Detectability of Small Low-Attenuation Lesions With Deep Learning CT Image Reconstruction: A 24-Reader Phantom Study.

BACKGROUND. Iterative reconstruction (IR) techniques are susceptible to contrast-dependent spatial resolution, limiting overall radiation dose reduction potential. Deep learning image reconstruction (DLIR) may mitigate this limitation. OBJECTIVE. The purpose of our study was to evaluate low-contrast detectability performance and radiation-saving potential of a DLIR algorithm in comparison with filtered back projection (FBP) and IR using a human multireader noninferiority study design and task-based observer modeling. METHODS. A dual-phantom construct, consisting of a low-contrast detectability module (21 low-contrast hypoattenuating objects in seven sizes [2.4-10.0 mm] and three contrast levels [-15, -10, -5 HU] embedded within liver-equivalent background) and a phantom, was imaged at five radiation exposures (CTDIvol range, 1.4-14.0 mGy; size-specific dose estimate, 2.5-25.0 mGy; 90%-, 70%-, 50%-, and 30%-reduced radiation levels and full radiation level) using an MDCT scanner. Images were reconstructed using FBP, hybrid IR (ASiR-V), and DLIR (TrueFidelity). Twenty-four readers of varying experience levels evaluated images using a two-alternative forced choice. A task-based observer model (detectability index [d']) was calculated. Reader performance was estimated by calculating the AUC using a noninferiority method. RESULTS. Compared with FBP and IR methods at routine radiation levels, DLIR medium and DLIR high settings showed noninferior performance through a 90% radiation reduction (except DLIR medium setting at 70% reduced level). The IR method was non-inferior to routine radiation FBP only for 30% and 50% radiation reductions. No significant difference in d' was observed between routine radiation FBP and DLIR high setting through a 70% radiation reduction. Reader experience was not correlated with diagnostic accuracy (R2 = 0.005). CONCLUSION. Compared with FBP or IR methods at routine radiation levels, certain DLIR algorithm weightings yielded noninferior low-contrast detectability with radiation reductions of up to 90% as measured by 24 human readers and up to 70% as assessed by a task-based observer model. CLINICAL IMPACT. DLIR has substantial potential to preserve contrast-dependent spatial resolution for the detection of hypoattenuating lesions at decreased radiation levels in a phantom model, addressing a major shortcoming of current IR techniques.

U.S. Diagnostic Reference Levels and Achievable Doses for 10 Pediatric CT Examinations.

Background Diagnostic reference levels (DRLs) and achievable doses (ADs) were developed for the 10 most commonly performed pediatric CT examinations in the United States using the American College of Radiology Dose Index Registry. Purpose To develop robust, current, national DRLs and ADs for the 10 most commonly performed pediatric CT examinations as a function of patient age and size. Materials and Methods Data on 10 pediatric (ie, patients aged 18 years and younger) CT examinations performed between 2016 and 2020 at 1625 facilities were analyzed. For head and neck examinations, dose indexes were analyzed based on patient age; for body examinations, dose indexes were analyzed for patient age and effective diameter. Data from 1 543 535 examinations provided medians for AD and 75th percentiles for DRLs for volume CT dose index (CTDIvol), dose-length product (DLP), and size-specific dose estimate (SSDE). Results Of all facilities analyzed, 66% of the facilities (1068 of 1625) were community hospitals, 16% (264 of 1625) were freestanding centers, 9.5% (154 of 1625) were academic facilities, and 3.5% (57 of 1625) were dedicated children's hospitals. Fifty-two percent of the patients (798 577 of 1 543 535) were boys, and 48% (744 958 of 1 543 535) were girls. The median age of patients was 14 years (boys, 13 years; girls, 15 years). The head was the most frequent anatomy examined with CT (876 655 of 1 543 535 examinations [57%]). For head without contrast material CT examinations, the age-based CTDIvol AD ranged from 19 to 46 mGy, and DRL ranged from 23 to 55 mGy, with both AD and DRL increasing with age. For body examinations, DRLs and ADs for size-based CTDIvol, SSDE, and DLP increased consistently with the patient's effective diameter. Conclusion Diagnostic reference levels and achievable doses as a function of patient age and effective diameter were developed for the 10 most commonly performed CT pediatric examinations using American College of Radiology Dose Index Registry data. These benchmarks can guide CT facilities in adjusting pediatric CT protocols and resultant doses for their patients. © RSNA, 2021 An earlier incorrect version appeared online. This article was corrected on October 29, 2021.

