Factors Contributing to Snorkel Drowning in Hawai'i.

Causes of the extraordinarily high and increasing incidence of snorkeler drownings in Hawai'i have remained unexplained for years. Defining the mechanisms and factors predisposing to drowning while snorkeling is needed to provide recommendations to substantially mitigate the incidence of this form of preventable death. The mechanisms of drowning are described and insight into the predisposing factors are explored in this study. Methods included measuring snorkel airway resistance characteristics, case reports from the State of Hawai'i Medical Examiner's office, and collating information by survey, principally from rescued survivors. This study identified 2 modes of drowning while snorkeling that need further investigation: accidental or inadvertent aspiration, and hypoxia resulting from acute negative pressure pulmonary edema. The incidence of drowning from mechanisms of hypoxia due to rapid onset pulmonary edema is an important focus of the study and a number of potentially significant predisposing factors are presented that need further investigation but provide bases that may become part of updated policies and practices for snorkelers to substantially lower the risk of death. This report is meant for both medical and public health information purposes.

Minimizing Radiation Dose Outliers Through Systematic Analysis, Computed Tomography Technologist Education, and Standardized System Solutions.

OBJECTIVES: The aims of the study were to systematically analyze causes for radiation dose outliers in emergency department noncontrast head computed tomographies (CTs), to develop and implement standardized system solutions, and audit program success for an extended period of time. METHODS: This study was performed in a large, tertiary academic center between January 2015 and September 2017. Four phases of radiation dose data collection with and without prior interventions were performed. Outliers from 5 categories were evaluated for appropriateness in consensus by 2 radiologists and a senior CT technologist. RESULTS: A total of 275 ± 15 CTs per period were included. Fifty-seven inappropriate scanning parameters were found in 24 (9%) of 254 CTs during the first analysis, 27 in 21 (7%) of 290 CTs during the second, 11 in 10 (4%) of 276 during the third assessment (P = 0.006). After a year without additional intervention, the number remained stable (14 in 11/281 CTs, 4%). CONCLUSIONS: Combining a dose reporting system, individual case analysis, staff education, and implementation of systemic solutions lead to sustained radiation exposure improvement.

Metal implants on CT: comparison of iterative reconstruction algorithms for reduction of metal artifacts with single energy and spectral CT scanning in a phantom model.

PURPOSE: To assess single energy metal artifact reduction (SEMAR) and spectral energy metal artifact reduction (MARS) algorithms in reducing artifacts generated by different metal implants. MATERIALS AND METHOD: Phantom was scanned with and without SEMAR (Aquilion One, Toshiba) and MARS (Discovery CT750 HD, GE), with various metal implants. Images were evaluated objectively by measuring standard deviation in regions of interests and subjectively by two independent reviewers grading on a scale of 0 (no artifact) to 4 (severe artifact). Reviewers also graded new artifacts introduced by metal artifact reduction algorithms. RESULTS: SEMAR and MARS significantly decreased variability of the density measurement adjacent to the metal implant, with median SD (standard deviation of density measurement) of 52.1 HU without SEMAR, vs. 12.3 HU with SEMAR, p < 0.001. Median SD without MARS of 63.1 HU decreased to 25.9 HU with MARS, p < 0.001. Median SD with SEMAR is significantly lower than median SD with MARS (p = 0.0011). SEMAR improved subjective image quality with reduction in overall artifacts grading from 3.2 ± 0.7 to 1.4 ± 0.9, p < 0.001. Improvement of overall image quality by MARS has not reached statistical significance (3.2 ± 0.6 to 2.6 ± 0.8, p = 0.088). There was a significant introduction of artifacts introduced by metal artifact reduction algorithm for MARS with 2.4 ± 1.0, but minimal with SEMAR 0.4 ± 0.7, p < 0.001. CONCLUSION: CT iterative reconstruction algorithms with single and spectral energy are both effective in reduction of metal artifacts. Single energy-based algorithm provides better overall image quality than spectral CT-based algorithm. Spectral metal artifact reduction algorithm introduces mild to moderate artifacts in the far field.

Computed tomography angiography for suspected pulmonary embolism: comparison of 2 adaptive statistical iterative reconstruction blends to filtered back-projection alone.

