Mouth breathing, another risk factor for asthma: the Nagahama Study.

BACKGROUND: Allergic rhinitis, a known risk factor for asthma onset, often accompanies mouth breathing. Mouth breathing may bypass the protective function of the nose and is anecdotally considered to increase asthma morbidity. However, there is no epidemiological evidence that mouth breathing is independently associated with asthma morbidity and sensitization to allergens. In this study, we aimed to clarify the association between mouth breathing and asthma morbidity and allergic/eosinophilic inflammation, while considering the effect of allergic rhinitis. METHODS: This community-based cohort study, the Nagahama Study, contained a self-reporting questionnaire on mouth breathing and medical history, blood tests, and pulmonary function testing. We enrolled 9804 general citizens of Nagahama City in the Shiga Prefecture, Japan. RESULTS: Mouth breathing was reported by 17% of the population and was independently associated with asthma morbidity. The odds ratio for asthma morbidity was 1.85 (95% CI, 1.27-2.62) and 2.20 (95% CI, 1.72-2.80) in subjects with mouth breathing alone and allergic rhinitis alone, which additively increased to 4.09 (95% CI, 3.01-5.52) when mouth breathing and allergic rhinitis coexisted. Mouth breathing in nonasthmatics was a risk for house dust mite sensitization, higher blood eosinophil counts, and lower pulmonary function after adjusting for allergic rhinitis. CONCLUSION: Mouth breathing may increase asthma morbidity, potentially through increased sensitization to inhaled allergens, which highlights the risk of mouth-bypass breathing in the 'one airway, one disease' concept. The risk of mouth breathing should be well recognized in subjects with allergic rhinitis and in the general population.

Fucosylated TGF-ß receptors transduces a signal for epithelial-mesenchymal transition in colorectal cancer cells.

BACKGROUND: Transforming growth factor-ß (TGF-ß) is a major inducer of epithelial-mesenchymal transition (EMT) in different cell types. TGF-ß-mediated EMT is thought to contribute to tumour cell spread and metastasis. Sialyl Lewis antigens synthesised by fucosyltransferase (FUT) 3 and FUT6 are highly expressed in patients with metastatic colorectal cancer (CRC) and are utilised as tumour markers for cancer detection and evaluation of treatment efficacy. However, the role of FUT3 and FUT6 in augmenting the malignant potential of CRC induced by TGF-ß is unclear. METHODS: Colorectal cancer cell lines were transfected with siRNAs for FUT3/6 and were examined by cell proliferation, invasion and migration assays. The expression and phosphorylation status of TGF-ß downstream molecules were analysed by western blot. Fucosylation of TGF-ß receptor (TßR) was examined by lectin blot analysis. RESULTS: Inhibition of FUT3/6 expression by siRNAs suppressed the fucosylation of type I TßR and phosphorylation of the downstream molecules, thereby inhibiting the invasion and migration of CRC cells by EMT. CONCLUSION: Fucosyltransferase 3/6 has an essential role in cancer cell adhesion to endothelial cells by upregulation of sialyl Lewis antigens and also by enhancement of cancer cell migration through TGF-ß-mediated EMT.

Stromal cells expressing hedgehog-interacting protein regulate the proliferation of myeloid neoplasms.

Aberrant reactivation of hedgehog (Hh) signaling has been described in a wide variety of human cancers including cancer stem cells. However, involvement of the Hh-signaling system in the bone marrow (BM) microenvironment during the development of myeloid neoplasms is unknown. In this study, we assessed the expression of Hh-related genes in primary human CD34(+) cells, CD34(+) blastic cells and BM stromal cells. Both Indian Hh (Ihh) and its signal transducer, smoothened (SMO), were expressed in CD34(+) acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS)-derived cells. However, Ihh expression was relatively low in BM stromal cells. Remarkably, expression of the intrinsic Hh-signaling inhibitor, human Hh-interacting protein (HHIP) in AML/MDS-derived stromal cells was markedly lower than in healthy donor-derived stromal cells. Moreover, HHIP expression levels in BM stromal cells highly correlated with their supporting activity for SMO(+) leukemic cells. Knockdown of HHIP gene in stromal cells increased their supporting activity although control cells marginally supported SMO(+) leukemic cell proliferation. The demethylating agent, 5-aza-2'-deoxycytidine rescued HHIP expression via demethylation of HHIP gene and reduced the leukemic cell-supporting activity of AML/MDS-derived stromal cells. This indicates that suppression of stromal HHIP could be associated with the proliferation of AML/MDS cells.

