Radiation Dose Reduction in Digital Mammography by Deep-Learning Algorithm Image Reconstruction: A Preliminary Study.

Purpose: To develop a denoising convolutional neural network-based image processing technique and investigate its efficacy in diagnosing breast cancer using low-dose mammography imaging. Materials and Methods: A total of 6 breast radiologists were included in this prospective study. All radiologists independently evaluated low-dose images for lesion detection and rated them for diagnostic quality using a qualitative scale. After application of the denoising network, the same radiologists evaluated lesion detectability and image quality. For clinical application, a consensus on lesion type and localization on preoperative mammographic examinations of breast cancer patients was reached after discussion. Thereafter, coded low-dose, reconstructed full-dose, and full-dose images were presented and assessed in a random order. Results: Lesions on 40% reconstructed full-dose images were better perceived when compared with low-dose images of mastectomy specimens as a reference. In clinical application, as compared to 40% reconstructed images, higher values were given on full-dose images for resolution (p < 0.001); diagnostic quality for calcifications (p < 0.001); and for masses, asymmetry, or architectural distortion (p = 0.037). The 40% reconstructed images showed comparable values to 100% full-dose images for overall quality (p = 0.547), lesion visibility (p = 0.120), and contrast (p = 0.083), without significant differences. Conclusion: Effective denoising and image reconstruction processing techniques can enable breast cancer diagnosis with substantial radiation dose reduction.

Correlation between MR Image-Based Radiomics Features and Risk Scores Associated with Gene Expression Profiles in Breast Cancer.

Purpose: To investigate the correlation between magnetic resonance (MR) image-based radiomics features and the genomic features of breast cancer by focusing on biomolecular intrinsic subtypes and gene expression profiles based on risk scores. Materials and Methods: We used the publicly available datasets from the Cancer Genome Atlas and the Cancer Imaging Archive to extract the radiomics features of 122 breast cancers on MR images. Furthermore, PAM50 intrinsic subtypes were classified and their risk scores were determined from gene expression profiles. The relationship between radiomics features and biomolecular characteristics was analyzed. A penalized generalized regression analysis was performed to build prediction models. Results: The PAM50 subtype demonstrated a statistically significant association with the maximum 2D diameter (p = 0.0189), degree of correlation (p = 0.0386), and inverse difference moment normalized (p = 0.0337). Among risk score systems, GGI and GENE70 shared 8 correlated radiomic features (p = 0.0008-0.0492) that were statistically significant. Although the maximum 2D diameter was most significantly correlated to both score systems (p = 0.0139, and p = 0.0008), the overall degree of correlation of the prediction models was weak with the highest correlation coefficient of GENE70 being 0.2171. Conclusion: Maximum 2D diameter, degree of correlation, and inverse difference moment normalized demonstrated significant relationships with the PAM50 intrinsic subtypes along with gene expression profile-based risk scores such as GENE70, despite weak correlations.

Predicting the level of tumor-infiltrating lymphocytes in patients with triple-negative breast cancer: Usefulness of breast MRI computer-aided detection and diagnosis.

PURPOSE: To evaluate the usefulness of magnetic resonance imaging (MRI) computer-aided detection and diagnosis (CAD) for the detection of tumor-infiltrating lymphocytes (TILs) in triple-negative breast cancer (TNBC) patients. TNBC is a heterogeneous malignancy with a varying prognosis. Recently, the importance of TILs in TNBC has been determined. MATERIALS AND METHODS: We retrospectively enrolled 60 lesions of TNBC. Either at 1.5T or 3T MRI, including T1 , T2 -weighted, and dynamic contrast-enhanced, images were obtained. The CAD results for all lesions were obtained, and we analyzed quantitative kinetic features including the initial peak enhancement and enhancement profiles. We divided the tumors into two groups: those with a TIL level of less than 50%, and those with a TIL level of 50% or more. Kinetic parameters were compared using Student's t-tests and chi-square tests. RESULTS: There were 48 low-TIL lesions and 12 high-TIL lesions. The portion of persistent enhancement of tumors was negatively associated with the TIL levels (P = 0.003). The persistent minus washout value of the low-TIL group was higher than that of the high-TIL group (P = 0.008). The odds ratios were 0.944 (P = 0.012) for the persistent portion and 0.971 (P = 0.008) for the persistent minus washout value. CONCLUSION: The prediction model using kinetic enhancement parameters, particularly persistent proportion and plateau minus washout value, could be helpful for identifying TIL levels in TNBC and may be used as an imaging biomarker to guide the treatment plan. LEVEL OF EVIDENCE: 4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:760-766.

