Reducing radiation dose in emergency computed tomography with automatic exposure control techniques

Crohn's Disease: Radiological Answers to Clinical Questions and Review of the Literature

Background: Crohn's disease (CD) is a chronic, progressive inflammatory condition, involving primarily the bowel, characterized by a typical remitting-relapsing pattern. Despite endoscopy representing the reference standard for the diagnosis and assessment of disease activity, radiological imaging has a key role, providing information about mural and extra-visceral involvement. Methods: Computed Tomography and Magnetic Resonance Imaging are the most frequently used radiological techniques in clinical practice for both the diagnosis and staging of CD involving the small bowel in non-urgent settings. The contribution of imaging in the management of CD is reported on by answering the following practical questions: (1) What is the best technique for the assessment of small bowel CD? (2) Is imaging a good option to assess colonic disease? (3) Which disease pattern is present: inflammatory, fibrotic or fistulizing? (4) Is it possible to identify the presence of strictures and to discriminate inflammatory from fibrotic ones? (5) How does imaging help in defining disease extension and localization? (6) Can imaging assess disease activity? (7) Is it possible to evaluate post-operative recurrence? Results: Imaging is suitable for assessing disease activity, extension and characterizing disease patterns. CT and MRI can both answer the abovementioned questions, but MRI has a greater sensitivity and specificity for assessing disease activity and does not use ionizing radiation. Conclusions: Radiologists are essential healthcare professionals to be involved in multidisciplinary teams for the management of CD patients to obtain the necessary answers for clinically relevant questions.

Trade-off between the radiation parameters and image quality using iterative reconstruction techniques in head computed tomography: a phantom study

BACKGROUND

Iterative reconstruction techniques (IRTs) are commonly used in computed tomography (CT) and help to reduce image noise.

PURPOSE

To determine the minimum radiation dose while preserving image quality in head CT using IRTs.

MATERIAL AND METHODS

The anthropomorphic phantom was used to scan nine head CT image series with varied radiation parameters. CT dose parameters, including volume CT dose index (CTDIvol [in mGy]) and dose length product (DLP [in mGy/cm]), were recorded for each scan series. Different noise levels (iDoseL1-6) were used in IRT reconstructions for soft and bone tissues. In total, 15 measurements were taken from five regions of interest (ROI) with an area of 10 mm2. The signal-to-noise ratio (SNR) and noise values obtained at different ROIs were compared among various reconstruction methods with repeated measures of statistical analysis.

RESULTS

In the head CT scan, applying IRT iDoseL5 had the lowest noise and highest SNR for soft tissue (P < 0.05), and increased iDose can decrease CT dose by 54.6% without compromising image quality. While for bone tissue reconstruction, no clear association was found between the level of iDose and noise. However, when CTDIvol is >20 mGy, iDoseL4 is slightly superior to other reconstruction methods (P < 0.065).

CONCLUSION

Using IRTs in head CTs reduces radiation dose while maintaining image quality. IDoseL5 provided optimal balance for soft tissue.

Performance of automatic exposure control on dose and image quality: comparison between slot-scanning and flat-panel digital radiography systems

BACKGROUND

EOSedge™^* (EOS Imaging, Paris, France) is an X-ray imaging system using automatic exposure control (AEC) with tube current modulation, in order to optimize dose deposition in patients.

PURPOSE

This study aims at characterizing EOSedge organ dose deposition in comparison to a digital radiography (DR) system and the previous EOS system (EOS-1st generation), in relation to their respective image quality levels.

METHOD

Organ doses were measured in an anthropomorphic female adult phantom and a 5-year-old pediatric phantom using optically stimulated luminescence (OSL) dosimeters, which were carefully calibrated within the studied energy range. Organ doses were recorded on the EOSedge and the Fuji Visionary DRF (Fujifilm Medical Systems U.S.A., Inc, Lexington, MA). The resulting effective doses were compared to the EOS-1st-generation values present in the literature. Image quality assessment was carried out on end-user images. Quantitative image quality metrics were computed for all tested modalities on a quality assurance phantom. Qualitative assessment of EOSedge image quality was based on anthropomorphic phantom acquisitions against the EOS-1st-generation system, and on clinical images against the tested DR system.

RESULTS

For a full-spine exam, and on the female adult phantom (respectively, the pediatric phantom), an effective dose of 92 μSv (respectively, 32 μSv) was obtained on EOSedge, and 572 μSv (respectively, 179 μSv) on the DR system; these values were compared to effective dose values of 290 μSv (respectively, 200 μSv) from the literature on EOS-1st generation, leading to an effective dose reduction factor of 6 with respect to the DR system, and of 3-6 with respect to EOS-1st generation. EOSedge provides the best compromise between contrast-to-noise ratio (CNR) and dose, with more consistent CNR values than the other tested modalities, in a range of attenuation from 10 to 40 cm of poly(methyl methacrylate) (PMMA). Within this range, EOSedge is also comparable to DR for 10 and 20 cm of PMMA, and better than DR for 30 and 40 cm of PMMA, both in terms of spatial resolution and low-contrast detection. The anatomical landmarks of interest in the follow-up of spinal deformities can be detected in all tested modalities.

CONCLUSION

Results showed that EOSedge provides significant dose reduction factors for full spine imaging in both adults and children compared to the other tested modalities, without compromising image quality. We believe that this work could help raise awareness on the capabilities of modern X-ray systems, when equipped with appropriate AEC strategies, to perform ultra-low-dose, long-axis images.

Limited parameter denoising for low-dose X-ray computed tomography using deep reinforcement learning

BACKGROUND

The use of deep learning has successfully solved several problems in the field of medical imaging. Deep learning has been applied to the CT denoising problem successfully. However, the use of deep learning requires large amounts of data to train deep convolutional networks (CNNs). Moreover, due to large parameter count, such deep CNNs may cause unexpected results.

