Screening mammography performance according to breast density: a comparison between radiologists versus standalone intelligence detection.

BACKGROUND: Artificial intelligence (AI) algorithms for the independent assessment of screening mammograms have not been well established in a large screening cohort of Asian women. We compared the performance of screening digital mammography considering breast density, between radiologists and AI standalone detection among Korean women. METHODS: We retrospectively included 89,855 Korean women who underwent their initial screening digital mammography from 2009 to 2020. Breast cancer within 12 months of the screening mammography was the reference standard, according to the National Cancer Registry. Lunit software was used to determine the probability of malignancy scores, with a cutoff of 10% for breast cancer detection. The AI's performance was compared with that of the final Breast Imaging Reporting and Data System category, as recorded by breast radiologists. Breast density was classified into four categories (A-D) based on the radiologist and AI-based assessments. The performance metrics (cancer detection rate [CDR], sensitivity, specificity, positive predictive value [PPV], recall rate, and area under the receiver operating characteristic curve [AUC]) were compared across breast density categories. RESULTS: Mean participant age was 43.5 ± 8.7 years; 143 breast cancer cases were identified within 12 months. The CDRs (1.1/1000 examination) and sensitivity values showed no significant differences between radiologist and AI-based results (69.9% [95% confidence interval [CI], 61.7-77.3] vs. 67.1% [95% CI, 58.8-74.8]). However, the AI algorithm showed better specificity (93.0% [95% CI, 92.9-93.2] vs. 77.6% [95% CI, 61.7-77.9]), PPV (1.5% [95% CI, 1.2-1.9] vs. 0.5% [95% CI, 0.4-0.6]), recall rate (7.1% [95% CI, 6.9-7.2] vs. 22.5% [95% CI, 22.2-22.7]), and AUC values (0.8 [95% CI, 0.76-0.84] vs. 0.74 [95% CI, 0.7-0.78]) (all P < 0.05). Radiologist and AI-based results showed the best performance in the non-dense category; the CDR and sensitivity were higher for radiologists in the heterogeneously dense category (P = 0.059). However, the specificity, PPV, and recall rate consistently favored AI-based results across all categories, including the extremely dense category. CONCLUSIONS: AI-based software showed slightly lower sensitivity, although the difference was not statistically significant. However, it outperformed radiologists in recall rate, specificity, PPV, and AUC, with disparities most prominent in extremely dense breast tissue.

Increased Apolipoprotein B/Apolipoprotein A-I Ratio Is Associated With Decline in Lung Function in Healthy Individuals: The Kangbuk Samsung Health Study.

BACKGROUND: Lung dysfunction and high apolipoprotein B/apolipoprotein A-I (apoB/apoA-I) ratio are both recognized risk factors for cardiovascular disease. However, few studies have examined the association between the apoB/ApoA-I ratio and lung function. Therefore, we investigated whether this ratio is associated with decreased lung function in a large healthy cohort. METHODS: We performed a cohort study on 68,418 healthy Koreans (34,797 males, mean age: 38.1 years) who underwent a health examination in 2019. ApoB/apoA-I ratio was categorized into quartiles. Spirometric values at the fifth percentile in our population were considered the lower limit of normal (LLN), which was used to define lung function impairment. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs), using the lowest quartile as the reference, were estimated to determine lung function impairment. RESULTS: Mean apoB/apoA-I ratio was 0.67 ± 0.21. Subjects with the highest quartile of this ratio had the lowest predicted forced expiratory volume in one second (FEV1%) and forced vital capacity (FVC%) after controlling for covariates (P < 0.001). However, FEV1/FVC ratio was not significantly different among the four quartiles (P = 0.059). Compared with the lowest quartile (Q1, reference), the aORs (95% CI) for FEV1% < LLN across increasing quartiles (from Q2 to Q4) were 1.216 (1.094-1.351), 1.293 (1.156-1.448), and 1.481 (1.311-1.672) (P for trend < 0.001), respectively. Similarly, the aORs for FVC% < LLN compared with the reference were 1.212 (1.090-1.348), 1.283 (1.147-1.436), and 1.502 (1.331-1.695) with increasing quartiles (P for trend < 0.001). However, the aORs for FEV1/FVC < LLN were not significantly different among groups (P for trend = 0.273). CONCLUSION: High apoB/apoA-I ratio was associated with decreased lung function. However, longitudinal follow-up studies are required to validate our findings.