Influence of medial meniscectomy on stress distribution of the femoral cartilage in porcine knees: a 3D reconstructed T2 mapping study.

OBJECTIVE: Previous studies have shown that meniscectomy results in an increase of local load transmission and may cause degeneration of the knee cartilage. Using 3D reconstructed T2 mapping, we examined the influence on the femoral cartilage under loading after medial meniscectomy. DESIGN: Ten porcine knees were imaged using a pressure device and a 3.0-T magnetic resonance imaging (MRI) system. Consecutive sagittal T2 maps were obtained in neutral alignment with and without compression, and under compression at 10° varus alignment. After medial meniscectomy, the aforementioned MRI was repeated. Cartilage T2 before and after meniscectomy under each condition were compared at the 12 regions of interest (ROIs) defined on the 3D weight-bearing area of the femoral cartilage. RESULTS: Before meniscectomy, large decreases in T2 under neutral compression were mainly seen at the anterior and central ROIs of the medial cartilage, which shifted to the posterior ROIs after meniscectomy. There were significant differences in decrease in T2 ratio with loading before and after meniscectomy (9.8%/4.3% at the anterior zone, 4.0%/11.4% at the posterior zone, P < 0.05). By applying varus compression, a more remarkable decrease in the cartilage T2 in posterior ROIs after meniscectomy was achieved. (Before/after meniscectomy: 8.7%/2.5% at the anterior zone, 7.2%/18.7% at the posterior zone, P < 0.05). CONCLUSIONS: Assuming a decrease in T2 with loading correlated with the applied pressure, a deficiency of the medial meniscus resulted in a shift of the primary area with a maximal decrease of cartilage T2 with loading posteriorly in the porcine knee joint, presumably reflecting the intraarticular environment of load transmission.

Ex vivo imaging of mouse brain using micro-CT with non-ionic iodinated contrast agent: a comparison with myelin staining.

OBJECTIVE: We investigated the use of micro-CT with contrast agent for the non-invasive characterisation of fixed mouse brain tissue specimens as a means to differentiate between grey and white matter. METHODS: Nine mice were divided into two groups for micro-CT (n=6) and myelin staining (n=3) experiments. Six mice underwent in vivo micro-CT and were then prepared for brain specimens by transcardiac perfusion with paraformaldehyde. The six mouse brains were soaked in two different concentrations of non-ionic iodinated contrast agents (60 and 150 mg ml(-1)). Immersion times used for each concentration of iodine were for 3, 7 and 14 days. Three-dimensional ex vivo micro-CT images were acquired with a resolution of 39 µm(3) to create isotropic images. The other three mice were stained for evaluation of the myelin structure. RESULTS: Soaking the brains in non-ionic iodinated contrast agent resulted in clear differences in signal between the grey matter, the white matter and the ventricular spaces. The 150 mg ml(-1) contrast agent solution yielded images with better contrast-to-noise ratio (CNR) than 60 mg ml(-1) iodine contrast agent solution. 14 days of soaking yielded images with better CNR than 3 and 7 days. The CT contrast of grey and white matter derived from the iodine-soaked fixed brains was strongly related to tissue myelin. CONCLUSION: The present study demonstrated that micro-CT can be used to detect the mouse brain myelin structure at 3, 7 and 14 days after fixation using a CT contrast agent.

Three-dimensional patterns of early acetabular cartilage damage in hip dysplasia; a high-resolutional CT arthrography study.

OBJECTIVE: The purpose of this study was to examine the three-dimensional (3D) progression patterns of early acetabular cartilage damage in hip dysplasia using high-resolutional computed tomography (CT) arthrography. DESIGN: Thirty-two dysplastic hips of 26 Japanese symptomatic females including 21 hips in pre-stage of osteoarthritis (Kellgren-Lawrence (K-L) grade 0; mean patient age, 32.0 years) and 11 hips in early stage of osteoarthritis (K-L grade 1 or 2; mean patient age, 32.8 years) were examined. Isotropic high-resolutional CT arthrography with an image resolution of 0.5 mm in any orthogonal direction was performed. A 3D acetabular cartilage model was generated and we evaluated distribution of cartilage thickness in 12 zones after dividing the weight-bearing area of the hip joint in radial and lateral/medial directions. RESULTS: In pre-stage of osteoarthritis, significant differences in cartilage thickness were observed between the lateral and medial zones in all radial regions, most prominently in the antero-superior region. In early stage of osteoarthritis, no significant differences in cartilage thickness were observed, except in the most posterior region. The lateral-medial (LM) ratio was defined as cartilage thickness in the lateral zone divided by that in the medial zone, and hips with the LM ratio in the antero-superior region of <1.4 had significantly more extensive involvement of labral tears than hips with the LM ratio of ≥1.4. CONCLUSIONS: In hip dysplasia, acetabular cartilage damage was probably occurred in the antero-superior lateral area. The LM ratio may be a sensitive index to quantify early cartilage damage associated with extent of labral disorders.

