Application of inorganic phosphate limitation to efficient isoprene production in Pantoea ananatis.

AIMS: Establishment of an efficient isoprene fermentation process by adopting inorganic phosphate limitation as the trigger to direct metabolic flux to the isoprene synthetic pathway. METHODS AND RESULTS: We constructed isoprene-producing strains of Pantoea ananatis (a member of the Enterobacteriaceae family) by integrating a heterologous mevalonate pathway and a metabolic switch that senses external inorganic phosphate (Pi) levels. This metabolic switch enabled dual-phase isoprene production, where the initial cell growth phase under Pi-saturating conditions was uncoupled from the subsequent isoprene production phase under Pi-limiting conditions. In fed-batch fermentation using our best strain (SWITCH-PphoC/pIspSM) in a 1-l bioreactor, isoprene concentration in the off-gas was maintained between 300 and 460 ppm during the production phase and at 20 ppm during the cell growth phase, respectively. The strain SWITCH-PphoC/pIspSM produced totally 2·5 g l-1 of isoprene from glucose with a 1·8% volumetric yield in 48 h. CONCLUSIONS: This proof-of-concept study demonstrated that our Pi-dependent dual-phase production system using a P. ananatis strain as a producer has potential for industrial-scale isoprene fermentation. SIGNIFICANCE AND IMPACT OF THE STUDY: This Pi-dependent dual-phase fermentation process could be an attractive and economically viable option for the production of various commercially valuable isoprenoids.

MRI study of atherosclerotic plaque progression using ultrasmall superparamagnetic iron oxide in Watanabe heritable hyperlipidemic rabbits.

OBJECTIVE: The purpose of this study was to evaluate plaque progression by using MRI with ultrasmall superparamagnetic iron oxide (USPIO) and by histopathological studies. METHODS: We divided 12 Watanabe heritable hyperlipidemic (WHHL) rabbits into 4 groups based on their age (3, 9, 14 and 26 months) and injected them intravenously with 0.8 mmol (Fe) kg(-1) of USPIO (size, 32 nm; concentration, 15 mg dl(-1)). On the fifth post-injection day, they were again given an intravenous injection with 40 µmol kg(-1) of the same USPIO, and MR angiography (MRA) was performed. The signal-to-noise ratio (SNR) in regions of interest in the wall of the upper abdominal aorta was calculated on coronal images. Specimens from the same level of the aorta were subjected to iron staining and RAM-11 immunostaining and used for histopathological study. For statistical analysis of the MRA and histopathological findings, we used analysis of variance [Tukey's honest significant difference (HSD) test]. RESULTS: In 9-month-old rabbits, the SNR was significantly lower than in rabbits of the other ages (p < 0.01), and the area of RAM-11 (DAKO Corporation, Glostrup, Denmark) and iron uptake in the aortic wall was significantly larger (RAM-11, p < 0.01; iron, p < 0.05). These areas were the smallest in 3-month-old rabbits. CONCLUSION: Histopathologically, the number of macrophages was the greatest in 9-month-old rabbits. Our findings indicate that the SNR on MRI scans reflects the number of macrophages in the aortic wall of WHHL rabbits. ADVANCES IN KNOWLEDGE: USPIO-enhanced MRI visualized the accumulation of macrophages in early atherosclerotic plaques of WHHL rabbits in the course of natural progression.

Direct measurement of speed of sound in cartilage in situ using ultrasound and magnetic resonance images.

This study verified the accuracy of the speed of sound (SOS) measured by the combination method, which calculates the ratio between the thickness values of cartilage measured by using the magnetic resonance imaging (MRI) and the ultrasonic pulse-echo imaging, and investigated in vivo application of this method. SOS specific to an ultrasound imaging device was used as a reference value to calculate the actual SOS from the ratio of cartilage thicknesses obtained from MR and ultrasound images. The accuracy of the thickness measurement was verified by comparing results obtained using MRI and a non-contact laser, and the accuracy of the calculated SOS was confirmed by comparing results of the pulse-echo and transmission methods in vitro. The difference between laser and MRI measurements was 0.05 ± 0.22 mm. SOS values in a human knee measured by the combination method in the medial and lateral femoral condyles were 1650 ± 79 and 1642 ± 78 m/s, respectively (p < 0.05). The results revealed the feasibility of in situ SOS measurement using the combination method.

