Sample content of kinesthetic educational training: Reducing scattered X-ray exposures to interventional physician operators of fluoroscopy.

Content used by Medical Physicists for fluoroscopy safety training to staff is deliverable via several formats, that is, online content or a live audience slide presentations. Here, we share one example of a kinesthetic (live, hands-on simulation) educational program in use at our facility for some time (~10 years). In this example, the format and content specifically target methods of reducing physician operator exposures from scattered x rays. A kinesthetic format identifies and promotes the adoption of exposure-reducing behaviors. Key kinesthetic elements of this type of training include: physician hands-on measurements of radiation levels at locations specific to their standing positions (e.g., primary arterial access points) in the room using handheld exposure rate meters, measurement of exposure rate reduction to physicians provided by using personal protective equipment, that is, wearable aprons, hanging lead drapes, and pull-down shields. Physician choice of procedure-specific tableside selectable controls affecting exposure rate from optional fluoroscopy, Cine or digital subtraction angiography (DSA), along with comparative measured contribution to physician exposure is demonstrated. The inverse square exposure rate reduction to physicians when stepping back from the table during DSA is a key observation. Kinesthetic simulations in the rooms used by physicians have been found to provide the highest level of understanding giving rise to adoption of practices that are impactful for physicians. Specific training scripts are in place for physician sub-specialization in interventional radiology, cardiology, neurosurgery, vascular surgery, and gastroenterology. This training is used for new physician staff while classroom presentations (whose content mimics in room training) are used with staff who have had previously had in room training.

Rapid kV-switching single-source dual-energy CT ex vivo renal calculi characterization using a multiparametric approach: refining parameters on an expanded dataset.

PURPOSE: We aimed to determine the best algorithms for renal stone composition characterization using rapid kV-switching single-source dual-energy computed tomography (rsDECT) and a multiparametric approach after dataset expansion and refinement of variables. METHODS: rsDECT scans (80 and 140 kVp) were performed on 38 ex vivo 5- to 10-mm renal stones composed of uric acid (UA; n = 21), struvite (STR; n = 5), cystine (CYS; n = 5), and calcium oxalate monohydrate (COM; n = 7). Measurements were obtained for 17 variables: mean Hounsfield units (HU) at 11 monochromatic keV levels, effective Z, 2 iodine-water material basis pairs, and 3 mean monochromatic keV ratios (40/140, 70/120, 70/140). Analysis included using 5 multiparametric algorithms: Support Vector Machine, RandomTree, Artificial Neural Network, Naïve Bayes Tree, and Decision Tree (C4.5). RESULTS: Separating UA from non-UA stones was 100% accurate using multiple methods. For non-UA stones, using a 70-keV mean cutoff value of 694 HU had 100% accuracy for distinguishing COM from non-COM (CYS, STR) stones. The best result for distinguishing all 3 non-UA subtypes was obtained using RandomTree (15/17, 88%). CONCLUSIONS: For stones 5 mm or larger, multiple methods can distinguish UA from non-UA and COM from non-COM stones with 100% accuracy. Thus, the choice for analysis is per the user's preference. The best model for separating all three non-UA subtypes was 88% accurate, although with considerable individual overlap between CYS and STR stones. Larger, more diverse datasets, including in vivo data and technical improvements in material separation, may offer more guidance in distinguishing non-UA stone subtypes in the clinical setting.

Ex Vivo Renal Stone Characterization with Single-Source Dual-Energy Computed Tomography: A Multiparametric Approach.