Through-the-Glass Portable Radiography of Patients in Isolation Units: Experience During the COVID-19 Pandemic.

OBJECTIVE. To reduce staff exposure to infection and maintain operational efficiency, we have developed a protocol to image patients using portable chest radiography through the glass of an isolation room. This technique is safe and easy to implement. Images are of comparable quality to standard portable radiographs. CONCLUSION. This protocol, used routinely by our department during the COVID-19 pandemic, can be applied to any situation in which the patient is placed in isolation.

CT Detectability of Small Low-Contrast Hypoattenuating Focal Lesions: Iterative Reconstructions versus Filtered Back Projection.

Purpose To investigate performance in detectability of small (≤1 cm) low-contrast hypoattenuating focal lesions by using filtered back projection (FBP) and iterative reconstruction (IR) algorithms from two major CT vendors across a range of 11 radiation exposures. Materials and Methods A low-contrast detectability phantom consisting of 21 low-contrast hypoattenuating focal objects (seven sizes between 2.4 and 10.0 mm, three contrast levels) embedded into a liver-equivalent background was scanned at 11 radiation exposures (volume CT dose index range, 0.5-18.0 mGy; size-specific dose estimate [SSDE] range, 0.8-30.6 mGy) with four high-end CT platforms. Data sets were reconstructed by using FBP and varied strengths of image-based, model-based, and hybrid IRs. Sixteen observers evaluated all data sets for lesion detectability by using a two-alternative-forced-choice (2AFC) paradigm. Diagnostic performances were evaluated by calculating area under the receiver operating characteristic curve (AUC) and by performing noninferiority analyses. Results At benchmark exposure, FBP yielded a mean AUC of 0.79 ± 0.09 (standard deviation) across all platforms which, on average, was approximately 2% lower than that observed with the different IR algorithms, which showed an average AUC of 0.81 ± 0.09 (P = .12). Radiation decreases of 30%, 50%, and 80% resulted in similar declines of observer detectability with FBP (mean AUC decrease, -0.02 ± 0.05, -0.03 ± 0.05, and -0.05 ± 0.05, respectively) and all IR methods investigated (mean AUC decrease, -0.00 ± 0.05, -0.04 ± 0.05, and -0.04 ± 0.05, respectively). For each radiation level and CT platform, variance in performance across observers was greater than that across reconstruction algorithms (P = .03). Conclusion Iterative reconstruction algorithms have limited radiation optimization potential in detectability of small low-contrast hypoattenuating focal lesions. This task may be further complicated by a high degree of variation in radiologists' performances, seemingly exceeding real performance differences among reconstruction algorithms. © RSNA, 2018 Online supplemental material is available for this article.

U.S. Diagnostic Reference Levels and Achievable Doses for 10 Adult CT Examinations.

Purpose To develop diagnostic reference levels (DRLs) and achievable doses (ADs) for the 10 most common adult computed tomographic (CT) examinations in the United States as a function of patient size by using the CT Dose Index Registry. Materials and Methods Data from the 10 most commonly performed adult CT head, neck, and body examinations from 583 facilities were analyzed. For head examinations, the lateral thickness was used as an indicator of patient size; for neck and body examinations, water-equivalent diameter was used. Data from 1 310 727 examinations (analyzed by using SAS 9.3) provided median values, as well as means and 25th and 75th (DRL) percentiles for volume CT dose index (CTDIvol), dose-length product (DLP), and size-specific dose estimate (SSDE). Applicable results were compared with DRLs from eight countries. Results More than 46% of the facilities were community hospitals; 13% were academic facilities. More than 48% were in metropolitan areas, 39% were suburban, and 13% were rural. More than 50% of the facilities performed fewer than 500 examinations per month. The abdomen and pelvis was the most frequently performed examination in the study (45%). For body examinations, DRLs (75th percentile) and ADs (median) for CTDIvol, SSDE, and DLP increased consistently with the patient's size (water-equivalent diameter). The relationships between patient size and DRLs and ADs were not as strong for head and neck examinations. These results agree well with the data from other countries. Conclusion DRLs and ADs as a function of patient size were developed for the 10 most common adult CT examinations performed in the United States. © RSNA, 2017.