Ensembles of neural networks based on the alteration of input feature values.

An ensemble performs well when the component classifiers are diverse yet accurate, so that the failure of one is compensated for by others. A number of methods have been investigated for constructing ensemble in which some of them train classifiers with the generated patterns. This study investigates a new technique of training pattern generation. The method alters input feature values of some patterns using the values of other patterns to generate different patterns for different classifiers. The effectiveness of neural network ensemble based on the proposed technique was evaluated using a suite of 25 benchmark classification problems, and was found to achieve performance better than or competitive with related conventional methods. Experimental investigation of different input values alteration techniques finds that alteration with pattern values in the same class is better for generalization, although other alteration techniques may offer more diversity.

Typing of O26 enterohaemorrhagic and enteropathogenic Escherichia coli isolated from humans and cattle with IS621 multiplex PCR-based fingerprinting.

AIMS: This study evaluated a typing method of O26:H11 enterohaemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC) based on the variation in genomic location and copy numbers of IS621. METHODS AND RESULTS: Two multiplex PCRs, targeting either the left (5') or right (3') IS/chromosome junction of 12 IS621 insertion sites and one PCR specific of another truncated copy, were developed. Thirty-eight amplification profiles were observed amongst a collection of 69 human and bovine O26:H11 EHEC and EPEC. Seventy-one per cent of the 45 EHEC and EPEC with identical IS621 fingerprints within groups of two, three or four isolates had >85% pulsed field gel electrophoresis (PFGE) profile similarity, including four groups of epidemiologically related EHEC or EPEC, while most of the groups had <85% similarity between each others. Epidemiologically related EHEC from each of three independent outbreaks in Japan and Belgium also exhibited identical IS621 fingerprints and PFGE profiles. CONCLUSIONS: The IS621 fingerprinting and the PFGE are complementary typing assays of EHEC and EPEC; though, the former is less discriminatory. SIGNIFICANCE AND IMPACT OF THE STUDY: The IS621 printing method represents a rapid (24 h) first-line surveillance and typing assay, to compare and trace back O26:H11 EHEC and EPEC during surveys in farms, multiple human cases and outbreaks.

Non-invasive ventilation in severe asthma attack, its possibilities and problems.

Asthma attack is characterized by episodic attacks of cough, dyspnea and wheeze occurring due to bronchoconstriction, airway hyperresponsiveness and mucous hypersecretion. Although nationwide clinical guidelines have been published to establish the standard care of asthma, choices in the treatment of fatal asthma attacks remain of clinical significance. Especially, in a severe asthma attack, despite the application of conventional medical treatment, respiratory management is critical. Even though non-invasive ventilation (NIV) has been shown to be effective in a wide variety of clinical settings, reports of NIV in asthmatic patients are scarce. According to a few prospective clinical trials reporting promising results in favour of the use of NIV in a severe asthma attack, a trial of NIV prior to invasive mechanical ventilation seems acceptable and may benefit patients by decreasing the need for intubation and by supporting pharmaceutical treatments. Although selecting the appropriate patients for NIV use is a key factor in successful NIV application, how to distinguish such patients is quite controversial. Larger high quality clinical trails are urgently required to confirm the benefits of NIV to patients with severe asthma attack. In this article, we focus on the body of evidence supporting the use of NIV in asthma attacks and discuss its advantages as well its problems.

Loading and knee alignment have significant influence on cartilage MRI T2 in porcine knee joints.

