Toward Engineered Biosynthesis of Drugs in Human Cells.

Biosynthetic genes are not only responsible for the formation of bioactive substances but also suited for other applications including gene therapy. To test the feasibility of human cells producing antibiotics in situ when provided with a heterologous biosynthetic gene, we focused on cytochrome P450, the class of enzymes important in conferring bioactivity to natural product precursors. We selected Fma-P450 that plays a central role in the fumagillin antimicrobial biosynthesis in Aspergillus fumigatus to examine fungal metabolite production by HeLa cells that express fma-P450 heterologously. Here we show that HeLa cells harboring fma-P450 can biosynthesize 5-hydroxyl-ß-trans-bergamoten and cytotoxic 5-epi-demethoxyfumagillol when supplemented with the nontoxic precursor ß-trans-bergamotene. While the production level was insufficient to effect cell death, we demonstrate that programming human cells to autogenerate antibiotics by introducing a heterologous biosynthetic gene is feasible.

Stool pattern is associated with not only the prevalence of tumorigenic bacteria isolated from fecal matter but also plasma and fecal fatty acids in healthy Japanese adults.

BACKGROUND: Colibactin-producing Escherichia coli containing polyketide synthase (pks+ E. coli) has been shown to be involved in colorectal cancer (CRC) development through gut microbiota analysis in animal models. Stool status has been associated with potentially adverse gut microbiome profiles from fecal analysis in adults. We examined the association between stool patterns and the prevalence of pks+ E. coli isolated from microbiota in fecal samples of 224 healthy Japanese individuals. RESULTS: Stool patterns were determined through factorial analysis using a previously validated questionnaire that included stool frequency, volume, color, shape, and odor. Factor scores were classified into tertiles. The prevalence of pks+ E. coli was determined by using specific primers for pks+ E. coli in fecal samples. Plasma and fecal fatty acids were measured via gas chromatography-mass spectrometry. The prevalence of pks+ E. coli was 26.8%. Three stool patterns identified by factorial analysis accounted for 70.1% of all patterns seen (factor 1: lower frequency, darker color, and harder shape; factor 2: higher volume and softer shape; and factor 3: darker color and stronger odor). Multivariable-adjusted odds ratios (95% confidence intervals) of the prevalence of pks+ E. coli for the highest versus the lowest third of the factor 1 score was 3.16 (1.38 to 7.24; P for trend = 0.006). This stool pattern exhibited a significant positive correlation with fecal isobutyrate, isovalerate, valerate, and hexanoate but showed a significant negative correlation with plasma eicosenoic acid and α-linoleic acid, as well as fecal propionate and succinate. No other stool patterns were significant. CONCLUSIONS: These results suggest that stool patterns may be useful in the evaluation of the presence of tumorigenic bacteria and fecal fatty acids through self-monitoring of stool status without the requirement for specialist technology or skill. Furthermore, it may provide valuable insight about effective strategies for the early discovery of CRC.

Occupational eye lens dose in endoscopic retrograde cholangiopancreatography using a dedicated eye lens dosimeter.

Increased x-ray exposure to physicians' eye lenses during radiology procedures is a significant concern. In this study, x-ray exposure to the eye was measured using an anthropomorphic head phantom, with and without radiation-protective devices, to examine the dose of x-ray radiation that physicians are exposed to during endoscopic retrograde cholangiopancreatography (ERCP). X-ray exposure of the eye was measured using novel dedicated direct eye lens dosimeters that could specifically measureHp(3) during the ERCP procedure. The spatial dose in the height direction of the physician was measured using an ionization chamber dosimeter. Eye dosimeters were attached inside and outside the lead (Pb) glasses attached to the head of the human phantom to demonstrate its protective effect. Irradiation from the system lasted for 30 min. When the overcouch x-ray tube system is used, the cumulative radiation dose over the 30 min x-ray fluoroscopy time, without the use of radiation-protective devices, to the left and right eyes was 3.7 and 1.5 mSv, respectively. This dose was estimated to be the dose to the lens per therapeutic ERCP examination. With radiation-protective glasses, the dose reduced to 1.8 and 1.0 mSv for the left and right eye, respectively. The results of our study indicated that radiation exposure to the eye was reduced by up to 80.0% using Pb glasses and by 96.8% using radiation-protective curtains. Our study indicates that a physician's maximum radiation exposure to the eyes during an ERCP procedure may be above the level recommended by the International Commission on Radiological Protection when the physician does not use radiation-protective devices. The eyewear, which is larger and fitted more closely to the face, provided a better protection effect even with a low lead equivalence, demonstrating that the shape of eyewear is important for protective function.