Targeted CT Dose Reduction Using a Novel Dose Metric and the American College of Radiology Dose Index Registry: Application to Thoracic CT Angiography.

OBJECTIVE: The purpose of this article is to illustrate the use of the American College of Radiology Dose Index Registry data with a novel measurement of exposure to guide quality improvement efforts. MATERIALS AND METHODS: Using information from the Dose Index Registry report covering July through December 2012, we examined our relative ranking compared with the national median CT dose for the 20 most frequently performed examinations at our institution. The total exposure variance, defined as the difference between institutional and median national dose multiplied by the local examination frequency and expressed in units of mGy-persons, was calculated. Using this metric, two examinations were selected for investigation: pulmonary and thoracic CT angiography (CTA). Protocol modifications were implemented, and postintervention dose data were assessed from the report 1 year later. RESULTS: As indicated by size-specific dose estimates (SSDEs), the 2012 pulmonary CTA was within the national interquartile range; however, total exposure variance analysis showed that it presented the greatest opportunity for improvement on a population basis. Thoracic CTA was a top quartile examination and offered the second highest potential savings. After protocol modification, the average pulmonary CTA SSDEs decreased by 16%, for a population exposure savings of 1776 mGy-persons in the 2013 report. Average thoracic CTA SSDEs decreased by 44%, for a population exposure savings of 1050 mGy-persons. CONCLUSION: Total exposure variance analysis can increase the usefulness of Dose Index Registry data by relating per-examination dose differences to the local examination frequency. This study exhibited reduction of dose metrics for two commonly performed examinations.

Variation in CT pediatric head examination radiation dose: results from a national survey.

OBJECTIVE. The purpose of this article is to examine the variation in radiation dose, CT dose index volume (CTDIvol), and dose-length product (DLP) for pediatric head CT examinations as a function of hospital characteristics across the United States. MATERIALS AND METHODS. A survey inquiring about hospital information, CT scanners, pediatric head examination protocol, CTDIvol, and DLP was mailed to a representative sample of U.S. hospitals. Follow-up mailings were sent to nonrespondents. Descriptive characteristics of respondents and nonrespondents were compared using design-based Pearson chi-square tests. Dose estimates were compared across hospital characteristics using Bonferroni-adjusted Wald test. Hospital-level factors associated with dose estimates were evaluated using multiple linear regressions and modified Poisson regression models. RESULTS. Surveys were sent out to 751 hospitals; 292 responded to the survey, of which 253 were eligible (35.5% response rate, calculated as number of hospitals who completed surveys [n = 253] divided by sum of number who were eligible and initially consented [n = 712] plus estimated number who were eligible among those who refused [n = 1]). Most respondents reported using MDCT scanners (99.2%) and having a dedicated pediatric head CT protocol (93%). Estimated mean reported CTDIvol values were 27.3 mGy (95% CI, 24.4-30.1 mGy), and DLP values were 390.9 mGy × cm (95% CI, 346.6-435.1 mGy × cm). These values did not vary significantly by region, trauma level, teaching status, CT accreditation, number of CT scanners, or report of a dedicated pediatric CT protocol. However, estimated CTDIvol reported by children's hospitals was 19% lower than that reported by general hospitals (p < 0.01). CONCLUSION. Most hospitals (82%) report doses that meet American College of Radiology accreditation levels. However, [corrected] the mean CTDI(vol) at children's hospitals was approximately 7 mGy (21%, adjusted for covariates), lower than that at nonchildren's hospitals.

Standard and reduced radiation dose liver CT images: adaptive statistical iterative reconstruction versus model-based iterative reconstruction-comparison of findings and image quality.