Correlation between apparent diffusion coefficient and viscoelasticity of articular cartilage in a porcine model.

OBJECTIVE: Quantitative MR imaging techniques of degenerative cartilage have been reported as useful indicators of degenerative changes in cartilage extracellular matrix, which consists of proteoglycans, collagen, non-collagenous proteins, and water. Apparent diffusion coefficient (ADC) mapping of cartilage has been shown to correlate mainly with the water content of the cartilage. As the water content of the cartilage in turn correlates with its viscoelasticity, which directly affects the mechanical strength of articular cartilage, ADC can serve as a potentially useful indicator of the mechanical strength of cartilage. The aim of this study was to investigate the correlation between ADC and viscoelasticity as measured by indentation testing. MATERIALS AND METHODS: Fresh porcine knee joints (n = 20, age 6 months) were obtained from a local abattoir. ADC of porcine knee cartilage was measured using a 3-Tesla MRI. Indentation testing was performed on an electromechanical precision-controlled system, and viscosity coefficient and relaxation time were measured as additional indicators of the viscoelasticity of cartilage. The relationship between ADC and viscosity coefficient as well as that between ADC and relaxation time were assessed. RESULTS: ADC was correlated with relaxation time and viscosity coefficient (R(2) = 0.75 and 0.69, respectively, p < 0.01). The mean relaxation time values in the weight-bearing and non-weight-bearing regions were 0.61 ± 0.17 ms and 0.14 ± 0.08 ms, respectively. CONCLUSIONS: This study found a moderate correlation between ADC and viscoelasticity in the superficial articular cartilage. Both molecular diffusion and viscoelasticity were higher in weight bearing than non-weight-bearing articular cartilage areas.

Anti-tumour effects of transcatheter arterial embolisation administered in combination with thalidomide in a rabbit VX2 liver tumour model.

OBJECTIVE: Using a liver tumour model we investigated whether thalidomide enhances the anti-tumour effect of transcatheter arterial embolisation (TAE). METHOD: First, the viability of VX2 tumour cells co-cultured with thalidomide in a 21% and 1% O(2) atmosphere was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Second, we randomly assigned 20 rabbits bearing VX2 liver tumours to 4 groups: Group 1 (thalidomide plus TAE), Group 2 (TAE only), Group 3 (thalidomide only) and Group 4 (control). Thalidomide was orally administered for 5 days. The anti-tumour effects were assessed by the tumour proliferation rate using MRI and by immunohistochemical analysis of the area of intratumoural vessels. Analysis of variance and Tukey's honestly significant difference test were used for statistical analysis. RESULTS: The viability of cells grown under hypoxic and normal conditions was not significantly different, nor was there a difference among the four groups. The tumour size increased by 55.9±29.3% in Group 1, 250.6±73.3% in Group 2, 355.2±51.7% in Group 3 and 424.7±110.7% in Group 4; the difference between Group 1 and the other three groups was significant. The area of intratumour vessels in specimens was 0.22±0.28% in Group 1, 0.42±0.29% in Group 2, 1.44±1.00% in Group 3 and 6.00±2.17% in Group 4; the difference between Group 1 and the other groups was statistically significant, as was the difference between Groups 3 and 4. CONCLUSION: Thalidomide used in combination with TAE enhanced anti-tumour effects in rabbits bearing VX2 liver tumours.

Treatment of spontaneous intradural vertebral artery dissections.

