[Show abstract][Hide abstract] ABSTRACT: We conducted a retrospective comparison of the hemotoxicity of the sequential administration of 5-Fluorouracil (5-FU) prior to Nedaplatin (NDP) (FN therapy) and that of its reverse sequence (NF therapy) for gynecological malignancy. From February 2002 to November 2004, a total of 15 gynecological malignancy patients were treated with radiation therapy combined with NDP and 5-FU. Of these 15 patients, 5 were treated with NF therapy, and 10 were treated with FN therapy. No significant differences were detected between the FN and NF groups with regard to white blood cell count (WBC), hemoglobin level (Hb), and platelet count. The results of this study do not show that the FN group has a lesser degree of hemotoxicity than the NF group.
Nagoya journal of medical science 02/2014; 76(1-2):11-6. · 0.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In an effort to reduce patient radiation dose during selective fallopian tube catheterization, the diagnostic adequacy of fluoroscopic images was compared with digital radiographic images in both a phantom study and a clinical study.
For the phantom study polyethylene tubes with inner diameters of 1.30, 0.95, 0.80, 0.57, and 0.45 mm were used. Randomly selected tubes with/without stenoses, recorded by digital radiographic and last-image hold fluoroscopic images, were presented to five blinded radiologists, and receiver-operating characteristic (ROC) analyses were performed. For the clinical study tubal visualization as well as detectability of stenoses and occlusions were analyzed in 14 women using a 2-way analysis of variance for nonrepeated measures.
The phantom study showed no significant differences between the two imaging techniques for 0.57-mm-diameter and larger tubes; in contrast, fluoroscopic images provided significantly lower detectability of stenoses in 0.45-mm-diameter tubes (p < 0.05). The clinical study showed inferior tubal visualization and diagnostic performance for fluoroscopic images.
Although fluoroscopic images have inferior diagnostic capability in detection of tubal stenoses and occlusions, these images may be adequate for documenting tubal patency with spill into the peritoneal cavity.
[Show abstract][Hide abstract] ABSTRACT: Inflamed atherosclerotic plaques may rupture and cause acute myocardial infarction, stroke and other thrombotic events. Early detection of these unstable plaques could, in many cases, prevent such potentially fatal events. 11C-choline or 18F-labelled choline derivatives for visualizing the synthesis of phospholipids, are promising markers of plaque inflammation with potential advantages over 18F-FDG. Their potential for plaque characterization in humans is, however, unclear. In this study the prevalence and distribution of 11C-choline uptake in the aortic and common carotid arterial walls of elderly male patients was evaluated with combined PET/CT. Additionally, the localization of radiotracer uptake and calcification was correlated in various vessel segments.
Image data from 93 consecutive male patients between 60 and 80 years old who had undergone whole-body 11C-choline PET/CT assessment for prostate cancer were evaluated retrospectively. 11C-choline uptake and calcification were analysed qualitatively and semiquantitatively and compared.
11C-choline uptake was found in 95% of patients, calcification in 94% throughout all vessel segments. In 6% of the patients radiotracer uptake was colocalized with calcifications, whereas less than 1% of calcification sites showed increased radiotracer uptake.
Both 11C-choline uptake and calcification in the aortic and common carotid arterial walls are common in elderly men. Radiotracer uptake and calcification are, however, only rarely colocalized. 11C-choline has the potential to provide information about atherosclerotic plaques independent of calcification measurement.
European Journal of Nuclear Medicine 06/2009; 36(10):1622-8. DOI:10.1007/s00259-009-1152-7 · 5.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The ground-glass opacity (GGO) of lung cancer is identified only subjectively on computed tomography (CT) images as no quantitative characteristic has been defined for GGOs. We sought to define GGOs quantitatively and to differentiate between GGOs and solid-type lung cancers semiautomatically with a computer-aided diagnosis (CAD).
High-resolution CT images of 100 pulmonary nodules (all peripheral lung cancers) were collected from our clinical records. Two radiologists traced the contours of nodules and distinguished GGOs from solid areas. The CT attenuation value of each area was measured. Differentiation between cancer types was assessed by a receiver-operating characteristic (ROC) analysis.