PURPOSE

In this study, we introduce a novel CT denoising framework, which has interpretable behaviour, and provides useful results with limited data.

METHODS

We employ bilateral filtering in both the projection and volume domains to remove noise. To account for non-stationary noise, we tune the σ parameters of the volume for every projection view, and for every volume pixel. The tuning is carried out by two deep CNNs. Due to impracticality of labelling, the two deep CNNs are trained via a Deep-Q reinforcement learning task. The reward for the task is generated by using a custom reward function represented by a neural network. Our experiments were carried out on abdominal scans for the Mayo Clinic TCIA dataset, and the AAPM Low Dose CT Grand Challenge.

RESULTS

Our denoising framework has excellent denoising performance increasing the PSNR from 28.53 to 28.93, and increasing the SSIM from 0.8952 to 0.9204. We outperform several state-of-the-art deep CNNs, which have several orders of magnitude higher number of parameters (p-value (PSNR) = 0.000, p-value (SSIM) = 0.000). Our method does not introduce any blurring, which is introduced by MSE loss based methods, or any deep learning artifacts, which are introduced by WGAN based models. Our ablation studies show that parameter tuning and using our reward network results in the best possible results.

CONCLUSIONS

We present a novel CT denoising framework, which focuses on interpretability to deliver good denoising performance, especially with limited data. Our method outperforms state-of-the-art deep neural networks. Future work will be focused on accelerating our method, and generalizing to different geometries and body parts. This article is protected by copyright. All rights reserved.

Image optimization and reduction of radiation dose in CT of the paranasal sinuses

INTRODUCTION

Due to use of ionization radiation in the computed tomography (CT), optimal parameters should be used to reduce the risk of incidence of secondary cancers in patients who are constantly exposed to x-rays. To reduce the dose delivered to patients in each scan, CT technologists can change the image acquisition parameters. However, this reduces image quality. The present study aimed to optimize and reduce radiation dose in a CT of the paranasal sinuses while minimizing deterioration of image quality.

METHODS

In this study patients were divided in two groups: Group A was scanned axially and coronally using default parameters, while Group B was scanned axially and coronally using new parameters. Common CT dose descriptors including weighted computed tomography dose index (CTDIw), volumetric CTDI (CTDIvol), dose length product (DLP), effective dose (ED) and image noise were measured for each group. The patients' organ doses were estimated using the ImPACT CT patient Dosimetry Calculator. The tube voltage, tube current, pitch, rotation time, and other parameters were then reduced and optimized. After reconstruction and analysis, all of the images were of good diagnostic quality in both groups Results: Using the new parameters, good agreement was found between the direct and reconstructed images. The CT parameters were reduced by the following proportions: kVp-16.6%, mA-75%, rotation time-20%, and mAs-80%. However, these reductions did not obscure any anatomical landmarks. These parameters reduced the CTDIw, CTDIvol and DLP by 88.2%, 91.3%, and 91.3% respectively.

CONCLUSION

The results suggest that the use of a Bone algorithm reduces the total amount of radiation used during CT of the sinuses. We recommend using these parameters in children, in the evaluation of facial trauma, and in emergency CT of the paranasal sinuses.

STRATEGY OF COMPUTED TOMOGRAPHY IMAGE OPTIMISATION IN CERVICAL VERTEBRAE AND NECK SOFT TISSUE IN EMERGENCY PATIENTS

INTRODUCTION

With regards to the use of ionisation radiation in the computed tomography (CT), optimal parameters should be used to reduce the risk of incidence of secondary cancers in patients who are constantly exposed to X-rays. The aim of this study was to optimise the parameters used in CT scan of cervical vertebrae and neck soft tissue with minimal loss of image quality in emergency patients.

MATERIALS AND METHODS

In this study, the patients were divided into two groups. The first group consisted of patients scanned with default parameters and the second group scanned with optimised parameters. All the study has been implemented in emergency settings. The cases included cervical vertebrae and soft tissue protocols. Common CT dose descriptors including weighted computed tomography dose index (CTDIw), volumetric CTDI (CTDIvol), dose length product (DLP), effective dose (ED) and image noise were measured for each group. The ImpactDose program was used to estimate the organs doses. Statistical analysis was performed using Kruskal-Wallis test using SPSS software.

RESULTS

There was no significant quality reduction in the optimised images. Decreasing in radiation dose parameters for the soft tissue was: kVp=16.7%, mAs=64.3% and pitch=24.1%, and for the cervical vertebrae was: kVp=16.7%, mAs=54.2% and pitch=48.3%. Consequently, decreasing these parameters reduced CTDIw=81.0%, CTDIvol=90.0% and DLP = 90.2% in the cervical vertebral protocol, as well as CTDIw=75.5%, CTDIvol=81.3% and DLP = 81.4% in the soft tissue protocol.

CONCLUSION

Regarding the results, the optimised parameters in the mentioned organ scan reduce the radiation dose in the target area and the organs surrounding. Therefore, these protocols can be used for reducing the risk of cancer.

Use of bismuth shield for protection of superficial radiosensitive organs in patients undergoing computed tomography: a literature review and meta-analysis

The study aimed to assess the effect of bismuth (Bi) shielding on dose reduction and image quality in computed tomography (CT) through a literature review. A search was conducted in the following databases: Web of Science, PubMed, Google Scholar, and Scopus. Studies that reported estimated dose reduction with bismuth shielding during imaging of the eye, thyroid, and breast were included, and a meta-regression analysis was used to examine the influence of the CT scanner type on the dose reduction. The studies included a total of 237 patients and 34 pediatric and adult anthropomorphic phantoms for whom the radiation dose was reported. Bismuth shielding was recommended in 88.89% of the studies based on the maintenance of appropriate image quality under shielding. Noise associated with Bi shielding was 7.5%, 263%, and 23.5% for the eye, thyroid, and breast, respectively. The fixed-effects pooled estimate of dose reduction was 34% (95% CI: 13-55; p < 0.001) for the eye, 37% (95% CI 14-61; p < 0.001) for the thyroid, and 36% (95% CI 36-55; p < 0.001) for the breast. The image quality, usage of foams, CT scanner type, beam energies, and backscatter radiation were important factors that directly affected the efficacy of Bi shielding to reduce the radiation dose at the superficial radiosensitive organs.

