Comparison of DLP-based effective dose to Monte Carlo-based effective dose in low dose chest CTs

Introduction: Lung cancer is very difficult to detect during its early stages, as outward symptoms are not typically expressed early in the disease process. Advances in low dose CT have made it possible to screen high-risk patients and make earlier diagnoses. It is important to strike a balance between radiation exposure and image resolution, and the recommended effective dose (ED) of radiation for these scans is 1.5 mSv, much lower than the 8 mSv dose of a typical diagnostic chest CT scan. The purpose of this study was to compare the rapid formulaic dose length product (DLP)-based method of calculating ED to the Monte Carlo-based method, which is regarded as the gold standard. Methods: This was a HIPAA compliant retrospective study. Dose data from 85 non-contrast low dose chest CT’s used for lung cancer screening were collected. Monte Carlo simulated organ based effective dose (EDMC) was calculated using Radimetrics software, a commercially available radiation dose tracking software. The DLP-based effective dose (EDDLP-B) was calculated using the formula ED = DLP * k, where k is the conversion coefficient, which are widely published. A k value of 0.015 was used for both sexes (kB), and female and male specific k-coefficients of 0.019 (kF) and 0.011 (kM) were also used respectively. ΔED was calculated as mean EDDLP – mean EDMC; and %ΔED was calculated as (mean ΔED/mean EDMC)*100. EDMC and EDDLP were compared using Wilcoxon signed rank test (WSRT) using kB, kF and kM to calculate EDDLP. Modified Bland-Altman plots were created, comparing ΔED to EDMC, and %ΔED was also plotted against patient diameter. Results: There was statistically significant difference between EDMC and EDDLP-B (pkB (0.015) coefficient, although this was heavily influenced by gender. EDDLP-B underestimates EDMC by a mean of 31% in women (pMC and EDDLP-B in male patients (p=0.3173). EDDLP underestimated EDMC by 13% in women when using the gender specific kF; this difference was significant (pDLP underestimated EDMC by 28% in men when using the gender specific kM; this difference remained significant (p Conclusion: DLP-based calculation of ED using the gender-neutral k-coefficient underestimates ED by 31% in women; use of female-specific k-coefficient decreases this underestimation to 13%. This should be factored into CT protocol development of low-dose chest CT’s in women. Gender-neutral k-coefficient is adequate for DLP-based ED calculation in men

Pre- and Post-Contrast Dual Energy CT: Is Post-Contrast Attenuation Different for Single and Dual Energy Modes?

Background: Dual energy CT (DECT) is increasingly being used in clinical practice due to its assortment of applications beyond those of conventional single energy CT (SECT). While SECT and DECT attenuations are relatively comparable, small differences in the soft tissue attenuation range are not well established. Thresholds for lesion enhancement were created with SECT and small deviations between SECT and DECT attenuations could affect interpretation for enhancement. As a result, differences in post-contrast attenuation values between SECT and DECT may result in the overcalling or undercalling of these lesions. The purpose of this study is to compare attenuations between SECT images and 70 keV dual energy monochromatic image reconstructions (70MI). Methods: Four rows of four tubes containing saline and three dilutions of iodinated contrast (with approximate SECT attenuations of 5, 15, 25, and 35 HU) were suspended in a plastic water filled abdominal phantom. The phantom was scanned five times in SECT (120 kVp) and DECT (100/140 kVp and 80/140 kVp) modes with a CTDIvol of 8 and 16 mGy and constant remaining settings. 70MI reconstructions, considered the 120 kVp SECT equivalent-image, were then created. SECT and 70MI attenuations and noise were measured for each tube using 2.0 cm2 regions of interest and were compared using the Wilcoxon signed rank test. Results: All tubes had greater attenuation on 70MI than SECT (p \u3c 0.01), with larger deviations at high attenuation tubes. The 70MI mode overestimated SECT attenuations by a mean of 6.5 ± 1.8 HU (range 2.1-10.6 HU) and 9.4 ± 2.3 HU (range 5.6 - 15.5 HU) for the 25 and 35 HU tubes respectively. There was no difference between deviations at CTDIvol of 8 and 16 mGy (p = 0.20). 70MI had slightly more noise than SECT with CTDIvol of 16 mGy (p \u3c 0.02), although there was no difference in noise levels at CTDIvol of 8 mGy. Conclusion: At high iodine concentrations, 70MI DECT post-contrast imaging can overestimate enhancement attenuation as compared to SECT. Radiologists should be aware of these deviations when measuring attenuations with 70MI DECT

Hemoglobin, Albumin, Lymphocyte, and Platelet Count is a Significant Biomarker Surrogate for Nutritional Status to Predict Overall Survival in Patients Post-radical Cystectomy