Spontaneous intradural vertebral artery dissections may cause subarachnoid hemorrhage and often result in devastating damage. Increased use of noninvasive imaging studies has allowed larger numbers of patients to be diagnosed. In addition, intracranial vertebral artery dissection tends to induce multiple lesions affecting both intracranial vertebral arteries recurrently. Although unruptured dissections in this area usually have a benign nature, some authors have reported on the incidence of rupture from this lesion. Once hemorrhage from a dissecting vessel wall has occurred, it needs to be treated in the acute phase because of the high risk of rebleeding resulting in high morbidity and mortality. From December 2004 to July 2010, we managed 47 patients with spontaneous vertebral artery dissection, 31 patients were ruptured and 16 were unruptured. All patients who suffered from subarachnoid hemorrhage were treated with endovascular procedures. Most of the patients with unruptured dissection received medical therapy, but if the aneurysmal dilatation persisted or grew, surgical interventions were performed. Stenting with or without coils was deployed for 13 patients with posterior inferior cerebellar artery involvement at the site of dissection and/or were affected on the dominant side. In some patients, stenting was performed even if they were in the acute phase. For other ruptured patients, internal coil trappings were performed. Six patients died due to severe initial subarachnoid hemorrhage and one patient, who underwent stent deployment with coils for the dominant vertebral artery, with bilateral dissection continuing to the basilar artery died due to rerupture while the next additional coiling was planning. There were two cases of complications related to the intervention. During the follow-up period no bleeding occurred in any of the patients except for the previously mentioned patient. In conclusion, internal coil trapping or stent placement with or without coils was effective in preventing rebleeding of ruptured vertebral artery dissection. If the dissection is unruptured, it is necessary to detect the risk of bleeding with careful watching and when progress appears to be made, patients should be treated promptly. Stent-assisted therapy for preserving the patency of the parent artery and major branches is a promising treatment for vertebral artery dissection, even in the acute stage of subarachnoid hemorrhage. However, the risk of acute rerupture and recurrence remains even with the porous stent placement with or without coils.

Does the concomitant intra-arterial injection of asialoerythropoietin and edaravone mitigate ischaemic mucosal damage after acute superior mesenteric artery thromboembolism in a rabbit autologous fibrin clot model?

To increase the survival rate of patients with acute superior mesenteric artery thromboembolism (ASMAT) treated by catheter thrombolysis, we examined the effects of delivering edaravone and asialoerythropoietin, agents with tissue-protective activities, using a rabbit autologous fibrin clot ASMAT model. Japanese white rabbits (n=32) were randomly separated into four equal groups. 45 min after introducing autologous fibrin clot, Group U received urokinase and heparin; Group E received urokinase and heparin plus edaravone; Group A received urokinase and heparin plus asialoerythropoietin; and Group EA received urokinase, heparin and edaravone plus asialoerythropoietin via a catheter. The intestines were removed 6 h later and intestinal mucosal damage was scored using the Park's injury score. Survival time was assessed. Average mucosal injury was 5.78+/-1.52 (Group U), 2.88+/-0.72 (Group E), 1.90+/-1.23 (Group A) and 1.18+/-1.25 (Group EA). The degree of mucosal injury was significantly lower in Group EA than in Groups U and E (p<0.05). Conversely, there was no significant difference between Group A and Group EA, or between Group A and Group E. The survival times were 31.50+/-13.30 h (Group U), 51.00+/-24.74 h (Group E), 48.00+/-16.97 h (Group A) and 82+/-51.07 h (Group EA); the difference among the four groups was not significant. In conclusion, the concomitant administration of asialoerythropoietin and edaravone reduced mucosal membrane injury significantly compared with edaravone alone. However, to improve the survival of ASMAT rabbit models, the delivery of an appropriate dose of asialoerythropoietin is required, together with the development of methods to assess peripheral recanalisation.

A combination of cisplatin-eluting gelatin microspheres and flavopiridol enhances anti-tumour effects in a rabbit VX2 liver tumour model.