OBJECTIVE: Physiological magnetic resonance imaging (MRI) under loading or knee malalignment conditions has not been thoroughly investigated. We assessed the influence of static loading and knee alignment on T2 (transverse relaxation time) mapping of the knee femoral cartilage of porcine knee joints using a non-metallic pressure device. METHODS: Ten porcine knee joints were harvested en bloc with intact capsules and surrounding muscles and imaged using a custom-made pressure device and 3.0-T MRI system. Sagittal T2 maps were obtained (1) at knee neutral alignment without external loading (no loading), (2) under mechanical compression of 140 N (neutral loading), and (3) under the same loading conditions as in (2) with the knee at 10 degrees varus alignment (varus loading). T2 values of deep, intermediate, and superficial zones of the medial and lateral femoral cartilages at the weight-bearing area were compared among these conditions using custom-made software. Cartilage contact pressure between the femoral and tibial cartilages, measured by a pressure-sensitive film, was correlated with cartilage T2 measurements. RESULTS: In the medial cartilage, mean T2 values of the deep, intermediate, and superficial zones decreased by 1.4%, 13.0%, and 6.0% under neutral loading. They further decreased by 4.3%, 19.3%, and 17.2% under varus loading compared to no loading. In the lateral cartilage, these mean T2 values decreased by 3.9%, 7.7%, and 4.2% under neutral loading, but increased by 1.6%, 9.6%, and 7.2% under varus loading. There was a significant decrease in T2 values in the intermediate zone of the medial cartilage under both neutral and varus loading, and in the superficial zone of the medial cartilage under varus loading (P<0.05). Total contact pressure values under neutral loading and varus loading conditions significantly correlated with T2 values in the superficial and intermediate zones of the medial cartilages. CONCLUSIONS: The response of T2 to change in static loading or alignment varied between the medial and lateral cartilages, and among the deep, intermediate, and superficial zones. These T2 changes were significantly related to the contact pressure measurements. Our results indicate that T2 mapping under loading allows non-invasive, biomechanical assessment of site-specific stress distribution in the cartilage.

Experimental verification of protective effect of hydrogen-rich water against cisplatin-induced nephrotoxicity in rats using dynamic contrast-enhanced CT.

Our aim was to assess the protective effect of hydrogen-rich water against cisplatin-induced nephrotoxicity in rats using dynamic contrast-enhanced CT (DCE-CT). DCE-CT studies were performed in 30 rats (8 weeks old) on days 0, 2, 4 and 7 using multidetector row CT. The rats were divided into three groups: a control group (n = 6) with free access to standard water and without cisplatin injection, a non-treatment group (n = 12) with free access to standard water and injected with cisplatin (3.6 mg kg(-1) body weight) intraperitoneally on day 0 and a treatment group (n = 12) with free access to hydrogen-rich water starting from 7 days before cisplatin injection. The contrast clearance per unit renal volume (K(1)) was estimated from the DCE-CT data using the Patlak model. The contrast clearance of the entire kidney (K) was obtained by multiplying K(1) by the renal volume. The serum creatinine level was also measured on day 7. The K(1) and K values normalised by those on day 0 in the treatment group were significantly greater than those in the non-treatment group on days 2, 4 and 7. There were no significant differences in the normalised K value between the treatment and control groups on days 2 and 7. The serum creatinine level in the treatment group was significantly lower than that in the non-treatment group and was not significantly different from that in the control group. This study demonstrated that hydrogen-rich water ameliorates renal dysfunction due to cisplatin-induced nephrotoxicity in rats.

Development of a method to quantitatively monitor the effect of inhibition of nitric oxide synthase on tumour vascular activity using dynamic contrast-enhanced computed tomography.

This study was undertaken to develop a method to quantitatively monitor the effect of inhibition of nitric oxide synthase (NOS) on tumour vascular activity using dynamic contrast-enhanced computed tomography (DCE-CT). The DCE-CT studies were performed in 13 anaesthetized rats bearing tumours. To investigate the effect of NOS inhibition, N-nitro-L-arginine (L-NNA) was intravenously administered in eight rats, while only the vehicle was administered in five rats. The contrast enhancement (CE) images were generated by subtracting the CT images before and after the administration of contrast agent. The tumour blood volume (TBV) images were also generated. The CE significantly decreased after L-NNA administration, while there were no significant changes when only the vehicle was administered. There was a good correlation between CE and TBV, suggesting that CE mainly reflects TBV. In conclusion, the present method appears to be useful for monitoring the effect of NOS inhibition on tumour vascular activity.

Evaluation of image quality in portal imaging using a combination of a storage phosphor plate and diagnostic cassette.