RATIONALE AND OBJECTIVES: We aimed to investigate a multiparametric approach using single-source dual-energy computed tomography (ssDECT) for the characterization of renal stones. MATERIALS AND METHODS: ssDECT scans were performed at 80 and 140 kVp on 32 ex vivo kidney stones of 3-10 mm in a phantom. True composition was determined by infrared spectroscopy to be uric acid (UA; n = 14), struvite (n = 7), cystine (n = 7), or calcium oxalate monohydrate (n = 4). Measurements were obtained for up to 52 variables, including mean density at 11 monochromatic keV levels, effective Z, and multiple material basis pairs. The data were analyzed with five multiparametric algorithms. After omitting 8 stones smaller than 5 mm, the remaining 24-stone dataset was similarly analyzed. Both stone datasets were also analyzed with a subset of 14 commonly used variables in the same fashion. RESULTS: For the 32-stone dataset, the best method for distinguishing UA from non-UA stones was 97% accurate, and for distinguishing the non-UA subtypes was 72% accurate. For the 24-stone dataset, the best method for distinguishing UA from non-UA stones was 100% accurate, and for distinguishing the non-UA subtypes was 75% accurate. CONCLUSION: Multiparametric ssDECT methods can distinguish UA from non-UA stones of 5 mm or larger with 100% accuracy. The best model to distinguish the non-UA renal stone subtypes was 75% accurate. Further refinement of this multiparametric approach may increase the diagnostic accuracy of separating non-UA subtypes and assist in the development of a clinical paradigm for in vivo use.

A primer on the use of dual-energy CT in the evaluation of commonly encountered neoplasms.

Technical improvements in the acquisition and display of dual-energy computed tomography (DECT) have made this technique increasingly applicable to clinical practice, particularly in the setting of oncologic imaging. DECT allows for qualitative and quantitative analysis of tissue composition beyond the standard anatomical evaluation possible with single-energy computed tomography. For example, DECT can be used to interrogate iodine and calcium concentrations and to increase iodine signal, which makes many pathologic processes more conspicuous and provides improved understanding of internal structure within mass lesions. A working understanding of common postprocessing DECT displays will allow radiologists to maximize the additional diagnostic information available in DECT examinations. In this article, we describe common strategies for DECT interrogation by organ system, which may improve the conspicuity and understanding of suspected malignancies.

Feasibility of ultra-low radiation dose reduction for renal stone CT using model-based iterative reconstruction: prospective pilot study.

PURPOSE: To compare dose, reader assessments, and noise between ultra-low-dose (ULD) and low-dose (LD) renal stone computed tomography (CT) using multiple reconstruction methods. MATERIALS AND METHODS: Prospective study of 19 patients having noncontrast LD and ULD renal stone CT reconstructed using filtered back projection, adaptive statistical iterative reconstruction (ASIR), and model-based iterative reconstruction (MBIR). Dose, noise measurements, and subjective image assessments were recorded. RESULTS: ULD volume CT dose index was 61% less. Noise was 50% less with ULD MBIR than with LD ASIR (P<.001); no other significant differences existed. CONCLUSION: ULD MBIR is comparable to our standard of care, LD ASIR, with 61% lower dose and 50% less noise.

Reducing the radiation dose for computed tomography colonography using model-based iterative reconstruction.

PURPOSE: To determine whether radiation doses during computed tomography (CT) colonography (CTC) can be further reduced while maintaining image quality using model-based iterative reconstruction (MBIR). METHODS: Twenty patients underwent CTC at a standard dose in supine and prone positions and at a reduced dose in the supine position. All other scan parameters (except noise index) were held constant. Acquisitions were reconstructed using 3 algorithms: filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and MBIR. Noise was assessed quantitatively by comparing the SD in Hounsfield units at 5 standard locations. Qualitative assessment was made by 2 experienced radiologists blinded to technique who subjectively scored image quality, noise, and sharpness (from 0 to 4). RESULTS: The standard-dose and reduced-dose CT dose index/dose-length product were 6.7/328 and 2.7 mGy/129 mGy-cm, respectively (60% reduction). Measured mean noise level increased from the standard to the reduced dose (FBP, from 58.6 to 97.2; ASIR from 35.8 to 60.6; and MBIR from 16.6 to 21.9). MBIR had significantly less noise than ASIR on 2-dimensional images at both standard and reduced doses (P < .01). CONCLUSIONS: Radiation dose in CTC using MBIR can be reduced by 60% while maintaining image quality and reducing image noise.

Methods for clinical evaluation of noise reduction techniques in abdominopelvic CT.