Extremely Low Prevalence of Amyloid Positron Emission Tomography Positivity in Parkinson's Disease without Dementia.

BACKGROUND: Most cases of dementia with Lewy bodies (DLB) show Alzheimer's disease pathology-like senile plaques and neurofibrillary tangles. Several studies have also revealed a high prevalence of positive amyloid imaging with positron emission tomography (PET) in DLB and moderate prevalence in Parkinson's disease (PD) with dementia. However, it remains unclear in PD without dementia as to when the brain ß amyloid (Aß) burden begins and progresses. Our study aimed to determine the prevalence of Aß deposition in PD without dementia using amyloid PET. METHODS: This was a cross-sectional study on 33 patients with PD without dementia, of whom 21 had normal cognition and 12 met the criteria for PD-mild cognitive impairment. All subjects underwent neuropsychological assessment and [18F] florbetaben (FBB) PET. RESULTS: All subjects had Lewy body-related disorders, displaying a significantly reduced myocardial [123I] metaiodobenzylguanidine uptake. The cortical FBB-binding pattern in all subjects, including APOE e4 carriers, suggested negative Aß deposition. CONCLUSION: Patients with PD without dementia exhibit an extremely low prevalence of Aß positivity compared with those reported in cognitively normal elderly controls. Further longitudinal imaging studies and long-term follow-up are needed; however, our findings provide novel insights for understanding Aß metabolism in PD.

Current awareness and use of transthoracic echocardiography in evaluation of valvular heart disease in Kumamoto Prefecture -a report from the Kumamoto cardiovascular echocardiography standardization project.

BACKGROUND: There are few reports on transthoracic echocardiography (TTE) for the evaluation of valvular heart disease in a specific area or region. METHODS AND RESULTS: This cross-sectional questionnaire-based survey was conducted in 2023 in Kumamoto Prefecture, where 106 hospitals provide cardiology services. Ninety-three (88%) of the hospitals completed questionnaires regarding TTE. The severity of low flow/low gradient AS was evaluated by dobutamine stress echocardiography in only 7% of hospitals and exercise stress echocardiography for asymptomatic mitral regurgitation in only 5%. Multivariate logistic regression analysis revealed that participation in remote multi-institutional echocardiographic meetings and use of the Kumamoto Prefecture echocardiographic manual were significantly associated with the use of a multi-window approach (P < 0.05). CONCLUSIONS: In Kumamoto Prefecture, echocardiographic measurements are performed according to the recommendations at a relatively low rate. Dissemination of recommendations through remote meetings and the use of the echocardiographic manual may increase the likelihood of TTE being performed according to the recommendations.

Current Awareness and Status of Venous Ultrasonography in Kumamoto Prefecture　- A Report of the Kumamoto Cardiovascular Echocardiography Standardization Project.

Background: There are few reports on the current awareness and status of venous ultrasonography, including the number of specialists who perform this procedure, in a specific regional area in Japan. Methods and Results: This cross-sectional survey study was conducted in Kumamoto Prefecture from October 2018 to March 2019. Of the 366 medical institutions providing cardiology services in Kumamoto Prefecture, 259 (101 general hospitals, 158 small clinics) responded to our questionnaire. In 2017, 21,773 venous ultrasound tests were performed, 21,101 (97%) of which were performed in hospitals and only 672 (3%) were performed in clinics. Both the number of institutions performing venous ultrasounds and the number of tests performed increased over time. Although 317 medical staff in Kumamoto Prefecture were performing transthoracic echocardiography (TTE) when the questionnaires were collected, only 210 performed venous ultrasounds. Although 91% (61/67) of medical institutions could perform TTE within 30 min, only 77% (53/69) performed venous ultrasounds within 30 min. The number of venous ultrasounds per population×100 was largest in the Kumamoto and Kamimashiki areas (1.67) and smallest in the Kamoto area (0.05). Conclusions: This is the first report to reveal the current awareness and status of venous ultrasonography in a specific region in Japan. There are several problems to be overcome, such as a lack of venous ultrasound specialists and the regional disparity in venous ultrasounds in Kumamoto Prefecture.