OBJECTIVE: The objective of this study was to analyze pulmonary computed tomography angiography image quality and pulmonary embolism (PE) depiction comparing 2 blends of adaptive statistical iterative reconstruction (ASIR) to filtered back-projection alone. METHODS: Seventy-nine consecutive patients (49 women, 30 men; 52 ± 18 years) underwent pulmonary computed tomography angiography (120 kVp, 100-600 mA) reconstructed with filtered back-projection alone (ASIR0), 30% ASIR (ASIR30), and 50% ASIR (ASIR50) for this institutional review board-approved study. Two radiologists independently assessed PE depiction and vascular characterization, which was correlated with body mass index. RESULTS: Twelve patients (15%) had PE. No difference in PE depiction (P = 0.536), pulmonary arterial attenuation (P = 0.22-0.99), or subjective vascular characterization score (P = 0.58-.016) was observed for either blend. ASIR30 and ASIR50 achieved higher signal-to-noise ratio (P = 0.001-0.003). Body mass index inversely correlated with vascular characterization scores (P < 0.001). CONCLUSIONS: ASIR0, ASIR30, and ASIR50 accurately depict PE using the imaging parameters described. ASIR30 and ASIR50 improve objective image quality without altering subjective vascular characterization scores particularly when body mass index was less than 30 kg/m.

Radiation dose reduction in soft tissue neck CT using adaptive statistical iterative reconstruction (ASIR).

PURPOSE: To compare objective and subjective image quality in neck CT images acquired at different tube current-time products (275 mAs and 340 mAs) and reconstructed with filtered-back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR). MATERIALS AND METHODS: HIPAA-compliant study with IRB approval and waiver of informed consent. 66 consecutive patients were randomly assigned to undergo contrast-enhanced neck CT at a standard tube-current-time-product (340 mAs; n = 33) or reduced tube-current-time-product (275 mAs, n = 33). Data sets were reconstructed with FBP and 2 levels (30%, 40%) of ASIR-FBP blending at 340 mAs and 275 mAs. Two neuroradiologists assessed subjective image quality in a blinded and randomized manner. Volume CT dose index (CTDIvol), dose-length-product (DLP), effective dose, and objective image noise were recorded. Signal-to-noise ratio (SNR) was computed as mean attenuation in a region of interest in the sternocleidomastoid muscle divided by image noise. RESULTS: Compared with FBP, ASIR resulted in a reduction of image noise at both 340 mAs and 275 mAs. Reduction of tube current from 340 mAs to 275 mAs resulted in an increase in mean objective image noise (p=0.02) and a decrease in SNR (p = 0.03) when images were reconstructed with FBP. However, when the 275 mAs images were reconstructed using ASIR, the mean objective image noise and SNR were similar to those of the standard 340 mAs CT images reconstructed with FBP (p>0.05). Subjective image noise was ranked by both raters as either average or less-than-average irrespective of the tube current and iterative reconstruction technique. CONCLUSION: Adapting ASIR into neck CT protocols reduced effective dose by 17% without compromising image quality.

Spectral CT with metal artifacts reduction software for improvement of tumor visibility in the vicinity of gold fiducial markers.

PURPOSE: To evaluate spectral computed tomography (CT) with metal artifacts reduction software (MARS) for reduction of metal artifacts associated with gold fiducial seeds. MATERIALS AND METHODS: Thirteen consecutive patients with 37 fiducial seeds implanted for radiation therapy of abdominal lesions were included in this HIPAA-compliant, institutional review board-approved prospective study. Six patients were women (46%) and seven were men (54%). The mean age was 61.1 years (median, 58 years; range, 29-78 years). Spectral imaging was used for arterial phase CT. Images were reconstructed with and without MARS in axial, coronal, and sagittal planes. Two radiologists independently reviewed reconstructions and selected the best image, graded the visibility of the tumor, and assessed the amount of artifacts in all planes. A linear-weighted κ statistic and Wilcoxon signed-rank test were used to assess interobserver variability. Histogram analysis with the Kolmogorov-Smirnov test was used for objective evaluation of artifacts reduction. RESULTS: Fiducial seeds were placed in pancreas (n = 5), liver (n = 7), periportal lymph nodes (n = 1), and gallbladder bed (n = 1). MARS-reconstructed images received a better grade than those with standard reconstruction in 60% and 65% of patients by the first and second radiologist, respectively. Tumor visibility was graded higher with standard versus MARS reconstruction (grade, 3.7 ± 1.0 vs 2.8 ± 1.1; P = .001). Reduction of blooming was noted on MARS-reconstructed images (P = .01). Amount of artifacts, for both any and near field, was significantly smaller on sagittal and coronal MARS-reconstructed images than on standard reconstructions (P < .001 for all comparisons). Far-field artifacts were more prominent on axial MARS-reconstructed images than on standard reconstructions (P < .01). Linear-weighted κ statistic showed moderate to perfect agreement between radiologists. CT number distribution was narrower with MARS than with standard reconstruction in 35 of 37 patients (P < .001). CONCLUSION: Spectral CT with use of MARS improved tumor visibility in the vicinity of gold fiducial seeds.