Most noise reduction methods involve nonlinear processes, and objective evaluation of image quality can be challenging, since image noise cannot be fully characterized on the sole basis of the noise level at computed tomography (CT). Noise spatial correlation (or noise texture) is closely related to the detection and characterization of low-contrast objects and may be quantified by analyzing the noise power spectrum. High-contrast spatial resolution can be measured using the modulation transfer function and section sensitivity profile and is generally unaffected by noise reduction. Detectability of low-contrast lesions can be evaluated subjectively at varying dose levels using phantoms containing low-contrast objects. Clinical applications with inherent high-contrast abnormalities (eg, CT for renal calculi, CT enterography) permit larger dose reductions with denoising techniques. In low-contrast tasks such as detection of metastases in solid organs, dose reduction is substantially more limited by loss of lesion conspicuity due to loss of low-contrast spatial resolution and coarsening of noise texture. Existing noise reduction strategies for dose reduction have a substantial impact on lowering the radiation dose at CT. To preserve the diagnostic benefit of CT examination, thoughtful utilization of these strategies must be based on the inherent lesion-to-background contrast and the anatomy of interest. The authors provide an overview of existing noise reduction strategies for low-dose abdominopelvic CT, including analytic reconstruction, image and projection space denoising, and iterative reconstruction; review qualitative and quantitative tools for evaluating these strategies; and discuss the strengths and limitations of individual noise reduction methods.

Ultra-low-dose computed tomographic angiography with model-based iterative reconstruction compared with standard-dose imaging after endovascular aneurysm repair: a prospective pilot study.

PURPOSE: An ultra-low-dose radiation protocol reconstructed with model-based iterative reconstruction was compared with our standard-dose protocol. METHODS: This prospective study evaluated 20 men undergoing surveillance-enhanced computed tomography after endovascular aneurysm repair. All patients underwent standard-dose and ultra-low-dose venous phase imaging; images were compared after reconstruction with filtered back projection, adaptive statistical iterative reconstruction, and model-based iterative reconstruction. Objective measures of aortic contrast attenuation and image noise were averaged. Images were subjectively assessed (1 = worst, 5 = best) for diagnostic confidence, image noise, and vessel sharpness. Aneurysm sac diameter and endoleak detection were compared. RESULTS: Quantitative image noise was 26% less with ultra-low-dose model-based iterative reconstruction than with standard-dose adaptive statistical iterative reconstruction and 58% less than with ultra-low-dose adaptive statistical iterative reconstruction. Average subjective noise scores were not different between ultra-low-dose model-based iterative reconstruction and standard-dose adaptive statistical iterative reconstruction (3.8 vs. 4.0, P = .25). Subjective scores for diagnostic confidence were better with standard-dose adaptive statistical iterative reconstruction than with ultra-low-dose model-based iterative reconstruction (4.4 vs. 4.0, P = .002). Vessel sharpness was decreased with ultra-low-dose model-based iterative reconstruction compared with standard-dose adaptive statistical iterative reconstruction (3.3 vs. 4.1, P < .0001). Ultra-low-dose model-based iterative reconstruction and standard-dose adaptive statistical iterative reconstruction aneurysm sac diameters were not significantly different (4.9 vs. 4.9 cm); concordance for the presence of endoleak was 100% (P < .001). CONCLUSION: Compared with a standard-dose technique, an ultra-low-dose model-based iterative reconstruction protocol provides comparable image quality and diagnostic assessment at a 73% lower radiation dose.

Dual-energy vs conventional computed tomography in determining stone composition.

