Can optimized model-based iterative reconstruction improve the contrast of liver lesions in CT?

BACKGROUND: Computed tomography is a standard imaging procedure for the detection of liver lesions, such as metastases, which can often be small and poorly contrasted, and therefore hard to detect. Advances in image reconstruction have shown promise in reducing image noise and improving low-contrast detectability. PURPOSE: To examine a novel, specialized, model-based iterative reconstruction (MBIR) technique for improved low-contrast liver lesion detection. MATERIAL AND METHODS: Patient images with reported poorly contrasted focal liver lesions were retrospectively reconstructed with the low-contrast attenuating algorithm (FIRST-LCD) from primary raw data. Liver-to-lesion contrast, signal-to-noise, and contrast-to-noise ratios for background and liver noise for each lesion were compared for all three FIRST-LCD presets with the established hybrid iterative reconstruction method (AIDR-3D). An additional visual conspicuity score was given by two experienced radiologists for each lesion. RESULTS: A total of 82 lesions in 57 examinations were included in the analysis. All three FIRST-LCD algorithms provided statistically significant increases in liver-to-lesion contrast, with FIRSTMILD showing the largest increase (40.47 HU in AIDR-3D; 45.84 HU in FIRSTMILD; P < 0.001). Substantial improvement was shown in contrast-to-noise metrics. Visual analysis of the lesions shows decreased lesion visibility with all FIRST methods in comparison to AIDR-3D, with FIRSTSTR showing the closest results (P < 0.001). CONCLUSION: Objective image metrics show promise for MBIR methods in improving the detectability of low-contrast liver lesions; however, subjective image quality may be perceived as inferior. Further improvements are necessary to enhance image quality and lesion detection.

Reliability of NI-RADS criteria in the interpretation of contrast-enhanced magnetic resonance imaging considering the potential role of diffusion-weighted imaging.

OBJECTIVES: To assess inter- and intrareader agreement of the Neck Imaging Reporting and Data System (NI-RADS) used in contrast-enhanced magnetic resonance imaging (MRI) including analysis of diffusion-weighted imaging (DWI), which is currently not part of the NI-RADS criteria. METHODS: This retrospective study included anonymized surveillance contrast-enhanced MRI datasets of 104 patients treated for different head and neck cancers. Three radiologists experienced in head and neck imaging reported findings for the primary site and the neck using NI-RADS criteria in a first step and evaluated DWI sequences for the primary site in a second step. Thirty randomly selected imaging datasets were again presented to the readers. Kappa statistics and observed agreement (Ao) were calculated. RESULTS: Interreader agreement across all MRI datasets was moderate (κFleiss = 0.53) for NI-RADS categories assigned to the primary site, substantial for NI-RADS categories of the neck (κFleiss = 0.67), and almost perfect for DWI of the primary site (κFleiss = 0.83). Interreader agreement for the primary site was particularly low in cases of cancer recurrence (κFleiss = 0.35) and when categories 2a, 2b, and 3 were combined (κFleiss = 0.30). Intrareader agreement was considerably lower for NI-RADS categories of the primary site (range Ao = 53.3-70.0%) than for NI-RADS categories of the neck (range Ao = 83.3-90.0%) and DWI of the primary site (range Ao = 93.3-100.0%). CONCLUSION: Interreader agreement of NI-RADS for reporting contrast-enhanced MRI findings is acceptable for the neck but limited for the primary site. Here, DWI has the potential to serve as a reliable additional criterion. KEY POINTS: • NI-RADS was originally designed for contrast-enhanced computed tomography with or without positron emission tomography but can also be used for contrast-enhanced magnetic resonance imaging alone. • Overall interreader agreement was acceptable for NI-RADS categories assigned to the neck but should be improved for the primary site, where it was inferior to DWI; similar tendencies were found for intrareader agreement. • DWI is currently no criterion of NI-RADS, but has shown potential to improve its reliability, especially for categories 2a, 2b, and 3 of the primary site.

Retrospective Evaluation of NI-RADS for Detecting Postsurgical Recurrence of Oral Squamous Cell Carcinoma on Surveillance CT or MRI.

