Ionizing Radiation in Medical Imaging and Efforts in Dose Optimization

Medical-related radiation is the largest source of controllable radiation exposure to humans and it accounts for more than 95% of radiation exposure from man-made sources. Its direct benefits in modern day medical practices are beyond doubt but risks-benefits ratios need to be constantly monitored as the use of ionizing radiation is increasing rapidly. From 1980 to 2006, the per-capita effective dose from diagnostic and interventional medical procedures in the United States increased almost six fold, from 0.5 to 3.0mSv, while contributions from other sources remained static (NCRP report no 160, 2009). This chapter will review radiation exposure from medical imaging initially starting from a historical viewpoint as well as discussing innovative technologies on the horizon. The challenges for the medical community in addressing the increasing trend of radiation usage will be discussed as well as the latest research in dose justification and optimization.link_to_OA_fulltex

Mosapride Reduces Prolonged Postoperative Ileus after Open Colorectal Surgery in the Setting of Enhanced Recovery after Surgery (ERAS): A Matched Case-Control Study

Objective: To evaluate the effects of mosapride, a selective 5-hydroxytryptamine-4 agonist, on gastrointestinal recovery in patients undergoing open colorectal surgery. Methods: A prospectively collected database of the patients undergoing elective ‘open’ colorectal resection under enhanced recovery after surgery (ERAS) from May 2013 to April 2017 was reviewed. From April 2016, mosparide was routinely given from postoperative day 1 to discharge date. Eighty-four patients receiving mosapride were matched to 168 control patients (historical comparison with a ratio of 1:2). Surgical outcomes and postoperative gastrointestinal recovery was compared. Results: The patient characteristics were comparable except more patients in control group had perioperative administration of NSAIDs. The mosapride group had a 1.5% higher compliance rate of ERAS protocol. The control group had higher incidences of prolonged postoperative ileus (17.3% vs 7.1%; p=0.029) and prolonged postoperative ileus requiring nasogastric tube decompression (8.9% vs 3.6%; p=0.19). Overall complication, clinical intestinal transit and length of hospitalization were not significantly different between groups. However, the patients with prolonged postoperative ileus had significantly prolonged hospitalization (p<0.001). Median length of hospital stay was 4 days (IQR 4-5) in those without prolonged ileus (n=217), 5 days (IQR 5-6) in those with prolonged ileus without a need of gastric decompression (n=17) and 10.5 days (IQR 7-14.5) in those with prolonged ileus requiring nasogastric tube decompression (n=18) (p<0.001). A multivariate analysis showed that administration of mosapride was only a protective factor for prolonged postoperative ileus (OR=0.37, 95% CI=0.15-0.93, p=0.029). Conclusion: Postoperative administration of mosapride reduced the incidence of prolonged postoperative ileus after open colorectal surgery

Towards visceral fat estimation at population scale: correlation of visceral adipose tissue assessment using three-dimensional cross-sectional imaging with BIA, DXA, and single-slice CT

BackgroundIn terms of assessing obesity-associated risk, quantification of visceral adipose tissue (VAT) has become increasingly important in risk assessment for cardiovascular and metabolic diseases. However, differences exist in the accuracy of various modalities, with a lack of up-to-date comparison with three-dimensional whole volume assessment.AimsUsing CT or MRI three-dimensional whole volume VAT as a reference, we evaluated the correlation of various commonly used modalities and techniques namely body impedance analysis (BIA), dual-energy x-ray absorptiometry (DXA) as well as single slice CT to establish how these methods compare.MethodsWe designed the study in two parts. First, we performed an intra-individual comparison of the 4558 participants from the UK Biobank cohorts with matching data of MRI abdominal body composition, DXA with VAT estimation, and BIA. Second, we evaluated 174 CT scans from the publicly available dataset to assess the correlation of the commonly used single-slice technique compared to three-dimensional VAT volume.ResultsAcross the UK Biobank cohort, the DXA-derived VAT measurement correlated better (R2 0.94, p&lt;0.0001) than BIA (R2 0.49, p&lt;0.0001) with reference three-dimensional volume on MRI. However, DXA-derived VAT correlation was worse for participants with a BMI of &lt; 20 (R2 = 0.62, p=0.0013). A commonly used single slice method on CT demonstrated a modest correlation (R2 between 0.51 – 0.64), with best values at L3- and L4 (R2 L3 = 0.63, p&lt;0.0001; L4 = 0.64, p&lt;0.0001) compared to reference three-dimensional volume. Combining multiple slices yielded a better correlation, with a strong correlation when L2-L3 levels were combined (R2 = 0.92, p&lt;0.0001).ConclusionWhen deployed at scale, DXA-derived VAT volume measurement shows excellent correlation with three-dimensional volume on MRI based on the UK Biobank cohort. Whereas a single slice CT technique demonstrated moderate correlation with three-dimensional volume on CT, with a stronger correlation achieved when multiple levels were combined

The effect of temperature and residence time on the distribution of carbon, sulfur, and nitrogen between gaseous and condensed phase products from low temperature pyrolysis of kraft black liquor

