Surveillance of Rabies Postexposure Prophylaxis in Greece: 4 Years Experience.

Rabies reemerged in Greek fauna during October 2012, 25 years after the last report in animals and 42 after the last human case. This study examined the administration of rabies postexposure prophylaxis (PEP) in humans over the period 2012-2016. A total of 1,454 individuals (62.6% males) received PEP. The vast majority (92.3%) of regimens was initiated in high risk for animal rabies areas (11.1 PEP per 100,000 residents per year). Among the exposed, 77.0% presented at a healthcare setting during the first 24 h after the incident; more severe injuries were associated with faster presentation (p < 0.05). A vaccine series was administered in 54.5% of exposed persons whereas 43.7% received both vaccine and immunoglobulin and 1.7% immunoglobulin only. Exposure to stray dogs represented 68.4% of all incidents. In exposures occurring in nonhigh risk for rabies areas, bat was the second most frequently involved animal (13.4% of incidents). All dogs and cats evaluated by a veterinarian and laboratory-confirmed rabid were initially deemed suspect for rabies during clinical examination or according to history. No human rabies cases were recorded during the period of the study. Surveillance of PEP represents a valuable tool for aiding assessment of present and future demands in prophylaxis biologicals, outlining the epidemiological profile of exposures and planning effective policies for the management of exposure incidents.

Contemporary Interventional Radiology Dosimetry: Analysis of 4,784 Discrete Procedures at a Single Institution.

PURPOSE: To report dosimetry of commonly performed interventional radiology procedures and compare dose analogues to known reference levels. MATERIALS AND METHODS: Demographic and dosimetry data were collected for gastrostomy, nephrostomy, peripherally inserted central catheter placement, visceral arteriography, hepatic chemoembolization, tunneled catheter placement, inferior vena cava filter placement, vascular embolization, transjugular liver biopsy, adrenal vein sampling, transjugular intrahepatic portosystemic shunt (TIPS) creation, and biliary drainage between June 12, 2014, and April 26, 2018, using integrated dosimetry software. In all, 4,784 procedures were analyzed. The study included 2,691 (56.2%) male subjects and 2,093 (43.8%) female subjects with mean age 55 ± 21 years (range: 0-104 years) and with mean weight of 76.9 ± 29.4 kg (range: 0.9-268.1 kg). Fluoroscopy time, dose area product (DAP), and reference dose were evaluated. RESULTS: TIPS had the highest mean fluoroscopy time (49.1 ± 16.0 min) followed by vascular embolization (25.2 ± 11.4 min), hepatic chemoembolization (18.8 ± 12.5 min), and visceral arteriography (17.7 ± 3.2 min). TIPS had the highest mean DAP (429.2 ± 244.8 grays per square centimeter [Gy·· cm2]) followed by hepatic chemoembolization (354.6 ± 78.6 Gy·· cm2), visceral arteriography (309.5 ± 39.0 Gy·· cm2), and vascular embolization (298.5 ± 29 Gy·· cm2). TIPS was associated with the highest mean reference dose (2.002 ± 1.420 Gy) followed by hepatic chemoembolization (1.746 ± 0.435 Gy), vascular embolization (1.615 ± 0.381 Gy), and visceral arteriography (1.558 ± 1.720 Gy). Of the six procedures available for comparison with the reference levels, the mean fluoroscopy time, DAP, and reference dose for each procedure were below the proposed reference levels. CONCLUSION: Advances in image acquisition technology and radiation safety protocols have significantly reduced the radiation exposure for a variety of interventional radiology procedures.

Utility and Associated Risk of Pulmonary Embolism Computed Tomography Scans in the Michigan Lupus Cohort.

OBJECTIVE: Systemic lupus erythematosus patients are frequently evaluated for chest pain and may have multiple pulmonary embolism (PE) computed tomography (CT) scans. This study was undertaken to determine the incidence of pulmonary embolism in the University of Michigan Lupus Cohort patients who have undergone PE CT scans and to estimate the associated increased risk of breast and lung cancer from radiation exposure. METHODS: We reviewed records of patients in the University of Michigan Lupus Cohort (n = 854) and determined the number and outcome of PE CT scans. Radimetrics software was used to perform individualized calculations of radiation dose to the lung and breast of each patient. We used this dose information, the patient's age at the time of scan, and risks according to the Biological Effects of Ionizing Radiation, report VII, to estimate the increased incidence risks of breast and lung cancer. RESULTS: A total of 182 of 856 patients (21%) underwent 357 PE CT scans. The overall rate of positivity was 7.5%. For patients undergoing their first through third scans, the rate of positivity for PE was 8.8%, whereas patients undergoing their fourth through tenth scans had 1.6% positivity. The highest increase in incidence risk was 0.87% for breast and 0.62% for lung. CONCLUSION: Patients with multiple previous PE CT scans had lower likelihood of a positive result on subsequent scans and higher risks of malignancy. The magnitude of risk should not discourage performance of PE CT when clinically indicated.

Radiation dose reduction during neurointerventional procedures by modification of default settings on biplane angiography equipment.