BACKGROUND. Imaging surveillance is important for the early diagnosis of recurrence after definitive treatment of oral squamous cell carcinoma (OSCC). The Neck Imaging Reporting and Data System (NI-RADS) includes a standardized template for surveillance imaging and categorizes probability of recurrence at the primary site and in the neck (cervical lymph nodes) by assigning categories of 1 (no evidence of recurrence), 2 (low suspicion, subdivided into 2a and 2b for the primary site), 3 (high suspicion), and 4 (definite recurrence). OBJECTIVE. The aim of this study was to determine the rate of locoregional and nodal OSCC recurrence stratified by NI-RADS category among patients undergoing surveillance CT or MRI. METHODS. This retrospective study included 158 patients enrolled in an institutional surveillance program after resection of OSCC with curative intent. A total of 503 contrast-enhanced CT or MRI examinations performed during surveillance were evaluated. Each examination was randomly assigned to one of four radiologists with expertise in head and neck imaging, who provided NI-RADS categories for the primary site and the neck (1006 assigned NI-RADS categories). NI-RADS performance in identifying recurrence was assessed by ROC curve analysis. All four readers evaluated 50 randomly assigned cases to determine interreader agreement by use of the Kendall W statistic. RESULTS. Cancer recurrence was confirmed in 7.6% (38/503) of cases for the primary site and in 6.2% (31/503) for the neck. For the primary site, recurrence rates were 1.0% in NI-RADS category 1, 7.1% in category 2a, 5.6% in category 2b, 66.7% in category 3, and 100.0% in category 4. For the neck, recurrence rates were 0.5% in category 1, 7.0% in category 2, 80.0% in category 3, and 100.0% in category 4. NI-RADS had AUC values of 0.934 for the primary site and 0.959 for the neck. Interreader agreement was 0.67 for the primary site and 0.81 for the neck. CONCLUSION. NI-RADS offers excellent discriminatory power in detection of OSCC recurrence, both for the primary site and the neck. CLINICAL IMPACT. Radiologists and maxillofacial surgeons should implement NI-RADS in surveillance regimens for postoperative OSCC to help detect recurrences in an effective and standardized manner using imaging.

Periradicular infiltration of the lumbar spine: is iterative reconstruction software necessary to establish ultra-low-dose protocols? A quantitative and qualitative approach.

PURPOSE: Computed tomography (CT)-guided periradicular infiltration therapy has emerged as an effective treatment option for patients with low back pain. Concern about radiation exposure requires approaches allowing significant dose reduction. The purpose of this study is to evaluate the need for iterative reconstruction software in CT-guided periradicular infiltration therapy with an ultra-low-dose protocol. MATERIALS AND METHODS: One hundred patients underwent CT-guided periradicular infiltration therapy of the lumbar spine using an ultra-low-dose protocol with adaptive iterative dose reduction 3D (AIDR 3D) for image reconstruction. In addition, images were reconstructed with filtered back-projection (FBP). Four experienced raters evaluated both reconstruction types for conspicuity of anatomical and instrumental features important for ensuring safe patient treatment. Image noise was measured as a quantitative marker of image quality. RESULTS: Interrater agreement was good for both AIDR 3D (Kendall's W = 0.83) and FBP (0.78) reconstructions. Readers assigned the same scores for all features and both reconstruction algorithms in 81.3% of cases. Image noise was significantly lower (average SD of 60.07 vs. 99.54, p < 0.05) for AIDR 3D-reconstructed images. CONCLUSION: Although it significantly lowers image noise, iterative reconstruction software is not mandatory to achieve adequate image quality with an ultra-low-dose CT protocol for guiding periradicular infiltration therapy of the lumbar spine.

Periradicular infiltration of the lumbar spine: testing the robustness of an interventional ultra-low-dose protocol at different body mass index levels.