OBJECTIVE: To compare the accuracy between conventional computed tomography (CT) and dual-energy CT (DECT) in predicting stone composition in a blinded, prospective fashion. METHODS: A total of 32 renal stones with known composition were scanned in vitro, first using standard CT techniques at 120 kilovolt peak (kV[p]) and then using fast-switched kilovolt DECT at 80 and 140 kilovolt peak (kV[p]). For the DECT scan, a spectral curve was created demonstrating the change of Hounsfield units (HU) across the kiloelectron volt spectrum. The composition of each stone was estimated by comparing each sample curve with curves of known materials. To attempt stone determination using single-energy CT, the HU of each stone was compared with ranges reported in previous studies. The accuracy of each method was compared. RESULTS: Included were 27 stones large enough to allow analysis. Single-energy measurements accurately identified 14 of 27 stones of all composition (52%), whereas the DECT spectral curves correctly identified 20 (74%). When analyzed by stone type, single-energy vs DECT correctly identified 12 vs 12 of the 12 uric acid stones, 2 vs 3 of the 6 struvite stones, 0 vs 3 of the 5 cystine stones, and 0 vs 2 of the 4 calcium oxalate stones, respectively. When simply attempting to differentiate uric acid vs nonuric acid stones, single-energy CT could accurately differentiate only 6 of 15 stones as nonuric acid (40%) compared with 14 of 15 stones (93%) for DECT. CONCLUSION: DECT appears to be superior to conventional CT in differentiating stone composition and is particularly accurate in differentiating nonuric acid from uric acid stones.

Reducing radiation dose in CT enterography.

Computed tomographic (CT) enterography is a diagnostic examination that is increasingly being used to evaluate disorders of the small bowel. An undesirable consequence of CT, however, is patient exposure to ionizing radiation. This is of particular concern with CT enterography because patients tend to be young and require numerous follow-up examinations. There are multiple strategies to reduce radiation dose at CT enterography, including adjusting acquisition parameters, reducing scan length, and reducing tube voltage or tube current. The drawback to dose reduction strategies is degradation of image quality due to increased image noise. However, image noise can be reduced with commercial iterative reconstruction and denoising techniques. With a combination of low-dose techniques and noise-control strategies, one can markedly reduce radiation dose at CT enterography while maintaining diagnostic accuracy.

Reducing body CT radiation dose: beyond just changing the numbers.

OBJECTIVE: CT dose reduction has become a top priority for many radiology practices as a result of federal and state initiatives and public concern. Implementing this in practice, however, is difficult because of the variability between practices, CT scanners, radiologist preferences, and institutional capacity. CONCLUSION: This article will discuss strategies for successful CT dose reduction instituted in multivendor practices.

Validation and initial clinical use of automatic peak skin dose localization with fluoroscopic and interventional procedures.

PURPOSE: To assess the accuracy and initial clinical use of a software tool that automatically maps and records values of skin dose, including peak skin dose (PSD), administered to patients undergoing fluoroscopically guided interventional procedures. MATERIALS AND METHODS: In this retrospective study, the institutional review board determined that this HIPAA-compliant study met the criteria as a quality assurance investigation. Informed consent was waived. After the initial validation and accuracy tests, distributed skin dose and PSD estimates were obtained for fluoroscopically guided interventional procedures performed in the radiology, cardiology, and gastroenterology practice areas between January and October 2011. A total of 605 procedures were performed in 520 patients (64% men; age range, 20-95 years). The accuracy of a skin dose tool to estimate patient dose distribution was verified with phantom studies by using an external dosimeter and direct exposure film. PSD distribution, PSD according to procedure type, and PSD for individual physician operators were assessed. RESULTS: Calculated PSD values agreed within ±9% of that measured by using film dosimetry under the condition of matched-phantom geometry. The area receiving the highest dose (greater than 95% of peak) agreed within ±17%. Of 605 patient procedures, 15 demonstrated PSD greater than 2 Gy, with a maximum PSD of 5.6 Gy. CONCLUSION: Knowledge of the patient skin dose can help direct treatment of patients who were administered relatively high skin dose and may be used to plan future procedures. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12112295/-/DC1.

Dual-energy (spectral) CT: applications in abdominal imaging.

Dual-energy imaging is a promising new development in computed tomography (CT) that has the potential to improve lesion detection and characterization beyond levels currently achievable with conventional CT techniques. In dual-energy CT (DECT), the simultaneous use of two different energy settings allows the differentiation of materials on the basis of their energy-related attenuation characteristics (material density). The datasets obtained with DECT can be used to reconstruct virtual unenhanced images as well as iodinated contrast material-enhanced material density images, obviating the standard two-phase (unenhanced and contrast-enhanced) scanning protocol and thus helping minimize the radiation dose received by the patient. Single-source DECT, which is performed with rapid alternation between two energy levels, can also generate computed monochromatic images, which are less vulnerable to artifacts such as beam hardening and pseudoenhancement and provide a higher contrast-to-noise ratio than polychromatic images produced by conventional CT. Familiarity with the capabilities of DECT may help radiologists improve their diagnostic performance.