[Study of setup margins in radiation therapy: how many verification times and patients are required].

INTRODUCTION: The purpose of this research is to require suitable numbers of verification times and patients for calculating the setup margin (SM) in radiotherapy. METHODS: 1) This simulation was performed using the standard normal distribution random number. The simulation used the seven levels of verification from 5 to 35 in 5 steps, and 35 patients. 2) The setup error in prostate radiotherapy at three hospitals was analyzed. Systematic error and random error were calculated from each patient's average value and standard deviation. Furthermore, we used the formula of J Stroom to calculate SM. Suitable numbers of verification times and patients were obtained from statistical analysis of the simulated results. RESULTS: 1) In the results of our simulations using random number, SM converged on 1.0 to 1.3 mm, regardless of the number of patients, when there were more than 15 verification times; 2) The results of clinical data were slightly different from the standard normal distribution, and more than 15 verification times and over 15 patients were required. CONCLUSIONS: In conclusion, calculation of the SM in radiotherapy required more than 15 verification times and over 15 patients.

[Energy characteristics and examination of the dose correction of each element type in small size radiophotoluminescence glass dosimetry element system].

We studied energy characteristics and examined dose correction when using a radiophotoluminescence glass dosimeter (GD). There are two types of GD. One type of GD is called GD-352, which consists of a glass element and Sn filter. Another type of GD is called GD-302, which has no additional filter. Energy characteristics of these two types of GDs were investigated using a diagnostic X-ray energy range. The equation is as follows: Cf (correction factor) = average of GD measured value/air kerma. The compensation formula for estimating air kerma with each X-ray energy was determined from an approximation formula based on the ratio between GD system reading and air kerma with a specific X-ray energy. From compensation results obtained using the formula, the error for air kerma using GD-352 was approximately 0%, and the error using GD-302 was about 1.0%.

Current Awareness and Status of Transthoracic Echocardiography in Kumamoto Prefecture　- A Report of the Kumamoto Cardiovascular Echocardiography Standardization Project.

Background: There are few reports on current awareness and status of transthoracic echocardiography (TTE), including the actual performance rate according to echocardiographic guidelines, in a specific area or region. Methods and Results: This cross-sectional survey study was conducted in Kumamoto Prefecture from October 2018 to March 2019. There are 366 medical institutions advocating cardiology in Kumamoto Prefecture. Of these, 259 (101 hospitals and 158 clinics) returned questionnaires regarding TTE. In all, 150,570 TTEs were performed in 2017. Of these, 132,771 (88%) were performed in hospitals and 17,799 (12%) were performed in clinics. Physicians performed only 5% of TTEs, whereas sonographers performed 86%. Although the modified Simpson method was performed in 90% of hospitals, 3-dimensional echocardiography was performed in only 2% of hospitals. In addition, the left atrial volume index was not examined in approximately 60% of hospitals, and the mean E/E' ratio was not examined in 80% of hospitals. Multivariable logistic regression analysis revealed that having a Fellow of the Japan Society of Ultrasonic in Medicine was significantly and independently associated with guideline-oriented TTE (odds ratio 9.43; 95% confidence interval 1.22-72.71, P<0.05). Conclusions: The rate of echocardiographic measurements performed according to echocardiographic guidelines is exceptionally low in Kumamoto Prefecture. Sufficient dissemination of echocardiographic guidelines may be important in improving this rate.

Evaluation of edge-preserving and noise-reducing effects using the nonlinear diffusion method in bone single-photon emission computed tomography.