Association of Focal Radiation Dose Adjusted on Cross Sections with Subsolid Nodule Visibility and Quantification on Computed Tomography Images Using AIDR 3D: Comparison Among Scanning at 84, 42, and 7 mAs

RATIONALE AND OBJECTIVES

The objectives of this study were to compare the visibility and quantification of subsolid nodules (SSNs) on computed tomography (CT) using adaptive iterative dose reduction using three-dimensional processing between 7 and 42 mAs and to assess the association of size-specific dose estimate (SSDE) with relative measured value change between 7 and 84 mAs (RMVC_7-84) and relative measured value change between 42 and 84 mAs (RMVC_42-84).

MATERIALS AND METHODS

As a Japanese multicenter research project (Area-detector Computed Tomography for the Investigation of Thoracic Diseases [ACTIve] study), 50 subjects underwent chest CT with 120 kV, 0.35 second per location and three tube currents: 240 mA (84 mAs), 120 mA (42 mAs), and 20 mA (7 mAs). Axial CT images were reconstructed using adaptive iterative dose reduction using three-dimensional processing. SSN visibility was assessed with three grades (1, obscure, to 3, definitely visible) using CT at 84 mAs as reference standard and compared between 7 and 42 mAs using t test. Dimension, mean CT density, and particular SSDE to the nodular center of 71 SSNs and volume of 58 SSNs (diameter >5 mm) were measured. Measured values (MVs) were compared using Wilcoxon signed-rank tests among CTs at three doses. Pearson correlation analyses were performed to assess the association of SSDE with RMVC_7-84: 100 × (MV at 7 mAs - MV at 84 mAs)/MV at 84 mAs and RMVC_42-84.

RESULTS

SSN visibilities were similar between 7 and 42 mAs (2.76 ± 0.45 vs 2.78 ± 0.40) (P = .67). For larger SSNs (>8 mm), MVs were similar among CTs at three doses (P > .05). For smaller SSNs (<8 mm), dimensions and volumes on CT at 7 mAs were larger and the mean CT density was smaller than 42 and 84 mAs, and SSDE had mild negative correlations with RMVC_7-84 (P < .05).

CONCLUSIONS

Comparable quantification was demonstrated irrespective of doses for larger SSNs. For smaller SSNs, nodular exaggerating effect associated with decreased SSDE on CT at 7 mAs compared to 84 mAs could result in comparable visibilities to CT at 42 mAs.

Evaluation of AAPM Reports 204 and 220: Estimation of effective diameter, water-equivalent diameter, and ellipticity ratios for chest, abdomen, pelvis, and head CT scans

Purpose

To confirm AAPM Reports 204/220 and provide data for the future expansion of these reports by: (a) presenting the first large‐scale confirmation of the reports using clinical data, (b) providing the community with size surrogate data for the head region which was not provided in the original reports, and additionally providing the measurements of patient ellipticity ratio for different body regions.

Method

A total of 884 routine scans were included in our analysis including data from the head, thorax, abdomen, and pelvis for adults and pediatrics. We calculated the ellipticity ratio and all of the size surrogates presented in AAPM Reports 204/220. We correlated the purely geometric‐based metrics with the “gold standard” water‐equivalent diameter (D_W).

Results

Our results and AAPM Reports 204/220 agree within our data's 95% confidence intervals. Outliers to the AAPM reports’ methods were caused by excess gas in the GI tract, exceptionally low BMI, and cranial metaphyseal dysplasia. For the head, we show lower correlation (R² = 0.812) between effective diameter and D_W relative to other body regions. The ellipticity ratio of the shoulder region was the highest at 2.28 ± 0.22 and the head the smallest at 0.85 ± 0.08. The abdomen pelvis, chest, thorax, and abdomen regions all had ellipticity values near 1.5.

Conclusion

We confirmed AAPM reports 204/220 using clinical data and identified patient conditions causing discrepancies. We presented new size surrogate data for the head region and for the first time presented ellipticity data for all regions. Future automatic exposure control characterization should include ellipticity information.

Sub-solid Nodule Detection Performance on Reduced-dose Computed Tomography with Iterative Reduction: Comparison Between 20 mA (7 mAs) and 120 mA (42 mAs) Regarding Nodular Size and Characteristics and Association with Size-specific Dose Estimate

RATIONALE AND OBJECTIVES

This study aimed to compare sub-solid nodule detection performances (SSNDP) on chest computed tomography (CT) with Adaptive Iterative Dose Reduction using Three Dimensional Processing (AIDR 3D) between 7 mAs (0.21 mSv) and 42 mAs (1.28 mSv) in total and in subgroups classified by nodular size, characteristics, and location, and analyze the association of SSNDP with size-specific dose estimate (SSDE).