Laminar entrained flow reactor (LEFR) was used to determine the effect of temperature and residence time on the distribution of carbon, sulfur and nitrogen between gaseous and condensed phase products from low temperature pyrolysis of kraft black liquor. The operating furnace temperatures were between 400°C-600°C where the effect of condensable organic and organic sulfur compounds may be important. The residence times ranged from 0.3 to 2.0 seconds. In the evolution of carbon as gases, an oxidizer was used to convert all oxidizable components in LEFR effluent gas to carbon dioxide which was detected by an infrared carbon dioxide meter. With this, measurement of total carbon in the gas phase, the fine particles, and the char residue were made. The carbon yield in the gas phase increased as residence time increased. The higher the temperature, the higher the carbon yield as gases phase at each residence time. The carbon yield in the fine particles differed very little with temperature at residence time below 1.1 seconds. At higher temperature, the carbon yield in the fine particles is about the same at 500°C and 600°C, but lower at 400°C. The carbon yield in the char residue decreased as residence time increased. The carbon yield in the char residue at 500°C and residence time above 1.1 seconds was a little lower than at temperature 600°C, due to an apparent loss of char at 500°C. The char yield at 500°C was lower than expected based on the 400°C and 600°C data because of accumulation of larger, more highly swollen char particles at the tip of collector at this temperature. The average of the sum of carbon recovered as char residue, gases, and fine particles was 96.2% at 600°C, 88.1% at 500°C, and 95.7% at 400°C. The main reason for the poorer carbon recovery at 500°C was the loss of char particles which accumulated on the tip of the collector. When the char yield at 500°C is increased so that the carbon balance closed to 96%, the char yield, carbon yield, and sulfur yield at 500°C fell between the values at 400°C and 600°C. The sulfur yield in the char residue decreased as residence time increased. The higher the temperature, the lower the sulfur yield in the char residue. The nitrogen yield in the char residue also decreased as residence time increased

Mosapride Reduces Prolonged Postoperative Ileus after Open Colorectal Surgery in the Setting of Enhanced Recovery after Surgery (ERAS): A Matched Case-Control Study

Objective: To evaluate the effects of mosapride, a selective 5-hydroxytryptamine-4 agonist, on gastrointestinal recovery in patients undergoing open colorectal surgery. Methods: A prospectively collected database of the patients undergoing elective ‘open’ colorectal resection under enhanced recovery after surgery (ERAS) from May 2013 to April 2017 was reviewed. From April 2016, mosparide was routinely given from postoperative day 1 to discharge date. Eighty-four patients receiving mosapride were matched to 168 control patients (historical comparison with a ratio of 1:2). Surgical outcomes and postoperative gastrointestinal recovery was compared. Results: The patient characteristics were comparable except more patients in control group had perioperative administration of NSAIDs. The mosapride group had a 1.5% higher compliance rate of ERAS protocol. The control group had higher incidences of prolonged postoperative ileus (17.3% vs 7.1%; p=0.029) and prolonged postoperative ileus requiring nasogastric tube decompression (8.9% vs 3.6%; p=0.19). Overall complication, clinical intestinal transit and length of hospitalization were not significantly different between groups. However, the patients with prolonged postoperative ileus had significantly prolonged hospitalization (p<0.001). Median length of hospital stay was 4 days (IQR 4-5) in those without prolonged ileus (n=217), 5 days (IQR 5-6) in those with prolonged ileus without a need of gastric decompression (n=17) and 10.5 days (IQR 7-14.5) in those with prolonged ileus requiring nasogastric tube decompression (n=18) (p<0.001). A multivariate analysis showed that administration of mosapride was only a protective factor for prolonged postoperative ileus (OR=0.37, 95% CI=0.15-0.93, p=0.029). Conclusion: Postoperative administration of mosapride reduced the incidence of prolonged postoperative ileus after open colorectal surgery

Effect of Intraoperative Hypothermia on Surgical Outcomes after Colorectal Surgery within an Enhanced Recovery after Surgery Pathway

Objective: The adverse effects of intraoperative hypothermia from the published literature were mainly based on nonenhanced recovery after surgery (ERAS) settings. This study aimed to determine association between intraoperative hypothermia and outcomes following colorectal surgery under ERAS pathway. Methods: A prospectively collected database of patients undergoing elective colorectal surgery under ERAS pathway from 2011 to 2015 was reviewed. Patients were divided into 2 groups: hypothermic group (core temperature <36oC continuously exceeding 30 minutes during an operation) and normothermic group. Short-term outcomes were compared. Results: This study included 195 patients: 150 (77%) in hypothermic group and 45 (23%) in normothermic group. Rectal surgery (OR=5.15), operative time exceeding 3 hours (OR=3.80), multi-organ resection (OR=3.12) and male gender (OR=2.62) were significant predictors for intraoperative hypothermia. Rates of postoperative complication and wound infection were comparable between hypothermic patients and normothermic patients (23% vs 13%; p=0.17 and 6.0 vs 6.7%; p=0.87, respectively). Hypothermic patients had a longer time to tolerate normal diet (2.0 days vs 1.3 days; p=0.023) but a comparable time to first bowel movement (2.6 days vs 2.6 days; p=0.84). Hypothermic patients had a significant longer hospitalization (5.7 days vs 4.4 days; p=0.048). A multivariate analysis showed that intraoperative hypothermia was an independent predictor for delayed food intake (OR=2.9, 95%CI=1.2-6.9; p=0.014) but not for prolonged hospitalization (OR=1.7, 95%CI=0.7-3.9; p=0.207). Conclusion: Intraoperative hypothermia prolonged time to tolerate food intake after colorectal surgery within an ERAS setting but it did not adversely affect the return of bowel function, wound infection, complication and length of hospitalization