The aim of this study was to investigate whether the combination of cisplatin-eluting gelatin microspheres (GMSs) and flavopiridol enhances anti-tumour effects in a rabbit VX2 liver tumour model. Tumour-bearing rabbits (n = 21) were divided into five groups and infused from the proper hepatic artery. Group 1 (n = 5) received cisplatin-eluting GMSs (1 mg kg(-1)) and flavopiridol (3 mg kg(-1)), group 2 (n = 5) cisplatin-eluting GMSs alone (1 mg kg(-1)), Group 3 (n = 5) flavopiridol (3 mg kg(-1)), Group 4 (n = 3) GMSs alone (1 mg kg(-1)), and Group 5 (n = 3) was the control group receiving physiological saline (1 ml kg(-1)). On days 0 and 7 after procedures the liver tumour volume was measured using a horizontal open MRI system and the relative tumour volume growth rates for 7 days after treatment were calculated. On T(1) weighted images, the tumours were visualised as circular, low-intensity areas just below the liver surface. After treatment, the signals remained similar. The relative tumour volume growth rate for 7 days after treatment was 54.2+/-22.4% in Group 1, 134.1+/-40.1% in Group 2,166.7+/-48.1% in Group 3, 341.8+/-8.6% in Group 4 and 583.1+/-46.9% in Group 5; the growth rate was significantly lower in Group 1 than the other groups (p<0.05). We concluded that in our rabbit model of liver tumours the combination of cisplatin-eluting GMSs and flavopiridol was effective.

Edaravone prevents bowel infarction after acute superior mesenteric artery thromboembolism using autologous fibrin clots in a rabbit model.

The aim of this study was to evaluate the effects of intra-arterial administration of edaravone after superior mesenteric artery (SMA) thromboembolism in a rabbit model. 24 Japanese white rabbits were randomly allocated to a urokinase group (group U) and a urokinase with edaravone group (group E). A further three rabbits, which were administered an autologous blood clot alone, served as a control group (group C). A 4-Fr sheath was inserted into an SMA. An autologous blood clot was administered to an SMA (group C). After 45 min, urokinase (6000 IU) and heparin (250 IU) were administered through the catheter, either alone (group U) or in conjuction with edaravone (0.5 mg kg(-1)) (group E). In eight rabbits from each of groups U and E, 6 h after reperfusion, the small intestine was harvested and divided into five equal parts. The degree of intestinal tissue injury in each part was rated on a scale of 0-8. After 1 week, survival times and blood biochemistry data were compared among rabbits in group U (four rabbits), group E (four rabbits) and group C (three rabbits), and significant differences (p<0.05) were recorded. Intestinal mucosal damage was significantly greater in group U (5.8 +/- 1.5) than in group E (2.9 +/- 0.7). Survival time tended to be longer in group E (p>0.4, not significant compared with group U). Liver and kidney function showed signs of deterioration over time whether or not edaravone was administered, but administration of edaravone reduced intestinal mucosal damage. An increase in survival rate requires improvements in evaluation methods to enable identification of ischaemic areas.

Cisplatin-conjugated degradable gelatin microspheres: fundamental study in vitro.

The object of this study was to generate cisplatin-conjugated gelatin microspheres (GMSs) and to confirm the subsequent release of cisplatin in vitro. The GMSs (1 mg) were immersed in 50 microl of a cisplatin solution (0.06, 0.15, 0.27, 0.30 or 0.54 mg ml(-1)) at 38 degrees C to allow conjugation. The cisplatin-conjugated GMSs were then extensively washed in double-distilled water and freeze-dried. The platinum concentration in the GMSs samples was investigated as a function of the concentration of cisplatin solution used in their preparation, the number of immersions in cisplatin (1, 2, 3, 4 or 5) and the period of immersion (1, 6 or 11 h). In vitro release tests were performed at different time intervals (1, 3, 6, 12 or 24 h) to allow the rate of cisplatin release to be calculated. The platinum concentration of the GMSs increased in proportion to the concentration of cisplatin solution and the length or number of immersions in cisplatin. In vitro release tests demonstrate that the release rate (%) from GMSs after 1, 3, 6, 12 or 24 h was 4.8, 5.5, 7.6, 10.0 and 12.4, respectively. We demonstrated the ability of GMSs to bind cisplatin forming cisplatin-conjugated GMSs. Moreover, we showed that cisplatin continued to bind GMSs strongly during the in vitro release test.

