CT Noise-Reduction Methods for Lower-Dose Scanning: Strengths and Weaknesses of Iterative Reconstruction Algorithms and New Techniques.

Iterative reconstruction (IR) algorithms are the most widely used CT noise-reduction method to improve image quality and have greatly facilitated radiation dose reduction within the radiology community. Various IR methods have different strengths and limitations. Because IR algorithms are typically nonlinear, they can modify spatial resolution and image noise texture in different regions of the CT image; hence traditional image-quality metrics are not appropriate to assess the ability of IR to preserve diagnostic accuracy, especially for low-contrast diagnostic tasks. In this review, the authors highlight emerging IR algorithms and CT noise-reduction techniques and summarize how these techniques can be evaluated to help determine the appropriate radiation dose levels for different diagnostic tasks in CT. In addition to advanced IR techniques, we describe novel CT noise-reduction methods based on convolutional neural networks (CNNs). CNN-based noise-reduction techniques may offer the ability to reduce image noise while maintaining high levels of image detail but may have unique drawbacks. Other novel CT noise-reduction methods are being developed to leverage spatial and/or spectral redundancy in multiphase or multienergy CT. Radiologists and medical physicists should be familiar with these different alternatives to adapt available CT technology for different diagnostic tasks. The scope of this article is (a) to review the clinical applications of IR algorithms as well as their strengths, weaknesses, and methods of assessment and (b) to explore new CT image reconstruction and noise-reduction techniques that promise to facilitate radiation dose reduction. ©RSNA, 2021.

The added value of contrast-enhanced ultrasound in evaluation of indeterminate small solid renal masses and risk stratification of cystic renal lesions.

OBJECTIVES: To investigate accuracy of contrast-enhanced ultrasound (CEUS) to characterize indeterminate small solid renal masses (sSRMs), excluding lipid-rich AMLs, and cystic renal masses (CRMs) according to the proposed Bosniak Classification 2019 MATERIALS AND METHODS: CEUS of pathology-proven CRMs and sSRMs (without definite enhancement or macroscopic fat on CT/MRI), and CRMs with ≥18 months follow-up were retrospectively reviewed. Two radiologists blindly categorized CRMs according to new Bosniak Classification on CT/MRI. On CEUS, two other radiologists evaluated arterial-phase enhancement of sSRMs relative to renal cortex and categorized CRMs following new Bosniak Classification. Fisher's exact/chi-squared test was used to compare categorical variables, and Cohen κ statistics for inter-observer agreement RESULTS: A total of 237 patients had 241 lesions: 161 pathology-proven sSRMs (122 malignant and 39 benign), 29 pathology-proven CRMs, 51 CRMs with adequate follow-up. Arterial-phase enhancement < renal cortex predicted malignancy with specificity of 97.4% (38/39) (CI 85.6-99.9%), and positive predictive value (PPV) of 98.2% (54/55) (CI 90.4-99.9%). Inter-observer kappa was 0.95. In pathology-proven CRMS, sensitivity of CEUS vs CT/MRI was 100% (15/15) (CI 79.6-100%) vs 60% (9/15) (CI 35.8-80.1%) (p value = .002) and negative predictive value (NPV) 100% (2/2) (CI 17.8-100%) vs 25% (2/8 ) (CI 4.4-59.1%) (p value < 0.0001), with similar specificity (50%) and PPV- 88.2% (15/17) (CI 65.7-97.9%) vs 81.8% (9/11) (CI 52.3-96.8%) ( p value = 0.586). Bosniak Classification inter-observer kappa was 0.92 for CEUS vs 0.68 for CT/MRI (p value = 0.009). CONCLUSION: In our cohort, CEUS had high specificity and PPV to diagnose RCC in sSRMs excluding lipid-rich AML. CEUS had significantly higher sensitivity/NPV to diagnose malignancy in CRMs as compared to CT/MRI. KEY POINTS: • Once lipid-rich AML is excluded by the other modalities, sSRM arterial phase hypo-enhancement relative to renal cortex on CEUS yielded high specificity (97.4%) and PPV (98.2%) to diagnose RCC. • When applying the proposed Bosniak Classification 2019, CEUS showed higher sensitivity compared to CT/MRI (100% vs 60%), p value=.0024, in the stratification of cystic renal masses to diagnose malignancy. • CEUS may reduce the number of CT/MRI Bosniak IIF lesions by assigning them to either II or III/IV categories.