MATERIALS AND METHODS

As part of the Area-detector Computed Tomography for the Investigation of Thoracic Diseases Study, a Japanese multicenter research project, 68 subjects underwent chest CT with 120 kV, 0.35 seconds per rotation, and three tube currents: 240 mA (84 mAs), 120 mA (42 mAs), and 20 mA (7 mAs). The research committee of the study project outlined and approved our study protocols. The institutional review board of each institution approved this study. Axial 2-mm-thick CT images were reconstructed using AIDR 3D. Standard reference was determined by CT images at 84 mAs. Four radiologists recorded SSN presence by continuously distributed rating on CT at 7 mAs and 42 mAs. Receiver operating characteristic analysis was used to evaluate SSNDP at both doses in total and in subgroups classified by nodular longest diameter (LD) (≥5 mm), characteristics (pure and part-solid), and locations (ventral, intermediate, or dorsal; central or peripheral; and upper, middle, or lower). Detection sensitivity was compared among five groups of SSNs classified based on particular SSDE to nodule on CT with AIDR 3D at 7 mAs.

RESULTS

Twenty-two part-solid and 86 pure SSNs were identified. For larger SSNs (LD ≥ 5 mm) as well as subgroups classified by nodular locations and part-solid nodules, SSNDP was similar in both methods (area under the receiver operating characteristics curve: 0.96 ± 0.02 in CT at 7 mAs and 0.97 ± 0.01 in CT at 42 mAs), with acceptable interobserver agreements in five locations. For larger SSNs (LD ≥ 5 mm), on CT at 42 mAs, no significant differences in detection sensitivity were found among the five groups classified by SSDE, whereas on CT with 7 mAs, four groups with SSDE of 0.65 or higher were superior in detection sensitivity to the other group, with SSDE less than 0.65 mGy.

CONCLUSIONS

For SSNs with 5 mm or more in cases with normal range of body habitus, CT at 7 mAs was demonstrated to have comparable SSNDP to CT at 42 mAs regardless of nodular location and characteristics, and SSDE higher than 0.65 mGy is desirable to obtain sufficient SSNDP.

The global incidence of lip, oral cavity, and pharyngeal cancers by subsite in 2012

By using data from the International Agency for Research on Cancer publication Cancer Incidence in 5 Continents and GLOBOCAN, this report provides the first consolidated global estimation of the subsite distribution of new cases of lip, oral cavity, and pharyngeal cancers by country, sex, and age for the year 2012. Major geographically based, sex-based, and age-based variations in the incidence of lip, oral cavity, and pharyngeal cancers by subsite were observed. Lip cancers were highly frequent in Australia (associated with solar radiation) and in central and eastern Europe (associated with tobacco smoking). Cancers of the oral cavity and hypopharynx were highly common in south-central Asia, especially in India (associated with smokeless tobacco, bidi, and betel-quid use). Rates of oropharyngeal cancers were elevated in northern America and Europe, notably in Hungary, Slovakia, Germany, and France and were associated with alcohol use, tobacco smoking, and human papillomavirus infection. Nasopharyngeal cancers were most common in northern Africa and eastern/southeast Asia, indicative of genetic susceptibility combined with Epstein-Barr virus infection and early life carcinogenic exposures (nitrosamines and salted foods). The global incidence of lip, oral cavity, and pharyngeal cancers of 529,500, corresponding to 3.8% of all cancer cases, is predicted to rise by 62% to 856,000 cases by 2035 because of changes in demographics. Given the rising incidence of lip, oral cavity, and pharyngeal cancers and the variations in incidence by subsites across world regions and countries, there is a need for local, tailored approaches to prevention, screening, and treatment interventions that will optimally reduce the lip, oral cavity, and pharyngeal cancer burden in future decades. CA Cancer J Clin 2017;67:51-64. © 2016 American Cancer Society.

Objective performance assessment of five computed tomography iterative reconstruction algorithms

OBJECTIVE

Iterative algorithms are gaining clinical acceptance in CT. We performed objective phantom-based image quality evaluation of five commercial iterative reconstruction algorithms available on four different multi-detector CT (MDCT) scanners at different dose levels as well as the conventional filtered back-projection (FBP) reconstruction.

METHODS

Using the Catphan500 phantom, we evaluated image noise, contrast-to-noise ratio (CNR), modulation transfer function (MTF) and noise-power spectrum (NPS). The algorithms were evaluated over a CTDIvol range of 0.75-18.7 mGy on four major MDCT scanners: GE DiscoveryCT750HD (algorithms: ASIR™ and VEO™); Siemens Somatom Definition AS+ (algorithm: SAFIRE™); Toshiba Aquilion64 (algorithm: AIDR3D™); and Philips Ingenuity iCT256 (algorithm: iDose4™). Images were reconstructed using FBP and the respective iterative algorithms on the four scanners.

RESULTS

Use of iterative algorithms decreased image noise and increased CNR, relative to FBP. In the dose range of 1.3-1.5 mGy, noise reduction using iterative algorithms was in the range of 11%-51% on GE DiscoveryCT750HD, 10%-52% on Siemens Somatom Definition AS+, 49%-62% on Toshiba Aquilion64, and 13%-44% on Philips Ingenuity iCT256. The corresponding CNR increase was in the range 11%-105% on GE, 11%-106% on Siemens, 85%-145% on Toshiba and 13%-77% on Philips respectively. Most algorithms did not affect the MTF, except for VEO™ which produced an increase in the limiting resolution of up to 30%. A shift in the peak of the NPS curve towards lower frequencies and a decrease in NPS amplitude were obtained with all iterative algorithms. VEO™ required long reconstruction times, while all other algorithms produced reconstructions in real time. Compared to FBP, iterative algorithms reduced image noise and increased CNR.

CONCLUSIONS

The iterative algorithms available on different scanners achieved different levels of noise reduction and CNR increase while spatial resolution improvements were obtained only with VEO™. This study is useful in that it provides performance assessment of the iterative algorithms available from several mainstream CT manufacturers.