Automatic monitoring of localized skin dose with fluoroscopic and interventional procedures.

This software tool locates and computes the intensity of radiation skin dose resulting from fluoroscopically guided interventional procedures. It is comprised of multiple modules. Using standardized body specific geometric values, a software module defines a set of male and female patients arbitarily positioned on a fluoroscopy table. Simulated X-ray angiographic (XA) equipment includes XRII and digital detectors with or without bi-plane configurations and left and right facing tables. Skin dose estimates are localized by computing the exposure to each 0.01 × 0.01 m(2) on the surface of a patient irradiated by the X-ray beam. Digital Imaging and Communications in Medicine (DICOM) Structured Report Dose data sent to a modular dosimetry database automatically extracts the 11 XA tags necessary for peak skin dose computation. Skin dose calculation software uses these tags (gantry angles, air kerma at the patient entrance reference point, etc.) and applies appropriate corrections of exposure and beam location based on each irradiation event (fluoroscopy and acquistions). A physicist screen records the initial validation of the accuracy, patient and equipment geometry, DICOM compliance, exposure output calibration, backscatter factor, and table and pad attenuation once per system. A technologist screen specifies patient positioning, patient height and weight, and physician user. Peak skin dose is computed and localized; additionally, fluoroscopy duration and kerma area product values are electronically recorded and sent to the XA database. This approach fully addresses current limitations in meeting accreditation criteria, eliminates the need for paper logs at a XA console, and provides a method where automated ALARA montoring is possible including email and pager alerts.

Abdominal CT: comparison of low-dose CT with adaptive statistical iterative reconstruction and routine-dose CT with filtered back projection in 53 patients.

OBJECTIVE: The purpose of this article is to retrospectively compare radiation dose, noise, and image quality of abdominal low-dose CT reconstructed with adaptive statistical iterative reconstruction (ASIR) and routine-dose CT reconstructed with filtered back projection (FBP). MATERIALS AND METHODS: Fifty-three patients (37 men and 16 women; mean age, 60.8 years) underwent contrast-enhanced abdominal low-dose CT with 40% ASIR. All 53 patients had previously undergone contrast-enhanced routine-dose CT with FBP. With the scanning techniques masked, two radiologists independently graded images for sharpness, image noise, diagnostic acceptability, and artifacts. Quantitative measures of radiation dose and image noise were also obtained. All results were compared on the basis of body mass index (BMI). RESULTS: The volume CT dose index (CTDI(vol)), dose-length product, and radiation dose for low-dose CT with ASIR were 17 mGy, 860 mGy, and 13 mSv, respectively, compared with 25 mGy, 1,193 mGy, and 18 mSv for routine-dose CT with FBP, representing an approximate overall dose reduction of 33%. Low-dose CT with ASIR had significantly reduced (p < 0.001) quantitative and qualitative assessment of image noise. Image sharpness, however, was significantly reduced for low-dose CT with ASIR (p < 0.001), although diagnostic acceptability and artifact scores were nearly identical to those for routine-dose CT with FBP. The average CTDI(vol) dose reduction was 66% for patients with a BMI of less than 20 and 23% for patients with a BMI of 25 or greater. CONCLUSION: Compared with routine-dose CT with FBP, abdominal low-dose CT with ASIR significantly reduces noise, thereby permitting diagnostic abdominal examinations with lower (by 23-66%) radiation doses. Despite reduced image sharpness in average and small patients, low-dose CT with ASIR had diagnostic acceptability comparable to that of routine-dose CT with FBP.

Iterative reconstruction technique for reducing body radiation dose at CT: feasibility study.