Metabolic-associated fatty liver disease is associated with colorectal adenomas in young and older Korean adults.

BACKGROUND AND AIMS: Given that the majority of colorectal cancers (CRCs) develop from high-risk adenomas, identifying risk factors for high-risk adenomas is important. The relationship between metabolic dysfunction-associated fatty liver disease (MAFLD) and the risk of colorectal adenoma in young adults remains unclear. We aimed to evaluate this relationship in adults <50 (younger) and ≥50 (older) years of age. METHODS: This cross-sectional study included 184 792 Korean adults (80% <50 years of age) who all underwent liver ultrasound and colonoscopy. Participants were grouped into those with and without MAFLD and classified by adenoma presence into no adenoma, low-risk adenoma, or high-risk adenoma (defined as ≥3 adenomas, any ≥10 mm, or adenoma with high-grade dysplasia/villous features). RESULTS: The prevalence of low- and high-risk adenomas among young and older adults was 9.6% and 0.8% and 22.3% and 4.8%, respectively. MAFLD was associated with an increased prevalence of low- and high-risk adenomas in young and older adults. Young adults with MAFLD had a 1.30 (95% CIs 1.26-1.35) and 1.40 (1.23-1.59) times higher prevalence of low- and high-risk adenomas, respectively, compared to those without MAFLD. These associations were consistent even in lean adults (BMI < 23 kg/m2 ) and those without a family history of CRC. CONCLUSIONS: MAFLD is associated with an increased prevalence of low- and high-risk adenomas in Korean adults, regardless of age or obesity status. Whether reducing metabolic risk factors, such as MAFLD, reduces the risk of precancerous lesions and ultimately reduces the risk of early-onset CRC requires further investigation.

Deep Learning With Chest Radiographs for Making Prognoses in Patients With COVID-19: Retrospective Cohort Study.

BACKGROUND: An artificial intelligence (AI) model using chest radiography (CXR) may provide good performance in making prognoses for COVID-19. OBJECTIVE: We aimed to develop and validate a prediction model using CXR based on an AI model and clinical variables to predict clinical outcomes in patients with COVID-19. METHODS: This retrospective longitudinal study included patients hospitalized for COVID-19 at multiple COVID-19 medical centers between February 2020 and October 2020. Patients at Boramae Medical Center were randomly classified into training, validation, and internal testing sets (at a ratio of 8:1:1, respectively). An AI model using initial CXR images as input, a logistic regression model using clinical information, and a combined model using the output of the AI model (as CXR score) and clinical information were developed and trained to predict hospital length of stay (LOS) ≤2 weeks, need for oxygen supplementation, and acute respiratory distress syndrome (ARDS). The models were externally validated in the Korean Imaging Cohort of COVID-19 data set for discrimination and calibration. RESULTS: The AI model using CXR and the logistic regression model using clinical variables were suboptimal to predict hospital LOS ≤2 weeks or the need for oxygen supplementation but performed acceptably in the prediction of ARDS (AI model area under the curve [AUC] 0.782, 95% CI 0.720-0.845; logistic regression model AUC 0.878, 95% CI 0.838-0.919). The combined model performed better in predicting the need for oxygen supplementation (AUC 0.704, 95% CI 0.646-0.762) and ARDS (AUC 0.890, 95% CI 0.853-0.928) compared to the CXR score alone. Both the AI and combined models showed good calibration for predicting ARDS (P=.079 and P=.859). CONCLUSIONS: The combined prediction model, comprising the CXR score and clinical information, was externally validated as having acceptable performance in predicting severe illness and excellent performance in predicting ARDS in patients with COVID-19.

Correction: Deep Learning With Chest Radiographs for Making Prognoses in Patients With COVID-19: Retrospective Cohort Study.

[This corrects the article DOI: 10.2196/42717.].

Erratum: Correction of Affiliations in the Article "Establishment of a Nationwide Korean Imaging Cohort of Coronavirus Disease 2019".

This corrects the article on p. e413 in vol. 35, PMID: 33258333.

DRG2 Depletion Promotes Endothelial Cell Senescence and Vascular Endothelial Dysfunction.