Improving the Quality of Imaging in the Emergency Department

Imaging is critical for the care of emergency department (ED) patients. However, much of the imaging performed for acute care today is overutilization, creating substantial cost without significant benefit. Further, the value of imaging is not easily defined, as imaging only affects outcomes indirectly, through interaction with treatment. Improving the quality, including appropriateness, of emergency imaging requires understanding of how imaging contributes to patient care. The six-tier efficacy hierarchy of Fryback and Thornbury enables understanding of the value of imaging on multiple levels, ranging from technical efficacy to medical decision-making and higher-level patient and societal outcomes. The imaging efficacy hierarchy also allows definition of imaging quality through the Institute of Medicine (IOM)'s quality domains of safety, effectiveness, patient-centeredness, timeliness, efficiency, and equitability and provides a foundation for quality improvement. In this article, the authors elucidate the Fryback and Thornbury framework to define the value of imaging in the ED and to relate emergency imaging to the IOM quality domains.

Reducing emergency CT radiation doses with simple techniques: A quality initiative project

INTRODUCTION

Use of indication-specific CT protocols and adjustment of scan parameters to decrease radiation exposure may result in significant dose reduction. We implemented these strategies and compare pre- and post-implementation radiation dose in emergency department (ED) patients.

METHOD

This was a descriptive, retrospective study. Patients older than 15 years who had undergone emergency CT examinations of the head, chest, abdomen, pelvis and abdominopelvic region in periods before and after dose-reduction implementation were included. The primary outcome was volume CT dose index (CTDIvol ) and dose length products (DLP).

RESULTS

There were 786 studies in the pre-implementation (group 1) and 955 studies in the post-implementation (group 2) periods. Radiation dose from all CT types significantly reduced in the post-implementation period. Average CTDIvol for head, chest, abdomen, pelvis and abdominopelvic region (doses during pre-implementation period in parentheses) were 51.5 (109), 8.1 (30.4), 13.1 (41.8), 11 (38), 11.2 (41.8) mGy, respectively. Average DLP was also significantly lower (pre-implementation dose in parentheses) in all CT types, which were 943 (2232), 324 (2517), 944 (5605), 280 (4024), 809 (7118) mGy●cm, respectively. Patients' age, gender, body mass index and size were not significantly different between the two groups. Image quality decreased but almost all examinations received an acceptable diagnostic subjective image quality.

CONCLUSION

Simple methods could help significantly reduce CT radiation exposure in ED patients while maintaining an acceptable level of diagnostic image quality.

The quality movement or making radiology fun again

Quality can be seen as the link between what we do as radiologists and patient health. The radiology quality movement represents an opportunity for radiologists to have more direct influence on patient health, including the quality domains of safety, effectiveness, patient centeredness, timeliness, efficiency, and equitability. Focusing on quality allows emergency radiologists to extend outside of the confines of the reading room, thereby enhancing a rewarding and clinically relevant practice.

CT of acute perianal abscesses and infected fistulae: a pictorial essay

Computed tomography (CT) is an effective, readily available diagnostic imaging tool for evaluation of the emergency room (ER) patients with the clinical suspicion of perianal abscess and/or infected fistulous tract (anorectal sepsis). These patients usually present with perineal pain, fever, and leukocytosis. The diagnosis can be easy if the fistulous tract or abscess is visible on inspection of the perianal skin. If the tract or abscess is deep, then the clinical diagnosis can be difficult. Also, the presence of complex tracts or supralevator extension of the infection cannot be judged by external examination alone. Magnetic resonance imaging (MRI) is the best imaging test to accurately detect fistulous tracts, especially when they are complex (Omally et al. in AJR 199:W43-W53, 2012). However, in the acute setting in the ER, this imaging modality is not always immediately available. Endorectal ultrasound has also been used to identify perianal abscesses, but this modality requires hands-on expertise and can have difficulty localizing the offending fistulous tract. It may also require the use of a rectal probe, which the patient may not be able to tolerate. Contrast-enhanced CT is a very useful tool to diagnose anorectal sepsis; however, this has not received much attention in the recent literature (Yousem et al. in Radiology 167(2):331-334, 1988) aside from a paper describing CT imaging following fistulography (Liang et al. in Clin Imaging 37(6):1069-1076, 2013). An infected fistula is indicated by a fluid-/air-filled soft tissue tract surrounded by inflammation. A well-defined round to oval-shaped fluid/air collection is indicative of an abscess. The purpose of this article is to demonstrate the usefulness of contrast-enhanced CT in the diagnosis of acute anorectal sepsis in the ER setting. We will discuss the CT appearance of infected fistulous tracts and abscesses and how CT imaging can guide the ER physician in the clinical management of these patients.

Diagnostic imaging in pediatric polytrauma management

Trauma is the cause of over 45% of deaths in children aged 1 to 14 years. Since multiple injuries are common among children, the emergency physician has to assess all the organs of a high-energy injured child, independent of mechanism of the trauma. Even if the principles of polytrauma management are identical both in children and in adults, the optimal pediatric patient care requires a specific understanding of some important anatomical, physiological, and psychological differences that play a significant role in the assessment and management of a pediatric patient. Emergency Radiology already plays a crucial role in the diagnostic process of a polytraumatized child according to the primary survey, through the use of multiple imaging modalities. Radiological and Ultrasound examinations play a basic role in the hemodynamically unstable patients. In the hemodynamically stable patients whole-body CT scanning is the most immediate radiological procedure that allows the examination of all the body parts of a polytraumatized child, reducing the number of minor injuries that might otherwise be neglected.

[State of the art and future trends in technology for computed tomography dose reduction]

The introduction of helical and multislice acquisitions in CT scanners together with decreased image reconstruction times has had a tremendous impact on radiological practice. Technological developments in the last 10 to 12 years have enabled very high quality images to be obtained in a very short time. Improved image quality has led to an increase in the number of indications for CT. In parallel to this development, radiation exposure in patients has increased considerably. Concern about the potential health risks posed by CT imaging, reflected in diverse initiatives and actions by official organs and scientific societies, has prompted the search for ways to reduce radiation exposure in patients without compromising diagnostic efficacy. To this end, good practice guidelines have been established, special applications have been developed for scanners, and research has been undertaken to optimize the clinical use of CT. Noteworthy technical developments incorporated in scanners include the different modes of X-ray tube current modulation, automatic selection of voltage settings, selective organ protection, adaptive collimation, and iterative reconstruction. The appropriate use of these tools to reduce radiation doses requires thorough knowledge of how they work.