BACKGROUND: Neurointerventional procedures represent a significant source of ionizing radiation. We sought to assess the effect during neurointerventional procedures of varying default rates of radiation dose in fluoroscopy (F) and image acquisition (IA) modes, and frame rates during cine acquisition (CINE) on total X-ray dose, acquisition exposures, fluoroscopy time, and complications. METHODS: We retrospectively reviewed procedures performed with two radiation dose and CINE settings: a factory setting dose cohort (30 patients, F 45 nGy/pulse, IA 3.6 µGy/pulse, factory CINE frame rate) and a reduced dose cohort (30 patients, F 32 nGy/pulse, IA 1.2 µGy/pulse, with a decreased CINE frame rate). Total radiation dose, dose area product, number of acquisition exposures, fluoroscopy time, and complications were compared between the groups. Means comparisons (t tests) were employed to evaluate differences in the outcome variables between the two groups. p Value <0.05 was considered significant. RESULTS: The reduced dose cohort had a significant reduction in mean radiation dose (factory, 3650 mGy; reduced, 1650 mGy; p=0.005) and dose area product (factory, 34 700 µGy×m(2); reduced, 15 000 µGy×m(2); p=0.02). There were no significant differences between cohorts in acquisition exposure (p=0.73), fluoroscopy time (p=0.45), or complications. CONCLUSIONS: Significant reductions in radiation dose delivered by neurointerventional procedures can be achieved through simple modifications of default radiation dose in F and IA and frame rate during CINE without an increase in procedural complexity (fluoroscopy time) or rate of complications.

Comparison of Effective Dose of Radiation During Pedicle Screw Placement Using Intraoperative Computed Tomography Navigation Versus Fluoroscopy in Children With Spinal Deformities.

BACKGROUND: We compared the effective dose of radiation associated with pedicle screw placement in posterior spinal fusion in children using intraoperative computed tomography (CT) navigation versus intraoperative fluoroscopy (C-arm). METHODS: In this review of posterior spinal fusion patients, height, weight, local density function, dose area product, body region, number of views, and part of the body were used to calculate the effective dose to the patient in millisieverts (mSv) in 37 children in whom pedicle screw placement was aided by intraoperative CT versus 44 children in whom pedicle screw placement was aided by C-arm. Both groups had posterior spinal fusions during the same time period by 3 surgeons between November 2012 and August 2013. Calculation of the radiation dose was made by the following method: for the C-arm, and the fluoroscopic/digital acquisitions part of the CT examinations, we estimated the effective dose using the program PCXMC 2.0. For the cross-sectional imaging part of the CT examinations, we used the dose-length product from the radiation dose reports of the CT unit and published dose-length product to effective dose conversion factors. The overall effective dose for the CT group was the total of the cross-sectional imaging dose and the fluoroscopic/digital acquisition imaging dose. An unpaired T test was used to determine significant difference between the C-arm and CT navigation groups. RESULTS: The average effective dose was 1.48±1.66 mSv for the CT patients and 0.34±0.36 mSv for the C-arm patients. These values for the 2 groups are significantly different (P=0.0012). Obese children had very high mSv values in the CT group. CONCLUSIONS: Intraoperative CT for navigational instrumentation placement associated with spinal fusion in children results in significantly more radiation to the child than C-arm. Families need to be counseled about radiation exposure associated with intraoperative CT, especially in obese children. Intraoperative CT use should be tailored to placing instrumentation where the benefit is the highest. LEVEL OF EVIDENCE: Level II.

Evaluation of pediatric VCUG at an academic children's hospital: is the radiographic scout image necessary?

BACKGROUND: There is heterogeneity in how pediatric voiding cystourethrography (VCUG) is performed. Some institutions, including our own, obtain a radiographic scout image prior to contrast agent instillation. OBJECTIVE: To demonstrate that the radiographic scout image does not augment VCUG interpretation or contribute management-changing information but nonetheless carries a non-negligible effective dose. MATERIALS AND METHODS: We evaluated 181 children who underwent VCUG in 2012, with an age breakdown of less than 1 year (56 children), 1-5 years (66 children), 6-10 years (43 children) and 11-18 years (16 children), with a mean age of 4.0 years. We investigated patient demographics, clinical indication for the examination, scout image findings and estimated effective radiation dose, as well as overall exam findings and impression. RESULTS: No clinically significant or management-changing findings were present on scout images, and no radiopaque urinary tract calculi or concerning incidental finding was identified. Scout image estimated effective radiation dose averaged 0.09 mSv in children younger than 1 y, 0.09 mSv in children age 1-5, 0.13 mSv in children age 6-10 and 0.18 mSv in children age 11-18. Total fluoroscopy time per examination averaged 36.7 s (range 34.8-39.6 s for all age group averages). Evaluation of known or suspected vesicoureteral reflux (VUR) and urinary tract infection (UTI) were the most common clinical indications, stated in 40.9% and 37.0% of exams, respectively. CONCLUSION: Although the estimated effective dose is low for VCUG radiographic scout images, this step did not augment VCUG interpretation or contribute management-changing information. This step should be omitted or substituted to further reduce dose in pediatric VCUG.

