Half-value layer measurement: simple process method using radiochromic film

Although the half-value layer (HVL) is one of the important parameters for QA and QC, constant monitoring has not been performed because the measurements using an ionization chamber (IC) are time-consuming and complicated. To solve these problems, the use of radiochromic film (GAFCHROMIC XR TYPE R: GAF-R) with step-shaped aluminum (Al) filters, referred to herein as the simple process method, has been developed. The measurement X-ray tube voltages were 120 kV, 100 kV, and 80 kV. The Al filter area, the full exposure area, and the unexposed area were set on the GAF-R so as to obtain correct data. The HVL was evaluated using the density attenuation ratio. The HVLs obtained using the GAF-R and an 1C dosimeter were compared. HVLs with X-ray tube voltages of 120 kV, 100 kV, and 80 kV using the GAF-R were 4.10 mm, 3.55 mm and 2.97 mm, respectively. The difference ratios of the HVLs using the GAF-R and the IC were 1.2%, 7.6%, and 10.0%, respectively. The HVL at 120 kV can be routinely and quickly measured using the simple process method. Therefore, an IC dosimeter is not needed for HVL measurements for QA and QC. However, the HVL measurements of low energy (100 kV and 80 kV) need attention.

[Subtraction image for dynamic liver MRI using free breath-hold at functional residual capacity: a clinical trial]

PURPOSE

Dynamic liver MRI images have been obtained under expiration breath holding (BH). However, problems with obtaining reproducible liver positions often observed. This study investigated ways to improve the reproducibility of liver position on dynamic liver MRI.

MATERIALS AND METHODS

After giving informed consent, 60 patients (32 males and 28 females, ages 33-85, median age 69) were examined by liver dynamic MRI under two types of BH. The BH phases were voluntary expiration (VE) phase without any explanations and functional residual capacity (FRC) phase after careful explanation was provided. Plain images, arterial phase images, portal phase images and parenchymal phase images were obtained. For statistical evaluation of reproducibility, the area of the 2nd or 3rd images from top of the liver was measured in each phase using a threshold value of half maximum. Misregistration areas were calculated by finding the remainder of the liver area in the plain-arterial (Pl-A) phase, arterial-portal (A-Po) phase, plain-parenchymal (Pl-Pa) phase. Contingency table analysis was done due to the misregistration was occurred or not.

RESULTS

Misregistration of liver image on the VE and the FRC of three phase types were statistical significant on the Pl-A (p < 0.01), on the A-Po (p < 0.01) and on the Pl-Pa (p < 0.05), respectively.

CONCLUSION

The FRC phase following careful explanation of the BH provided significantly improved reproducibility of liver position on dynamic liver MRI. Therefore, precise subtraction images could be obtained for routine clinical examinations without slice matching.

Beneficial effect of angiotensin-converting enzyme inhibitor on dilated cardiomyopathy induced by autoimmune mechanism against beta1-adrenoceptor

We have shown that a peptide corresponding to the sequence of the second extracellular loop of the human beta1-adrenoceptor (beta1-peptide) was able to induce an autoimmune cardiomyopathy in rabbits. In this study, we examined the effect of angiotensin-converting enzyme inhibitor (ACEI) on beta1-peptide-induced cardiomyopathy. Rabbits were divided into four groups: (1) control group (n= 6) receiving saline injection; (2) beta1-peptide group (n = 8) immunized with beta1-peptide; (3) ACEI group (n = 6), lisinopril (3 mg/day) given orally and receiving saline injection; and (4) ACEI + beta1-peptide group (n = 7), lisinopril (3 mg/day) given orally and immunized with beta1-peptide. Our results showed that, after 1 year, all rabbits in the beta1-peptide group had an increase in heart weight, wall thinning and dilatations of both ventricles as compared with rabbits in the ACEI + beta1-peptide group that had normal heart weight and shape. All rabbits in the beta1-peptide group exhibited multifocal degeneration and necrosis of myocardial cells with moderate infiltration of inflammatory cells. In the ACEI + beta1-peptide group, three rabbits showed focal degeneration and necrosis of myocardial cells accompanied by mononuclear cells. The lesions in this group were apparently less marked than those in the beta1-peptide group. In conclusion, ACEI protects the myocardium from injury induced by an autoimmune mechanism against beta1-adrenoceptor.