The mean CT attenuation of the GGO areas was -618.4 +/- 212.2 HU, whereas that of solid areas was -68.1 +/- 230.3 HU. CAD differentiated between solidand GGO-type lung cancers with a sensitivity of 86.0% and specificity of 96.5% when the threshold value was -370 HU. Four nodules of mixed GGOs were incorrectly classified as the solid type. CAD detected 96.3% of GGO areas when the threshold between GGO and solid areas was 194 HU.
Objective definition of GGO area by CT attenuation is feasible. This method is useful for semiautomatic differentiation between GGOs and solid types of lung cancer.
Japanese journal of radiology 03/2009; 27(2):91-9. DOI:10.1007/s11604-008-0306-z · 0.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Image diagnosis is the task in which a physician searches for abnormal findings on the medical images that potentially involve a large amount of anatomical and pathological information, and identifies dis-eases from such findings. Since this task aims to reduce the risk (e.g., insult or death) that will occur in the near future, it can be seen as a case of chance discoveries. To investigate the cognitive process underlying the task, we conducted an experiment in which two independent physicians diagnosed the same CT images. Analysis of disagreements about final diagnosis and verbal protocols revealed that when observing the CT im-ages on which one disagreed with the other, the physicians engaged in iterative cycles of the image-feature search and the schema construction. The result suggests the importance of investigating cyclic interactions between humans and environments when considering chance discovery.
[Show abstract][Hide abstract] ABSTRACT: We investigated the possibility of using computer analysis of high-resolution CT images to radiologically classify the shape of pulmonary nodules. From a total of 107 HRCT images of solid, solitary pulmonary nodules with prior differentiation as benign (n=55) or malignant (n=52), we extracted the desired pulmonary nodules and calculated two quantitative parameters for characterizing nodules: circularity and second central moment. Using discriminant analysis for two thresholds in differentiating malignant from benign states resulted in a sensitivity of 76.9%, a specificity of 80%, a positive predictive value of 78.4%, and a negative predictive value of 78.6%.
Computerized Medical Imaging and Graphics 08/2008; 32(5):416-22. DOI:10.1016/j.compmedimag.2008.04.001 · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: If we consider the Brier Score (B) in the context of the signal detection theory and assume that it makes sense to consider the existence of B as a parameter for the population (let B be this B), and if we assume that the calibration in the observer’s probability estimate is perfect, we find that there is a theoretical relationship between B and the area under the binormal receiver operating characteristic (ROC) curve,. We have derived this theoretical functional relationship between B and, by using the parameter a and b in the binormal ROC model and the prior probability of signal events ( α); here, the two underlying normal distributions are N μs,σ s
[Show abstract][Hide abstract] ABSTRACT: In this study, we selected medical image diagnosis as a task to investigate how expertise influences the relations between perceptual and conceptual processing. In an experiment, participants, namely five novices and five experts, made diagnoses on 13 CT images. We obtained two types of data concerning verbal protocols and manipulating computational systems. The segments related to perceptual and conceptual processing were extracted from these data, and the interrelations of the two components were analyzed. Consequently, we confirmed three salient features in the experts: (1) the experts verbalized more types of findings and more types of hypotheses than novices; (2) the experts generated several hypotheses in the early phases of the task; and (3) they newly verbalized many perceptual features during conceptual activities, and verbalized conceptual words during perceptual activities. These results suggest that expertise in medical image diagnosis involves not only the development of both perceptual and conceptual processing, but also the development of an ability to connect the two components.