It is useful to utilise a computed radiography system with a combination of storage phosphor plates and therapy cassettes for portal images. However, the therapy cassette has some disadvantages. The objective of the present study was to determine whether the disadvantages of a diagnostic cassette could be overcome to obtain clinically useful portal images. A storage phosphor plate has 0.3 mm of lead foil on the distal surface to reduce backscattered radiation. When the plate is reversed, the lead foil acts as a front intensifying screen, similar to the metal plate of a therapy cassette. We reversed a combination of the diagnostic cassette and storage phosphor plate and obtained portal images of the contrast-detail phantom and the Rando phantom (The Phantom Laboratory, Salem, NY) using three types of cassettes: a reversed diagnostic cassette, a therapy cassette and a diagnostic cassette. The image quality was subjectively evaluated. The Friedman and Wilcoxon tests were applied for statistical analyses. Evaluation of images for the contrast-detail phantom revealed that the reversed diagnostic cassette was inferior to the therapy cassette and superior to the diagnostic cassette, and that the differences were significant (p<0.017). There was no significant difference between the reversed diagnostic cassette and therapy cassette (p>0.05) for the Rando phantom. Portal images obtained using the reversed diagnostic cassette were of sufficiently high quality for clinical use as determined by Rando phantom studies.

A quantitative method for estimating hepatic blood flow using a dual-input single-compartment model.

The purpose of this study was to investigate the accuracy of a quantitative method for estimating arterial hepatic blood flow and portal hepatic blood flow separately using a dual-input single-compartment model compared with the maximum slope method using computer simulations and clinical data. In computer simulations, the rate constants for the transfer of contrast agent (CA) from the hepatic artery to the liver (K(1a)), from the portal vein to the liver (K(1p)) and from the liver to the blood (k(2)) were estimated from simulated time-density curves with various transit times of CA from the aorta to the liver (tau(a)) and from the portal vein to the liver (tau(p)) using the linear least-squares (LLSQ) method. In clinical studies, dynamic CT data were acquired from 27 patients, and parametric maps of K(1a), K(1p) and k(2) were generated by applying the LLSQ method pixel by pixel. In simulation studies, tau(a) and tau(p) were found to have a large and a small effect on the estimates of K(1a) and K(1p), respectively. In clinical studies, the K(1a) and K(1p) values estimated with the maximum slope method were underestimated by 60+/-29% and 37+/-12%, respectively, compared with those estimated by the LLSQ method. In conclusion, our results suggest that correction of tau(a) is necessary for accurately estimating K(1a) and K(1p). Our method is therefore promising for the evaluation of hepatic blood flow in various liver diseases because it allows us to evaluate arterial hepatic blood flow and portal hepatic blood flow separately and visually.

Promotion of medial collateral ligament healing using a high-voltage electrical field.

PURPOSE: To assess the biomechanical and histological effects of a high-voltage electrical field on ligament healing. METHODS: 54 male Wistar rats were used. The medial collateral ligaments (MCLs) of 6 rats were measured for normal biomechanical failure load and stiffness. MCLs of the remaining 48 rats were transected and randomly assigned; half were subjected to a high-voltage electrical field for 8 hours a day (experimental group), and the other half were kept under normal conditions (control group). Eight rats from each group were killed 2, 4, and 6 weeks after the transection and their MCLs were tested biomechanically and histologically. RESULTS: Failure load and stiffness of the MCLs in the experimental group were significantly higher than those in the control group 2 weeks after transection, but not thereafter. At week 2, the granulation tissue completely occupied the space between the cut ends of the MCL in the experimental group, whereas some gaps remained in the control group. CONCLUSION: A high-voltage electrical field appear to accelerate ligament healing in the initial 2 weeks. Earlier initial healing may allow earlier start of the rehabilitation.

An efficient method for calculating kinetic parameters in a dual-input single-compartment model.

Quantitative measurement of hepatic perfusion has the potential to provide important information in the assessment and management of various liver diseases. The utility of hepatic perfusion characterization relies on the resolution of each component of its dual blood supply, i.e. the hepatic artery and portal vein. In this study, a linear equation was derived by integrating the differential equation describing the kinetic behaviour of contrast agent (CA) in a dual-input single-compartment model, from which the kinetic parameters can be easily obtained using the linear least-squares method. The usefulness of this method was investigated using computer simulations, in comparison with the non-linear least-squares (NLSQ) method. This method calculated the kinetic parameters faster than the NLSQ method by a factor of approximately 10, with almost the same accuracy as the NLSQ method. This method will be useful for analysing the kinetic behaviour of CA in the unique liver environment, especially by generating the functional images of kinetic parameters.

Relationship between variations in the circle of Willis and flow rates in internal carotid and basilar arteries determined by means of magnetic resonance imaging with semiautomated lumen segmentation: reference data from 125 healthy volunteers.