PURPOSE: To investigate whether reduced radiation dose liver computed tomography (CT) images reconstructed with model-based iterative reconstruction ( MBIR model-based iterative reconstruction ) might compromise depiction of clinically relevant findings or might have decreased image quality when compared with clinical standard radiation dose CT images reconstructed with adaptive statistical iterative reconstruction ( ASIR adaptive statistical iterative reconstruction ). MATERIALS AND METHODS: With institutional review board approval, informed consent, and HIPAA compliance, 50 patients (39 men, 11 women) were prospectively included who underwent liver CT. After a portal venous pass with ASIR adaptive statistical iterative reconstruction images, a 60% reduced radiation dose pass was added with MBIR model-based iterative reconstruction images. One reviewer scored ASIR adaptive statistical iterative reconstruction image quality and marked findings. Two additional independent reviewers noted whether marked findings were present on MBIR model-based iterative reconstruction images and assigned scores for relative conspicuity, spatial resolution, image noise, and image quality. Liver and aorta Hounsfield units and image noise were measured. Volume CT dose index and size-specific dose estimate ( SSDE size-specific dose estimate ) were recorded. Qualitative reviewer scores were summarized. Formal statistical inference for signal-to-noise ratio ( SNR signal-to-noise ratio ), contrast-to-noise ratio ( CNR contrast-to-noise ratio ), volume CT dose index, and SSDE size-specific dose estimate was made (paired t tests), with Bonferroni adjustment. RESULTS: Two independent reviewers identified all 136 ASIR adaptive statistical iterative reconstruction image findings (n = 272) on MBIR model-based iterative reconstruction images, scoring them as equal or better for conspicuity, spatial resolution, and image noise in 94.1% (256 of 272), 96.7% (263 of 272), and 99.3% (270 of 272), respectively. In 50 image sets, two reviewers (n = 100) scored overall image quality as sufficient or good with MBIR model-based iterative reconstruction in 99% (99 of 100). Liver SNR signal-to-noise ratio was significantly greater for MBIR model-based iterative reconstruction (10.8 ± 2.5 [standard deviation] vs 7.7 ± 1.4, P < .001); there was no difference for CNR contrast-to-noise ratio (2.5 ± 1.4 vs 2.4 ± 1.4, P = .45). For ASIR adaptive statistical iterative reconstruction and MBIR model-based iterative reconstruction , respectively, volume CT dose index was 15.2 mGy ± 7.6 versus 6.2 mGy ± 3.6; SSDE size-specific dose estimate was 16.4 mGy ± 6.6 versus 6.7 mGy ± 3.1 (P < .001). CONCLUSION: Liver CT images reconstructed with MBIR model-based iterative reconstruction may allow up to 59% radiation dose reduction compared with the dose with ASIR adaptive statistical iterative reconstruction , without compromising depiction of findings or image quality.

Estimated skin dose look-up tables and their effect on dose awareness in the fluoroscopy-guided imaging suite.

OBJECTIVE: The displayed air kerma during a fluoroscopy-guided procedure often does not represent the entrance skin dose. The purpose of this work is to develop a system-specific air kerma-to-entrance skin dose look-up table (LUT) for immediate reference and to evaluate its clinical utility. MATERIALS AND METHODS: Physicists are often involved in retrospective dosimetry and risk estimates. Conservative dosimetry conversion factors, represented by the total conversion factor, prospectively estimate the maximum potential skin dose from the displayed air kerma. Air kerma-to-skin dose LUTs with corresponding tissue reactions and approximate time-of-onset can be posted for reference. By developing skin dose LUTs, physicians can actively evaluate during the procedure the potential for deterministic skin reactions. System user surveys evaluated the impact of LUTs on dose awareness. RESULTS: The range of the total conversion factor to the displayed air kerma for the nine systems evaluated was 0.8-1.6 for frontal x-ray tubes. Skin dose LUTs were posted in all imaging suites, and two surveys reported user feedback. Radiology technologists indicated that LUTs improved user dose awareness. Twelve of 14 physician respondents indicated an understanding that entrance skin dose is not equal to the displayed air kerma. CONCLUSION: Our efforts focused on educating fluoroscopy users about differences between displayed air kerma and the entrance skin dose while increasing dose awareness using an accessible and easy-to-understand tool. Skin dose LUTs provide physicians and staff an immediate reference for the maximum estimated entrance skin dose and the associated deterministic skin effects, allowing appropriate patient management.

Dual-energy liver CT: effect of monochromatic imaging on lesion detection, conspicuity, and contrast-to-noise ratio of hypervascular lesions on late arterial phase.