OBJECTIVES: This study aims to evaluate nonlinear diffusion (NLD) processing to smoothen images while suppressing resolution degradation in single-photon emission computed tomography (SPECT) images. Phantom data were used for NLD method optimization. The resultant optimal settings were used for NLD processing of clinical images. MATERIALS AND METHODS: Tc was used to simulate tumors and normal soft tissues. Using the data collected, images were reconstructed. Images were processed using various k values and iteration. The background region's coefficient of variation (CV) was determined, and the effects of parameters on image properties were examined. NLD-processed images with optimal parameters were compared with Butterworth (BW)-filtered and nine-point smoothing (SM)-processed images to evaluate smoothing filter properties in real and frequency space. Receiver operating characteristic curve analysis was carried out on NLD-processed and BW048-processed bone SPECT images. RESULTS: From CVs in background, with NLD, increased k value and iteration led to a low CV, indicating enhanced smoothing effect. At k=0.9, a strong noise-reducing effect with less iteration was achieved. Contrasts and recovery coefficients of NLD were the highest. The visual score for SPECT image quality was significantly higher with NLD than with BW048, BW090, and SM. In the low-frequency and high-frequency ranges, BW048, BW090, and NLD showed similar signal strengths and NLD and BW090 showed high signal strength, respectively. SM processing reduced the signal strength at all frequency ranges. On receiver operating characteristic analysis, noise reduction using NLD processing enhanced diagnostic performance than with the use of BW processing. CONCLUSION: NLD processing of bone SPECT images using optimized parameters enabled smoothing with less resolution degradation.

Preclinical evaluation of heat-denatured [18F]FDG-labeled red blood cells for detecting splenic tissues with PET in rats.

INTRODUCTION: Heat-denatured 99mTc-labeled red blood cells (RBCs) are used for detecting splenic tissues with scintigraphy. The present study aimed to evaluate the feasibility of using heat-denatured [18F]fluorodeoxyglucose ([18F]FDG)-labeled RBCs in detecting splenic tissues using positron emission tomography (PET) in rats. METHODS: RBCs were washed with phosphate buffered saline, labeled with [18F]FDG at 38°C, and heat-denatured at 50°C for 15 min. In vitro stability was assessed by measuring extracellular radioactivity during the 0-180 min incubation at 37°C. Thin layer chromatography (TLC) of the extracellular fluid was performed. The autologous RBCs were intravenously injected in four rats and PET scanning was simultaneously performed for 30 min. Time-activity curves of several organs, including the spleen, were analyzed on the PET images. RESULTS: Labeling efficiency was 92%. Low levels of radioactivity were released from the labeled RBCs for 180 min. TLC revealed that 80% of the released radioactivity was due to [18F]FDG-6-phosphate. Whole body images showed strong uptake of heat-denatured [18F]FDG-labeled RBCs in the spleen soon after injection in all four rats. Time-activity curves revealed that the splenic uptake continued to increase for 30 min and the amount of radioactivity in the other organs, except the urinary bladder, decreased after the initial surge. CONCLUSIONS: Heat-denatured [18F]FDG-labeled RBCs are suitable spleen-specific agents for PET. This method is clinically relevant as an alternative for heat-denatured 99mTc-labeled RBC scintigraphy.

Quantitative evaluation of the tracer distribution in dopamine transporter SPECT for objective interpretation.

PURPOSE: Quantification of the tracer distribution would add objectivity to the visual assessments of dopamine transporter (DAT) single photon emission computed tomography (SPECT) data. Our study aimed to evaluate the diagnostic utility of fractal dimension (FD) as a quantitative indicator of tracer distribution and compared with the conventional quantitative value: specific binding ratio (SBR). We also evaluated the utility of the combined index SBR/FD (SBR divided by FD). MATERIALS AND METHODS: We conducted both clinical and phantom studies. In the clinical study, 150 patients including 110 patients with Parkinsonian syndrome (PS) and 40 without PS were enrolled. In the phantom study, we used a striatal phantom with the striatum chamber divided into two spaces, representing the caudate nucleus and putamen. The SBR, FD, and SBR/FD were calculated and compared between datasets for evaluating the diagnostic utility. Mann-Whitney test and receiver-operating characteristics (ROC) analysis were used for analysis. RESULTS: ROC analysis revealed that the FD value had high diagnostic performance [the areas under the curve (AUC) = 0.943] and the combined use of SBR and FD (SBR/FD) delivered better results than the SBR alone (AUC, 0.964 vs 0.899; p < 0.001). The sensitivity, specificity, and accuracy, respectively, were 79.1, 85.0, and 80.7% with SBR, 84.5, 97.5, and 88.0% with FD, and 92.7, 87.5, and 91.3% with SBR/FD. CONCLUSION: Our results confirmed that the FD value is a useful diagnostic index, which reflects the tracer distribution in DAT SPECT images. The combined use of SBR and FD was more useful than either used alone.