BACKGROUND AND PURPOSE: Volume flow rates in the feeding arteries of the brain are measured to evaluate blood flow dynamics in vascular disease. Although these flow values are thought to be effected by anatomic variations in the circle of Willis, few reports have described the effect. This study reports on the relationship between variations in the circle of Willis and volume flow rates in the bilateral internal carotid and basilar arteries of normal volunteers. METHODS: We prospectively examined 125 healthy volunteers by MR imaging. Variations in the circle of Willis were classified as "textbook" type, hypoplasia of the precommunicating segment of the anterior cerebral artery (A1), hypoplasia of the precommunicating segment of the posterior cerebral artery (P1), or "other." Volume flow rates were measured by 2D cine phase-contrast MR imaging. Lumen boundaries and volume flow rates were semiautomatically determined by pulsatility-based segmentation. RESULTS: Of the 117 subjects (61 men, 56 women; mean age, 23.6 years) considered suitable for flow measurement, 105 showed textbook type, and 6 each showed A1 hypoplasia and P1 hypoplasia. Total flow rates for the 3 variations were 781 +/- 151 mL/min (mean +/- SD), 744 +/- 119, and 763 +/- 129, respectively. Relative contributions by flow rates of the internal carotid arteries and the basilar artery for the 3 variations were 39.8%:38.9%:21.3%, 31.8%:49.1%:19.0%, and 46.6%:41.6%:11.7%, respectively, showing statistically significant differences. CONCLUSIONS: Variations in the circle of Willis correlate significantly with relative contributions by the flow rates of the bilateral internal carotid and basilar arteries.

Composite hypo-hyper-d-intermetallic and interionic phases as supported interactive electrocatalysts.

Interactive, strong interbonding and highly electron conductive nonstoichiometric titanium suboxide catalytic supports, Magneli phases (Ti(n)O(2n-1), on average Ti(4)O(7)), have been used in the electrocatalysis of hydrogen (HELR) and oxygen (OELR) electrode reactions with remarkable consequences and advanced achievements. The theory of hypo-hyper-d-interelectronic bonding of transition metal ions and atoms has been employed for selective ordered grafting and shown to stay in the core of the strong metal-support interaction (SMSI) in heterogeneous catalysis and electrocatalysis, and thereby the substantial cause for the improved synergistic activity of composite (electro)catalysts. The same fundament has been the thermodynamic basis for the thermal production of symmetric intermetallic Laves type phases of nanostructured electrocatalysts, in particular the ones with higher oxophilic properties of hypo-d-elements. Remarkably advanced in electrocatalytic activity, highly monatomically dispersed deposits of Pt upon Magneli phases are shown to be unique and highly promising electrocatalysts for the cathodic oxygen reduction (ORR). Nanostructured Au upon a thin nanocrystalline film of anatase titania has been confirmed by X-ray photoelectron spectroscopy (XPS) as a typical classical paradigm of the SMSI, and at the same time affording the basis for gold with strained d-orbitals, as the reversible hydrogen electrode. Magneli phases have been shown to be the best electrocatalytic supports with unique properties both for low temperature PEM fuel cells (LT PEM FCs) with pronounced CO tolerance and water electrolysis in membrane type hydrogen generators.

Comparison of patient doses in 256-slice CT and 16-slice CT scanners.

The 256-slice CT-scanner has been developed at the National Institute of Radiological Sciences. Nominal beam width was 128 mm in the longitudinal direction. When scanning continuously at the same position to obtain four-dimensional (4D) images, the effective dose is increased in proportion to the scan time. Our purpose in this work was to measure the dose for the 256-slice CT, to compare it with that of the 16-slice CT-scanner, and to make a preliminary assessment of dose for dynamic 3D imaging (volumetric cine imaging). Our group reported previously that the phantom length and integration range for dosimetry needed to be at least 300 mm to represent more than 90% of the line integral dose with the beam width between 20 mm and 138 mm. In order to obtain good estimates of the dose, we measured the line-integral dose over a 300 mm range in PMMA (polymethylmethacrylate) phantoms of 160 mm or 320 mm diameter and 300 mm length. Doses for both CT systems were compared for a clinical protocol. The results showed that the 256-slice CT generates a smaller dose than the 16-slice CT in all examinations. For volumetric cine imaging, we found an acceptable scan time would be 6 s to 11 s, depending on examinations, if dose must be limited to the same values as routine examinations with a conventional multidetector CT. Finally, we discussed the studies necessary to make full use of volumetric cine imaging.