Radiation-Induced DNA Damage in Operators Performing Endovascular Aortic Repair.

BACKGROUND: Radiation exposure during fluoroscopically guided interventions such as endovascular aortic repair (EVAR) is a growing concern for operators. This study aimed to measure DNA damage/repair markers in operators perfoming EVAR. METHODS: Expression of the DNA damage/repair marker, γ-H2AX and DNA damage response marker, phosphorylated ataxia telangiectasia mutated (pATM), were quantified in circulating lymphocytes in operators during the peri-operative period of endovascular (infrarenal, branched, and fenestrated) and open aortic repair using flow cytometry. These markers were separately measured in the same operators but this time wearing leg lead shielding in addition to upper body protection and compared with those operating with unprotected legs. Susceptibility to radiation damage was determined by irradiating operators' blood in vitro. RESULTS: γ-H2AX and pATM levels increased significantly in operators immediately after branched endovascular aortic repair/fenestrated endovascular aortic repair (P<0.0003 for both). Only pATM levels increased after infrarenal endovascular aortic repair (P<0.04). Expression of both markers fell to baseline in operators after 24 hours (P<0.003 for both). There was no change in γ-H2AX or pATM expression after open repair. Leg protection abrogated γ-H2AX and pATM response after branched endovascular aortic repair/fenestrated endovascular aortic repair. The expression of γ-H2AX varied significantly when operators' blood was exposed to the same radiation dose in vitro (P<0.0001). CONCLUSIONS: This is the first study to detect an acute DNA damage response in operators performing fluoroscopically guided aortic procedures and highlights the protective effect of leg shielding. Defining the relationship between this response and cancer risk may better inform safe levels of chronic low-dose radiation exposure.

Effect of the American Heart Association 2007 Guidelines on the Practice of Dental Prophylaxis for the Prevention of Infective Endocarditis in Olmsted County, Minnesota.

OBJECTIVE: To determine the adherence of dental providers to the 2007 American Heart Association (AHA) infective endocarditis prevention guidelines regarding antibiotic drug administration before invasive dental procedures. PATIENTS AND METHODS: The study included all adults (≥18 years old) with a moderate-risk (MR) or high-risk (HR) cardiac condition who received dental care at participating dental offices from January 1, 2005, through June 1, 2015, in Olmsted County, Minnesota. Data collected included the date and type of dental procedure performed and receipt of antibiotic prophylaxis (AP). RESULTS: A total of 1351 patients underwent 8854 dental visits at participating dental offices during the study period; 1236 patients had an MR cardiac condition and 115 had an HR condition. The percentage of visits in which antibiotic drugs were used for indicated dental procedures in the MR group declined from 64.6% before to 8.6% after publication of the 2007 AHA guidelines (P<.001); for the HR group, AP declined from 96.9% before to 81.3% after publication of the guidelines (P=.02). CONCLUSION: In this historical cohort in Olmsted County there was a statistically significant reduction in AP in the MR group before invasive dental procedures. In addition, there was an unanticipated significant reduction in AP in the HR group after publication of the 2007 AHA guidelines. These findings can be used to provide feedback and education to medical and dental professionals who are involved in decision making regarding the use of dental prophylaxis for their patients.

Implementation of iterative metal artifact reduction in the pre-planning-procedure of three-dimensional physical modeling.