Magnetic Resonance in Crohn's Disease: Diagnosis, Disease Burden, and Classification.

Magnetic resonance enterography (MRE) is an established test in patients with Crohn because of its ability to display transmural enteric inflammation and treatment response throughout the gastrointestinal tract without the very low potential risk of ionizing radiation. This article discusses how and when to diagnose Crohn disease with MRE (including discussion of the main differential diagnosis), how to describe the burden of enteric inflammation and its complications, and how to accurately classify disease based on interdisciplinary consensus. In addition, brief overviews of expected future MRE developments and alternative imaging modalities are also discussed.

State of the Art in Abdominal CT: The Limits of Iterative Reconstruction Algorithms.

The development and widespread adoption of iterative reconstruction (IR) algorithms for CT have greatly facilitated the contemporary practice of radiation dose reduction during abdominal CT examinations. IR mitigates the increased image noise typically associated with reduced radiation dose levels, thereby maintaining subjective image quality and diagnostic confidence for a variety of clinical tasks. Mounting evidence, however, points to important limitations of this method involving radiologists' ability to perform low-contrast diagnostic tasks, such as the detection of liver metastases or pancreatic masses. Radiologists need to be aware that use of IR can result in a decline of spatial resolution for low-contrast structures and degradation of low-contrast detectability when radiation dose reductions exceed approximately 25%. This article will review the principles of IR algorithm technology, describe the various commercial implementations of IR in CT, and review published studies that have evaluated the ability of IR to preserve diagnostic performance for low-contrast diagnostic tasks. In addition, future developments in CT noise reduction techniques and methods to rigorously evaluate their diagnostic performance will be discussed.

Retinoblastoma in a pediatric oncology reference center in Southern Brazil.

BACKGROUND: Retinoblastoma (Rb) is the most common intraocular tumor diagnosed in children in Brazil. However, detailed information is lacking regarding patient clinical demographics. This study aimed to determine the clinical profile of patients with Rb who were treated in a public university hospital in southern Brazil from 1983 to 2012. METHODS: Patients' medical records were reviewed to retrospectively identify patients with a principal diagnosis of Rb. Rb was classified as hereditary or non-hereditary. Clinical staging was reviewed by an ophthalmologist. Statistical analysis was performed using SPSS. RESULTS: Of 165 patients with a diagnosis of Rb during this period, 140 were included in the study. Disease was unilateral in 65.0 % of patients, bilateral in 32.9 %, and trilateral in 2.1 %. The mean age at onset of the first sign/symptom was 18.1 month, and 35.7 % of patients were diagnosed during the first year of life. The most common presenting signs were leukocoria (73.6 %) and strabismus (20.7 %). The mean age at diagnosis was 23.5 months, and time to diagnosis was 5.4 months. In patients with clinical features of hereditary Rb, both onset of the first sign/symptom and diagnosis were at an earlier age than in patients without these features (12.3 vs 21.6 months [P = 0.001] and 15.9 vs 28.0 months [P < 0.001], respectively). However, there was no significant difference in overall survival between the two groups. Ocular stage at diagnosis was advanced in 76.5 % (Reese V) and 78.1 % (International Classification D or E). Of patients with unilateral and bilateral disease, 35.2 % and 34.8 %, respectively, had extraocular disease at diagnosis; 10.7 % had metastatic disease at diagnosis. Enucleation was observed in 88.1 % and exenteration in 11.9 % of patients; 93.6 % patients were followed until 2012, and 22.9 % relapsed. Overall survival was 86.4 %. CONCLUSIONS: Most Rb diagnoses are still diagnosed in advanced stages of the disease, considerably reducing overall survival time and the rate of eye and vision preservation.