OBJECTIVE: The purpose of this study was to evaluate the effect of use of dual-energy CT monochromatic imaging in the late hepatic arterial phase on hyperenhancing focal lesion detection and lesion conspicuity. SUBJECTS AND METHODS: This prospective study included 72 patients imaged with a single-source dual-energy CT scanner. Late arterial phase imaging was performed with dual energies of 140 and 80 kVp, and the portal venous and delayed phases were performed with a single energy of 120 kVp. Two deidentified image sets were created: set A consisted of 77-keV images only, and set B consisted of 40-, 50-, 70-, and 77-keV images and iodine-based contrast material decomposition images. Two independent reviewers identified hypervascular lesions and subjectively scored lesion conspicuity. Contrast-to-noise ratios were calculated, and radiation dose (volume CT dose index) was recorded. RESULTS: The 128 lesions identified had a mean size of 1.7 ± 1.4 cm. There was no difference in lesion detection between the two reviewers or the two image sets. The contrast-to-noise ratio at 50 keV was 72% greater than that at 77 keV (p < 0.0001). Subjective conspicuity was statistically greatest at 50 keV (p < 0.0001). There was no statistical difference in mean volume CT dose index between the dual-energy (12.8 mGy) and the two single-energy (14.4 and 14.2 mGy) phases. CONCLUSION: Viewing dual-energy CT images may result in the greatest subjective lesion conspicuity and measured contrast-to-noise ratio at 50 keV with equal detection of hyperenhancing liver lesions compared with viewing 77-keV images alone. In addition, the radiation doses of dual-energy CT may be similar to those of single-energy CT.

Effective and organ specific radiation doses from videourodynamics in children.

PURPOSE: Effective and organ specific doses of ionizing radiation during videourodynamics are unknown. We estimated radiation exposure in children undergoing videourodynamics, and identified patient and examination factors that contribute to higher dosing. MATERIALS AND METHODS: Fluoroscopy data were collected from consecutive patients undergoing videourodynamics. Documented dose metrics were used to calculate entrance skin dose after applying a series of correction factors. Effective doses and organ specific doses (ovaries/testes) were estimated from entrance skin dose using Monte Carlo methods on a mathematical anthropomorphic phantom (ages 0, 1, 5, 10 and 15 years). Regression analysis was performed to determine patient and procedural factors associated with higher dosing. RESULTS: A total of 100 children (45% male, mean ± SD age 9.3 ± 5.7 years) were studied. Diagnoses included neurogenic bladder (73%), anatomical abnormality (14%) and functional/nonneurogenic disorder (13%). Mean fluoroscopy time was 0.17 ± 0.12 minutes. Mean age adjusted entrance skin dose, effective dose, and testis and ovary doses were 2.18 ± 2.00 mGy, 0.07 ± 0.05 mSv, 0.09 ± 0.10 mGy and 0.20 ± 0.13 mGy, respectively. On univariate analysis age, height, weight, body mass index, bladder capacity and fluoroscopy time were associated with effective dose. On multivariate adjusted analysis, body mass index, bladder capacity and fluoroscopy time were independently associated with effective dose. CONCLUSIONS: The average effective dose of ionizing radiation from videourodynamics was less compared to voiding cystourethrogram dose reported in the literature. Greater fluoroscopy time, body mass index and bladder capacity are independently associated with higher dosing.

Implementation of the ACR dose index registry at a large academic institution: early experience.

A rising conciousness within both the medical community and in the public has been created by the current levels of radiation exposure from increased use of computed tomography. The concern has prompted the need for more data collection and analysis of hospital and imaging center exam doses. This has spurred the American College of Radiology (ACR) to develop the Dose Index Registry (DIR), which will allow participating insitutions to compare the radiation dose from their CT exams to aggregate national CT dose data based on exam type and body part. We outline the steps involved in the process of enrolling in the DIR, the technical requirements, the challenges we encountered, and our solutions to those challenges. A sample of the quaterly report released by the ACR is presented and discussed. Enrolling in the ACR dose registry is a team effort with participation from IT, a site physicist, and a site radiologist. Participation in this registry is a great starting point to initiate a QA process for monitoring CT dose if none has been established at an institution. The ACR has developed an excellent platform for gathering, analyzing, and reporting CT dose data. Even so, each insititutions will have its own unique issues in joining the project.