3D SPECT/CT fusion using image data projection of bone SPECT onto 3D volume-rendered CT images: feasibility and clinical impact in the diagnosis of bone metastasis.

PURPOSE: We developed a method of image data projection of bone SPECT into 3D volume-rendered CT images for 3D SPECT/CT fusion. The aims of our study were to evaluate its feasibility and clinical usefulness. METHODS: Whole-body bone scintigraphy (WB) and SPECT/CT scans were performed in 318 cancer patients using a dedicated SPECT/CT systems. Volume data of bone SPECT and CT were fused to obtain 2D SPECT/CT images. To generate our 3D SPECT/CT images, colored voxel data of bone SPECT were projected onto the corresponding location of the volume-rendered CT data after a semi-automatic bone extraction. Then, the resultant 3D images were blended with conventional volume-rendered CT images, allowing to grasp the three-dimensional relationship between bone metabolism and anatomy. WB and SPECT (WB + SPECT), 2D SPECT/CT fusion, and 3D SPECT/CT fusion were evaluated by two independent reviewers in the diagnosis of bone metastasis. The inter-observer variability and diagnostic accuracy in these three image sets were investigated using a four-point diagnostic scale. RESULTS: Increased bone metabolism was found in 744 metastatic sites and 1002 benign changes. On a per-lesion basis, inter-observer agreements in the diagnosis of bone metastasis were 0.72 for WB + SPECT, 0.90 for 2D SPECT/CT, and 0.89 for 3D SPECT/CT. Receiver operating characteristic analyses for the diagnostic accuracy of bone metastasis showed that WB + SPECT, 2D SPECT/CT, and 3D SPECT/CT had an area under the curve of 0.800, 0.983, and 0.983 for reader 1, 0.865, 0.992, and 0.993 for reader 2, respectively (WB + SPECT vs. 2D or 3D SPECT/CT, p < 0.001; 2D vs. 3D SPECT/CT, n.s.). The durations of interpretation of WB + SPECT, 2D SPECT/CT, and 3D SPECT/CT images were 241 ± 75, 225 ± 73, and 182 ± 71 s for reader 1 and 207 ± 72, 190 ± 73, and 179 ± 73 s for reader 2, respectively. As a result, it took shorter time to read 3D SPECT/CT images than 2D SPECT/CT (p < 0.0001) or WB + SPECT images (p < 0.0001). CONCLUSIONS: 3D SPECT/CT fusion offers comparable diagnostic accuracy to 2D SPECT/CT fusion. The visual effect of 3D SPECT/CT fusion facilitates reduction of reading time compared to 2D SPECT/CT fusion.

RADIATION EXPOSURE TO OPERATORS PERFORMING PHARMACOLOGIC STRESS TESTING IN 99mTc MYOCARDIAL PERFUSION IMAGING: A PROSPECTIVE STUDY.

This prospective study investigated radiation exposure dose (RED) to main operator (MO) and supervisory operator (SO) performing dypiridamole stress testing in a 1-d rest/stress 99mTc tetrofosmin single-photon emission computed tomography (SPECT) of consecutive 42 patients. MO was instructed to be close to the patients during the entire procedures including the vasodilator and radiotracer injection. SO mainly recorded the data on the procedures apart from the patients. RED, procedure time (PT) and internal radioactivity (IR) of patients were measured before and after a secondary tracer injection for stress SPECT, respectively. RED was significantly greater to MO than to SO (6.2 ± 2.7 vs 2.5 ± 2.1 µSV per stress procedure, p < 0.0001). Multivariate analyses revealed that IR and PT were significantly independent factors to predict RED to both operators. Operators performing pharmacologic stress procedure should be aware that IR and PT are independent factors for RED in 99mTc myocardial perfusion imaging.