Associations between gene expression profiles of invasive breast cancer and Breast Imaging Reporting and Data System MRI lexicon.

PURPOSE: To evaluate whether the Breast Imaging Reporting and Data System (BI-RADS) MRI lexicon could reflect the genomic information of breast cancers and to suggest intuitive imaging features as biomarkers. METHODS: Matched breast MRI data from The Cancer Imaging Archive and gene expression profile from The Cancer Genome Atlas of 70 invasive breast cancers were analyzed. Magnetic resonance images were reviewed according to the BI-RADS MRI lexicon of mass morphology. The cancers were divided into 2 groups of gene clustering by gene set enrichment an alysis. Clinicopathologic and imaging characteristics were compared between the 2 groups. RESULTS: The luminal subtype was predominant in the group 1 gene set and the triple-negative subtype was predominant in the group 2 gene set (55 of 56, 98.2% vs. 9 of 14, 64.3%). Internal enhancement descriptors were different between the 2 groups; heterogeneity was most frequent in group 1 (27 of 56, 48.2%) and rim enhancement was dominant in group 2 (10 of 14, 71.4%). In group 1, the gene sets related to mammary gland development were overexpressed whereas the gene sets related to mitotic cell division were overexpressed in group 2. CONCLUSION: We identified intuitive imaging features of breast MRI associated with distinct gene expression profiles using the standard imaging variables of BI-RADS. The internal enhancement pattern on MRI might reflect specific gene expression profiles of breast cancers, which can be recognized by visual distinction.

Characteristics, Trends, and Quality of Systematic Review and Meta-Analysis in General Radiology between 2007 and 2015.

RATIONALE AND OBJECTIVES: To evaluate the trends, characteristics, and quality of systematic review and meta-analysis in general radiology journals. MATERIALS AND METHODS: We performed a PubMed search to identify systematic reviews and meta-analyses that had been carried out in the field of radiology between 2007 and 2015. The following data were extracted: journal, impact factor, type of research, year of publication, radiological subspecialty, imaging modalities used, number of authors, affiliated department of the first and corresponding authors, presence of a radiologist and a statistician among the authors, discordance between the first and corresponding authors, funding, country of first author, methodological quality, methods used for quality assessment, and statistics. RESULTS: Ultimately, we included 210 articles from nine general radiology journals. The European Journal of Radiology was the most common journal represented (47 of 210; 22.4%). Meta-analyses (n = 177; 84.3%) were published about five times more than systematic reviews without meta-analysis (n = 33; 15.7%). Radiology of the gastrointestinal tract was the most commonly represented subspecialty (n = 49, 23.3%). The first authors were most frequently located in China (n = 64; 30.3%). In terms of modality, magnetic resonance imaging was used most often (n = 59; 28.1%). The number of authors tended to progressively increase over time, and the ratio of discordance between the first and corresponding authors also increased significantly, as did the proportion of research that has received funding from an external source. The mean AMSTAR assessment score improved over time (5.87/11 in 2007-2009, 7.11/11 in 2010-2012, and 7.49/11 in 2013-2015). In this regard, the journal Radiology had the highest score (7.59/11). CONCLUSIONS: The quantity and quality of radiological meta-analyses have significantly increased over the past 9 years; however, specific weak areas remain, providing the opportunity for quality improvement.

Correlation Between MRI and the Level of Tumor-Infiltrating Lymphocytes in Patients With Triple-Negative Breast Cancer.

OBJECTIVE: Increased levels of tumor-infiltrating lymphocytes (TILs) positively correlate with the pathologic complete response rate and increased survival in patients with triple-negative breast cancer (TNBC). The purpose of this study was to investigate associations between TIL levels and MRI findings in patients with TNBC. MATERIALS AND METHODS: From February 2006 through December 2014, a total of 112 women with TNBC were selected for inclusion in the study. All lesions were evaluated by radiologists in accordance with the BI-RADS lexicon. Lymph node involvement and multifocality were also assessed. Tumors were divided into two groups: those with a TIL level of less than 50% were included in the group with low TIL levels (hereafter referred to as the "low-TIL group"), and those with a TIL level of 50% or more were included in the group with high TIL levels (hereafter referred to as the "high-TIL group"). Associations between TIL levels and imaging features were evaluated. RESULTS: Tumors in the high-TIL group had a more round shape (46.0%), a circumscribed margin (76.0%), homogeneous enhancement (32.0%), and absence of multifocality (88.0%) (p < 0.005). Tumors in the low-TIL group had a more irregular shape (69.3%), no circumscribed margin (79.0%), heterogeneous enhancement (75.8%), and multifocality (70.9%) (p < 0.005). CONCLUSION: The well-known typical features of TNBC on MRI, including a round shape, a circumscribed margin, homogeneous enhancement, and lack of multifocality, are a major pattern of TNBC with high TIL levels. This information could provide added diagnostic benefit for the identification of tumors with a good prognosis, which could further assist in optimal pretreatment planning.

