The iron lung: a device for the continuous delivery of fine particulate matter

In aerosol research, bag-sampling techniques are commonly used for temporary storage of aerosols. They have been used for aging studies and to integrate over fluctuations in aerosol properties and concentrations. Here, we describe the design and operation of an iron lung aerosol sampler consisting of a large volume (∼277 l) drum and a conductive drum liner. This iron lung is used for the continuous delivery of fine particulate matter. Its performance for storage and sampling of fine particulate matter has been evaluated with soot from a kerosene lamp by characterizing the change of particle number and size distribution as function of time with a scanning mobility particle sizer. Changes in these properties have been shown to be smooth, demonstrating the utility of the iron lung described here.

[Magnetic resonance angiography with three-dimensional dynamic technique after contrast media administration for the study of the portal system ]

PURPOSE

To evaluate the feasibility of a contrast enhanced MR angiography (MRA) technique, using the latest 1.5 T MR tomoscan, to obtain optimal imaging of the portal system and compare the angiographic images with those obtained by color-Doppler and DSA.

MATERIAL AND METHODS

Thirty patients (9 women and 21 men: average 53 years old) underwent contrast MRA of the portal vein, after portal hypertension had been diagnosed on the basis of clinical and chemical data and by color-Doppler. We used a dynamic 3D FFE T1-weighted breath - hold sequence during the arterial and venous phase after administering. 0.2 mmol/Kg of gadolinium-DTPA were at the rate of 2 ml/s. The contrast bolus was monitored using a 2D FFE T1-weighted sequence on a coronal plane. A FFE T1-weighted sequence was performed on axial plane before and after the dynamic sequence to obtain evaluate the a hepatic parenchyma. In the post processing phase MIP (maximum intensity projection) were reconstructed. We considered the patency of the portal venous system and the presence of cavernomatous and collateral circles; portal thrombosis was classified as partial or complete and as proximal or distal.

RESULTS

Good quality MR angiographic images were obtained in 28 of the 30 cases examined; in 2 patients movement artefacts compromised the image quality. We observed a concordance between MRA and Doppler ultrasound in 79 vessels out of 84 (94%). A 97.5% concordance was found between MRA and DSA (82 vessels out of 84) with a sensitivity of 100% and a specificity of 97.3%. MRA was superior to DSA and Doppler ultrasound for evaluating large collateral shunts, above all gastro-esophageal and paraumbilical shunts, and complex anatomical conditions.

CONCLUSIONS

Where available, advanced MRA technology with contrast enhancement should be used as a routine modality to study the anatomy and pathology and the portal system in all patients in whom Doppler ultrasound has yielded doubtful information. MRA is well-suited to obtain good vascular imaging before surgical or interventional procedures.

Optical gain in silicon nanocrystals

Adding optical functionality to a silicon microelectronic chip is one of the most challenging problems of materials research. Silicon is an indirect-bandgap semiconductor and so is an inefficient emitter of light. For this reason, integration of optically functional elements with silicon microelectronic circuitry has largely been achieved through the use of direct-bandgap compound semiconductors. For optoelectronic applications, the key device is the light source--a laser. Compound semiconductor lasers exploit low-dimensional electronic systems, such as quantum wells and quantum dots, as the active optical amplifying medium. Here we demonstrate that light amplification is possible using silicon itself, in the form of quantum dots dispersed in a silicon dioxide matrix. Net optical gain is seen in both waveguide and transmission configurations, with the material gain being of the same order as that of direct-bandgap quantum dots. We explain the observations using a model based on population inversion of radiative states associated with the Si/SiO2 interface. These findings open a route to the fabrication of a silicon laser.

[Breath-hold gadolinium enhanced tree-dimensional MR angiography: personal experience in the thoracic-abdominal area]

PURPOSE

To investigate different clinical applications of gadolinium-enhanced MR angiography (Gd MRA) using three-dimensional breath-hold GE sequences, without bolus time calculation, in patients with vascular diseases.

MATERIAL AND METHODS

Forty-seven patients were examined (49 studies in all). Eleven of them had an abdominal aortic aneurysm, 6 surgical bypass, 7 renal artery stenosis, 3 aortoiliac Wallstent, 7 aortic stent-graft; 11 patients had a suspected condition in the thoracic aorta and pulmonary arteries, 1 had subclavian artery stenosis and 1 suspected axillary artery compression. All patients were submitted to breath-hold Gd MRA, after 30-40 mL Gd, with a 1.5 T magnet (Gyroscan ACS-NT, Philips, The Netherlands) and a standard body coil. The GE sequences were acquired with TR = 8.8, TE = 2.7, FA = 60 degrees, matrix = 163 x 512, with 28 seconds acquisition time. Digital subtraction angiography and intraoperative findings were the reference standards to evaluate the results.

RESULTS

Thoracopulmonary district: metastatic compression of axillary vessels was found in 1 breast cancer patient; the true and the false lumens and the intimal flap were identified in 2 patients with chronic aortic dissection (Stanford A), and graft patency and complete resolution of the aortic dissection was seen in the patient operated on for acute aortic dissection (Stanford A). The thrombus, lumen, extent and diameter were studied in 2 patients with thoracic aortic aneurysms. Subclavian artery stenosis was demonstrated in 1 patient, which was treated with transluminal angioplasty and stenting. The other 6 patients had normal findings. Abdominal aortic aneurysms (AAA): as for disease extent, breath-hold Gd MRA had 100% sensitivity and specificity compared with surgical findings. Juxtarenal aneurysm extent, which had been missed at DSA, was detected in 1 patient and then confirmed at surgery. Stenosis: comparing DSA and MRA findings in the whole series of patients we had 97.4% agreement (155/159 arteries), that is 76.4% (13/17) arteries) considering only stenoses > 50%. Breath-hold Gd MRA sensitivity and specificity were 100 and 87.5%, respectively, in our 28 stenoses. Bypass, aortoiliac stent, vascular endograft: patency was demonstrated in all the 6 surgical bypass patients, and there was agreement with color Doppler findings in 5 of 6. Breath-hold Gd MRA seems to have no possible applications in the follow-up of percutaneously implanted iliac stents, but we had excellent findings about patency and position of nichel-titanium endografts used for AAA treatment.