Incidental spade-shaped FDG uptake in the left ventricular apex suggests apical hypertrophic cardiomyopathy.

PURPOSE: Apical wall thickening with an "ace-of-spades" configuration is a unique sign of apical hypertrophic cardiomyopathy (AHCM). We investigated spade-shaped FDG uptake around the left ventricular apex (SSUA) incidentally found in routine oncological FDG PET. METHODS: Cases showing SSUA were selected based on retrospective review. The pattern or intensity of SSUA was compared with the results of electrocardiogram (ECG), echocardiography, and stress myocardial perfusion SPECT. The diagnosis of ACHM was based on the presence of giant negative T wave in ECG, thickness of spade-shaped hypertrophy in the apex in echocardiography, and increased tracer uptake in the apex in rest SPECT. RESULTS: Among the 34 patients in 36 PET scans showing SSUA, SSUA was weak in 17 and intense in 17. There were isolated SSUA (n = 29) and SSUA with diffuse or other focal left ventricular uptake (n = 5). Three patients with the latter uptake pattern turned out to have coexistence of AHCM and asymmetric septal hypertrophy. Of the 16 SSUA-positive patients who underwent echocardiography, 13 (81%) were diagnosed as AHCM and the remaining 3 were regarded as borderline AHCM (apical wall thickness, 14-15 mm). There were 16 patients with SSUA who also underwent PET scans after the study period among which 11 (69%) had persistent SSUA in the follow-up PET. In the remaining 5, follow-up PET scans showed diffuse left ventricular uptake and SSUA was barely visible. The intensity of SSUA was significantly or marginally associated with giant negative T wave (p < 0.01), apical asynergy (p = 0.08), and impaired coronary flow reserve (p < 0.05). There were no other factors correlated with the pattern or intensity of SSUA. CONCLUSION: SSUA incidentally found in oncological FDG PET appeared to be associated with AHCM, especially in ischemic conditions. The moderate repeatability of SSUA was probably due to obscurity by physiological uptake.

Novel display technique for reference images for visibility of temporal change on radiographs--color digital summation radiography.

PURPOSE: The present study investigated color digital summation radiography (CDSR) as a novel display technique for reference images for the visibility of temporal change on radiographs. In CDSR, only the parts with temporal differences are displayed in color. Moreover, all other parts are displayed in gray scale. MATERIALS AND METHODS: CDSR was defined as "radiographs combined by the additive color mixture method". The visibility of simulated nodules located in the lung fields and mediastinum was evaluated by 12 radiologists (mean experience, 9.8 years; range, 1-26 years) for 24 conventional radiographs and CDSR for 6 color patterns. A five-point rating system (5, very good; 4, good; 3, adequate; 2, poor; 1, very poor) was used. RESULTS: The mean scores (average +/- standard deviation) for the visibility of simulated nodules were as follows: magenta, 3.88 +/- 0.90; blue, 3.08 +/- 0.72; green, 3.04 +/- 0.86; red, 3.00 +/- 0.98; cyan, 2.71 +/- 0.86; and yellow, 2.50 +/- 0.72. Compared to conventional radiography in gray scale, at 1.21 +/- 0.41, all six color patterns for CDSR displayed significantly improved scores (p<0.001). CONCLUSION: CDSR might represent a useful technique for reference images from chest digital radiography.

Evaluation of the usefulness of color digital summation radiography in temporally sequential digital radiographs: a phantom study.