Endothelial cell senescence is involved in endothelial dysfunction and vascular diseases. However, the detailed mechanisms of endothelial senescence are not fully understood. Here, we demonstrated that deficiency of developmentally regulated GTP-binding protein 2 (DRG2) induces senescence and dysfunction of endothelial cells. DRG2 knockout (KO) mice displayed reduced cerebral blood flow in the brain and lung blood vessel density. We also determined, by Matrigel plug assay, aorta ring assay, and in vitro tubule formation of primary lung endothelial cells, that deficiency in DRG2 reduced the angiogenic capability of endothelial cells. Endothelial cells from DRG2 KO mice showed a senescence phenotype with decreased cell growth and enhanced levels of p21 and phosphorylated p53, γH2AX, senescence-associated ß-galactosidase (SA-ß-gal) activity, and senescence-associated secretory phenotype (SASP) cytokines. DRG2 deficiency in endothelial cells upregulated arginase 2 (Arg2) and generation of reactive oxygen species. Induction of SA-ß-gal activity was prevented by the antioxidant N-acetyl cysteine in endothelial cells from DRG2 KO mice. In conclusion, our results suggest that DRG2 is a key regulator of endothelial senescence, and its downregulation is probably involved in vascular dysfunction and diseases.

Effectiveness of radiologist training in improving reader agreement for Lung-RADS 4X categorization.

OBJECTIVES: To identify the agreement on Lung CT Screening Reporting and Data System 4X categorization between radiologists and an expert-adjudicated reference standard and to investigate whether training led to improvement of the agreement measures and diagnostic potential for lung cancer. METHODS: Category 4 nodules in the Korean Lung Cancer Screening Project were identified retrospectively, and each 4X nodule was matched with one 4A or 4B nodule. An expert panel re-evaluated the categories and determined the reference standard. Nineteen radiologists were asked to determine the presence of CT features of malignancy and 4X categorization for each nodule. A review was performed in two sessions, and training material was given after session 1. Agreement on 4X categorization between radiologists and the expert-adjudicated reference standard and agreement between radiologist-assessed 4X categorization and lung cancer diagnosis were evaluated. RESULTS: The 48 expert-adjudicated 4X nodules and 64 non-4X nodules were evenly distributed in each session. The proportion of category 4X decreased after training (56.4% ± 16.9% vs. 33.4% ± 8.0%; p < 0.001). Cohen's κ indicated poor agreement (0.39 ± 0.16) in session 1, but agreement improved in session 2 (0.47 ± 0.09; p = 0.03). The increase in agreement in session 2 was observed among inexperienced radiologists (p < 0.05), and experienced and inexperienced reviewers exhibited comparable agreement performance in session 2 (p > 0.05). All agreement measures between radiologist-assessed 4X categorization and lung cancer diagnosis increased in session 2 (p < 0.05). CONCLUSION: Radiologist training can improve reader agreement on 4X categorization, leading to enhanced diagnostic performance for lung cancer. KEY POINTS: • Agreement on 4X categorization between radiologists and an expert-adjudicated reference standard was initially poor, but improved significantly after training. • The mean proportion of 4X categorization by 19 radiologists decreased from 56.4% ± 16.9% in session 1 to 33.4% ± 8.0% in session 2. • All agreement measures between the 4X categorization and lung cancer diagnosis increased significantly in session 2, implying that appropriate training and guidance increased the diagnostic potential of category 4X.

Tristetraprolin posttranscriptionally downregulates PFKFB3 in cancer cells.

The enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases 3 (PFKFB3) catalyzes the first committed rate-limiting step of glycolysis and is upregulated in cancer cells. The mechanism of PFKFB3 expression upregulation in cancer cells has not been fully elucidated. The PFKFB3 3'-UTR is reported to contain AU-rich elements (AREs) that are important for regulating PFKFB3 mRNA stability. However, the mechanisms by which PFKFB3 mRNA stability is determined by its 3'-UTR are not well known. We demonstrated that tristetraprolin (TTP), an ARE-binding protein, has a critical function regulating PFKFB3 mRNA stability. Our results showed that PFKFB3 mRNA contains three AREs in the 3'-UTR. TTP bound to the 3rd ARE and enhanced the decay of PFKFB3 mRNA. Overexpression of TTP decreased PFKFB3 expression and ATP levels but increased GSH level in cancer cells. Overexpression of PFKFB3 cDNA without the 3'-UTR rescued ATP level and GSH level in TTP-overexpressing cells. Our results suggested that TTP post-transcriptionally downregulated PFKFB3 expression and that overexpression of TTP may contribute to suppression of glycolysis and energy production of cancer cells in part by downregulating PFKFB3 expression.