Background Computed tomography (CT)-guided periradicular infiltration remains a frequent interventional procedure for treatment of low back pain. Purpose To present an interventional ultra-low-dose protocol for CT-guided periradicular infiltration therapy and assess its application at different body mass index (BMI) levels. Material and Methods Over a period of 14 months, 79 patients underwent 183 CT-guided interventions for single-site lumbar periradicular therapy using an ultra-low-dose protocol with a basic setup of 100 kV and 5 mAs. Procedures were performed via intermittent fluoroscopy. A retrospective review was performed to analyze the parameters tube current and tube voltage, dose-length product, and BMI. Results The interventional ultra-low-dose protocol allowed safe treatment of 91.1% of the patients without a need for adapting the protocol. In seven patients with a higher BMI (range, 31-38 kg/m2; mean, 34 kg/m2), the tube current had to be increased to retain sufficient image quality. Only patients with a BMI of 30 and higher showed a significant correlation between BMI and dose-length product ( P value = 0.02), resulting in a slightly increased dose ( P value = 0.002). Conclusion The protocol presented for the interventional part of CT-guided periradicular infiltration allows to safely treat patients with a median calculated effective dose of 0.045 mSv (converted from a dose-length-product of 2.26 mGy*cm). Patients with a BMI of 30 and higher required a higher calculated effective dose with just one patient slightly exceeding 0.1 mSv.

Ultra-low-dose periradicular infiltration of the lumbar spine: spot scanning and its potential for further dose reduction by replacing helical planning CT.

PURPOSE: Computed tomography (CT)-guided periradicular infiltration has become an accepted procedure for treating radiculopathy-associated low back pain. The purpose of this study is to compare spot scanning and segmental helical planning CT in terms of dose reduction. MATERIALS AND METHODS: Eighty-five patients underwent CT-guided single-site lumbar periradicular therapy. Prior imaging was not available for planning. Sixty-three patients were examined with a new dedicated spot scanning technique (group I), and twenty-two patients underwent conventional segmental planning CT examinations with helical image acquisition serving as controls (group II). Examinations were reviewed retrospectively for dose-length product (DLP) and number of acquisitions required for intervention. Pain reduction accomplished with the intervention was recorded for quality assurance. RESULTS: Median DLP was 0.80 mGy cm for spot scanning versus 6.50 mGy cm for segmental planning CT. Thus, the contribution of the planning scan to the total interventional dose decreased from 73 to 25%. As a result, the total interventional dose was reduced significantly from a median DLP of 8.90 mGy cm to 3.20 mGy cm (-64%). Acquisitions required during the intervention had a median DLP of 2.40 mGy cm for group I and 2.35 mGy cm for group II, showing no significant difference. Median pain reduction in both groups was two points on the numeric rating scale. CONCLUSION: Dedicated spot scanning for planning reduced the total median effective dose of the intervention by more than 64% without increasing the number of images required during the interventional procedure. Significant pain reduction was achieved with both approaches. Spot scanning is recommended for dose reduction.

The role of iodinated contrast media in computed tomography structured Reporting and Data Systems (RADS): a narrative review.

Background and Objective: In recent years, there has been a large-scale dissemination of guidelines in radiology in the form of Reporting & Data Systems (RADS). The use of iodinated contrast media (ICM) has a fundamental role in enhancing the diagnostic capabilities of computed tomography (CT) but poses certain risks. The scope of the present review is to summarize the current role of ICM only in clinical reporting guidelines for CT that have adopted the "RADS" approach, focusing on three specific questions per each RADS: (I) what is the scope of the scoring system; (II) how is ICM used in the scoring system; (III) what is the impact of ICM enhancement on the scoring. Methods: We analyzed the original articles for each of the latest versions of RADS that can be used in CT [PubMed articles between January, 2005 and March, 2023 in English and American College of Radiology (ACR) official website]. Key Content and Findings: We found 14 RADS suitable for use in CT out of 28 RADS described in the literature. Four RADS were validated by the ACR: Colonography-RADS (C-RADS), Liver Imaging-RADS (LI-RADS), Lung CT Screening-RADS (Lung-RADS), and Neck Imaging-RADS (NI-RADS). One RADS was validated by the ACR in collaboration with other cardiovascular scientific societies: Coronary Artery Disease-RADS 2.0 (CAD-RADS). Nine RADS were proposed by other scientific groups: Bone Tumor Imaging-RADS (BTI-RADS), Bone­RADS, Coronary Artery Calcium Data & Reporting System (CAC-DRS), Coronavirus Disease 2019 Imaging-RADS (COVID-RADS), COVID-19-RADS (CO-RADS), Interstitial Lung Fibrosis Imaging-RADS (ILF-RADS), Lung-RADS (LU-RADS), Node-RADS, and Viral Pneumonia Imaging-RADS (VP-RADS). Conclusions: This overview suggests that ICM is not strictly necessary for the study of bones and calcifications (CAC-DRS, BTI-RADS, Bone-RADS), lung parenchyma (Lung-RADS, LU-RADS, COVID-RADS, CO-RADS, VP-RADS and ILF-RADS), and in CT colonography (C-RADS). On the other hand, ICM plays a key role in CT angiography (CAD-RADS), in the study of liver parenchyma (LI-RADS), and in the evaluation of soft tissues and lymph nodes (NI-RADS, Node-RADS). Future studies are needed in order to evaluate the impact of the new iodinated and non-iodinate contrast media, artificial intelligence tools and dual energy CT in the assignment of RADS scores.