International Journal of Human-Computer Studies 05/2008; 66(5-66):370-390. DOI:10.1016/j.ijhcs.2007.11.004 · 1.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to assess the effects of the reconstructed thickness of axial images on image quality of CT pancreatic arteriography with 16-channel multislice CT. In 31 consecutive patients, raw data of arterial-phase scanning with 0.5 mm collimation were reconstructed in the following three ways: 0.5 mm thickness (effective thickness of 0.75 mm) at 0.4 mm intervals in Group 1; 1 mm thickness at 0.5 mm intervals in Group 2; and 2 mm thickness at 1 mm intervals in Group 3. For the visualization of major arteries and small arteries of the pancreatic head, four blinded readers independently performed side-by-side comparison of the CT arteriographic images generated from each axial dataset for the same patient using a three-dimensional volume-rendered technique. In all comparisons using a continuous rating scale, CT arteriographic images generated from thinner axial images were found to be significantly superior (p<0.01). The difference was more pronounced for small arteries. The degree of degradation from Group 1 to Group 2 was markedly smaller than that from Group 1 to Group 3 or from Group 2 to Group 3. For small arteries, paired images were assigned a grade of "almost equivalent" in 73%, 6% and 15% of the comparison between Group 1 and Group 2, Group 1 and Group 3, and Group 2 and Group 3, respectively. We concluded that the image quality of CT pancreatic arteriography, especially for small arteries, can be improved by reconstructing axial images with thinner thickness from the data obtained with submillimetre collimation.
The British journal of radiology 03/2008; 81(962):99-106. DOI:10.1259/bjr/66098431 · 2.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: PURPOSE
The purpose of the study is to validate the performance of a novel image compression method using a neural network realizing up to hundred-to-one lossy compression without degradation of the diagnostic quality for digital radiography.
METHOD AND MATERIALS
The encoding consists of following processes; prediction block based on an artificial intelligence, the compressible residual data by differential process, the transformation and quantization process, the final organization and modification process and the entropy encoding block which enables the bit-stream for transfer and storage. The decoding follows the reverse order process of the encoding steps with an additional de-blocking filter process. The predicted image will be compared to the original image on pixel-by-pixel basis to create the residual image. In addition, a newly developed discrete cosine transform is used to isolate the DC-coefficient thus enables a high compression rate. The digital images of chest X-ray, KUB, MMG, (10 images for each) were compressed using JIS lossy-compression. Five-to-one, ten-to-one, twenty five-to-one, fiftty-to-one, seventy five-to-one and one hundred-to-one compression rate images were generated out of one original DICOM image. Four staff radiologists were asked to categorize the compressed images compared to the original image into 3 groups; indistinguishable, distinguoshable but still diagnostic, unacceptable. Thus the compression threshold to maintain the diagnostic quality was determined for image modality.
For all tested images, the threshold between indistinguishable and distinguishable still diagnositc was fifty-to-one and the highest compression rate images tested with one hundred-to-one still maintained diagnostic quality.
A novel image compression method (JIS compression) showed higher compression rate up to one hundred-to-one for chest X-rays, MMGs and KUBs compared to the conventional methods such as JPEG still maintaining the diagnostic image quality.
A novel lossy image compression method with neural network enabled significantly higher compression rate than conventional JPEG methods while maintaining the diagnostic quility.
Radiological Society of North America 2007 Scientific Assembly and Annual Meeting; 11/2007
[Show abstract][Hide abstract] ABSTRACT: PURPOSE
The purpose of the study is to validate the performance of a novel image compression method using a neural network realizing up to eight-to-one lossless compression rate for each imaging modality.
METHOD AND MATERIALS
The compression encoding consists of following processes; prediction block based on an artificial intelligence, the compressible residual data by differential process, the transformation and quantization process, the final organization and modification process and the entropy encoding block which enables the bit-stream for transfer and storage. The decoding follows the reverse order process of the encoding steps with an additional de-blocking filter process. The predicted image is first divided into 16x16 macro-blocks using the original image as a teacher, and the each block will be re-divided into sixteen 4x4 sub-blocks. The prediction image will be compared to the original image on pixel-by-pixel basis in order to create the residual image. The spatial and the frequency data of the residual image will be compared and transformed. In addition, a newly developed discrete cosine transform is utilized to isolate the DC-coefficient thus enables a high compression rate. The digital images of chest X-ray, CT, MRI, RI, MMG (Mammography), US and DSA were compressed using JIS lossless-compression method and the compression rate were calculated according to the file size before and after the compression. Also the pixel value comparison software (Microsoft Corporation) were used to demonstrate that each compression was truly lossless.
The compression rates were around one-to-eight for chest X-ray, MMG and CT and one-to-four for MRI, RI and US. The data-loss rate measured by the pixel value comparison tool was 0% for all of the images. JIS compression method enables higher compression for lossless mode than conventional JPEG, JPEG2000 and wavelet compression methods.