OBJECTIVE: The purpose of this study was to evaluate the image noise, low-contrast resolution, image quality, and spatial resolution of adaptive statistical iterative reconstruction in low-dose body CT. MATERIALS AND METHODS: Adaptive statistical iterative reconstruction was used to scan the American College of Radiology phantom at the American College of Radiology reference value and at one-half that value (12.5 mGy). Test objects in low- and high-contrast and uniformity modules were evaluated. Low-dose CT with adaptive statistical iterative reconstruction was then tested on 12 patients (seven men, five women; average age, 67.5 years) who had previously undergone routine-dose CT. Two radiologists blinded to scanning technique evaluated images of the same patients obtained with routine-dose CT and low-dose CT with and without adaptive statistical iterative reconstruction. Image noise, low-contrast resolution, image quality, and spatial resolution were graded on a scale of 1 (best) to 4 (worst). Quantitative noise measurements were made on clinical images. RESULTS: In the phantom, low- and high-contrast and uniformity assessments showed no significant difference between routine-dose imaging and low-dose CT with adaptive statistical iterative reconstruction. In patients, low-dose CT with adaptive statistical iterative reconstruction was associated with CT dose index reductions of 32-65% compared with routine imaging and had the least noise both quantitatively and qualitatively (p < 0.05). Low-dose CT with adaptive statistical iterative reconstruction and routine-dose CT had identical results for low-contrast resolution and nearly identical results for overall image quality (grade 2.1-2.2). Spatial resolution was better with routine-dose CT (p = 0.004). CONCLUSION: These preliminary results support body CT dose index reductions of 32-65% when adaptive statistical iterative reconstruction is used. Studies with larger statistical samples are needed to confirm these findings.

Dynamics of diastolic sounds caused by partially occluded coronary arteries.

The aim of this project is to improve the detection of coronary occlusions using an approach based on the recording and analysis of isolated diastolic heart sounds associated with turbulent blood flow in occluded coronary arteries. The nonlinear dynamic analysis method based on approximate entropy has been proposed for the analysis of diastolic heart sounds. A commercially available electronic stethoscope was used to record the diastolic heart sounds from patients diagnosed with or without coronary artery disease (CAD) based on their coronary angiography examination. The nonlinear dynamical analysis (approximate entropy) measures of the diastolic heart sounds recorded from 30 patients with coronary occlusions and ten normal subjects were estimated. Results suggest the presence of the high nonlinear (approximate entropy) values of diastolic heart sounds associated with CAD (p < 0.05). This approach led to a sensitivity of 77%, a specificity of 80%, and an overall accuracy of 78%. As a summary, 23 out of 30 abnormal patients and eight out of ten normal patients were correctly detected.

Metal artifact reduction image reconstruction algorithm for CT of implanted metal orthopedic devices: a work in progress.

INTRODUCTION: Despite recent advances in CT technology, metal orthopedic implants continue to cause significant artifacts on many CT exams, often obscuring diagnostic information. We performed this prospective study to evaluate the effectiveness of an experimental metal artifact reduction (MAR) image reconstruction program for CT. MATERIALS AND METHODS: We examined image quality on CT exams performed in patients with hip arthroplasties as well as other types of implanted metal orthopedic devices. The exam raw data were reconstructed using two different methods, the standard filtered backprojection (FBP) program and the MAR program. Images were evaluated for quality of the metal-cement-bone interfaces, trabeculae < or = 1 cm from the metal, trabeculae 5 cm apart from the metal, streak artifact, and overall soft tissue detail. The Wilcoxon Rank Sum test was used to compare the image scores from the large and small prostheses. Interobserver agreement was calculated. RESULTS: When all patients were grouped together, the MAR images showed mild to moderate improvement over the FBP images. However, when the cases were divided by implant size, the MAR images consistently received higher image quality scores than the FBP images for large metal implants (total hip prostheses). For small metal implants (screws, plates, staples), conversely, the MAR images received lower image quality scores than the FBP images due to blurring artifact. The difference of image scores for the large and small implants was significant (p = 0.002). Interobserver agreement was found to be high for all measures of image quality (k > 0.9). CONCLUSION: The experimental MAR reconstruction algorithm significantly improved CT image quality for patients with large metal implants. However, the MAR algorithm introduced blurring artifact that reduced image quality with small metal implants.