Impact of double reading on NI-RADS diagnostic accuracy in reporting oral squamous cell carcinoma surveillance imaging - a single-center study.

OBJECTIVES: The Neck Imaging Reporting and Data System (NI-RADS) is an increasingly utilized risk stratification tool for imaging surveillance after treatment for head and neck cancer. This study aims to measure the impact of supervision by subspecialized radiologists on diagnostic accuracy of NI-RADS when initial reading is performed by residents. METHODS: 150 CT and MRI datasets were initially read by two trained residents, and then supervised by two subspecialized radiologists. Recurrence rates by NI-RADS category were calculated, and receiver operating characteristic (ROC) curves were plotted. After dichotomization of the NI-RADS system (category 1 vs categories 2 + 3+4 and categories 1 + 2 vs 3 + 4), sensitivity, specificity, positive and negative predictive value were calculated. RESULTS: 26% of the reports were modified by the supervising radiologists. Area under the curve of ROC plots values of the supervision session were higher than those of the initial reading session for both the primary site (0.89 vs 0.86) and the neck (0.94 vs 0.91), but the difference was not statistically significant. For dichotomized NI-RADS category assignments, differences between the initial reading and the supervision session were statistically significant regarding specificity and PPV for the primary site (1 + 2 vs 3 + 4 and 1 vs 2 + 3+4) or even for both sites combined (1 vs 2 + 3+4). CONCLUSION: NI-RADS enables trained resident radiologists to report surveillance imaging in patients with treated oral squamous cell carcinoma with high discriminatory power. Additional supervision by a subspecialized head and neck radiologist particularly improves specificity of radiological reports.

Multifrequency magnetic resonance elastography-based tomoelastography of the parotid glands-feasibility and reference values.

OBJECTIVES: Accurate radiological differentiation of parotid tumors remains challenging despite recent technical advances in quantitative medical imaging. Multifrequency magnetic resonance elastography (MRE) could provide additional information on viscoelastic properties of normal and abnormal biological tissues. This study investigates the feasibility of MRE of the parotid glands in healthy participants and provides first reference values. METHODS: 20 healthy participants underwent multifrequency MRE of both parotid glands at 3 Tesla. Shear waves at frequencies of 25, 30, 40, and 50 Hz were introduced into the participants' heads through the occiput using pressurized-air actuators. Shear wave speed (SWS) and loss angle of the shear modulus (φ) were reconstructed by tomoelastography post-processing as surrogate parameters for tissue stiffness and viscosity or fluidity. 10 participants underwent repeated MRE to determine test-retest reliability based on intraclass correlation coefficients. RESULTS: All MRE datasets acquired could be included in the analysis. Mean SWS was 0.97 ± 0.13 m/s, and mean φ was 0.59 ± 0.05 rad, each for both sides combined and without notable lateral difference (p = 0.88/0.87). Test-retest reliability was good for SWS (ICC = 0.84 for both sides/ICC = 0.77 for the right side/ICC = 0.79 for the left side) and good to excellent for φ(ICC = 0.94/0.86/0.90). CONCLUSIONS: Multifrequency MRE of the parotid glands is feasible and reliable. This technique, therefore, is a promising method for investigating the viscoelastic properties of salivary gland tumors in future studies.