Applications of justification and optimization in medical imaging: examples of clinical guidance for computed tomography use in emergency medicine

Availability, reliability, and technical improvements have led to continued expansion of computed tomography (CT) imaging. During a CT scan, there is substantially more exposure to ionizing radiation than with conventional radiography. This has led to questions and critical conclusions about whether the continuous growth of CT scans should be subjected to review and potentially restraints or, at a minimum, closer investigation. This is particularly pertinent to populations in emergency departments, such as children and patients who receive repeated CT scans for benign diagnoses. During the last several decades, among national medical specialty organizations, the American College of Emergency Physicians and the American College of Radiology have each formed membership working groups to consider value, access, and expedience and to promote broad acceptance of CT protocols and procedures within their disciplines. Those efforts have had positive effects on the use criteria for CT by other physician groups, health insurance carriers, regulators, and legislators.

Applications of justification and optimization in medical imaging: examples of clinical guidance for computed tomography use in emergency medicine

Availability, reliability, and technical improvements have led to continued expansion of computed tomography (CT) imaging. During a CT scan, there is substantially more exposure to ionizing radiation than with conventional radiography. This has led to questions and critical conclusions about whether the continuous growth of CT scans should be subjected to review and potentially restraints or, at a minimum, closer investigation. This is particularly pertinent to populations in emergency departments, such as children and patients who receive repeated CT scans for benign diagnoses. During the last several decades, among national medical specialty organizations, the American College of Emergency Physicians and the American College of Radiology have each formed membership working groups to consider value, access, and expedience and to promote broad acceptance of CT protocols and procedures within their disciplines. Those efforts have had positive effects on the use criteria for CT by other physician groups, health insurance carriers, regulators, and legislators.

Low tube voltage intermediate tube current liver MDCT: sinogram-affirmed iterative reconstruction algorithm for detection of hypervascular hepatocellular carcinoma

OBJECTIVE

The purpose of this study was to compare image quality and lesion detectability in the evaluation of hypervascular hepatocellular carcinoma (HCC) on low-tube-voltage half-dose liver CT scans subjected to sinogram-affirmed iterative reconstruction (SAFIRE) with the quality and detectability on full-dose scans reconstructed with filtered back projection (FBP).

MATERIALS AND METHODS

A total of 126 patients with suspected HCC who underwent liver CT including arterial phase scanning at 80 kVp in the dual-source mode (300 mAs for each tube) were included in the study. The half-dose arterial scans were reconstructed with FBP, iterative reconstruction in image space (IRIS), and five SAFIRE strengths (S1-S5) and were compared with full-dose virtual scans (600 mA) reconstructed with FBP. We assessed image noise, contrast-to-noise ratio (CNR) of the liver and blood vessels, and lesionto-liver CNR. Two radiologists evaluated image quality and lesion detectability attained with the different imaging sets.

RESULTS

Image noise on SAFIRE images was significantly lower than that on the other images, and the CNRs on SAFIRE images were higher than those on half-dose FBP images (p < 0.001). In addition, lesion-to-liver CNR on the half-dose S5 SAFIRE images was higher than on IRIS and full-dose FBP images (p < 0.05). Among the half-dose scans, SAFIRE images had significantly better image quality than FBP images (p < 0.05). Regarding lesion detection, half-dose SAFIRE images were better than half-dose FBP images and were comparable with full-dose FBP images (observer 1, 91.8% vs 96%; observer 2, 98% vs 98%; p > 0.05).

CONCLUSION

Performing half-dose 80-kVp liver CT with SAFIRE technique may increase image quality and afford comparable lesion detectability of hypervascular HCC at a reduced radiation dose compared with full-dose CT with FBP.

Radiology stewardship and quality improvement: the process and costs of implementing a CT radiation dose optimization committee in a medium-sized community hospital system

PURPOSE

The aims of this study were to measure the effectiveness of a multidisciplinary CT dose optimization committee and estimate its costs and to describe a radiation stewardship quality improvement initiative in one CT department at a medium-sized community hospital system that used a participatory design committee methodology.

METHODS

A CT dose optimization committee was conceived, funded, and formed, consisting of the following stakeholders: radiologists, technologists, consultant medical physicists, and an administrator. Volume CT dose index (CTDIvol) and repeat rate were monitored for 1 month, for one scan type, during which iterative protocol adjustments were made through committee interaction. Effects on repeat rate and CTDIvol were quantified and benchmarked against national diagnostic reference levels after retrospective medical record review of 100 consecutive patients before and after the intervention. Labor hours were reported and wage resources estimated.

RESULTS

Over 3 months, the committee met in person twice and exchanged 128 e-mails in establishing a process for protocol improvement and measurement of success. Repeat rate was reduced from 13% (13 of 100) to 0% (0 of 100). Scans meeting the ACR reference level for CTDIvol (75 mGy) improved by 34% (38 of 100 before, 51 of 100 after; Fisher's exact 2-tailed P = .09), and those meeting ACR pass/fail criterion (80 mGy) improved by 29% (58 of 100 before, 75 of 100 after; Fisher's exact 2-tailed P = .01). Committee evolution and work, and protocol development and implementation, required 57 person-hours, at an estimated labor cost of $12,488.