Body tumor CT perfusion protocols: optimization of acquisition scan parameters in a rat tumor model.

PURPOSE: To evaluate the effects of total scanning time (TST), interscan delay (ISD), inclusion of image at peak vascular enhancement (IPVE), and selection of the input function vessel on the accuracy of tumor blood flow (BF) calculation with computed tomography (CT) in an animal model. MATERIALS AND METHODS: All animal protocols and experiments were approved by the institutional animal care and use committee prior to study initiation. After injection of 0.2 or 0.4 mL of iodinated contrast material, six rats with mammary adenocarcinoma (three tumors each) were scanned in the axial mode for 5 minutes with 1-second ISD (reference scan), 2.5-mm section thickness, 2.5-mm interval, pitch of 1.3, 120 kV, 240 mA, and 0.5-second rotation time. A total of 126 dynamic data sets were created with commercial software by varying TST and ISD, including or excluding the IPVE, and using the aorta or inferior vena cava (IVC) as the input function. Comparative analyses were used to test for significant differences (t test, Wilcoxon signed rank test). Regression analysis was performed to assess the relationship between attenuation of the input function vessel and BF. RESULTS: No significant difference was observed (P > .05) when TST was as short as 30 seconds (range, 20-23 mL/100 g). In sequences performed with an ISD longer than 8 seconds, BF was significantly elevated (P < .01). Inclusion of the IPVE eliminated this difference (P > .10). Use of the IVC as the input function resulted in significantly higher BF (P < .02), with a correlation between peak attenuation and BF (R(2) = 0.43). CONCLUSION: To reduce radiation dose in tumor perfusion with CT, TST can be reduced without causing significant changes in BF calculation in an animal model. Scanning the aortic reference with peak contrast enhancement reduces variability sufficiently to allow for longer ISDs.

Perfusion MDCT enables early detection of therapeutic response to antiangiogenic therapy.

OBJECTIVE: The objective of our study was to determine whether perfusion CT can be used to detect early changes in therapeutic response to antiangiogenic therapy in an animal tumor model. MATERIALS AND METHODS: Twenty-five rats implanted with R3230 mammary adenocarcinoma (diameter, 1.2-2.0 cm) randomly received 7.5 or 30 mg/kg of an antiangiogenic agent, sorafenib, by daily gavage for 4 (n = 4), 9 (n = 9), or 14 (n = 5) days. Seven untreated animals served as a control group. Perfusion MDCT was performed at days 0, 4, 9, and 14 with 0.4 mL of ioversol (350 mg/mL) and included four 5-mm slices covering the entire tumor volume. Changes in tumor growth were determined by volumetric analysis of CT data. Serial changes in tumor volume and blood flow were assessed and correlated with pathology findings. RESULTS: All control tumors grew larger (from 2.0 +/- 0.7 cm(3) at day 0 to 5.9 +/- 1.0 cm(3) at day 14), whereas all treated tumors shrank (from 2.5 +/- 1.1 to 2.1 +/- 1.0 cm(3)), with a statistically significant rate of growth or shrinkage in both groups (p < 0.05). Although perfusion in the control tumors changed little from day 0 to day 14 (day 0, 18.1 +/- 9.2 mL/min/100 g; day 4, 15.8 +/- 5.6; day 9, 21.7 +/- 12.2; day 14, 27.7 +/- 34), in the sorafenib group, the mean blood flow was significantly lower at day 4 (5.2 +/- 3.2 mL/min/100 g, 77% decrease), day 9 (6.4 +/- 4.0 mL/min/100 g, 66% decrease), and day 14 (6.3 +/- 5.2 mL/min/100 g, 83% decrease) compared with day 0 (23.8 +/- 11.6 mL/min/100 g) (p < 0.05). Poor correlation was seen between changes in blood flow and tumor volume for days 0-9 (r(2) = 0.34), 4-9 (r(2) = 0.0004), and 9-14 (r(2) = 0.16). However, when comparing day 4 images with days 9 and 14 images, seven of 14 (50%) sorafenib-treated tumors had focal areas of new perfusion that correlated with areas of histopathologic viability despite the fact that these tumors were shrinking in size from day 4 onward (day 4, 2.18 +/- 0.8 cm(3); day 9, 1.98 +/- 0.8 cm(3)). CONCLUSION: Perfusion MDCT can detect focal blood flow changes even when the tumor is shrinking, possibly indicating early reversal of tumor responsiveness to antiangiogenic therapy. Given that changes in tumor volume after antiangiogenic therapy do not necessarily correlate with true treatment response, physiologic imaging of tumor perfusion may be necessary.