Ionizing radiation exposure is still increasing in Crohn's disease: Who should be blamed?

BACKGROUND AND AIM: Crohn's disease (CD) patients undergo many radiological studies employing ionizing radiation for diagnosis and management purposes. Our aim was to assess the total radiation exposure of our patients over the years, to estimate the risk factors for exposure to high doses, and to correlate radiation exposure to immunosuppression. METHODS: The cumulative effective dose of radiation (CEDR) was calculated multiplying the number of imaging studies by the effective dose of each examination. RESULTS: A total of 451 patients with CD (226 female) were followed during 11.0 years (interquartile range [IQR]: 6.0-16.0), with 52.1% of the patients being classified with penetrating (B3) and 38.6% being steroid-dependent. About 16% were exposed to high-radiation dose levels (CEDR >50 mSv) and 4% were exposed to CEDR >100 mSv. The mean CEDR between age 26 and 35 years was 12.539 mSv and a significant dose of radiation (over 50 mSv) was achieved at a median age of 40 (IQR: 29.0-47.0). Abdominal-pelvic computed tomography scan was the examination that contributed the most for CEDR. Patients with B3 phenotype, previous surgery, azathioprine, and anti-tumor necrosis factor (TNF)-α therapy were exposed earlier on the course of the disease to CEDR >50 mSv (p < 0.001). The value of CEDR in the patients under immunosuppression mainly increased in the first year of immunosuppression. CONCLUSION: Penetrating phenotype, abdominal surgery, steroid resistance or steroid dependence, and treatment with anti-TNF-α and azathioprine were predictive factors for high CEDR. It was also demonstrated that immunosuppression and anti-TNF-α treatment were followed by a sustained increment of radiation exposure and that a significant dose of radiation was achieved <40 years of age.

Invasive micropapillary carcinoma of the breast: imaging features with clinical and pathologic correlation.

OBJECTIVE: The purpose of this article is to present imaging findings of invasive ductal carcinoma with micropapillary features with clinical and pathologic correlation. MATERIALS AND METHODS: We retrospectively searched our institution's surgical pathology database for patients with pathologically proven invasive ductal carcinoma with micropapillary features. Forty-one patients with images available for review were included in the study. Mammographic, sonographic, and MRI findings were assessed using the American College of Radiology's BI-RADS lexicon. Molecular breast imaging findings were reviewed using a molecular breast imaging lexicon. Imaging findings were correlated with clinical presentation and pathologic findings. RESULTS: Mammographically, the most common finding was an irregular spiculated mass. Sonographically, the most common finding was an irregular hypoechoic mass with spiculated margins and posterior acoustic shadowing. With MRI, the most common finding was an irregular mass with washout kinetics, but we also observed diffuse heterogeneous nonmasslike enhancement throughout the breast. Molecular breast imaging was available for one patient and showed multicentric radiotracer uptake. Analysis of 39 pathologic specimens showed 27 (69%) with angiolymphatic invasion. Axillary nodal metastases were present in 23 patients (59%), nine (23%) with extranodal extension. CONCLUSION: The imaging features of invasive ductal carcinoma of the breast with micropapillary features typically were highly suggestive of malignancy. The malignancies were strongly associated with lymphovascular invasion and lymph node metastases. Radiologists should be aware of the imaging features of this unusual variant and should consider axillary sonography if this entity is found in a core needle biopsy specimen.

Noise reduction to decrease radiation dose and improve conspicuity of hepatic lesions at contrast-enhanced 80-kV hepatic CT using projection space denoising.