BACKGROUND: To assess the impact of metal artifact reduction techniques in 3D printing by evaluating image quality and segmentation time in both phantom and patient studies with dental restorations and/or other metal implants. An acrylic denture apparatus (Kilgore Typodent, Kilgore International, Coldwater, MI) was set in a 20 cm water phantom and scanned on a single-source CT scanner with gantry tilting capacity (SOMATOM Edge, Siemens Healthcare, Forchheim, Germany) under 5 scenerios: (1) Baseline acquisition at 120 kV with no gantry tilt, no jaw spacer, (2) acquisition at 140 kV, (3) acquisition with a gantry tilt at 15°, (4) acquisition with a non-radiopaque jaw spacer and (5) acquisition with a jaw spacer and a gantry tilt at 15°. All acquisitions were reconstructed both with and without a dedicated iterative metal artifact reduction algorithm (MAR). Patients referred for a head-and-neck exam were included into the study. Acquisitions were performed on the same scanner with 120 kV and the images were reconstructed with and without iterative MAR. Segmentation was performed on a dedicated workstation (Materialise Interactive Medical Image Control Systems; Materialise NV, Leuven, Belgium) to quantify volume of metal artifact and segmentation time. RESULTS: In the phantom study, the use of gantry tilt, jaw spacer and increased tube voltage showed no benefit in time or artifact volume reduction. However the jaw spacer allowed easier separation of the upper and lower jaw and a better display of the teeth. The use of dedicated iterative MAR significantly reduced the metal artifact volume and processing time. Same observations were made for the four patients included into the study. CONCLUSION: The use of dedicated iterative MAR and jaw spacer substantially reduced metal artifacts in the head-and-neck CT acquisitions, hence allowing a faster 3D segmentation workflow.

The constant work rate critical power protocol overestimates ramp incremental exercise performance.

PURPOSE: The parameters of the power-duration relationship (i.e., the critical power, CP, and the curvature constant, W') may theoretically predict maximal performance capability for exercise above the CP. The CP and W' are associated with the parameters of oxygen uptake ([Formula: see text]O2) kinetics, which can be altered by manipulation of the work-rate forcing function. We tested the hypothesis that the CP and W' derived from constant work-rate (CWR) prediction trials would overestimate ramp incremental exercise performance. METHODS: Thirty subjects (males, n = 28; females, n = 2) performed a ramp incremental test, and 3-5 CWR prediction trials for the determination of the CP and W'. Multiple ramp incremental tests and corresponding CP and W' estimates were available for some subjects such that in total 51 ramp test performances were predicted. RESULTS: The ramp incremental test performance (729 ± 113 s) was overestimated by the CP and W' estimates derived from the best (751 ± 114 s, P < 0.05) and worst (749 ± 111 s, P < 0.05) individual fits of CWR prediction trial data. The error in the prediction was inversely correlated with the magnitude of the W' for the best (r = -0.56, P < 0.05) and worst individual fits (r = -0.36, P < 0.05). CONCLUSIONS: The overestimation of ramp incremental performance suggests that the CP and W' derived from different work-rate forcing functions, thus resulting in different [Formula: see text]O2 kinetics, cannot be used interchangeably. The present findings highlight a potential source of error in performance prediction that is of importance to both researchers and applied practitioners.

Dosimetric distribution to tooth-bearing areas in intensity-modulated radiation therapy for head and neck cancer: a pilot study.

OBJECTIVES: Dosimetric distribution of intensity-modulated radiotherapy (IMRT) to tooth-bearing areas for common head and neck (H&N) cancer sites were analyzed to facilitate minimization of osteoradionecrosis (ORN) risk through preradiation dental treatment planning. STUDY DESIGN: Fifty-four patients received IMRT with prescribed doses ranging from 6000 centigrays (cGy) (adjuvant) to 6930 cGy (primary) to treat base of tongue (BOT), tonsil, larynx, nasopharynx, and hypopharynx cancers. The average maximal radiation dose delivered was recorded in tooth-bearing areas (anteriors, premolars, and first, second, and third molars) of the maxilla and mandible. RESULTS: All tooth-bearing areas in laryngeal cancer cases received less than 2500 cGy. Maxillary and mandibular molar regions for BOT, tonsil, and hypopharynx cancers received 5000 cGy or higher. In nasopharynx cancers, maxillary teeth received higher doses than mandibular teeth. CONCLUSIONS: Among 5 H&N subsites, mandibular molar regions for BOT, tonsil, and hypopharynx cancers received higher IMRT doses on average, posing the greatest ORN risk.