CONCLUSIONS

An efficient process was established as a proof of concept for the use of a multidisciplinary committee to reduce patient radiation dose, repeat rate, and variability in image quality. The committee and process ultimately improved the quality of patient care, fostered a culture of safety and ongoing quality improvement, and calculated costs for such an endeavor.

Size-specific dose estimates for adult patients at CT of the torso

PURPOSE

To determine relationships among patient size, scanner radiation output, and size-specific dose estimates (SSDEs) for adults who underwent computed tomography (CT) of the torso.

MATERIALS AND METHODS

Informed consent was waived for this institutional review board-approved study of existing data from 545 adult patients (322 men, 223 women) who underwent clinically indicated CT of the torso between April 1, 2007, and May 13, 2007. Automatic exposure control was used to adjust scanner output for each patient according to the measured CT attenuation. The volume CT dose index (CTDI(vol)) was used with measurements of patient size (anterioposterior plus lateral dimensions) and the conversion factors from the American Association of Physicists in Medicine Report 204 to determine SSDE. Linear regression models were used to assess the dependence of CTDI(vol) and SSDE on patient size.

RESULTS

Patient sizes ranged from 42 to 84 cm. In this range,CTDI(vol) was significantly correlated with size (slope = 0.34 mGy/cm; 95% confidence interval [CI]: 0.31, 0.37 mGy/cm; R(2) = 0.48; P < .001), but SSDE was independent of size (slope = 0.02 mGy/cm; 95% CI: -0.02, 0.07 mGy/cm; R(2) = 0.003; P = .3). These R(2) values indicated that patient size explained 48% of the observed variability in CTDI(vol) but less than 1% of the observed variability in SSDE. The regression of CTDI(vol) versus patient size demonstrated that, in the 42-84-cm range, CTDI(vol) varied from 12 to 26 mGy. However, use of the evaluated automatic exposure control system to adjust scanner output for patient size resulted in SSDE values that were independent of size.

CONCLUSION

For the evaluated automatic exposure control system,CTDI(vol) (scanner output) increased linearly with patient size; however, patient dose (as indicated by SSDE) was independent of size.

Determination of a standard deviation that could minimize radiation exposure in an automatic exposure control for pulmonary thin-section computed tomography

PURPOSE

The aim of this study was to determine a standard deviation (SD) that most reduces the radiation dose without sacrificing the diagnostic accuracy of thin-section computed tomography (CT) for clinical use.

MATERIALS AND METHODS

A total of 120 patients were examined by multidetector CT. They were assigned to one of four SD groups: 8, 9, 11, and 12. Each SD group consisted of 30 patients. The CT images of the same patients with SD10 that had formerly been examined were used for comparison. Two radiologists independently evaluated the degrees of image noise and diagnostic acceptability of the pulmonary diseases using a point score grading system. We compared the scores between each SD and the SD10 group.

RESULTS

Generally, image noise was significantly more prominent in the higher-SD groups. The mean score of diagnostic acceptability was significantly lower in the SD12 group (4.2 ± 1.6) than in the SD10 group (4.6 ± 1.1) group (P < 0.001), whereas no difference was present between the SD8 (4.9 ± 0.7), SD9 (4.8 ± 1.0), and SD11 (4.4 ± 1.5) groups and the SD10 group (4.7 ± 1.1, 4.6 ± 1.4, 4.6 ± 1.1, respectively).

CONCLUSION

Thin-section CT with SD12 is not acceptable. SD11 seems to be the setting with the lowest radiation dose while providing acceptable imaging quality for pulmonary thin-section CT.

Minimizing dose during fluoroscopic tracking through geometric performance feedback

PURPOSE

There is a growing concern regarding the dose delivered during x-ray fluoroscopy guided procedures, particularly in interventional cardiology and neuroradiology, and in real-time tumor tracking radiotherapy and radiosurgery. Many of these procedures involve long treatment times, and as such, there is cause for concern regarding the dose delivered and the associated radiation related risks. An insufficient dose, however, may convey less geometric information, which may lead to inaccuracy and imprecision in intervention placement. The purpose of this study is to investigate a method for achieving the required tracking uncertainty for a given interventional procedure using minimal dose.

METHODS

A simple model is used to demonstrate that a relationship exists between imaging dose and tracking uncertainty. A feedback framework is introduced that exploits this relationship to modulate the tube current (and hence the dose) in order to maintain the required uncertainty for a given interventional procedure. This framework is evaluated in the context of a fiducial tracking problem associated with image-guided radiotherapy in the lung. A particle filter algorithm is used to robustly track the fiducial as it traverses through regions of high and low quantum noise. Published motion models are incorporated in a tracking test suite to evaluate the dose-localization performance trade-offs.

RESULTS

It is shown that using this framework, the entrance surface exposure can be reduced by up to 28.6% when feedback is employed to operate at a geometric tracking uncertainty of 0.3 mm.

CONCLUSIONS

The analysis reveals a potentially powerful technique for dynamic optimization of fluoroscopic imaging parameters to control the applied dose by exploiting the trade-off between tracking uncertainty and x-ray exposure per frame.

Radiation Trends in Trauma Patients

Today, computed tomography (CT) and other studies are used more often early in a trauma case than X-rays, exposing patients to more radiation. The long-term effects of radiation exposure (RE) in trauma patients are of great concern. Investigators randomly selected 60 patients (injury severity scores 15-25) each from the years 2000, 2003, and 2006. The cumulative effective dose (CED) was calculated from the RE of all X-rays and CTs performed during the patient's hospital stay. Total CED/patient increased from 15.97 (2000) to 16.67 (2003) to 23.27 mSv (2006); the increase from 2000 to 2006 was significant ( P < 0.05). X-rays increased over the 6-year period from 9.6/patient (pt) to 11.4/pt to 15.4/pt. CT scans increased from 2.2/pt (15.19 mSv) to 3.5/pt (21.85 mSv, P < 0.05). The CED in children increased: 12.88 versus 13.17 versus 15.32 mSv/pt ( P > 0.05). RE was 19.5 versus 22.0 versus 27.1 mSv in 16 to 45-year-olds compared with 15.5 versus 14.3 versus 27.0 mSv in older adults. Sixteen to 45-year-olds had significantly higher RE than children ( P < 0.05). RE in the first hour and first 24 hours increased but not significantly ( P > 0.05). CED increased from 2000 to 2006, due primarily from CT scans. Children had no significant CED increase during the same period and had lower RE than 16 to 45-year-old adults.