OBJECTIVE: The purpose of this study was to investigate the combined potential of 80-kV CT and noise reduction using a projection space denoising algorithm to reduce radiation dose reduction or to improve the image quality of hepatic CT. MATERIALS AND METHODS: Twenty patients with 56 liver lesions underwent dual-energy (80 and 140 kV) contrast-enhanced hepatic CT. Low-dose 80-kV-only images (comprising 26-54% of the total radiation dose), low-dose 80-kV projection space denoising images (routine and sharper reconstruction kernel), and full-dose mixed-kilovoltage with projection space denoising images were evaluated by three radiologists for lesion conspicuity, image noise, and sharpness. Lesions were compared with full-dose images using 5-point scales (0 = no change, +2 = markedly better, and -2 = markedly worse). Quantitative conspicuity in the form of lesion-to-liver contrast-to-noise ratio (CNR), image noise, and image sharpness were measured. RESULTS: For all readers, the mean conspicuity rating of low-dose 80-kV projection space denoising images was better than that for full-dose images (mean conspicuity, 0.36-0.57; p < 0.001), with only 1.2% of lesions less conspicuous on 80-kV projection space denoising images. Eighty-kilovolt projection space denoising images reconstructed with a sharper kernel were subjectively similar to full-dose mixed-kilovoltage images comparing image noise (-0.054 to 0.018; p < 0.001 to p = 0.058) and sharpness (-0.64 to -0.09; p < 0.001 to p = 0.057). For 80-kV projection space denoising images with a sharper kernel, lesion-to-liver CNR was slightly higher than that for full-dose mixed-kilovoltage images (p < 0.001), whereas image sharpness and noise were unchanged (p = 0.74 and p = 0.02). CONCLUSION: Eighty-kilovolt imaging with noise reduction can simultaneously increase lesion conspicuity and facilitate radiation dose reduction and image quality improvement at contrast-enhanced hepatic CT.

Identification of intraarticular and periarticular uric acid crystals with dual-energy CT: initial evaluation.

PURPOSE: To estimate the accuracy, sensitivity, specificity, and interobserver agreement of dual-energy computed tomography (CT) in detection of uric acid crystals in joints or periarticular structures in patients with arthralgia and patients suspected of having gout, with joint aspiration results as reference standard. MATERIALS AND METHODS: With institutional review board approval, patient consent, and HIPAA compliance, 94 patients (age range, 29-89 years) underwent dual-source, dual-energy (80 and 140 kVp) CT of a painful joint. A material decomposition algorithm was used to identify uric acid. Two blinded musculoskeletal radiologists evaluated the dual-energy CT images and classified the examination findings as positive or negative for the presence of uric acid crystals. Reference standard was the result of joint aspiration. RESULTS: Forty-three of 94 patients (46%) underwent attempted joint aspiration within 1 month of dual-energy CT. Aspiration was successful in 31 of 43 patients (72%). In 12 of 31 patients (39%), uric acid crystals were identified at joint aspiration; in 19 patients, they were not. Readers 1 and 2 had no false-negative findings for uric acid at dual-energy CT. Sensitivity was 100% (12 of 12; 95% confidence interval (CI): 74%, 100%) for both readers. Specificity was 89% (17 of 19; 95% CI: 67%, 99% ) for reader 1 and 79% (15 of 19; 95% CI: 54%, 94%) for reader 2, with near-perfect agreement between the readers (κ = 0.87; range, 0.70-1.00) in the 31 patients who underwent aspiration. CONCLUSION: Initial retrospective assessment suggests that dual-energy CT is a sensitive, noninvasive, and reproducible method for identifying uric acid deposits in joints and periarticular soft tissues in patients suspected of having gout.

Prospective blinded comparison of wireless capsule endoscopy and multiphase CT enterography in obscure gastrointestinal bleeding.