Light intensity distribution in the externally illuminated cylindrical photo-bioreactor and its application to hydrogen production by Rhodobacter capsulatus

The light distribution in the externally illuminated cylindrical photo-bioreactor for production of hydrogen by a photosynthetic bacterium Rhodobacter capsulatus ST-410 was estimated. The estimation was performed on the basis of the Matsuura and Smith's diffuse model [1]. In the diffuse model, the incident light rays are assumed to proceed in every direction and the local intensity is calculated as the sum of the intensities of light. Since Lambert-Beer's law, extensively used in photometry, was not useful for explaining the decrease in the intensity of light by the biomass, an empirical expression was used. The measurement of the intensities from every direction was conducted in an externally illuminated cylindrical photo-bioreactor having an inner diameter of 60mm and a working volume of 550ml. The obtained results confirmed our estimation. The light distribution was applied to estimate the hydrogen production by R. capsulatus ST-410 using the same photo-bioreactor. The overall hydrogen-production rate was successfully estimated.

Effects of Ethanolamine as a nitrogen source on hydrogen production by Rhodobacter capsulatus

Ethanolamine was examined as a nitrogen source in the production of hydrogen by Rhodobacter capsulatus ST-410, a hydrogenase-deficient mutant of the strain B-100. It was found that ethanolamine supports cell growth as the sole nitrogen source and permits a large amount of hydrogen evolution, detected at 138 micromol/ml-culture from 3.5 mM ethanolamine and 30 mM DL-malate. The amount corresponded to a stoichiometric yield of 77% and was close to that obtained from 7.0 mM L-glutamate and 30 mM DL-malate. The hydrogen evolution rate per unit biomass (cells) was higher than that with L-glutamate, and the cells grown with ethanolamine had higher nitrogenase activity than the cells grown with L-glutamate. In terms of bioconversion of cellulosic and hemicellulosic biomass to hydrogen, D-glucose, D-xylose, and D-cellobiose were tested as substrates. The results indicated that those sugars permit a large evolution of hydrogen through cultivation with ethanolamine as a nitrogen source. For instance, the cells grown with 3.5 mM ethanolamine evolved hydrogen of 289 micromol/ml-culture (80% yield) from 30 mM D-glucose under a controlled pH of 6.4 to 6.9.

Oxygen administration during hepatic DSA

The research presented in this article examined the role of oxygen in preventing diaphragmatic motion artifacts in delayed-phase hepatic digital subtraction angiography (DSA). The results demonstrate that administering oxygen to patients before the examination substantially reduces artifacts due to motion.

Reducing misregistration of mask image in hepatic DSA

When performing hepatic digital subtraction angiography, misregistration of the mask image can cause artifacts that obscure pathology. For this article, researchers analyzed the breath expiration times of 59 patients and found that expiration times ranged from 1.8 seconds to 6 seconds. Thirty DSA series were obtained taking into account the patient's breath expiration time, and 35 series were obtained without taking the expiration time into consideration. Artifacts were detected in 20% of the DSA series where expiration time was taken into consideration and in 42.9% of series where it was not (p < 0.05). The research showed that misregistration of the mask image during hepatic DSA can be reduced by starting the exposure at the end of breath expiration.

Types of diaphragmatic motion during hepatic angiography

To determine the types and causes of diaphragmatic motion during hepatic angiography, the authors used transarterial cut-film portography (TAP) to study movement of the diaphragm during breath-holding. Thirty-three TAP sequences were studied, and the patients' diaphragmatic motions were classified into four categories according to the distance their diaphragms moved. Results showed that the diaphragm was stationary in 33% of the TAP studies, while perpetual motion occurred in 15% of the studies, early-phase motion occurred in 12% and late-phase motion occurred in 40%. Ten sequences showed diaphragmatic motion of more than 10 mm, with eight sequences showing caudal motion and two showing cranial motion. This article discusses the cause of diaphragmatic motion during breath-holding for hepatic angiography and presents suggestions to reduce motion artifacts during the exam.