Imaging of trauma: Part 2, Abdominal trauma and pregnancy--a radiologist's guide to doing what is best for the mother and baby.

OBJECTIVE: The pregnant trauma patient requires imaging tests to diagnose maternal injuries and diagnostic tests to evaluate the viability of her pregnancy. This article will discuss abdominal trauma in pregnancy and the specific role of diagnostic imaging. Radiation concerns in pregnancy will be addressed. CONCLUSION: Trauma is the leading cause of nonobstetric maternal mortality and a significant cause of fetal loss. Both major and minor trauma result in an increased risk of fetal loss. In major trauma, when there is concern for maternal injury, CT is the mainstay of imaging. The risks of radiation to the pregnancy are small compared with the risk of missed or delayed diagnosis of trauma. In minor trauma, when there is no concern for maternal injury but there is concern about the pregnancy, ultrasound is performed but is insensitive in diagnosing placental abruption. External fetal monitoring is used to dictate patient care.

Strategies to Optimize Nephrolithiasis Emergency Care (STONE): Prospective Evaluation of an Emergency Department Clinical Pathway.

OBJECTIVE: To convene a multi-disciplinary panel to develop a pathway for Emergency Department (ED) patients with suspected nephrolithiasis and then prospectively evaluate its effect on patient care. MATERIALS AND METHODS: The STONE Pathway was developed and linked to order sets within our Electronic Health Record in April 2019. Records were prospectively reviewed for ED patients who underwent ultrasound or Computerized Tomography (CT) to evaluate suspected nephrolithiasis between January 2019 and August 2019 within our institution. The primary outcome measure was the proportion of patients whose ED CT was low dose (<4 mSv). Secondary outcome measures included receipt of pathway-concordant pain medications and urine strainers. Order set utilization was evaluated as a process measure. Balance measures assessed included repeat ED visits, imaging, hospitalizations, and a urologic clinic visit or surgery within 30 days of discharge. RESULTS: 441 patients underwent ED imaging, of whom 261 (59%) were evaluated for suspected nephrolithiasis. The STONE Pathway was used in 50 (30%) eligible patients. Patients treated with the Pathway were more likely to undergo low-dose CTs (49% vs 23%, P <.001), and receive guideline-concordant pain medications such as NSAIDs (90% vs 62%, P <.001), and were less likely to return to the ED within 30 days (13% vs 2%, P = .01). These measures demonstrated special cause variation following Pathway release. CONCLUSION: Clinical pathways increase compliance with evidence-based practices for pain control and imaging in nephrolithiasis emergency care and may improve the delivery of value-based care.

Image noise and liver lesion detection with MDCT: a phantom study.

OBJECTIVE: The purpose of this study was to determine the upper limit of noise for detection of small low-contrast lesions in a liver phantom. MATERIALS AND METHODS: A CT liver phantom containing 21 low-contrast, low-attenuation, circular simulated lesions ranging in size from 2.4 to 10 mm was scanned 23 times at different tube current ranges (varying noise index) on a 64-MDCT scanner with automatic tube current modulation. The attenuation of the simulated lesions was 20 HU less than that of the liver-equivalent background. Three radiologists independently reviewed the resultant CT images, which contained either a low-contrast lesion or no lesion and scored certainty of lesion detection using a 4-point Likert scale. Overall performance was evaluated by sensitivity analysis with receiver operator curve and area under the curve (A(z)) computation for ranges of noise index. RESULTS: The reviewers achieved 100% sensitivity with a noise index of 15 or less for lesions measuring 6.3-10.0 mm (A(z) = 0.96). Increasing noise index to the 17-21 range resulted in a minor decrease in sensitivity and overall performance (sensitivity, 92.3%; A(z) = 0.93). A further increase in noise index to the 23-27 range resulted in a moderate decrease in sensitivity (sensitivity, 81.4%; A(z) = 0.77). Beyond the noise index 23-27 range, sensitivity dropped markedly from 81.4% to 39%. Agreement between the three readers in assessing the image sets was moderate. CONCLUSION: For detection of small low-contrast lesions in the liver phantom model used in this study, the upper limit of noise index may be in the 15-21 range for sensitivity greater than 90%.