This novel method should be a useful technology for the efficient handling of the increasing medical imaging data.
Neural network based novel image compression method which enables up to eight-to-one lossless compression rate has been developed and tested to demonstate the clinical performance.
Radiological Society of North America 2007 Scientific Assembly and Annual Meeting; 11/2007
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to assess the influence of liquid crystal display (LCD) monitors on the detectability of diffuse pulmonary diseases depicted on chest radiographs by comparing them with a high-resolution cathode ray tube (CRT) monitor.
A group of 17 radiologists interpreted 87 soft-copy images on LCD monitors with pixel arrays of 1024 x 1280, 1200 x 1600, 1536 x 2048, and 2048 x 2560 and on a CRT monitor with a pixel array of 2048 x 2560. They were asked to indicate their individual confidence levels regarding the presence of diffuse pulmonary diseases. The luminance distributions of all monitors were adjusted to the same distributions, and the ambient illumination was 200 lux. Observer performance was analyzed in terms of the receiver operating characteristics (ROC).
The average ROC curves for the five monitor types were similar, and there were no statistically reliable effects of the five monitor types on the readers' diagnostic performances (P = 0.7587).
The detectability of diffuse pulmonary disease on the LCD monitors with a spatial resolution equal to or higher than a matrix size of 1024 x 1280 was found to be equivalent to that on the high-resolution CRT monitor.
Radiation Medicine 07/2007; 25(5):211-7. DOI:10.1007/s11604-007-0126-6
[Show abstract][Hide abstract] ABSTRACT: We compared the efficacies of (18)F-FDG PET and (99m)Tc-bone scintigraphy for the detection of bone metastases in patients with differentiated thyroid carcinoma (DTC).
We examined 47 patients (32 women, 15 men; mean age +/- SD, 57.0 +/- 10.7 y) with DTC who had undergone total thyroidectomy and were hospitalized to be given (131)I therapy. All patients underwent both whole-body (18)F-FDG PET and (99m)Tc-bone scintigraphy. The skeletal system was classified into 11 anatomic segments and assessed for the presence of bone metastases. Bone metastases were verified either when positive findings were obtained on >2 imaging modalities--(201)Tl scintigraphy, (131)I scintigraphy, and CT--or when MRI findings were positive if vertebral MRI was performed.
Bone metastases were confirmed in 59 of 517 (11%) segments in 18 (38%) of the 47 study patients. The sensitivities (visualization rate) for bone metastases on a segment basis using (18)F-FDG PET and (99m)Tc-bone scintigraphy were 50 of 59 (84.7%) and 46 of 59 (78.0%), respectively; the difference between these values was not statistically significant. There were only 2 (0.4%) false-positive cases in a total of 451 bone segments without bone metastases when examined by (18)F-FDG PET, whereas 39 (8.6%) were false-positive when examined by (99m)Tc-bone scintigraphy. Therefore, the specificities of (18)F-FDG PET and (99m)Tc-bone scintigraphy were 449 of 451 (99.6%) and 412 of 451 (91.4%), respectively; the difference between these values was statistically significant (P < 0.001). The overall accuracies of (18)F-FDG PET and (99m)Tc-bone scintigraphy were 499 of 510 (97.8%) and 458 of 510 (89.8%), respectively; the difference between these was also statistically significant (P < 0.001).
The specificity and the overall accuracy of (18)F-FDG PET for the diagnosis of bone metastases in patients with DTC are higher than those of (99m)Tc-bone scintigraphy, whereas the difference in the sensitivities of both modalities is not statistically significant. In comparison with (99m)Tc-bone scintigraphy, (18)F-FDG PET is superior because of its lower incidence of false-positive results in the detection of bone metastases of DTC.
