizer. Serial sputum samples were fluroimmunoassayed for tobramycin in nine patients. A mean of 8.0 (SEM 1.0) mg tobramycin reached the lungs. There was no relationship between the total pulmonary deposition and indices of pulmonary damage in cystic fibrosis. Sixteen percent of the lung tobramycin reached the periphery. The greater the lung damage as indicated by FEV1 and Chrispin-Norman scores, the smaller the proportion of pulmonary tobramycin that reached the periphery. The mean penetration index increased with increase in the FRC, but bore no relation to other respiratory function tests or to chest X-ray scores. Sputum tobramycin concentrations reached levels bactericidal for Pseudomonas aeruginosa. Airway obstruction and damage affected the proportion of pulmonary tobramycin reaching the periphery. The proportion of tobramycin reaching the lungs was small and variable.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative study of velocity measurements in major blood vessels using magnetic resonance imaging and Doppler ultrasound.

Velocity measurements in major blood vessels were obtained in studies of volunteers using magnetic resonance imaging (MRI) and compared with Doppler ultrasound (US). The vessels studied were the abdominal aorta, superior mesenteric artery, common carotid artery, superficial femoral artery and middle cerebral artery. Using a paired t-test, no significant difference was found between velocity values estimated by MRI and US (p > 0.08). The relative advantages of each technique in radiological practice are discussed.

Gastric emptying and enterogastric reflux after conservative and conventional pancreatoduodenectomy.

BACKGROUND: Retention of the entire stomach during pancreatoduodenectomy should theoretically improve postoperative nutrition, but some studies have reported a high incidence of delayed gastric emptying (GE). An intact pylorus should also prevent enterogastric reflux and its attendant problems, provided that the operation does not impair sphincteric competence. METHODS: We studied pyloric function in 24 patients who underwent pylorus-preserving pancreatoduodenectomy (PPP) and 12 who underwent a conventional Whipple resection including distal hemigastrectomy. Resection had been performed for benign (n = 19) or malignant (n = 17) disease. A double isotope technique was used to measure liquid and solid GE, and enterogastric reflux was measured by means of cholescintigraphy. RESULTS: Only two patients who underwent PPP required nasogastric intubation beyond 8 days. At follow-up (median, 5 months; range, 2 to 42 months) one patient with persistent vomiting required remedial surgery after PPP (apart from two with recurrent carcinoma affecting the anastomosis); after Whipple resection there were three patients with intermittent vomiting and one with dumping. Median half-time for liquid GE was not significantly different (65 minutes for PPP vs 103 minutes for Whipple resection; n < 70 minutes); likewise, the median half-time for solid GE was not significantly different (140 minutes for PPP vs 180 minutes for the Whipple procedure; n < 110 minutes). Persistent enterogastric reflux was seen in three of 20 patients who underwent PPP and three of eight who underwent Whipple resection. CONCLUSIONS: Isotopic test results of GE are frequently abnormal after either type of pancreatoduodenectomy, but symptoms are uncommon. The retained pylorus is competent to prevent enterogastric reflux and does not itself impair emptying of the stomach.

Fat-suppression magnetic resonance imaging in the preoperative localization of parathyroid adenomas.

Prospective localization of parathyroid adenomas was attempted in 16 patients with hyperparathyroidism prior to surgery. All patients had magnetic resonance imaging (MRI) using T1-weighted spin-echo (SE) sequences and a fat-suppression sequence, the short-tau inversion recovery (STIR) sequence. Correlation with the results of surgery yielded an overall sensitivity of 71% and a specificity of 94%. Performance was good in patients with previous surgery and with ectopic tumours. We believe that fat-suppression MRI is a valuable technique in the preoperative localization of parathyroid adenomas in patients with hyperparathyroidism.

Failure of peripheral arterial balloon angioplasty: does platelet deposition play a role?

The pathophysiological response to peripheral percutaneous transluminal balloon angioplasty in 20 patients was investigated using 111-Indium labelled platelets. Platelet deposition was quantified by measuring the degree of radioactivity uptake at angioplasty and control sites using a computer linked system and expressing the uptake as a ratio of angioplasty/control. Following platelet labelling, scans were performed before angioplasty and at 1, 24 and 48 h after angioplasty. To assess patency of the angioplasty, ankle brachial Doppler pressure indices were performed and supported by repeat angiograms if doubt of patency existed. All patients were followed-up at 1 week, 1 month and 6 months to correlate the degree of early platelet uptake with failure. The mean +/- sem platelet radioactivity ratio at the angioplasty site increased from 1.1 +/- 0.1 prior to the procedure to a peak of 2.1 +/- 0.3 at 1 h (p less than 0.01), 1.6 +/- 0.2 at 24 h (p less than 0.05), and 1.7 +/- 0.3 at 48 h (p less than 0.05). Angioplasties that failed within 6 months tended to have a higher maximum early platelet uptake (3.1 +/- 0.6) compared to successful angioplasties (1.9 +/- 0.3) but the difference was not significant in the numbers studied. This study provides a suitable model to assess the role of platelet accumulation in angioplasty failure and the influence of various antiplatelet regimes.