Doxorubicin inhibits PD-L1 expression by enhancing TTP-mediated decay of PD-L1 mRNA in cancer cells.

Recent research revealed that doxorubicin (DOX) decreased expression of programmed death-ligand 1 (PD-L1) in cancer cells. However, the detailed mechanisms underlying this effect are not well established. Here, we demonstrate that doxorubicin down-regulates PD-L1 expression through induction of AU-rich element (ARE) binding protein tristetraprolin (TTP) in cancer cells. PD-L1 mRNA contain three AREs within its 3'UTR. Doxorubicin induced expression of TTP, increased TTP binding to the 3rd ARE of the PD-L1 3'UTR, and increased decay of PD-L1 mRNA. Inhibition of TTP abrogates the inhibitory effect of doxorubicin on PD-L1 expression. Our data suggest that TTP plays a key role in doxorubicin-mediated down-regulation of PD-L1 by enhancing degradation of PD-L1 mRNA in cancer cells.

Complications after 100 sessions of cone-beam computed tomography-guided lung radiofrequency ablation: a single-center, retrospective experience.

Objective: To evaluate complications after consecutive 100 sessions of cone-beam computed tomography (CBCT)-guided radiofrequency ablation (RFA) of lung tumorsMaterials and methods: A retrospective study was conducted from January 2016 and October 2018. All procedures were performed using a CBCT virtual navigation guidance system, combining three-dimentional CBCT, needle planning software, and real-time fluoroscopy. Complications were evaluated for each RFA session in 63 consecutive patients (31 male, 32 female; mean age 58.0 years) with 121 lung tumors who underwent 100 sessions of CBCT-guided lung ablation with an internally cooled RFA system. Complications were recorded using the Common Terminology Criteria of Adverse Events (CTCAE) 5.0. A major complication was defined as a grade 3 or 4 adverse event.Results: There was no postprocedural mortality. The major and minor complication rates were 5% and 28%, respectively. The major complications were significant pulmonary hemorrhage (1%), large hemothorax requiring drainage (1%), pneumonia treated with antibiotics (2%), and delayed bronchopleural fistula (1%). The minor complications were pneumothorax (15%), hemoptysis (11%), and subcutaneous emphysema (2%). Of the 15 pneumothoraces, percutaneous catheter drainage was required in six sessions. Pneumothorax was more likely to occur if RFA was performed on two or more tumors at one session. Immediate, periprocedural and delayed complications were 23%, 9%, and 1%, respectively.Conclusion: CBCT-guided RFA of lung tumors is a relatively safe procedure with acceptable morbidity.

Establishment of a Nationwide Korean Imaging Cohort of Coronavirus Disease 2019.

BACKGROUND: The Korean Society of Thoracic Radiology (KSTR) recently constructed a nation-wide coronavirus disease 2019 (COVID-19) database and imaging repository, referred to the Korean imaging cohort of COVID-19 (KICC-19) based on the collaborative efforts of its members. The purpose of this study was to provide a summary of the clinico-epidemiological data and imaging data of the KICC-19. METHODS: The KSTR members at 17 COVID-19 referral centers retrospectively collected imaging data and clinical information of consecutive patients with reverse transcription polymerase chain reaction-proven COVID-19 in respiratory specimens from February 2020 through May 2020 who underwent diagnostic chest computed tomography (CT) or radiograph in each participating hospital. RESULTS: The cohort consisted of 239 men and 283 women (mean age, 52.3 years; age range, 11-97 years). Of the 522 subjects, 201 (38.5%) had an underlying disease. The most common symptoms were fever (n = 292) and cough (n = 245). The 151 patients (28.9%) had lymphocytopenia, 86 had (16.5%) thrombocytopenia, and 227 patients (43.5%) had an elevated CRP at admission. The 121 (23.4%) needed nasal oxygen therapy or mechanical ventilation (n = 38; 7.3%), and 49 patients (9.4%) were admitted to an intensive care unit. Although most patients had cured, 21 patients (4.0%) died. The 465 (89.1%) subjects underwent a low to standard-dose chest CT scan at least once during hospitalization, resulting in a total of 658 CT scans. The 497 subjects (95.2%) underwent chest radiography at least once during hospitalization, which resulted in a total of 1,475 chest radiographs. CONCLUSION: The KICC-19 was successfully established and comprised of 658 CT scans and 1,475 chest radiographs of 522 hospitalized Korean COVID-19 patients. The KICC-19 will provide a more comprehensive understanding of the clinical, epidemiological, and radiologic characteristics of patients with COVID-19.