Formation of porous GaSb compound nanoparticles by electronic-excitation-induced vacancy clustering.

Porous semiconductor compound nanoparticles have been prepared by a new technique utilizing electronic excitation. The porous structures are formed in GaSb particles, when vacancies are efficiently introduced by electronic excitation and the particle size is large enough to confine the vacancy clusters. The capture cross section of the surface layer in particles for the vacancies is smaller than that for the interstitials. Under the condition of supersaturation of vacancies in the particle core, porous structures are produced through the vacancy clusters to a void formation.

An outbreak of psittacosis in a bird park in Japan.

An outbreak of psittacosis related to a bird park occurred in Matsue City, Shimane Prefecture, Japan, during winter 2001. Seventeen cases of psittacosis (12 visitors, three staff, and two student interns) were confirmed. A cohort study was conducted among the park staff and students to determine the risk factors for the development of acute serologically confirmed psittacosis (SCP) infection. Being 'bird staff' had an increased risk of SCP infection (RR 3.96, 95% CI 1.48-10.58). Entering the staff building, where ill birds were maintained without proper isolation, was also associated with an increased risk of SCP infection (RR 3.61, 95% CI 1.03-12.6). Isolation of ill birds and quarantine measures were found to be insufficient. Dehumidifiers and a high-pressure water spray under a closed ventilation environment may have raised the concentration of Chlamydophila psittaci in the hothouses. Bird park staff and visitors should be educated about psittacosis.

Ultrasonic measurement of vascular scaffold elasticity using catheter system.

Characterization of grafted vascular scaffold is essential for evaluating its biocompatibility, maturity and structural intensity. Quantitative elastic modulus measurement of vascular scaffold powerfully assists its characterization because the mechanical property is closely related with the biocompatibility, maturity and structural intensity of the vascular scaffold. We have presented an in vitro or in vivo measurement system for the tissue-engineered vessel before and after grafting in the previous study, we present a novel and modified method for in vivo assessment and follow-up of the vascular scaffold in this study. The measured quantitative elastic modulus is converted into the regeneration score for in vivo assessment. The effectiveness of the proposed evaluation method was validated by in vivo experimental data using canines.

Fat-saturated diffusion-weighted imaging of the rat pelvis using three-dimensional MP-RAGE MR sequence.

In this work we report on the development of a novel technique for fat-saturated three-dimensional (3D) diffusion-weighted (DW) MRI sequence based upon 3D magnetization-prepared rapid gradient-echo (3D-MP-RAGE). In order to saturate fat, two kinds of procedures were competed CHESS-DW-3D-MP-RAGE sequence (CHESS-3D-DWI) and DW-3D-MP-WE-RAGE sequence (WE-3D-DWI) "chemical shift selective: CHESS method vs. water-excitation: WE method". The CHESS-3D-DWI sequence and WE-3D-DWI sequence were compared in terms of their degree of fat suppression. In CHESS-3D-DWI sequence a preparation phase with a "CHESS-90 degrees RF-motion probing gradient: MPG-180 degrees RF-MPG-90 degrees RF" pulse-train was used to sensitize the magnetization to fat-saturated diffusion. In contrast, WE-3D-DWI sequence a RAGE-excitation pulse with a "binominal-pulse 1-1 or 1-2-1" was selected to water-excited (fat-saturated) diffusion imaging. These imaging were done during in vivo studies using an animal experiment. From experimental results obtained with a phantom, the effect of diffusion weighting and the effect of fat-saturation were confirmed. Fat-saturation was much better in the WE-3D-DWI sequence than CHESS-3D-DWI sequence. From rat experimental results, fat-saturated diffusion-weighted image data were obtained. This sequence was useful for in vivo imaging.