CT perfusion for determination of pharmacologically mediated blood flow changes in an animal tumor model.

PURPOSE: To prospectively compare single- and multisection computed tomographic (CT) perfusion for tumor blood flow determination in an animal model. MATERIALS AND METHODS: All animal protocols and experiments were approved by the institutional animal care and use committee before the study was initiated. R3230 mammary adenocarcinoma was implanted in 11 rats. Tumors (18-20 mm) were scanned with dynamic 16-section CT at baseline and after administration of arsenic trioxide, which is known to cause acute reduction in blood flow. The concentration of arsenic was titrated (0-6 mg of arsenic per kilogram of body weight) to achieve a defined blood flow reduction (0%-75%) from baseline levels at 60 minutes, as determined with correlative laser Doppler flowmetry. The mean blood flow was calculated for each of four 5-mm sections that covered the entire tumor, as well as for the entire tumor after multiple sections were processed. Measurements obtained with both methods were correlated with laser Doppler flowmetry measurements. Interobserver agreement was determined for two blinded radiologists, who calculated the percentage of blood flow reduction for the "most representative" single sections at baseline and after arsenic administration. These results were compared with the interobserver variability of the same radiologists obtained by summing blood flow changes for the entire tumor volume. RESULTS: Overall correlations for acute blood flow reduction were demonstrated between laser Doppler flowmetry and the two CT perfusion approaches (single-section CT, r=0.85 and r(2)=0.73; multisection CT, r=0.93 and r(2)=0.87; pooled data, P=.01). CT perfusion disclosed marked heterogeneity of blood flow, with variations of 36% +/- 13 between adjacent 5-mm sections. Given these marked differences, interobserver agreement was much lower for single-section CT (standard deviation, 0.22) than for multisection CT (standard deviation, 0.10; P=.01). CONCLUSION: Multisection CT perfusion techniques may provide an accurate and more reproducible method of tumor perfusion surveillance than comparison of single representative tumor sections.

Therapeutic massage and healing touch improve symptoms in cancer.

Complementary therapies are increasingly used to reduce side effects of cancer treatment, without evidence for their effectiveness. In a randomized, prospective, 2-period, crossover intervention study, the authors tested the effects of therapeutic massage (MT) and healing touch (HT), in comparison to presence alone or standard care, in inducing relaxation and reducing symptoms in 230 subjects. MT and HT lowered blood pressure, respiratory rate (RR), and heart rate (HR). MT lowered anxiety and HT lowered fatigue, and both lowered total mood disturbance. Pain ratings were lower after MT and HT, with 4-week nonsteroidal antiinflammatory drug use less during MT. There were no effects on nausea. Presence reduced RR and HR but did not differ from standard care on any measure of pain, nausea, mood states, anxiety, or fatigue. MT and HT are more effective than presence alone or standard care in reducing pain, mood disturbance, and fatigue in patients receiving cancer chemotherapy.