Comparison of chest radiography, chest digital tomosynthesis and low dose MDCT to detect small ground-glass opacity nodules: an anthropomorphic chest phantom study.

OBJECTIVES: The purpose of this study was to evaluate the diagnostic performance of chest radiography (CXR), chest digital tomosynthesis (DT) and low dose multidetector computed tomography (LDCT) for the detection of small pulmonary ground-glass opacity (GGO) nodules, using an anthropomorphic chest phantom. METHODS: Artificial pulmonary nodules were placed in a phantom and a total of 40 samples of different nodule settings underwent CXR, DT and LDCT. The images were randomly read by three experienced chest radiologists. Free-response receiver-operating characteristics (FROC) were used. RESULTS: The figures of merit for the FROC curves averaged for the three observers were 0.41, 0.37 and 0.76 for CXR, DT and LDCT, respectively. FROC analyses revealed significantly better performance of LDCT over CXR or DT for the detection of GGO nodules (P < 0.05). The difference in detectability between CXR and DT was not statistically significant (P = 0.73). CONCLUSION: The diagnostic performance of DT for the detection of pulmonary small GGO nodules was not significantly different from that of CXR, but LDCT performed significantly better than both CXR and DT. DT is not a suitable alternative to CT for small GGO nodule detection, and LDCT remains the method of choice for this purpose. KEY POINTS: For GGO nodule detection, DT was not significantly different from CXR. DT is not a suitable alternative to CT for GGO nodule detection. LDCT is the method of choice for GGO nodule detection.

The impact of insulin resistance on the association between metabolic syndrome and lung function: the Kangbuk Samsung Health Study.

BACKGROUND/OBJECTIVE: Metabolic syndrome (MS) is related to lung dysfunction. However, its impact according to insulin resistance (IR) remains unknown. Therefore, we evaluated whether the relation of MS with lung dysfunction differs by IR. SUBJECT/METHODS: This cross-sectional study included 114,143 Korean adults (mean age, 39.6 years) with health examinations who were divided into three groups: metabolically healthy (MH), MS without IR, and MS with IR. MS was defined as presence of any MS component, including IR estimated by HOMA-IR ≥ 2.5. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for lung dysfunction were obtained in MS, MS without IR, and MS with IR groups compared with the MH (reference) group. RESULTS: The prevalence of MS was 50.7%. The percent predicted forced expiratory volume in 1 s (FEV1%) and forced vital capacity (FVC%) showed statistically significant differences between MS with IR and MH and between MS with IR and MS without IR (all P < 0.001). However, those measures did not vary between MH and MS without IR (P = 1.000 and P = 0.711, respectively). Compared to MH, MS was not at risk for FEV1% < 80% (1.103 (0.993-1.224), P = 0.067) or FVC% < 80% (1.011 (0.901-1.136), P = 0.849). However, MS with IR was clearly associated with FEV1% < 80% (1.374 (1.205-1.566) and FVC% < 80% (1.428 (1.237-1.647) (all p < 0.001), though there was no evident association for MS without IR (FEV1%: 1.078 (0.975-1.192, P = 0.142) and FVC%: 1.000 (0.896-1.116, p = 0.998)). CONCLUSION: The association of MS with lung function can be affected by IR. However, longitudinal follow-up studies are required to validate our findings.

Clinical outcomes and prognostic factors of cone-beam CT-guided radiofrequency ablation for pulmonary metastases in colorectal cancer patients.

AIM: Radiofrequency ablation (RFA) has been increasingly used for the treatment of pulmonary metastases in various malignancies. METHODS: A retrospective analysis was performed to establish the safety and efficacy of cone-beam computed tomography (CBCT)-guided RFA in patients with metastatic colorectal cancer between 2016 and 2019, and the prognostic factors of local tumor control were assessed. RESULTS: A total of 31 patients with colorectal cancer underwent 48 sessions of lung RFA. The mean diameter of metastases targeted for RFA was 11 mm (range: 4-32), and the RFA was technically successful in 43 sessions (90%). There were 14 complications (29%), the majority of which required no intervention, with no cases of mortality. The median follow-up duration from RFA in the surviving 29 patients was 18.0 months. Only two patients (6%) died of disease progression, and the 3-year overall survival rate was 91% (95% CI: 83-99). Local tumor progression (LTP) of the RFA site was observed in 27%, and the LTP-free survival rates at 1 and 2 years were 81% (95% CI: 70-82) and 64% (95% CI: 50-77), respectively. Multivariate analysis showed that the progression of extra-RFA sites and the presence of extrapulmonary metastasis were independent prognostic factors significantly associated with LTP at RFA site. CONCLUSION: Lung RFA using CBCT guidance is a comparatively safe and effective option for the treatment of lung metastases from colorectal cancer. However, the control of extrapulmonary metastases should be accompanied by combined or sequential systemic treatment and local treatment.