Gastrointestinal tract perforation: CT diagnosis of presence, site, and cause.

Gastrointestinal tract perforation is an emergent condition that requires prompt surgery. Diagnosis largely depends on imaging examinations, and correct diagnosis of the presence, level, and cause of perforation is essential for appropriate management and surgical planning. Plain radiography remains the first imaging study and may be followed by intraluminal contrast examination; however, the high clinical efficacy of computed tomographic examination in this field has been well recognized. The advent of spiral and multidetector-row computed tomographic scanners has enabled examination of the entire abdomen in a single breath-hold by using thin-slice sections that allow precise assessment of pathology in the alimentary tract. Extraluminal air that is too small to be detected by conventional radiography can be demonstrated by computed tomography. Indirect findings of bowel perforation such as phlegmon, abscess, peritoneal fluid, or an extraluminal foreign body can also be demonstrated. Gastrointestinal mural pathology and associated adjacent inflammation are precisely assessed with thin-section images and multiplanar reformations that aid in the assessment of the site and cause of perforation.

Pattern recognition as a caring partnership in families with cancer.

Pattern recognition as a caring partnership in families with cancer The purpose of this study was to address the process of a caring partnership by elaborating pattern recognition as nursing intervention with families with cancer. It is based on Newman's theory of health as expanding consciousness within the unitary-transformative paradigm and is an extension of a previous study of Japanese women with ovarian cancer. A hermeneutic, dialectic method was used to engage 10 Japanese families in which the wife-mothers were hospitalized because of cancer diagnosis. The family included at least the woman with cancer and her primary caregiver. Each of four nurse-researchers entered into partnership with a different family and conducted three interviews with each family. The participants were asked to describe the meaningful persons and events in their family history. The family's story was transmuted into a diagram of sequential patterns of interactional configurations and shared with the family at the second meeting. Evidence of pattern recognition and insight into the meaning of the family pattern were identified further in the remaining meetings. The data revealed five dimensions of a transformative process. Most families found meaning in their patterns and made a shift from separated individuals within the family to trustful caring relationships. One-third of them went through this process within two interviews. The families showed increasing openness, connectedness and trustfulness in caring relationships. In partnership with the family, each nurse-researcher grasped the pattern of the family as a whole and experienced the meaning of caring. Pattern recognition as nursing intervention was a meaning-making transforming process in the family-nurse partnership.

A retrospective study of speech development in patients with submucous cleft palate treated by four operations.

Fifty patients with submucous cleft palate (SMCP) who had had four different operations were reviewed. The operations were pushback palatoplasty (n = 18), pharyngeal flap (n = 21), pushback palatoplasty combined with a pharyngeal flap (n = 8), and Furlow palatoplasty (n = 3). Postoperatively the speech of 8, 19, 7, and 2 patients, respectively, improved so that it was within normal limits. A secondary pharyngeal flap was done for six patients, each of whom had previously had a pushback palatoplasty. They all improved, five achieving relatively normal speech, and one good speech. No patient developed hyponasality or airway compromise associated with the pharyngeal flap. The results show that pharyngeal flap and pushback palatoplasty combined with a pharyngeal flap seem to be more reliable procedures than pushback palatoplasty for patients with SMCP.

The Effect of Hydrostatic Weighting on the Vertical Temperature Structure of the Solar Corona.