Endovascular Treatment for Extracranial Carotid Stenosis: A 10-Year Bibliometric Analysis.

INTRODUCTION: Bibliometric analysis is a quantitative method that can evaluate publications related to a specific topic. METHODS: A PubMed database search was conducted from 2003 to 2012 using the search term "carotid" AND "stenos*" as a part of the title or abstract. RESULTS: A total of 1590 articles were published in 329 different journals. A total of 751 (47.2%) publications were original articles, 1501 (94.4%) were written in English, 153 (9.6%) received funding, 584 (36.7%) were published by the United States, and 673 (42.3%) resulted from multidisciplinary collaboration. Of the original articles, 538 (71.6%) had retrospective design and 275 (36.6%) had sample size of <50. Vascular surgery departments produced the most articles (n = 339, 21.3%), followed by radiology (n = 270, 17.0%), cardiology (n = 260, 16.4%), neurosurgery (n = 198, 12.5%), and neurology (n = 196, 12.3%). Five major departments published only a small portion (5.1%-26.5%) of articles in their own specialty journals. CONCLUSION: The publication in journals across disciplines and multidisciplinary collaboration are 2 peculiar characteristics of research in this topic.

Harmonic ultrasonography for the detection of microlithiasis in the gallbladder.

PURPOSE: To validate the use of harmonic ultrasonography (US) in the detection of gallbladder microlithiasis. METHODS: From November 30, 2012, to January 18, 2014, fundamental US (FUS) and harmonic US with a high background noise (HUS-N) were performed for evaluation of gallbladder during the routine abdomen US. During the US, a dot-like stone (or stones) with Brownian motion was regarded as a positive finding of microlithiasis. Fifty-five patients with microlithiasis in the gallbladder detected on US were enrolled as the subjects of a retrospective review. With respect to the obtained images, two abdominal radiologists independently scored the conspicuity of gallbladder microlithiasis on FUS and HUS-N by using a 4-grade scale. The statistical analysis employed a kappa test and a Wilcoxon rank-sum test. RESULTS: For FUS, the conspicuity grades of gallbladder microlithiasis were G1 in 25 and 37, G2 in 21 and 9, G3 in 6 and 6, G4 in 3 and 3 patients, while HUS-N showed G1 in 0 and 0, G2 in 3 and 2, G3 in 12 and 15, and G4 in 40 and 38 patients, respectively, by each of the two radiologists. The kappa value was 0.633 for FUS between the two radiologists and 0.708 for HUS-N. HUS-N showed better conspicuity of gallbladder microlithiasis than FUS with significant P-values of less than 0.001 and 0.001 for the two radiologists, respectively. CONCLUSION: Compared with FUS, HUS-N enables better detection of microlithiasis in the gallbladder.

Comparison of emergency cranial CT interpretation between radiology residents and neuroradiologists: transverse versus three-dimensional images.

PURPOSE: Three-dimensional (3D) reformatted images provide a more inclusive representation of abnormalities than transverse images in cranial computed tomography (CT). The purpose of this study was to assess the value of 3D reformations for radiology residents in the interpretation of emergency cranial CTs. MATERIALS AND METHODS: In total, 218 consecutive patients who underwent emergency cranial CT scans with 3D reformation were included in this retrospective study. Four blinded readers (three radiology residents and a neuroradiologist) interpreted the transverse and 3D images in two separate sessions. Each reader assessed 1) abnormal finding(s) and the confidence score(s) (5-point scale) for transverse and 3D images, 2) added value score of 3D images (5-point scale), and 3) interpretation time for both transverse and 3D images. We analyzed discordance between each radiology resident and the neuroradiologist on a lesion-by-lesion basis. RESULTS: In total, 509 lesions were detected in 218 patients. Discordance rates between the three residents and the neuroradiologist were 11.4%-20.2% (mean, 15.0%) and 8.8%-16.9% (mean, 12.1%) in the interpretation of transverse and 3D images, respectively. Confidence scores were higher for 3D images than for transverse images for all readers. The added value scores for the 3D images were relatively higher for the inexperienced residents. Interpretation times for 3D images were significantly higher than for transverse images for all readers. CONCLUSION: The 3D reformations assist radiology residents in the interpretation of emergency cranial CT examinations.