PURPOSE: To compare the performance of multiphase computed tomographic (CT) enterography with that of capsule endoscopy in a group of patients with obscure gastrointestinal bleeding (OGIB). MATERIALS AND METHODS: This prospective HIPAA-compliant study was approved by the institutional review board and the institutional conflict of interest committee. All patients provided written informed consent. Two radiologists, blinded to clinical data and results of capsule endoscopy, interpreted images from CT enterography independently, with discordant interpretations resolved by consensus. Results were compared with those from a reference standard (surgery or endoscopy) and clinical follow-up. Sensitivity and 95% confidence intervals were calculated for each modality. RESULTS: Fifty-eight adult patients, referred for the evaluation of OGIB (occult, 25 patients [43%]; overt, 33 patients [57%]), underwent both tests. A small bowel bleeding source was identified in 16 of the 58 patients (28%). The sensitivity of CT enterography was significantly greater than that of capsule endoscopy (88% [14 of 16 patients] vs 38% [six of 16 patients], respectively; P = .008), largely because it depicted more small bowel masses (100% [nine of nine patients] vs 33% [three of nine patients], respectively; P = .03). No additional small bowel tumors were discovered during the follow-up period (range, 5.6-45.9 months; mean, 16.6 months). CONCLUSION: In this referral population, the sensitivity of CT enterography for detecting small bowel bleeding sources and small bowel masses was significantly greater than that of capsule endoscopy. On the basis of these findings, the addition of multiphase CT enterography to the routine diagnostic work-up of patients with OGIB should be considered, particularly in patients with negative findings at capsule endoscopy.

Pilot multi-reader study demonstrating potential for dose reduction in dual energy hepatic CT using non-linear blending of mixed kV image datasets.

OBJECTIVE: To determine the potential for radiation dose reduction using sigmoidally-blended mixed-kV images from dual energy (DE) hepatic CT. METHODS: Multiple contrast-enhanced, DE (80 kV/140 kV) datasets were reconstructed from 34 patients undergoing clinically-indicated examinations using routine CTDI(vol). Noise was inserted in projection-space to simulate six dose levels reflecting 25-100% of the original dose. Three radiologists, blinded to dose, evaluated image preference, image quality, and diagnostic confidence (scale 1 to 5) using sigmoidally-blended, mixed-kV images, identifying the lowest acceptable dose (both image quality and confidence scores ≥4). At this lowest acceptable dose, the sigmoidal, 0.5 and 0.3 linear blended images were ranked in order of preference. RESULTS: Radiation dose level correlated with image preference (correlation coefficients = 0.94, 0.81, 0.94). However, 82% (28/34) and 97% (33/34) of examinations corresponding to dose reductions of 45% and 30%, respectively, yielded acceptable image quality and confidence for all three radiologists. These frequencies were similar whether or not a lesion was present. Each radiologist had specific preferences between mixed-kV image display techniques (p ≤ 0.006), with two most often preferring sigmoidally-blended images. CONCLUSIONS: There is potential for further dose reduction utilizing DE hepatic CT. Radiologist visual preference for mixed-kV images is idiosyncratic.

Appropriate patient selection at abdominal dual-energy CT using 80 kV: relationship between patient size, image noise, and image quality.

PURPOSE: To determine the computed tomographic (CT) detector configuration, patient size, and image noise limitations that will result in acceptable image quality of 80-kV images obtained at abdominal dual-energy CT. MATERIALS AND METHODS: The Institutional Review Board approved this HIPAA-compliant retrospective study from archival material from patients consenting to the use of medical records for research purposes. A retrospective review of contrast material-enhanced abdominal dual-energy CT scans in 116 consecutive patients was performed. Three gastrointestinal radiologists noted detector configuration and graded image quality and artifacts at specified levels-midliver, midpancreas, midkidneys, and terminal ileum-by using two five-point scales. In addition, an organ-specific enhancement-to-noise ratio and background noise were measured in each patient. Patient size was measured by using the longest linear dimension at the level of interest, weight, lean body weight, body mass index, and body surface area. Detector configuration, patient sizes, and image noise levels that resulted in unacceptable image quality and artifact rankings (score of 4 or higher) were determined by using multivariate logistic regression. RESULTS: A 14 × 1.2-mm detector configuration resulted in fewer images with unacceptable quality than did the 64 × 0.6-mm configuration at all anatomic levels (P = .004, .01, and .02 for liver, pancreas, and kidneys, respectively). Image acceptability for the kidneys and ileum was significantly greater than that for the liver for all readers and detector configurations (P < .001). For the 14 × 1.2-mm detector configuration, patient longest linear dimensions yielding acceptable image quality across readers ranged from 34.9 to 35.8 cm at the four anatomic levels. CONCLUSION: An 80-kV abdominal CT can be performed with appropriate diagnostic quality in a substantial percentage of the population, but it is not recommended beyond the described patient size for each anatomic level. The 14 × 1.2-mm detector configuration should be preferred.