We investigate the effect of hydrostatic scale heights lambda(T) in coronal loops on the determination of the vertical temperature structure T&parl0;h&parr0; of the solar corona. Every method that determines an average temperature at a particular line of sight from optically thin emission (e.g., in EUV or soft X-ray wavelengths) of a mutlitemperature plasma is subject to the emission measure-weighted contributions dEM&parl0;T&parr0;&solm0;dT from different temperatures. Because most of the coronal structures (along open or closed field lines) are close to hydrostatic equilibrium, the hydrostatic temperature scale height introduces a height-dependent weighting function that causes a systematic bias in the determination of the temperature structure T&parl0;h&parr0; as function of altitude h. The net effect is that the averaged temperature seems to increase with altitude, dT&parl0;h&parr0;&solm0;dh>0, even if every coronal loop (of a multitemperature ensemble) is isothermal in itself. We simulate this effect with differential emission measure distributions observed by SERTS for an instrument with a broadband temperature filter such as Yohkoh/Soft X-Ray Telescope and find that the apparent temperature increase due to hydrostatic weighting is of order DeltaT approximately T0h&solm0;r middle dot in circle. We suggest that this effect largely explains the systematic temperature increase in the upper corona reported in recent studies (e.g., by Sturrock et al., Wheatland et al., or Priest et al.), rather than being an intrinsic signature of a coronal heating mechanism.

Relation between Flare-associated X-Ray Ejections and Coronal Mass Ejections.

In an attempt to identify the direct signatures of coronal mass ejections (CMEs) in soft X-ray wavelengths, we have searched for plasma ejections in Yohkoh soft X-ray telescope (SXT) images in a total of 17 limb flares, and compared the results with the Solar and Heliospheric Observatory LASCO data. A general correlation exists between the presence/absence of the X-ray ejection and the CME. Although the height versus time relation often indicates (under the assumption of constant speed) that the CME onset coincides with the X-ray ejection, the latter probably does not represent the CME front, because the CME speed must result from acceleration, which would put the estimated onset at an earlier time. In some cases, the estimated CME onset time comes well before the impulsive phase of the associated flare. Although the role of the flare-associated plasma ejection in a CME is still unclear, we propose that its occurrence depends on the presence of open field lines, which can be due to a preceding CME. Lastly, we present a rare example of SXT observations of what appeared to be the three-part structure of a CME, which was seen a few minutes before a major flare started.

Ultra low-dose helical CT of the chest: evaluation in clinical cases.

OBJECTIVE: To compare the visibility of normal lung structures and pulmonary abnormalities between ultra low-dose helical CT (ULHCT: 6 mA) and low-dose helical CT (LHCT: 50 mA), and to assess the feasibility of ULHCT for lung cancer screening. MATERIALS AND METHODS: The reduction of tube current to 6 mA was achieved by using an alminum filter installed in an X-ray tube. After obtaining informed consent, both ULHCT and LHCT of the whole lung were performed in five volunteers and 51 patients, with scanning parameters of 120 kV, 1 rotation/second, 10 mm collimation, and 20 mm/second table speed, during a single breath hold. Images were reconstructed every 5 mm with a 180-degree interpolation algorithm. Three chest radiologists were independently asked to compare the visibilities of normal lung structures using a four-point grading scale, and the scores were compared between ULHCT and LHCT. Pulmonary abnormalities including nodules (less than 20 mm) and other abnormalities (mass, consolidation) were evaluated using four decision levels (A: ULHCT equal to LHCT, B: inferior to LHCT but acceptable, C: much inferior to LHCT and not acceptable, D: not visible) and compared between ULHCT and LHCT. Visibility was also compared between the apical and non-apical regions. RESULTS: 99% of the normal lung structures were judged to be visible in ULHCT, and 236 of 345 (68%) of the nodules were judged as "A" and 92 (27%) as "B". Even with nodules of less than 5 mm, judgements of "A" and "B" were made in 74% and 23%, respectively. The visibility of nodules on the ULHCT was worse in the apical region than in the non-apical region (p<0.01). Other lung abnormalities were also graded as "A" (61%) or "B" (34%). No nodules or abnormalities were graded as "D". CONCLUSION: ULHCT has the potential to be utilized in lung cancer screening.