The effect of different adaptation strengths on image quality and radiation dose using Siemens Care Dose 4D

The purpose of this study was to evaluate the effect of different choices of adaptation strengths on image quality and radiation exposure to the patient with Siemens automatic exposure control system called CARE Dose 4D. An anthropomorphic chest phantom was used to simulate the patient and computed tomography scans were performed with a Siemens SOMATOM Sensation 16 and 64. Owing to adaptation strengths, a considerable reduction (26.6-51.5 % and 27.5-49.5 % for Sensation 16 and Sensation 64, respectively) in the radiation dose was found when compared with using a fixed tube current. There was a substantial difference in the image quality (image noise) between the adaptation strengths. Independent of selected adaptation strengths, the level of image noise throughout the chest phantom increased when CARE Dose 4D was used (p < 0.0001). We conclude that the adaptation strengths can be used to obtain user-specified modifications to image quality or radiation exposure to the patient.

Establishing a CT colonography service

This article describes the steps involved in establishing a screening computed tomographic colonography (CTC) practice and integrating that practice within a gastroenterology practice. The standard operating procedures followed at the National Naval Medical Center's Colon Health Initiative are presented and are followed by a discussion of practical aspects of establishing a CTC practice, such as equipment specifications, CTC performance, and interpretation training requirements for radiologists and nonradiologists. Regulatory considerations involved in establishing a screening CTC program are examined along with the salient features of a CTC business plan. Finally, reimbursement issues, quality control, and the potential impact of screening CTC on colonoscopy practice are discussed.

Diagnostic imaging of cervical spine injuries following blunt trauma: a review of the literature and practical guideline

Patients with a (potential) cervical spine injury can be subdivided into low-risk and high-risk patients. With a detailed history and physical examination the cervical spine of patients in the "low-risk" group can be "cleared" without further radiographic examinations. X-ray imaging (3-view series) is currently the primary choice of imaging for patients in the "low-risk" group with a suspected cervical spine injury after blunt trauma. For patients in the "high-risk"group because of its higher sensitivity a computed tomography scan is primarily advised or, alternatively, the cervical spine is immobilised until the patient can be reliably questioned and examined again. For the imaging of traumatic soft tissue injuries of the cervical spine magnetic resonance imaging is the technique of choice.

Imaging of the acetabulum in the era of multidetector computed tomography

Acetabular fractures are often complex injuries and the result of high-energy trauma with associated injuries. Understanding and classification of these rare injuries using radiography can be difficult and are much facilitated by the addition of computed tomography (CT). The purpose of this paper is to briefly review some of the underlying physical principles and technical factors for multidetector CT (MDCT) and to describe its use and imaging findings in the evaluation of acetabular fractures. Using MDCT with two-dimensional multiplanar reformatted (MPR) images and three-dimensional volume rendered images, the supplemental oblique radiographic Judet views can be omitted. MDCT is now an indispensable tool in preoperative imaging of acetabular fractures and also in postoperative imaging in complicated cases. Not only is MDCT excellent for a general overview but also for detailed imaging of fracture extent, joint congruency, step-offs or gaps in the joint surface, and entrapped osteochondral fragments.

Advanced Trauma Life Support. ABCDE from a radiological point of view

Accidents are the primary cause of death in patients aged 45 years or younger. In many countries, Advanced Trauma Life Support® (ATLS®) is the foundation on which trauma care is based. We will summarize the principles and the radiological aspects of the ATLS®, and we will discuss discrepancies with day to day practice and the radiological literature. Because the ATLS® is neither thorough nor up-to-date concerning several parts of radiology in trauma, it should not be adopted without serious attention to defining the indications and limitations pertaining to diagnostic imaging.

MDCT in the evaluation of skeletal trauma: principles, protocols, and clinical applications

Multidetector computed tomography (MDCT) scanners have made volume imaging possible and are used extensively to study polytrauma patients, especially in the evaluation of the spine and peripheral skeleton. An MDCT scanner coupled with a modern workstation has become an essential diagnostic tool for any emergency department. Familiarity with the basic physical principles of MDCT such as projection data, section collimation, and beam collimation is important to achieve high-quality imaging while keeping unnecessary radiation to a minimum. After a polytrauma MDCT examination, images can be reconstructed to obtain different slice thickness, slice interval, fields of view, or reconstruction kernels. No additional scanning is needed for imaging the thoracolumbar spine or bony pelvis. High-quality multiplanar reformation (MPR) and three-dimensional (3-D) images can be created at the workstation using the volumetric data. However, MDCT is a high-dose examination, and care should be taken to use as low a dose as possible. In the musculoskeletal system, MDCT has long been used for evaluation of spinal and pelvic trauma; however, the frequency of its use in extremity trauma has been low. In the extremities, radiography seems to underestimate the extent and severity of injury, especially in complex areas such as the shoulder, elbow, wrist, knee, and ankle. MDCT in the extremities is helpful in fracture detection, evaluation, characterization, and treatment planning. The MPR images give excellent structural detail, and the 3-D images help in understanding the spatial relations, which is important for fracture classification and for preoperative planning. MDCT is also helpful in the follow-up of postoperative results, even in the presence of hardware. Tendon injuries can also be evaluated with MDCT.