An evaluation of the accuracy of flow measurements using magnetic resonance imaging (MRI).

A study was undertaken to examine the accuracy and precision of the measurement of flow by magnetic resonance imaging (MRI) with consideration to the equipment and patient related parameters that might be encountered in vivo. For this purpose, test objects were devised consisting of PVC tubing, in which the internal diameter simulated the size of the arteries in the body. The design of the test objects ensured that steady laminar flow was obtained in the sections being imaged. The calibration study suggests that, using MRI, flow can be measured in vitro with systematic error of better than 7.0 +/- 5.0% and random error of better than 7.5%. In general, flow measurements obtained from MRI were found to correlate well with the known flows. However, the results indicated that there are prerequisite conditions for the validity of the measurements, such as the selection of appropriate flow pulse sequences and velocity limits. Measurements taken at vertically 40 mm away from the isocentre of the magnetic field were significantly different (p less than 0.01) from that at the isocentre.

Optical attenuation characteristics of breast tissues at visible and near-infrared wavelengths.

Optical experiments are described for measuring the attenuation characteristics of breast tissues at visible and near-infrared wavelengths. Total attenuation coefficients post mortem were measured directly in thin tissue sections. They are usually within the range from 10 to 30 mm-1, are rather higher in fat than in fibroglandular specimens and decrease with increasing wavelength. The scattering phase function is strongly forward-peaked with the mean cosine of scattering in the range from 0.85 to 0.97 and appearing more forward-peaked in fat than in fibroglandular tissue. The reduced scattering coefficient is of the order of 1 mm-1 in all tissues. Absorption coefficients were measured indirectly in optically thick sections. They are typically between 0.1 and 0.5 mm-1 at wavelengths around 580 nm and an order of magnitude lower at 850 nm. At 580 nm and shorter wavelengths the absorption in carcinoma is significantly higher than in adjacent uninvolved tissue. Significant differences were observed in the first-order derivatives of the transmission spectra of carcinoma and surrounding tissues at certain infrared wavelengths. Transmission spectra measured in vivo across the wavelength range from 500 to 860 nm have a similar form to the spectra of excised samples. Linear absorption coefficients are generally of the same order of magnitude as those found in vitro although they are lower at green wavelengths.

Monte Carlo modelling of light propagation in breast tissue.

Light transport in three-dimensional plane-parallel tissue slabs has been modelled by Monte Carlo analogue simulation. The model design has allowed the study of transmission properties that are pertinent to imaging systems for the detection of breast cancer. An important aspect of the investigations is that they make use of data obtained from quantitative measurements of light scattering and absorption in normal and pathological breast tissues. It is shown that an imaging technique which used a raster scanning laser and detector arrangement and plane-parallel compression of the breast could have considerable advantages in terms of improved transmittance, spatial unsharpness and contrast. Time-of-flight gating of images is also found to be beneficial provided that the light intensities after temporal filtering remain adequate.

CT appearances of relapse of lymphoma in the lung.

The patterns of pulmonary relapse were studied in 15 patients with Hodgkin's disease and one patient with Non-Hodgkin's lymphoma. All the patients with Hodgkin's disease had mediastinal lymphadenopathy at initial diagnosis. For those patients with no prior episodes of relapse the mean time to pulmonary involvement was 2 years 11 months compared to over 8 years for those who first relapsed elsewhere. Thirteen patients are still alive; five have been followed up for more than 2 years. Pulmonary involvement consisted of: 1. nodules, either central (12 patients) or peripheral (10 patients), often with connection to the pleura or mediastinum, and sometimes with cavitation; 2. consolidation with or without cavitation (four patients); 3. mediastinal extension into the lung parenchyma (three patients). In seven patients there was evidence of newly enlarged mediastinal nodes. Pleural effusions or masses were seen in six patients and pericardial involvement in one. The chest wall was involved in five. A combination of three or more of these signs were present in 11 patients. The pattern of involvement seen in the patient with Non-Hodgkin's lymphoma was indistinguishable from that seen in Hodgkin's disease. This study has demonstrated a variety of CT appearances useful in establishing or suggesting the diagnosis of pulmonary relapse. Enlarged mediastinal nodes were not a prerequisite but had been present in all patients at some stage in the course of the disease.

Pulmonary uptake in 67-gallium citrate scintigraphy-the 'negative heart' sign.

