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

Comparison of Two Techniques for Humeral Reconstruction in Unconstrained Shoulder Arthroplasty

There has been an increasing interest in achieving true anatomic replication of native anatomy in unconstrained shoulder arthroplasty. Reconstruction of the humerus is generally done in one of two ways: guided resection of the humeral head using intramedullary cutting guides and version bars and reconstruction with a fixed angle prosthesis or freehand resection of the native humeral head, based on perceived anatomic neck anatomy and reconstruction with a variable angle prosthesis. The purpose of this study is to determine which technique used for proximal humerus reconstruction in shoulder arthroplasty more reliably reproduces native anatomy. Ten sets of cadaveric upper limbs (20 shoulders) were scanned for a pre-resection CT scan to establish preoperative version, neck-shaft angle, center of rotation (COR), and head height. The cadavers were then divided into two groups so that both groups had an equal number of right limbs. Half of the cadavers underwent a freehand cut based on surgeon defined anatomic neck. The other half underwent humeral head resections using a fixed intramedullary guide. The free-hand cut group was reconstructed with a prosthesis that allows the head to be matched to the anatomic cut with 15º of variability in all planes (Depuy-Synthes Global AP). The group cut with the intramedullary guide was reconstructed using a fixed angle stem (Zimmer BF Shoulder). The limbs were then again scanned and the measurements from the reconstructed proximal humeri were compared to those from the native cadavers. The following measurements were taken: humeral head height, neck shaft angle, humeral version (based off the humeral epicondylar axis), and COR in the axial, craniocaudal (CC), and medial to lateral planes (TX). There were no statistically significant differences between the two groups’ delta values with respect to head height (p=.2794), neck shaft angle (p=.8311), version (.1197), or center of rotation as measured in the axial (p=.109), craniocaudal (p=.1754), or medial to lateral planes (p=.7343). However, the fixed angle prosthesis tended to more accurately reproduce native anatomy with regard to humeral height, version, and neck shaft angle. The variable angle prosthesis tended to more accurately replicate COR in the axial, craniocaudal, and medial to lateral planes of reference with standard deviation values that reflected this trend when compared to the fixed angle prosthesis. The results of our study suggest that, with respect to the accuracy of proximal humerus reconstruction in TSA, variable and fixed angle prostheses are equally accurate in reconstructing native proximal humerus anatomy

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