PURPOSE: The purpose of this study was to assess the usefulness of color digital summation radiography (CDSR) for detection of nodules on chest radiographs by observers with different levels of experience. MATERIALS AND METHODS: A total of 30 radiographs of chest phantoms with abnormalities and 30 normal ones were arranged at random. Set A was conventional radiographs only. Set B consisted of both conventional radiographs and CDSR images, which were colored with magenta. Five chest radiologists and five residents evaluated both image sets on a TFT monitor. The observers were asked to rate each image set using a continuous rating scale. The reading time for each set was also recorded. RESULTS: In set A, the performance of chest radiologists was significantly superior to that of the residents (P < 0.05). However, in set B, there was no significant difference in the performance of the chest radiologists and the residents. In both observer groups, the mean reading time per case in set B was significantly shorter than that in set A (P < 0.01). CONCLUSION: By using CDSR, the detection capability of observers with little experience improves and is comparable to that of experienced observers. Moreover, the reading time becomes much shorter using CDSR.

Evaluation of usefulness of color digital summation radiography for solitary pulmonary nodules on chest radiographs.

PURPOSE: The aim of this study was to evaluate the usefulness of novel color digital summation radiography (CDSR) for detecting solitary pulmonary nodules on chest radiographs by observers with different levels of experience. MATERIALS AND METHODS: A total of 30 healthy controls and 30 patients with newly detected solitary pulmonary nodules were evaluated. Six radiologists and five residents evaluated three image sets: set A, current and prior radiographs only; set B, set A with temporal subtraction images; and set C, set A with CDSR. The observers were asked to rate each image set using a continuous rating scale. In addition, the reading time required for each set was recorded. RESULTS: The radiologists showed no significant differences in the mean A(z) value between set A, set B, and set C. However, the residents showed significant differences between set A and set B and between set A and set C. In addition, for set B and set C, the mean reading time per case of all readers was significantly shorter than that for set A. CONCLUSION: The detection capability of observers with little experience is comparable to that of experienced observers when reading radiographs with temporal subtraction images or with CDSR. The usefulness of CDSR is comparable to that of temporal subtraction.

Air microbubbles as MR susceptibility contrast agent at 1.5 Tesla.

Air microbubbles have been investigated recently at high magnetic field strength (2 Tesla or greater) as potential MR susceptibility contrast agents. We used a phantom to measure their susceptibility at 1.5 T to clarify their usefulness for this purpose. The phantom, filled with fresh Levovist suspension at 4 different doses (67 to 125 mg/mL), was continuously scanned with a gradient-echo technique at a temporal resolution of 10 s. The transverse relaxation increase (R2*) by microbubbles demonstrated a time course of exponential decay at each dose (time-constant, 39 to 57 s). The dependency of R2* on microbubble volume fraction was linear, with a slope of 89 s-1 per percentage microbubble volume fraction. Our study represents the first step towards applying microbubbles as susceptibility contrast agents at 1.5 T.

Full-size digital storage phosphor chest radiography: effect of 4K versus 2K matrix size on observer performance in detection of subtle interstitial abnormalities.

PURPOSE: To compare observer performance in the detection of subtle interstitial abnormalities on 3,520 x 3,520 (4K) matrix and 1,760 x 1,760 (2K) matrix full-size digital storage phosphor (DSP) chest radiographs. MATERIALS AND METHODS: Thirty-five 4K DSP chest radiographs with subtle interstitial abnormalities (n=27) or normal lungs (n=8) were processed with a half-band low-pass filter to produce 2K DSP radiographs. Although the actual matrix size of the 2K DSP radiographs remained 4K, the effective matrix size was reduced to 2K. Four chest radiologists independently evaluated full-sized hard-copy of the 4K and 2K DSP radiographs, and scored the presence of interstitial abnormalities for both right and left lungs on a five-point confidence scale. With findings on high-resolution computed tomography as the reference standard, observer performance was evaluated using multireader-multicase receiver operating characteristic (ROC) analysis. RESULTS: The average area under the ROC curve (Az) values for 4K and 2K DSP radiographs were 0.791+/-0.055 and 0.804+/-0.050, respectively. Both individual and averaged Az values showed no statistically significant differences (p>0.05) between 4K and 2K DSP radiographs. CONCLUSION: Observer performance in the detection of subtle interstitial abnormalities on 4K full-size DSP chest radiographs was equivalent to that on 2K full-size DSP chest radiographs.