Using compensating filters to reduce radiation dose

The study described in this article explores the role of compensating filters in reducing radiation exposure. Radiation exposure levels with and without filters were compared in skull radiographs, hepatic angiographs and one-shot full-length lower extremity radiographs. Absorbed doses were measured with and without a skull filter in a phantom at a depth of 5 cm. Results showed that filters reduced exposure by 29% in skull radiographs, 47% in hepatic angiographs and 80% in one-shot full-length lower extremity radiographs. Absorbed doses were reduced by more than 26% in the skull phantom in the filtered area. To reduce patient dose, the filters were positioned between the x-ray tube and the patient.

Absolute frequency stability of a diode-laser-pumped Nd:YAG laser stabilized to a high-finesse optical cavity

We report the frequency stabilization of a diode-laser-pumped monolithic ring Nd:YAG laser locked to a high-finesse optical cavity. With an independent cavity as a frequency discriminator, the absolute frequency noise was measured to be as low as 2 × 10(-2) Hz/Hz(1/2) at the Fourier frequency of approximately 3 kHz. We also measured the heterodyne beat note between two lasers locked to the independent cavities. The beat linewidth is narrower than 30 Hz and the minimum root Allan variance is approximately 6 × 10(-14).

Reducing motion artifacts during hepatic DSA

In hepatic digital subtraction angiography, artifacts caused by diaphragmatic motion can interfere with the correct diagnosis of hepatic lesions. This article describes the feasibility of using the exhalation holding method in reducing diaphragmatic motion artifacts in hepatic DSA. The authors compared respiratory holding methods in 30 patients who underwent hepatic DSA. They performed a blind comparison of images to assess diaphragmatic motion artifacts. Results showed the images obtained by the exhalation holding method were superior to those obtained by the inhalation holding method in 20 out of 30 series (66.7%).

Effect of cadmium on osteogenesis within diffusion chambers by bone marrow cells: biochemical evidence of decreased bone formation capacity

The biological and biochemical effects of cadmium administration on bone marrow in rats were examined. When young adult rats were administered cadmium (Cd) repeatedly at a dose of 750 micrograms/kg body wt for up to 4 weeks, metallothionein mRNA was detected by a gene expression analysis in their bone marrow at 2 weeks after the first Cd administration, though the amounts were lower than those in liver. To determine the direct effect of cadmium on bone formation, the potential of Cd-treated bone marrow cells and demineralized bone matrix (DBM) to form bone and cartilage was assessed using a diffusion chamber (DC) in vivo, by histological examination, and by biochemical parameters such as alkaline phosphatase (ALP) activity, total calcium and phosphorus content, and the bone-specific vitamin K-dependent Gla-containing protein (BGP) content, relative to mineralization. Diffusion chambers were inoculated with DBM and bone marrow cells from either Cd-treated or nontreated rats (control) and were then implanted subcutaneously into syngeneic nontreated rats. The accumulation of BGP in DCs with Cd-treated bone marrow was significantly lower than that in control DCs. Unlike in control DC, a peak of ALP activity did not occur at 4 weeks postimplantation in DC implants inoculated with Cd-treated bone marrow; the ALP activity and calcium content in these implants were also significantly lower than those of the control bone marrow-containing chambers at the early stage of implantation. Histological examinations of chambers with Cd-treated marrow showed a decreased area of cartilage and bone foci compared with those in control chambers. These findings suggest that Cd administration inhibits the osteoblastic and chondroblastic differentiation pathway in bone marrow through direct effects on these cells.

A diaphragmatic compensating filter for hepatic angiography

To enhance the clarity of angiographic images, a diaphragmatic compensating filter (DCF) covering the sub-phrenic portion was constructed. The required shape of a DCF for a high optical density part of the angiograms was determined by the distribution limit of the outline of the diaphragms, but the shape of the low optical density part could not be specified. The smallest tolerance of a DCF for the respiratory motion of a diaphragm was 13.2 mm at the film. Thus, a DCF was effective in more than 95.8% of angiograms. Our clinical results showed remarkable improvement in those images. The clinical areas between radiographic images with and without a DCF were improved by more than 27% according to an image analysis system. Therefore a DCF is indispensable in conventional hepatic angiography and digital subtraction angiography. In addition, only one type of a DCF is possible for use in combination with lateral compensating filters.