Feasibility of dose reduction using novel denoising techniques for low kV (80 kV) CT enterography: optimization and validation.

RATIONALE AND OBJECTIVES: The aim of this study was to optimize and validate projection-space denoising (PSDN) strategies for application to 80-kV computed tomographic (CT) data to achieve 50% dose reduction. MATERIALS AND METHODS: Image data obtained at 80 kV (mean CT dose index volume, 7.9 mGy) from dual-source, dual-energy CT enterographic (CTE) exams in 42 patients were used. For each exam, nine 80 kV image data sets were reconstructed using PSDN (three levels of intensity) with or without image-based denoising and compared to commercial reconstruction kernels. For optimization, qualitative analysis selected optimal denoising strategies, with quantitative analysis measuring image contrast, noise, and sharpness (full width at half maximum bowel wall thickness, maximum CT number gradient). For validation, two radiologists examined image quality, comparing low-dose 80-kV optimally denoised images to full-dose mixed-voltage images. RESULTS: PSDN algorithms generated the best 80-kV image quality (41 of 42 patients), while the commercial kernels produced the worst (39 of 42) (P < .001). Overall, 80-kV PSDN approaches resulted in higher contrast (mean, 332 vs 290 Hounsfield units), slightly less noise (mean, 20 vs 26 Hounsfield units), but slightly decreased image sharpness (relative bowel wall thickness, 1.069 vs 1.000) compared to full-dose mixed-voltage images. Mean image quality scores for full-dose CTE images were 4.9 compared to 4.5 for optimally denoised half-dose 80-kV CTE images and 3.1 for nondenoised 80-kV CTE images (P < .001). CONCLUSION: Optimized denoising strategies improve the quality of 80-kV CTE images such that CT data obtained at 50% of routine dose levels approaches the image quality of full-dose exams.

Assessment of appropriateness of indications for CT enterography in younger patients.

BACKGROUND: The small potential risk of radiation-induced cancer is increased in younger patients undergoing serial imaging with computed tomography enterography (CTE). We sought to determine the appropriateness of CTEs based on clinical indication in patients < or =35 years old, and the potential impact of evolution of practice to alternative magnetic resonance enterography (MRE). METHODS: Over a 7-year period, the medical records of all patients < or =35 years old undergoing CTE were reviewed to determine the clinical indications for each CTE exam. An interdisciplinary consensus panel evaluated the appropriateness of all CTE exams based on American College of Radiology appropriateness criteria and peer-reviewed literature, classifying indications into "appropriate" or "inappropriate." For repeat CTEs, an "alternative MRE suggested" pathway was created. Criteria for evolution of practice to "alternative MRE" were suspicion of obstruction and evaluation of disease activity/therapeutic response in the absence of new symptoms. RESULTS: In all, 2022 patients < or =35 years old underwent 2295 CTEs. Ninety-nine percent (2008/2022) of first-time CTE exams were "appropriate" by the defined criteria. A total of 197 patients (9.7%) underwent multiple exams, with 73% of these patients having Crohn's disease. Repeat exams occurred in 9% (18/197) with obstructive symptoms and evaluation of disease activity/therapeutic response in the absence of new symptoms in 41% (80/197). CONCLUSIONS: A multidisciplinary expert panel concluded that the vast majority of young patients underwent clinically appropriate first-time CTE exams. However, a shift in clinical practice to MRE appears warranted for approximately half of young patients undergoing repeat CTE examinations.