Comparative Study of Health-Related Quality of Life between Colorectal Cancer Patients with Temporary and Permanent Stoma

Objective: To compare the health-related quality of life (HRQOL) between colorectal cancer (CRC) patients with temporary and permanent stoma. Methods: This survey was a cross-sectional study that was conducted on 110 CRC patients living with stoma. A validated Thai version of Padilla and Grant’s HRQOL (as a cancer nursing outcome variable) was used. Enrolled patients must have age between 40-60 years and live with stoma over a period of 3 months. Results: There were 83 patients with temporary stoma and 27 patients with permanent stoma. The majority was male and got married. The common indication for temporary and permanent stoma was low anterior resection and abdominoperineal resection, respectively. Overall mean HRQOL index was not significantly different between groups. There was also no difference in the mean QOL of each domain - namely physical well-being, psychological well-being, body image concerns about stoma, social support concern, and diagnosis/treatment response between those with temporary and permanent stoma. Notably, the domain of body image concern had the lowest QOL index in both groups. Conclusion: Postoperative health-related quality of life was not different between Thai colorectal cancer patients with temporary or permanent stoma. However, the patients with permanent stoma appeared to have non-significant higher score in every domain of health-related quality of life than those with temporary stoma

Rethinking annotation granularity for overcoming deep shortcut learning: A retrospective study on chest radiographs

Deep learning has demonstrated radiograph screening performances that are comparable or superior to radiologists. However, recent studies show that deep models for thoracic disease classification usually show degraded performance when applied to external data. Such phenomena can be categorized into shortcut learning, where the deep models learn unintended decision rules that can fit the identically distributed training and test set but fail to generalize to other distributions. A natural way to alleviate this defect is explicitly indicating the lesions and focusing the model on learning the intended features. In this paper, we conduct extensive retrospective experiments to compare a popular thoracic disease classification model, CheXNet, and a thoracic lesion detection model, CheXDet. We first showed that the two models achieved similar image-level classification performance on the internal test set with no significant differences under many scenarios. Meanwhile, we found incorporating external training data even led to performance degradation for CheXNet. Then, we compared the models' internal performance on the lesion localization task and showed that CheXDet achieved significantly better performance than CheXNet even when given 80% less training data. By further visualizing the models' decision-making regions, we revealed that CheXNet learned patterns other than the target lesions, demonstrating its shortcut learning defect. Moreover, CheXDet achieved significantly better external performance than CheXNet on both the image-level classification task and the lesion localization task. Our findings suggest improving annotation granularity for training deep learning systems as a promising way to elevate future deep learning-based diagnosis systems for clinical usage.Comment: 22 pages of main text, 18 pages of supplementary table

Effect of Intraoperative Hypothermia on Surgical Outcomes after Colorectal Surgery within an Enhanced Recovery after Surgery Pathway

Objective: The adverse effects of intraoperative hypothermia from the published literature were mainly based on non-enhanced recovery after surgery (ERAS) settings. This study aimed to determine association between intraoperative hypothermia and outcomes following colorectal surgery under ERAS pathway. Methods: A prospectively collected database of patients undergoing elective colorectal surgery under ERAS pathway from 2011 to 2015 was reviewed. Patients were divided into 2 groups: hypothermic group (core temperature <36oC continuously exceeding 30 minutes during an operation) and normothermic group. Short-term outcomes were compared. Results: This study included 195 patients: 150 (77%) in hypothermic group and 45 (23%) in normothermic group. Rectal surgery (OR=5.15), operative time exceeding 3 hours (OR=3.80), multi-organ resection (OR=3.12) and male gender (OR=2.62) were significant predictors for intraoperative hypothermia. Rates of postoperative complication and wound infection were comparable between hypothermic patients and normothermic patients (23% vs 13%; p=0.17 and 6.0 vs 6.7%; p=0.87, respectively). Hypothermic patients had a longer time to tolerate normal diet (2.0 days vs 1.3 days; p=0.023) but a comparable time to first bowel movement (2.6 days vs 2.6 days; p=0.84). Hypothermic patients had a significant longer hospitalization (5.7 days vs 4.4 days; p=0.048). A multivariate analysis showed that intraoperative hypothermia was an independent predictor for delayed food intake (OR=2.9, 95%CI=1.2-6.9; p=0.014) but not for prolonged hospitalization (OR=1.7, 95%CI=0.7-3.9; p=0.207). Conclusion: Intraoperative hypothermia prolonged time to tolerate food intake after colorectal surgery within an ERAS setting but it did not adversely affect the return of bowel function, wound infection, complication and length of hospitalization