INTRODUCTION: Nutritional status is an independent predictor of overall survival after radical cystectomy. Various biomarkers of nutritional status are proposed to predict postoperative outcome, including albumin, anemia, thrombocytopenia, and sarcopenia. Recently, a score comprising hemoglobin, albumin, lymphocyte, and platelet counts was postulated as an encompassing biomarker to predict overall survival post-radical cystectomy in a single-institution study. However, cutoffs for hemoglobin, albumin, lymphocyte, and platelet count are not well defined. In this study, we analyzed hemoglobin, albumin, lymphocyte, and platelet count thresholds predicting overall survival and examined the platelet-to-lymphocyte as an additional prognostic biomarker. METHODS: Fifty radical cystectomy patients were retrospectively evaluated from 2010-2021. American Society of Anesthesiologists classification, pathological data, and survival were extracted from our institutional registry. Univariable and multivariable Cox regression analysis was fit to the data to predict overall survival. RESULTS: Median follow-up was 22 (12-54) months. Hemoglobin, albumin, lymphocyte, and platelet count (continuous) was a significant predictor of overall survival on multivariable Cox regression analysis (HR 0.95, 95% CI: 0.90-0.99, = .03), adjusting for Charlson Comorbidity Index, lymphadenopathy (pN \u3eN0), muscle-invasive disease, and neoadjuvant chemotherapy. Optimal hemoglobin, albumin, lymphocyte, and platelet count cutoff was 25.0. Patients with hemoglobin, albumin, lymphocyte, and platelet count \u3c25.0 had inferior overall survival (median, 33 months) vs with those with hemoglobin, albumin, lymphocyte, and platelet count ≥25.0 (median, not reached) ( = .03). CONCLUSIONS: Low hemoglobin, albumin, lymphocyte, and platelet count \u3c25.0 was an independent predictor of inferior overall survival

General acts passed by the General Court of Massachusetts

Imprint varies.Vols. for 1915-19 published in 2 v.: General acts; Special acts.Vols. for some years issued in parts.Separate vols. issued for extra session, 1916, and for extra session, 1933.Vol. 12 (May 1831-Mar. 1833) in Jan. session, 1833; Jan. 1834-Apr. 1836 in vol. for extra session 1835/Jan. session 1836; May 1824-Mar. 1828; June 1828-June 1831, Jan. 1832-Apr. 1834, Jan. 1835-Apr. 1838, each bound with corresponding vol.Resolves issued separately, 1780-1838

Comparing dose-length product⇓based and Monte Carlo simulation organ⇓based calculations of effective dose in 16- and 64-MDCT examinations using automatic tube current modulation

© American Roentgen Ray Society. OBJECTIVE. The purpose of this study is to compare dose-length product (DLP)-based calculation of effective dose (EDDLP) with Monte Carlo simulation organ-based calculation of effective dose (EDMCO) in 16- and 64-MDCT examinations, with the use of clinical examinations with automatic tube current modulation. MATERIALS AND METHODS. Dose data were obtained from 50 consecutive unenhanced head CT examinations, unenhanced chest CT examinations, and unenhanced and contrast-enhanced abdominopelvic CT examinations performed using 16- and 64-MDCT scanners, as well as from 50 pulmonary CT angiography (CTA) examinations performed using a 64-MDCT scanner and 31 pulmonary CTA examinations performed using a 16-MDCT scanner. The EDMCO and the mean patient effective diameter were calculated using commercially available software. The EDDLP was also calculated. Both the mean difference and percentage difference between EDDLP and EDMCO were calculated, and they were statistically compared according to patient sex, type of examination performed, and type of scanner used. RESULTS. EDDLP significantly underestimated the EDMCO by 0.3 mSv (19%) for men who underwent unenhanced head CT, 0.5 mSv (29%) for women who underwent unenhanced head CT, 0.9-1.4 mSv (9-13%) for men who underwent chest CT, and 4.7-4.8 mSv (39%) for women who underwent chest CT (p \u3c 0.001). The EDDLP overestimated the EDMCO by 1.9-2.0 mSv (12-14%) for men who underwent abdominopelvic CT (p \u3c 0.001), with no significant difference noted for women who underwent abdominopelvic CT’s. No significant difference was noted in the percentage difference in ED between the 16- and 64-MDCT scanners (p ≥ 0.13). CONCLUSION. EDDLP underestimates EDMCO, the reference standard for dose calculation, by 19-39% in unenhanced head CT examinations and, among women, in chest CT examinations. EDDLP deviates from EDMCO by less than 15% for chest CT examinations of men and for abdominopelvic CT. These differences can be attributed to variable patient body habitus, automatic tube current modulation, and sex-neutral k-coefficients, and they should be considered when calculating ED, particularly in women