Periradicular Infiltration of the Cervical Spine: How New CT Scanner Techniques and Protocol Modifications Contribute to the Achievement of Low-Dose Interventions.

PURPOSE: CT-guided periradicular infiltration of the cervical spine is an effective symptomatic treatment in patients with radiculopathy-associated pain syndromes. This study evaluates the robustness and safety of a low-dose protocol on a CT scanner with iterative reconstruction software. MATERIALS AND METHODS: A total of 183 patients who underwent periradicular infiltration therapy of the cervical spine were included in this study. 82 interventions were performed on a new CT scanner with a new intervention protocol using an iterative reconstruction algorithm. Spot scanning was implemented for planning and a basic low-dose setup of 80 kVp and 5 mAs was established during intermittent fluoroscopy. The comparison group included 101 prior interventions on a scanner without iterative reconstruction. The dose-length product (DLP), number of acquisitions, pain reduction on a numeric analog scale, and protocol changes to achieve a safe intervention were recorded. RESULTS: The median DLP for the whole intervention was 24.3 mGy*cm in the comparison group and 1.8 mGy*cm in the study group. The median pain reduction was -3 in the study group and -2 in the comparison group. A 5 mAs increase in the tube current-time product was required in 5 patients of the study group. CONCLUSION: Implementation of a new scanner and intervention protocol resulted in a 92.6 % dose reduction without a compromise in safety and pain relief. The dose needed here is more than 75 % lower than doses used for similar interventions in published studies. An increase of the tube current-time product was needed in only 6 % of interventions. KEY POINTS: · The presented ultra-low-dose protocol allows for a significant dose reduction without compromising outcome.. · The protocol includes spot scanning for planning purposes and a basic setup of 80 kVp and 5 mAs.. · The iterative reconstruction algorithm is activated during fluoroscopy.. CITATION FORMAT: · Elsholtz FH, Kamp JE, Vahldiek JL et al. Periradicular Infiltration of the Cervical Spine: How New CT Scanner Techniques and Protocol Modifications Contribute to the Achievement of Low-Dose Interventions. Fortschr Röntgenstr 2019; 191: 54 - 61.

The CDD System in Computed Tomographic Diagnosis of Diverticular Disease.

Purpose This overview sums up the Classification of Diverticular Disease (CDD) with regard to its application in computed tomographic diagnosis and briefly recapitulates its targeted advantages over preliminary systems. Primarily, application of the CDD in computed tomography diagnostics is described. Differences with respect to the categories of the older systems are pointed out on the level of each CDD type using imaging examples. Materials and Methods The presented images are derived from our institute according to the S2k criteria. Literature was researched on PubMed. Results The CDD constitutes an improvement compared to older systems for categorizing the stages of diverticular disease. It provides more discriminatory power on the descriptive-morphological level and defines as well as differentiates more courses of the disease. Furthermore, the categories translate more directly into state-of-the-art decision-making concerning hospitalization and therapy. Conclusion The CDD should be applied routinely in the computed tomographic diagnosis of diverticular disease. Typical imaging patterns are presented. Key points · The CDD is superior to its predecessors. It better stratifies categories of diverticular disease by morphology, course and modern options for treatment of the disease.. · Computed tomography is the dominant imaging modality. Different stages show typical imaging patterns.. · Non-abscessed phlegmonous peridiverticulitis is now interpreted as an uncomplicated course.. · Minimal paracolic air does not constitute a full-fledged perforation in terms of a pneumoperitoneum (CDD type 2c).. Citation Format · Pustelnik D, Elsholtz FH, Bojarski C et al. The CDD System in Computed Tomographic Diagnosis of Diverticular Disease. Fortschr Röntgenstr 2017; 189: 740 - 747.