Journal of Nuclear Medicine 06/2007; 48(6):889-95. DOI:10.2967/jnumed.106.039479 · 5.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We experienced a case of relapsed malignant lymphoma with multiple bone marrow or bone lesions. The case was diagnosed as follicular lymphoma by cytological biopsy of the right iliac bone, with (67)Ga scintigraphy showing abnormal, intense uptake in multiple bones. After about 10 months of systemic chemotherapy, a relapse was suspected because of pain in the bilateral legs and a high level of lactate dehydrogenase. Assessment of the lesions in the patient was difficult by computed tomography because the affected sites were localized mainly in the bone marrow. (18)F-Fluorodeoxyglucose (FDG) positron emission tomography (PET) was useful for detecting accurately the relapse sites in the bone marrow and enabled us to determine the field for radiotherapy. There are only a few reports of FDG-PET findings for such bone marrow malignant lymphomas. Therefore, we report the findings of FDG-PET for this case and review some of the literature about bone marrow lymphomas.
Radiation Medicine 05/2007; 25(3):130-4. DOI:10.1007/s11604-006-0110-6
[Show abstract][Hide abstract] ABSTRACT: To compare the clinical value of diffusion-weighted (DW) and T2-weighted (T2W) imaging in detecting prostate cancer using a 3-Tesla (3T) magnetic resonance (MR) system.
Thirty-seven patients with suspected prostate cancer underwent T2W and DW imaging at 3T using an 8-channel phased-array coil. These images and apparent diffusion coefficient (ADC) maps were read retrospectively and blindly. The results were compared with histopathologic findings, and receiver operating characteristic (ROC) analysis was used to compare the cancer detection performance of T2W and DW imaging.
The areas under the ROC curves for DW imaging and T2W imaging were 0.89 and 0.82, respectively. The performance of DW imaging in prostate cancer detection was significantly better than that of T2W imaging (P=0.0371).
With a 3T MR system, the performance of DW imaging in detecting prostate cancer was better than that of T2W imaging. DW imaging appears to be a robust and reliable method to examine the whole prostate within an acceptable scan time in clinical settings.
European Journal of Radiology 03/2007; 61(2):297-302. DOI:10.1016/j.ejrad.2006.10.002 · 2.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We measured the sound level and frequencies of the acoustic noise generated by a 3 Tesla (T) MR scanner, and investigated the subjective sound level for 30 healthy volunteers with either earplugs, headphones or both. The sound level of 3T was found to be higher than that of 1.5T in all sequences. The peak sound pressure level of 3T ranged from 125.7 dB for MR angiography to 130.7 dB for single shot EPI on the linear scale. The equivalent noise level was from 110.0 dB for FLAIR to 115.8 dB for T1-IR on the A-weighted scale, which exceeded 99 dB, the level regulated by the International Electrotechnical Commission (IEC). The study of the subjective sound level showed that the effect of noise reduction was not significantly different between earplugs and headphones. However, the use of both devices could reduce the subjective sound level significantly better than either one alone (P < 0.01). Thus we propose wearing both devices for ear-protection during 3T examinations.
Nagoya journal of medical science 02/2007; 69(1-2):23-8. · 0.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To assess the capabilities of 16-channel multislice CT in acquiring almost exclusively arterial-phase images of the pancreas and depicting small pancreatic arteries in coronal reformatted images.
In 45 consecutive patients, arterial-phase contrast enhancement was measured in the aorta and its branches, portal venous system, and pancreas. Coronal reformatted images of 1.2- or 1.3-mm slice thickness at 0.8- or 0.9-mm intervals were generated from axial images acquired with 0.5-mm collimation. Two radiologists evaluated the quality of imaging in the arterial phase and the visibility of the pancreatic arteries in coronal reformatted images.
Mean enhancement in the aorta and its branches was greater than 300 HU, while that in the portal venous system and pancreas was less than 100 HU. The images were judged to be suitable for delineating the pancreatic arteries in all patients. The following arteries were visualized: anterior superior pancreaticoduodenal (39 patients), posterior superior pancreaticoduodenal (41), anterior inferior pancreaticoduodenal (39), posterior inferior pancreaticoduodenal (33), dorsal pancreatic (42), its right branch (34), and transverse pancreatic (37).
Multislice CT can depict small pancreatic arteries using coronal reformatted images generated from almost exclusively arterial-phase axial images acquired with 0.5-mm collimation.