Citation classics in radiology journals: the 100 top-cited articles, 1945-2012.

OBJECTIVE: The number of citations an article receives after its publication reflects its impact in the scientific community. The aim of this study was to identify and characterize the 100 top-cited articles published in radiology journals. MATERIALS AND METHODS: The top-cited articles published in 12 radiology journals were identified using the database of Science Citation Index Expanded (1945-2012). The 100 top-cited articles were selected and analyzed with regard to the number of citations, year of publication, publishing journal, authorship, institution and country of origin, type of article, radiologic subspecialty, main topic, and radiologic technique. RESULTS: The 100 top-cited articles were published in eight radiology journals, led by Radiology (n=67) and followed by the American Journal of Roentgenology (n=11). These articles were published between 1939 and 2006 with a mean of 664.3 citations per article (range, 371-6931). Seventy-eight articles were published after 1979, 57 originated from the United States, and 69 were original articles. The most common subspecialties of study were interventional radiology (n=19), neuroradiology (n=15), and breast imaging (n=11). The main topics of articles were radiofrequency ablation of hepatic tumors (n=9), followed by receiver operating characteristic curves (n=6). CONCLUSION: Our study presents a detailed list and analysis of the 100 top-cited articles published in radiology journals, which provides insight into historical developments in the field of radiology.

An analysis of radiological research publications in high impact general medical journals between 1996 and 2010.

OBJECTIVE: To evaluate scientific papers published by radiologists in high impact general medical journals between 1996 and 2010. METHODS: A MEDLINE search was performed in five high impact general medical journals (AIM, BMJ, JAMA, Lancet, and NEJM) for all articles of which a radiologist was the first author between 1996 and 2010. The following information was abstracted from the original articles: radiological subspecialty, imaging technique used, type of research, sample size, study design, statistical analysis, study outcome, declared funding, number of authors, collaboration, and country of the first author. RESULTS: Of 216 (0.19%) articles were published by radiologists in five general medical journals between 1996 and 2010, 83 were original articles. Fifteen (18.1%) original articles were concerned with the field of vascular/interventional radiology, 24 (28.9%) used combined imaging techniques, 76 (91.6%) were clinical research, 63 (75.9%) had a sample size of >50, 65 (78.3%) were prospective, 78 (94.0%) performed statistical analysis, 83 (100%) showed positive study outcomes, 57 (68.7%) were funded, 49 (59.0%) had from four to seven authors, and 79 (95.2%) were collaborative studies. CONCLUSIONS: A very small number (0.19%) in five high impact general medical journals was published by radiologists between 1996 and 2010.

Korea's contribution to radiological research included in Science Citation Index Expanded, 1986-2010.

OBJECTIVE: To evaluate scientific papers published by Korean radiologists in the Science Citation Index Expanded (SCIE) radiology journals, between 1986 and 2010. MATERIALS AND METHODS: The Institute for Scientific Information Web of Knowledge-Web of Science (SCIE) database was searched for all articles published by Korean radiologists, in SCIE radiology journals, between 1986 and 2010. We performed the analysis by typing "Korea" and "radiol" in the address section and selecting the subject area of "Radiology, Nuclear Medicine, and Medical Imaging" with the use of the general search function of the software. Analyzed parameters included the total number of publications, document types, journals, and institutions. In addition, we analyzed where Korea ranks, compared to other countries, in terms of the number of published articles. All these data were analyzed according to five time periods: 1986-1990, 1991-1995, 1996-2000, 2001-2005, and 2006-2010. RESULTS: Overall, 4974 papers were published by Korean radiologists, in 99 different SCIE journals, between 1986 and 2010, of which 4237 (85.2%) were article-type papers. Of the total 115395 articles, worldwide, published in radiology journals, Korea's share was 3.7%, with an upward trend over time (p < 0.005). The journal with the highest number of articles was the American Journal of Roentgenology (n = 565, 13.3%). The institution which produced the highest number of publications was Seoul National University (n = 932, 22.0%). CONCLUSION: The number of scientific articles published by Korean radiologists in the SCIE radiology journals has increased significantly between 1986 and 2010. Korea was ranked 4th among countries contributing to radiology research during the last 5 years.