Digital breast tomosynthesis: studies of the effects of acquisition geometry on contrast-to-noise ratio and observer preference of low-contrast objects in breast phantom images.

The effect of acquisition geometry in digital breast tomosynthesis was evaluated with studies of contrast-to-noise ratios (CNRs) and observer preference. Contrast-detail (CD) test objects in 5 cm thick phantoms with breast-like backgrounds were imaged. Twelve different angular acquisitions (average glandular dose for each ~1.1 mGy) were performed ranging from narrow angle 16° with 17 projection views (16d17p) to wide angle 64d17p. Focal slices of SART-reconstructed images of the CD arrays were selected for CNR computations and the reader preference study. For the latter, pairs of images obtained with different acquisition geometries were randomized and scored by 7 trained readers. The total scores for all images and readings for each acquisition geometry were compared as were the CNRs. In general, readers preferred images acquired with wide angle as opposed to narrow angle geometries. The mean percent preferred was highly correlated with tomosynthesis angle (R = 0.91). The highest scoring geometries were 60d21p (95%), 64d17p (80%), and 48d17p (72%); the lowest scoring were 16d17p (4%), 24d9p (17%) and 24d13p (33%). The measured CNRs for the various acquisitions showed much overlap but were overall highest for wide-angle acquisitions. Finally, the mean reader scores were well correlated with the mean CNRs (R = 0.83).

Radiation dosimetry in digital breast tomosynthesis: report of AAPM Tomosynthesis Subcommittee Task Group 223.

The radiation dose involved in any medical imaging modality that uses ionizing radiation needs to be well understood by the medical physics and clinical community. This is especially true of screening modalities. Digital breast tomosynthesis (DBT) has recently been introduced into the clinic and is being used for screening for breast cancer in the general population. Therefore, it is important that the medical physics community have the required information to be able to understand, estimate, and communicate the radiation dose levels involved in breast tomosynthesis imaging. For this purpose, the American Association of Physicists in Medicine Task Group 223 on Dosimetry in Tomosynthesis Imaging has prepared this report that discusses dosimetry in breast imaging in general, and describes a methodology and provides the data necessary to estimate mean breast glandular dose from a tomosynthesis acquisition. In an effort to maximize familiarity with the procedures and data provided in this Report, the methodology to perform the dose estimation in DBT is based as much as possible on that used in mammography dose estimation.

Evaluation of dual energy quantitative CT for determining the spatial distributions of red marrow and bone for dosimetry in internal emitter radiation therapy.

PURPOSE: To evaluate a three-equation three-unknown dual-energy quantitative CT (DEQCT) technique for determining region specific variations in bone spongiosa composition for improved red marrow dose estimation in radionuclide therapy. METHODS: The DEQCT method was applied to 80/140 kVp images of patient-simulating lumbar sectional body phantoms of three sizes (small, medium, and large). External calibration rods of bone, red marrow, and fat-simulating materials were placed beneath the body phantoms. Similar internal calibration inserts were placed at vertebral locations within the body phantoms. Six test inserts of known volume fractions of bone, fat, and red marrow were also scanned. External-to-internal calibration correction factors were derived. The effects of body phantom size, radiation dose, spongiosa region segmentation granularity [single (∼17 × 17 mm) region of interest (ROI), 2 × 2, and 3 × 3 segmentation of that single ROI], and calibration method on the accuracy of the calculated volume fractions of red marrow (cellularity) and trabecular bone were evaluated. RESULTS: For standard low dose DEQCT x-ray technique factors and the internal calibration method, the RMS errors of the estimated volume fractions of red marrow of the test inserts were 1.2-1.3 times greater in the medium body than in the small body phantom and 1.3-1.5 times greater in the large body than in the small body phantom. RMS errors of the calculated volume fractions of red marrow within 2 × 2 segmented subregions of the ROIs were 1.6-1.9 times greater than for no segmentation, and RMS errors for 3 × 3 segmented subregions were 2.3-2.7 times greater than those for no segmentation. Increasing the dose by a factor of 2 reduced the RMS errors of all constituent volume fractions by an average factor of 1.40 ± 0.29 for all segmentation schemes and body phantom sizes; increasing the dose by a factor of 4 reduced those RMS errors by an average factor of 1.71 ± 0.25. Results for external calibrations exhibited much larger RMS errors than size matched internal calibration. Use of an average body size external-to-internal calibration correction factor reduced the errors to closer to those for internal calibration. RMS errors of less than 30% or about 0.01 for the bone and 0.1 for the red marrow volume fractions would likely be satisfactory for human studies. Such accuracies were achieved for 3 × 3 segmentation of 5 mm slice images for: (a) internal calibration with 4 times dose for all size body phantoms, (b) internal calibration with 2 times dose for the small and medium size body phantoms, and (c) corrected external calibration with 4 times dose and all size body phantoms. CONCLUSIONS: Phantom studies are promising and demonstrate the potential to use dual energy quantitative CT to estimate the spatial distributions of red marrow and bone within the vertebral spongiosa.