CONCLUSIONS

We optimized breath-hold 3D MRA without bolus transit time calculation and with high-dose Gd in different clinical vascular conditions. In our opinion, 3D GE sequences can replace DSA in selected cases, providing a fast, accurate and noninvasive examination.

[Computerized tomography of the lungs in patients with congenital immunodeficiency. Comparison with clinicoradiologic assessment]

PURPOSE

Primary immunodeficiencies (PI) are a heterogeneous and relatively uncommon group of conditions. As a result of one or more immune system abnormalities, PI decrease the body resistance to infections. The respiratory tract is affected in most cases as a result of its natural exposure to pathogenic agents; repeated infections can lead to pulmonary alterations. We investigated the yield of High Resolution CT (HRCT) and Helical CT in pediatric patients with different PI and then correlated the CT patterns with the patients' clinical history and physical status.

MATERIAL AND METHODS

We examined 19 pediatric patients with different types of PI. All patients presented recurrent infections (rhinosinusitis, bronchitis, bronchopneumonia) with cough and chronic catarrh for at least 3 months a year. Fifteen patients were examined with HRCT and 4 with Helical CT. Images were evaluated for presence and severity of alveolitis, bronchiectasis, peribronchial thickening, mucous plugs, air trapping, bronchiolitis, consolidation, abscesses, bullae, emphysema and fibrotic changes. All parameters were given a score and a partial and an overall score calculated for each parameter. All scores were compared to study the correlations between CT patterns, clinical history and patients' status and for possible characterization of the different groups by CT patterns. Finally, all alterations were classified by their anatomical distribution in each pulmonary lobe.

RESULTS

Scores ranged 0 to 18, with a mean of 8.1 points. There were no correlations between CT patterns, patients' history and clinical status and any disease type. The midlobe was the preferential site for bronchiectasis while lower lobes were more involved by other conditions, such as consolidation, air trapping and alveolitis.

CONCLUSIONS

Both HRCT and Helical CT proved to be useful tools for monitoring PI patients. The two techniques can be especially valuable in symptomatic patients with negative radiographic findings because they can show (non-)reversible damage, which helps improve planning of drug and/or physical therapy. The scoring system, even if not closely correlated with clinical signs, could be a major tool for PI follow-up and for monitoring treatment success.

The relationship of dietary intake and serum levels of retinol and beta-carotene with breast cancer. Results of a case-control study

The possible association between the risk of breast cancer, blood level, and dietary intake of preformed Vitamin A (retinol) and beta-carotene was investigated in a case-control study carried out from May 1982 to June 1985. The patients studied were 214 previously untreated individuals with T1-2, N0-1, M0 breast cancer admitted to the National Cancer Institute of Milan and 215 controls admitted for conditions other than neoplastic or metabolic disorders. Both cases and controls were selected from an age group ranging from 30 to 65 years old. Plasma levels of retinol and beta-carotene were tested from blood samples drawn during the first day after admission to the hospital. A questionnaire about diet was used to estimate the mean intake of 69 food items from which a daily dietary index of retinol and beta-carotene intake was computed. Information relating to the woman's history, socioeconomic status, and known risk factors for breast cancer was also collected. No association was found between beta-carotene (in the diet or blood) or dietary retinol and the risk of breast cancer. As for blood retinol, our data show a significant trend of increasing risk with higher levels; multivariate relative risk for subsequent serum levels based on the control quintiles, are 1, 1.5, 1.8, 1.7; (test for linear trend: chi-square = 8.26). Thus, these findings, together with the results of other studies, suggest that retinol and beta-carotene are unlikely to be related to the risk of breast cancer.

Vitamin A and female lung cancer: a case-control study on plasma and diet

Plasma and dietary levels of retinol and beta-carotene were evaluated in a consecutive series of 47 females with histologically proven primary lung cancer and 159 nonneoplastic hospital controls. The dietary questionnaire included 69 different items: special care was given to foods rich in vitamin A and seasonal foods (e.g., vegetables and fruits), whereas serum analysis was focused on retinol and beta-carotene. Age-adjusted mean values for cases and controls were, respectively, 458.3 vs. 551.3 mg for plasma retinol, 276.1 vs. 390.1 mg for plasma carotene; 598.1 vs 820.6 mg for daily retinol, and 628.0 vs. 882.5 mg for dietary carotene. The odds ratios for low vs. high tertile, adjusted for age, smoking, retinol or carotene, cholesterol, and triglycerides by multivariate analysis were, respectively, 1.13 for plasma retinol, 5.04 for plasma carotene, 3.27 for dietary retinol, and 2.93 for dietary carotene. For all the examined items, there was a trend of increased risk for the second and third tertile, and statistical significance was reached for plasma beta-carotene (p less than 0.05). The hypothesis that a higher risk of lung cancer is related to a low vitamin A consumption is supported by these data.