Comparative study of two image space noise reduction methods for computed tomography: bilateral filter and nonlocal means.

Optimal noise control is important for improving image quality and reducing radiation dose in computed tomography. Here we investigated two image space based nonlinear filters for noise reduction: the bilateral filter (BF) and the nonlocal means (NLM) algorithm. Images from both methods were compared against those from a commercially available weighted filtered backprojection (WFBP) method. A standard phantom for quality assurance testing was used to quantitatively compare noise and spatial resolution, as well as low contrast detectability (LCD). Additionally, an image dataset from a patient's abdominal CT exam was used to assess the effectiveness of the filters on full dose and simulated half dose acquisitions. We found that both the BF and NLM methods improve the tradeoff between noise and high contrast spatial resolution with no significant difference in LCD. Results from the patient dataset demonstrated the potential of dose reduction with the denoising methods. Care must be taken when choosing the NLM parameters in order to minimize the generation of artifacts that could possibly compromise diagnostic value.

Metal artifact reduction from reformatted projections for hip prostheses in multislice helical computed tomography: techniques and initial clinical results.

PURPOSE: Hip prosthesis is one of the most common types of metal implants and can cause significant artifacts in computed tomography (CT) examinations. The purpose of this work was to develop a projection-based method for reducing metal artifacts caused by hip prostheses in multislice helical CT. METHOD AND MATERIALS: The proposed method is based on a novel concept, reformatted projection, which is formed by combining the projection data at the same view angle over the full longitudinal scan range. Detection and segmentation of the metal were performed on each reformatted projection image. Two dimensional interpolation based on Delaunay triangulation was used to fill voids left after removal of the metal in the reformatted projection. The corrected data were then reconstructed using a commercially available algorithm. The main advantage of this method is that both the detection of the metal objects and the interpolations are performed on complete reformatted projections with the entire metal region present, which is particularly useful for long hip prostheses. Twenty clinical abdominal/pelvis exams with hip prostheses were corrected and clinically evaluated. RESULTS: The overall image quality and the conspicuity in some critical organs were significantly improved compared with the uncorrected images: overall quality (P = 0.0024); bladder base (P = 0.0027), and rectum (P = 0.0078). The average noise level in the bladder base was reduced from 86.7 HU to 36.2 HU. In 17 of 20 cases, the radiologists preferred either coronal (13) or axial (4) views of the corrected images. CONCLUSIONS: A novel method for reducing metal artifact in multislice helical CT was developed. Initial clinical results showed that the proposed method can effectively reduce the artifacts caused by metal implants for the cases of unilateral and bilateral hip prothesis.

Small bowel obstruction: what to look for.

Small bowel obstruction (SBO) is a common clinical syndrome for which effective treatment depends on a rapid and accurate diagnosis. Despite advances in imaging and a better understanding of small bowel pathophysiology, SBO is often diagnosed late or misdiagnosed, resulting in significant morbidity and mortality. A comprehensive approach that includes clinical findings, patient history, and triage examinations such as plain abdominal radiography will help the clinician develop an individualized treatment plan. When an SBO is accompanied by signs of strangulation, emergent surgical treatment is advised. If surgery cannot be performed immediately or if a partial obstruction is suspected, then a more detailed radiologic work-up is needed. The imaging techniques used subsequently vary according to the initial findings. If a low-grade partial obstruction is suspected, volume-challenge enteral examinations such as enteroclysis and computed tomographic (CT) enteroclysis are preferred. If a complete or high-grade obstruction is suspected, cross-sectional studies such as ultrasonography or multidetector CT are used to exclude strangulation. An algorithmic approach to imaging is proposed for the management of SBO to achieve accurate diagnosis of the obstruction; determine its severity, site, and cause; and assess the presence of strangulation. Radiologists have a pivotal role in clinical decision making in cases of SBO by providing answers to specific questions that significantly affect management.