The effect of metabolic health and obesity on lung function: A cross sectional study of 114,143 participants from Kangbuk Samsung Health Study.

OBJECTIVE: Although the role of obesity-induced metabolic abnormalities in impaired lung function is well-established, the risk of impaired lung function among obese individuals without metabolic abnormalities, referred to metabolically-healthy obesity (MHO), is largely unexplored. Therefore, we evaluated the impact of MHO on lung function in a large health-screening cohort. METHODS: 114,143 subjects (65,342 men, mean age and BMI: 39.6 years and 23.6) with health examinations in 2019 were divided into four groups as follows: metabolically healthy non-obese (MHNO), MHO, metabolically unhealthy non-obese (MUHNO), and metabolically unhealthy obese (MUHO). Metabolic health was defined as fewer than two metabolic syndrome components. Obesity was defined as BMI ≥25 kg/m2. Adjusted odds ratios (aORs), using MHNO as a reference, were calculated to determine lung function impairment. RESULTS: Approximately one-third (30.6%) of the study subjects were obese. The prevalence of MHO was 15.1%. Subjects with MHO had the highest FEV1% and FVC% values but the lowest FEV1/FVC ratio (p<0.001). These results persisted after controlling for covariates. Compared with MHNO, the aORs (95% confidence interval) for FEV1% < 80% in MHO, MUHNO and MUHO were 0.871 (0.775-0.978), 1.274 (1.114-1.456), and 1.176 (1.102-1.366), respectively (P for trend = 0.014). Similarly, the aORs in MHO, MUHNO, and MUHO were 0.704 (0.615-0.805), 1.241 (1.075-1.432), and 1.226 (1.043-1.441), respectively, for FVC% < 80% (p for trend = 0.013). However, the aORs for FEV1/FVC<0.7 were not significantly different between groups (p for trend = 0.173). CONCLUSIONS: The MHO group had better lung function than other groups. However, longitudinal follow-up studies are required to validate our findings.

Radiation dose reduction in extremity multi-detector CT: A comparison of image quality with a standard dose protocol.

PURPOSE: To analyze the quantitative and qualitative image quality of computed tomography (CT) of the extremities (shoulder, wrist, pelvis, and ankle joints) with low-dose radiation and standard-dose radiation. MATERIALS AND METHODS: In this study, we included 400 individuals who underwent CT of the extremities, comprising 50 cases of each joint (shoulder, wrist, pelvis, and ankle) at low and standard dose regimens. Low-dose CTs were performed using identical voltage and parameters with the exception of decreased (half of standard dose) tube current. Low-dose and standard-dose images were compared in terms of radiation dose, objective image quality according to the standard deviation (SD) of the Hounsfield unit value of the medulla, cortex, muscle, subcutaneous fat, and air, and subjective image quality according to noise, sharpness, diagnostic acceptability, and artifacts. RESULTS: In the shoulder and pelvis, the mean value of the SD for all tissue on low dose CT images was significantly higher than that of standard dose CT, except for the SD of cortex in the shoulder joint and marrow in the pelvis. In the wrist, the mean value of the SD for all tissue was not significantly different between low dose and standard CT (p > 0.05). In the ankle, the mean value of the SD of the medulla and cortex was not different (p > 0.05), but the remaining measurements were significantly higher in low dose CT. Subjective image quality in the shoulder and pelvis were significantly reduced in low dose CT. In the wrist, all categories of subjective image quality except artifacts were similar. In the ankle, all categories of subjective image quality except for artifacts were degraded in low dose CT. CONCLUSIONS: Objective image noise is more increased in low dose CT images of the shoulder and pelvis. Although diagnostic performance was acceptable, mean subjective image quality also decreased. In the wrist, objective image noise and subjective image quality were not degraded in low dose CT. In the ankle, some measurements of objective and subjective image quality were similar between low dose and standard dose CT.