Characteristics and trends of radiology research: a survey of original articles published in AJR and Radiology between 2001 and 2010.

PURPOSE: To determine the characteristics and trends of the original articles published in two major American radiology journals, AJR American Journal of Roentgenology (AJR) and Radiology, between 2001 and 2010. MATERIALS AND METHODS: This was a retrospective bibliometric analysis that did not involve human subjects and was exempt from institutional review board approval. All 6542 original articles published in AJR and Radiology between 2001 and 2010 were evaluated. The following information was abstracted from each article: radiologic subspecialty, radiologic technique used, type of research, sample size, study design, statistical analysis, study outcome, declared funding, number of authors, affiliation of the first author, and country of the first author. In addition, all the variables examined were presented along with the trend over time. RESULTS: The most common subspecialty of study was abdominal (1219 of 6542, 18.6%), followed by vascular/interventional (804 of 6542, 12.3%). A total of 3744 (57.2%) original articles used magnetic resonance (MR) imaging or computed tomography (CT), 5495 (84.1%) were clinical research articles, 3060 (46.8%) had sample size of more than 50, 4087 (62.5%) were retrospective, 4714 (72.1%) performed statistical analysis, 6225 (95.2%) showed positive study outcome, 4784 (73.1%) were not funded, 3942 (60.3%) had four to seven authors, and 5731 (87.6%) were written by the primary author who was from a department of radiology or radiology-related specialties. The United States published 45.5% (2975 of 6542) of the articles, followed by Japan (n = 525, 8.0%), Germany (n = 485, 7.4%), and South Korea (n = 455, 7.0%). In the time trend analysis, the following variables showed a significantly positive trend: cardiac subspecialty, CT and MR imaging as the radiologic techniques, type of research as other (nonbasic, nonclinical), sample size of more than 50, four to seven as the number of authors, medicine-related department of the first author, and South Korea and Italy as countries of the first author. On the other hand, pediatric subspecialty, combined (basic and clinical) type of research, and number of authors fewer than four showed a significantly negative trend. CONCLUSION: The bibliometric analysis of the AJR and Radiology journals with articles published between 2001 and 2010 revealed characteristics and trends of the current radiology research that may provide useful information to researchers and editorial staff in radiology.

Detection of neck recurrence in patients with differentiated thyroid cancer: comparison of ultrasound, contrast-enhanced CT and (18)F-FDG PET/CT using surgical pathology as a reference standard: (ultrasound vs. CT vs. (18)F-FDG PET/CT in recurrent thyroid cancer).

OBJECTIVES: To compare the diagnostic performance of ultrasound, contrast-enhanced computed tomography (CT) and (18)F-FDG positron emission tomography (PET)/CT for detecting recurrent differentiated thyroid cancer in the neck. METHODS: Twenty patients who had undergone previous surgery for differentiated thyroid cancer (19 papillary carcinomas; 1 medullary carcinoma) and presented with pathologically proven recurrence in the neck were included. All patients had undergone ultrasound, CT and PET/CT in the 2 months before further surgery. In each patient, ultrasound, CT and PET/CT images were retrospectively reviewed to determine the presence of loco-regional recurrence by level-by-level analysis. Imaging results were correlated with the histological evaluation of the neck dissection as a standard of reference. RESULTS: Recurrences were found at 52 out of 110 cervical nodal levels surgically explored. The sensitivity, specificity and accuracy were 69.2 %, 89.7 % and 80.0 % for ultrasound; 63.5 %, 94.8 % and 80.0 % for CT; and 53.8 %, 79.3 % and 67.3 % for PET/CT, respectively. ROC analysis revealed higher diagnostic performance with ultrasound than with PET/CT for detecting recurrent tumour. CONCLUSIONS: Although no significant difference was found among the three techniques, the sensitivity and specificity of ultrasound and CT were higher than those of PET/CT for the evaluation of cervical recurrence in patients with differentiated thyroid cancer. KEY POINTS : • Ultrasound, CT and ( 18 ) F-FDG PET/CT can all detect recurrent thyroid cancer. • Ultrasound and CT have higher sensitivity and specificity. • Ultrasound, CT and ( 18 ) F-FDG PET/CT frequently demonstrated discordant findings.