Diffuse pulmonary uptake in 67-gallium citrate (67-Ga) scintigraphy occurs in a large number of neoplastic and inflammatory conditions. Discrimination between normal and abnormal 67-Ga uptake over the chest can be difficult and a simple visual method for identifying abnormal studies is described. A series of 39 gallium scintigrams was retrospectively reviewed by the authors and reported without knowledge of the patients' clinical condition. Subsequent clinical follow up was obtained to establish the accuracy of the scintigram interpretation. Comparison of pulmonary uptake with that over the cardiac area is recommended as a simple and reliable method of confirming that the level of pulmonary activity is abnormal. In highly abnormal cases the cardiac area is seen as a 'negative heart' image due to the considerably increased activity in the lungs. This sign is best seen with abnormal diffuse uptake but is also seen with abnormal focal uptake. Care must be taken, as the sign may be masked, if uptake over the cardiac area itself is increased.

Diagnostic imaging of post-irradiation changes in the chest.

Thirty-nine patients were studied with regard to post-irradiation changes in the chest. Twenty of these were reviewed retrospectively and 19 studied prospectively. All patients had chest radiographs and computed tomography (CT) of the chest following radiotherapy. Nineteen also had ventilation and perfusion studies of the lung, including single photon emission computed tomography (SPECT) and these were correlated with the chest radiographs and computed tomography. The majority showed abnormalities on computed tomography, the commonest being areas of lung opacification and evidence of volume loss. Several patients also showed a reduction in the size of pulmonary vessels. In most but not all, the changes were also seen on the chest radiographs. Abnormalities were not confined to the radiation fields, the vascular changes being present in large areas of lung which had not been directly irradiated. The structural and functional abnormalities correlated well as shown by ventilation and perfusion scintigraphy. However, single photon emission computed tomography was more sensitive than planar scintigraphy in showing perfusion defects, and it also showed some defects in areas of lung which appeared normal on computed tomography and the chest film. Computed and photon emission tomography were considerably more sensitive than chest radiography in showing the changes due to irradiation. The chest radiograph is clearly an insensitive indicator of post-irradiation change in the lung. Functional abnormalities are more profound and extensive than the chest film suggests, even when it is positive. There are clear implications for the planning of radiotherapy fields affecting the chest in patients who have good prospects of long-term survival. The maximum damage is related to irradiation of the hilum or mediastinum and this should be avoided wherever possible.

The accuracy of digital subtraction angiography for the quantification of atherosclerosis.

Digital subtraction angiography (DSA) allows the degree of arterial patency or stenosis to be rapidly quantified. We have assessed the accuracy with which a single-plane DSA system is able to quantify area patency by densitometric and geometric methods. Arterial phantoms were designed to test for systematic error; intra-arterial DSA images of critical lesions of the carotid bifurcation and the lower abdominal and peripheral vessels were used to determine intra- and interobserver reproducibility. The densitometric method, which was more accurate than the geometric method, had a mean systematic error of up to 4% and a mean intra-observer variability of about 15% (coefficient of variation). We have identified the principal sources of inaccuracy and ways in which it may be reduced.

Osteoporosis and amenorrhea in young women.

Bone density of the radius was measured using both standard photon absorptiometry and X-ray computed tomography (CT) scanning, and of the femur using CT, in 21 young women with amenorrhea and estrogen deficiency due to hyperprolactinemia, 8 due to ovarian failure or weight loss, 17 postmenopausal women with bone fractures presumed to be due to osteoporosis, and 36 young normal controls. Bone density in the postmenopausal women was reduced by 18-20% in the radius and 11% in the femur (p less than 0.001). In the hyperprolactinemic group bone density was significantly reduced only in the femur (by 4%, p less than 0.01). Bone density appeared to be reduced in the other young amenorrheic women both in the radius (by 2-5%) and the femur (3%) but the difference was not significant, although the group was small. This and other studies of bone density suggest the need for prophylactic treatment to prevent osteoporosis in young women with amenorrhea and estrogen deficiency, whatever the cause.

Carcinoma of the breast in women aged 35 or less.

Breast cancer in young women is an unusual problem which has acquired a poor prognostic reputation in the eyes of many clinicians. We have reviewed all 59 patients with malignant disease of the breast aged 35 years or less managed in the Breast Unit at Charing Cross Hospital between 1974 and 1984. After exclusion of 5 patients (2 with lymphomas, 1 with fibrosarcoma, and 2 with inadequate available data), 54 patients were available for analysis. More than 3 months delay from first symptoms to presentation was seen in 45 per cent and 36 per cent were considered 'late' at initial clinical staging (T3-4, N2-3 or M1). Nevertheless, a 5-year survival of 66 per cent was seen among the 29 patients with sufficient length of follow-up. Distribution among the main histological types was very similar to that found in a consecutive series of 264 breast cancers of all age groups in our unit. We conclude that breast carcinomas in young patients do not significantly differ in type or behaviour from other age groups and that with treatment similar to other premenopausal patients, a prognosis comparable to older patients can be expected.