[Show abstract][Hide abstract] ABSTRACT: F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) is an excellent modality for non-invasive functional imaging of malignant lymphoma and is highly sensitive and specific for the detection of lymphoma lesions. Here, we report the findings of FDG-PET for three cases of diffuse large B cell type lymphoma (DLBCL) with extranodal tumors in the breast, stomach, and liver plus spleen, respectively. The whole body FDG-PET findings showed no evidence of lymph node (LN) involvement or distant metastasis. Strong FDG accumulations were observed in the only extranodal sites by whole body FDG-PET. Therefore, we could confirm that these cases were extranodal primary origins. Whole body PET is useful to determine the primary sites, that is, extranodal origin DLBCL with its clear images.
Annals of Nuclear Medicine 01/2007; 20(10):689-93. DOI:10.1007/BF02984681 · 1.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to determine the effectiveness of the combination of intraarterial and intravenous concurrent chemoradiation therapy (CIAIV-CCRT) for the treatment of high-risk uterine cervical cancer.
Between January 2000 and November 2004, we reviewed 45 cervical cancer patients treated by CIAIV-CCRT. The numbers of patients with stage IB2, IIA, IIB, IIIA, IIIB, and IVA were 3, 6, 14, 1, 17, and 4, respectively. Patients with stage III and IVA or patients with tumors >3 cm in diameter were enrolled in this study. Two sessions of CCRT were administered every 3 weeks using a combination of 70 mg/m2 x h(-1) cisplatin or 50 mg/m2 x h(-1) nedaplatin via the bilateral uterine artery and 2800 mg/m2 x 96 h(-1) 5-fluorouracil intravenously. Patients concurrently received external beam radiation therapy and brachytherapy. A nonrandomized control group of 47 patients who underwent radiation therapy alone between 1993 and 2000 was used for comparison.
Of the 45 patients, 28 (62%) exhibited complete response and 16 (36%) exhibited partial response. One IIIB patient (2%) did not show any response. The 5-year overall survival (OAS) rates in the CCRT group and control group were 80.6% and 54.9%, respectively. With regard to late toxicities, no statistically significant differences were observed between the two groups. In uni- and multivariate analyses, positive pelvic lymph node showed a statistically significant influence on the OAS in the CIAIV-CCRT group (P = 0.049).
These preliminary results suggest that CIAIV-CCRT can improve the prognosis of patients with high-risk cervical cancer.
[Show abstract][Hide abstract] ABSTRACT: The objective of our study was to assess the capabilities of MDCT for the diagnosis of an anomalous pancreaticobiliary ductal junction using high-resolution multiplanar reformatted (multiplanar reconstruction) images.
This study included nine patients with and 54 without an anomalous pancreaticobiliary ductal junction confirmed on direct cholangiopancreatography. Multiplanar reconstruction images with 0.5-mm continuous slices were generated from isotropic or nearly isotropic pancreatic phase images. By mainly interpreting the multiplanar reconstruction images using the Scrolling mode, two blinded reviewers independently determined whether the confluence of the pancreatic and biliary ducts joined in the pancreatic parenchyma (in other words, outside the duodenal wall). The results were correlated with the findings of direct cholangiopancreatography. The diagnostic capabilities of CT for revealing associated pancreatobiliary diseases were assessed in patients with this anomaly.
Interobserver agreement in the classification of the duct confluence was high (kappa = 0.804). The duct confluence was identified in all patients except four without an anomalous pancreaticobiliary ductal junction. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of CT for diagnosing an anomalous pancreaticobiliary ductal junction were 100% (9 of 9 patients), 87% (47 of 54 patients), 89% (56 of 63 patients), 75% (9 of 12 patients), and 100% (47 of 47 patients) in the final decisions, respectively. CT showed all associated pancreatobiliary diseases except bile duct stones in two patients.
MDCT enabled the diagnosis of an anomalous pancreaticobiliary ductal junction by showing whether the pancreatic and biliary ducts join within the pancreatic parenchyma on high-resolution multiplanar reconstruction images.
American Journal of Roentgenology 10/2006; 187(3):668-75. DOI:10.2214/AJR.05.0824 · 2.74 Impact Factor