The obese emergency patient: imaging challenges and solutions.

The dramatic rise in the prevalence of obesity among children and adults in the United States over the last several decades has brought several new challenges to the delivery of healthcare. The increased utilization of and dependence on imaging for accurate and timely diagnosis has placed the radiology department in a unique position in the provision of care for the obese emergency patient. Radiology practices must be cognizant of the imaging challenges presented by the obese patient and adjust their imaging algorithms accordingly to optimize all types of diagnostic studies. The article systematically reviews common pitfalls and offers methods to improve image quality when using radiography, ultrasonography, and computed tomography to image the obese patient population.

Utility of multiplanar and three-dimensional reconstructions from computed tomography performed for maternal indications for visualizing fetal anatomy and estimating gestational age.

OBJECTIVE: The purpose of this article was to determine the usefulness of multiplanar and 3-dimensional (3D) reconstructions of computed tomographic (CT) data from scans performed for maternal indications for visualizing fetal anatomy and estimating gestational age. MATERIALS AND METHODS: Eighteen pregnant patients who had abdominopelvic CT scanning performed for maternal indications formed the study group. Two independent reviewers created multiplanar and 3D-reconstructed images of the fetus from these CT scans and analyzed them for fetal anatomy and gestational age. Fetal dose estimates were also obtained. RESULTS: Computed tomographic fetal biometry generally agreed well with ultrasound estimates. Computed tomographic and ultrasound estimates were within 3 to 4 weeks of each other 95% of the time for the 2 reviewers. Pearson correlation coefficients were 0.989 for reviewer 1 and 0.985 for reviewer 2. Fetal anatomic survey revealed that it was easier to see bones and fluid-filled structures such as the stomach and urinary bladder than intracranial, intrathoracic, and intra-abdominal soft tissue structures. Estimated fetal dose was 28.5 (10.7) mGy using the Imaging Performance Assessment of CT Scanner calculator and 23.7 (7.7) mGy when taking maternal perimeter and fetal depth into account with the method of Angel et al. CONCLUSIONS: It is technically feasible to produce clinically useful images of the fetus using standard multiplanar reconstructions and 3D algorithms already in place for CT scanning. As CT scans continue to be performed under certain circumstances, particularly the emergency department setting, evaluation of maternal CT scans for potentially useful information about the fetus such as gestational age and gross anatomic survey can be obtained at estimated fetal radiation doses much lower than the actionable level of 150 mGy.

Findings of the AAPM Ad Hoc committee on magnetic resonance imaging in radiation therapy: Unmet needs, opportunities, and recommendations.

The past decade has seen the increasing integration of magnetic resonance (MR) imaging into radiation therapy (RT). This growth can be contributed to multiple factors, including hardware and software advances that have allowed the acquisition of high-resolution volumetric data of RT patients in their treatment position (also known as MR simulation) and the development of methods to image and quantify tissue function and response to therapy. More recently, the advent of MR-guided radiation therapy (MRgRT) - achieved through the integration of MR imaging systems and linear accelerators - has further accelerated this trend. As MR imaging in RT techniques and technologies, such as MRgRT, gain regulatory approval worldwide, these systems will begin to propagate beyond tertiary care academic medical centers and into more community-based health systems and hospitals, creating new opportunities to provide advanced treatment options to a broader patient population. Accompanying these opportunities are unique challenges related to their adaptation, adoption, and use including modification of hardware and software to meet the unique and distinct demands of MR imaging in RT, the need for standardization of imaging techniques and protocols, education of the broader RT community (particularly in regards to MR safety) as well as the need to continue and support research, and development in this space. In response to this, an ad hoc committee of the American Association of Physicists in Medicine (AAPM) was formed to identify the unmet needs, roadblocks, and opportunities within this space. The purpose of this document is to report on the major findings and recommendations identified. Importantly, the provided recommendations represent the consensus opinions of the committee's membership, which were submitted in the committee's report to the AAPM Board of Directors. In addition, AAPM ad hoc committee reports differ from AAPM task group reports in that ad hoc committee reports are neither reviewed nor ultimately approved by the committee's parent groups, including at the council and executive committee level. Thus, the recommendations given in this summary should not be construed as being endorsed by or official recommendations from the AAPM.