Magnetic Resonance Imaging of Pulmonary and Paranasal Sinus Abnormalities in Children with Primary Ciliary Dyskinesia Compared to Children with Cystic Fibrosis

Rationale: Primary ciliary dyskinesia (PCD) and cystic fibrosis (CF) are characterized by inherited impaired mucociliary clearance leading to chronic progressive lung disease as well as chronic rhinosinusitis (CRS). The diseases share morphological and functional commonalities on magnetic resonance imaging (MRI) of the lungs and paranasal sinuses, but comparative MRI studies are lacking. Objectives: To determine whether PCD shows different associations of pulmonary and paranasal sinus abnormalities on MRI and lung function test results in children (infants to adolescents) compared with children with CF. Methods: Eighteen children with PCD (median age, 9.5 [IQR, 3.4-12.7] yr; range, 0-18 yr) and 36 age-matched CF transmembrane conductance regulator modulator-naive children with CF (median age, 9.4 [3.4-13.2] yr; range, 0-18 yr) underwent same-session chest and paranasal sinus MRI as well as spirometry (to determine forced expiratory volume in 1 s percent predicted) and multiple-breath washout (to determine lung clearance index z-score). Pulmonary and paranasal sinus abnormalities were assessed using previously validated chest MRI and CRS-MRI scoring systems. Results: Mean chest MRI global score was similar in children with PCD and CF (15.0 [13.5-20.8] vs. 15.0 [9.0-15.0]; P = 0.601). Consolidations were more prevalent and severe in children with PCD (56% vs. 25% and 1.0 [0.0-2.8] vs. 0.0 [0.0-0.3], respectively; P < 0.05). The chest MRI global score correlated moderately with forced expiratory volume in 1 second percent predicted in children with PCD and children with CF (r = -0.523 and -0.687; P < 0.01) and with lung clearance index in children with CF (r = 0.650; P < 0.001) but not in PCD (r = 0.353; P = 0.196). CRS-MRI sum score and mucopyocele subscore were lower in children with PCD than in children with CF (27.5 [26.3-32.0] vs. 37.0 [37.8-40.0] and 2.0 [0.0-2.0] vs. 7.5 [4.8-9.0], respectively; P < 0.01). CRS-MRI sum score did not correlate with chest MRI score in PCD (r = 0.075-0.157; P = 0.557-0.788) but correlated moderately with MRI morphology score in CF (r = 0.437; P < 0.01). Conclusions: MRI detects differences in lung and paranasal sinus abnormalities between children with PCD and those with CF. Lung disease does not correlate with CRS in PCD but correlates in CF.

Elexacaftor/tezacaftor/ivacaftor improves chronic rhinosinusitis detected by magnetic resonance imaging in children with cystic fibrosis on long-term therapy with lumacaftor/ivacaftor

INTRODUCTION

Previous studies using magnetic resonance imaging (MRI) demonstrated early onset and progression of chronic rhinosinusitis (CRS) from infancy to school age, and response to lumacaftor/ivacaftor (LUM/IVA) therapy in children with cystic fibrosis (CF). However, the effect of elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) on CRS detected by MRI in children with CF and at least one F508del mutation, and potential incremental effects of ELX/TEZ/IVA compared to LUM/IVA in F508del homozygous children have not been studied.

METHODS

30 children with CF with at least one F508del mutation underwent three longitudinal paranasal sinus MRI before (MRI1), without (n = 16) or with LUM/IVA therapy (n = 14, MRI2), and with ELX/TEZ/IVA therapy (MRI3, mean age at therapy initiation 11.1 ± 3.4y, range 6-16y). MRI were evaluated using the CRS-MRI score.

RESULTS

After therapy initiation with ELX/TEZ/IVA, the prevalence and in maxillary and sphenoid sinuses the dominance of mucopyoceles decreased (35% vs. 0 %, p<0.001 and 26% vs. 8 %, p < 0.05, respectively). This leads to a reduction in mucopyocele subscore (-3.4 ± 1.9, p < 0.001), and sinus subscores in MRI3 (maxillary sinus: -5.3 ± 3.1, p < 0.001, frontal sinus: -1.0 ± 1.9, p < 0.01, sphenoid subscore: -2.8 ± 3.5, p < 0.001, ethmoid sinus: -1.7 ± 1.9, p < 0.001). The CRS-MRI sum score decreased after therapy initiation with ELX/TEZ/IVA by -9.6 ± 5.5 score points (p < 0.001). The strength in reduction of mucopyoceles subscore and CRS-MRI sum score was independent of a pretreatment with LUM/IVA from MRI1-MRI2 (p = 0.275-0.999).

CONCLUSIONS

ELX/TEZ/IVA therapy leads to improvement of CRS in eligible children with CF. Our data support the role of MRI for comprehensive monitoring of CRS disease severity and response to therapy in children with CF.

Detection and Quantitative Assessment of Arthroscopically Proven Long Biceps Tendon Pathologies Using T2 Mapping

This study evaluates how far T2 mapping can identify arthroscopically confirmed pathologies in the long biceps tendon (LBT) and quantify the T2 values in healthy and pathological tendon substance. This study comprised eighteen patients experiencing serious shoulder discomfort, all of whom underwent magnetic resonance imaging, including T2 mapping sequences, followed by shoulder joint arthroscopy. Regions of interest were meticulously positioned on their respective T2 maps, capturing the sulcal portion of the LBT and allowing for the quantification of the average T2 values. Subsequent analyses included the calculation of diagnostic cut-off values, sensitivities, and specificities for the detection of tendon pathologies, and the calculation of inter-reader correlation coefficients (ICCs) involving two independent radiologists. The average T2 value for healthy subjects was measured at 23.3 ± 4.6 ms, while patients with tendinopathy displayed a markedly higher value, at 47.9 ± 7.8 ms. Of note, the maximum T2 value identified in healthy tendons (29.6 ms) proved to be lower than the minimal value measured in pathological tendons (33.8 ms), resulting in a sensitivity and specificity of 100% (95% confidence interval 63.1-100) across all cut-off values ranging from 29.6 to 33.8 ms. The ICCs were found to range from 0.93 to 0.99. In conclusion, T2 mapping is able to assess and quantify healthy LBTs and can distinguish them from tendon pathology. T2 mapping may provide information on the (ultra-)structural integrity of tendinous tissue, facilitating early diagnosis, prompt therapeutic intervention, and quantitative monitoring after conservative or surgical treatments of LBT.

3-Tesla T2 Mapping Magnetic Resonance Imaging for Evaluation of SLAP Lesions in Patients with Shoulder Pain: An Arthroscopy-Controlled Study

This study investigated the ability of T2 mapping to assess the glenoid labrum and to differentiate between healthy labral substances and superior labral anterior posterior (SLAP) lesions using arthroscopy as the gold standard. Eighteen patients (mean age: 52.4 ± 14.72 years, 12 men) with shoulder pain were examined using 3-Tesla T2 mapping. All the patients underwent shoulder arthroscopy. Using morphological sequences for correlation, regions of interest covering the entire labral substance were placed in the corresponding T2 maps. The diagnostic cutoff values, sensitivities, and specificities, as well as the inter-reader correlation coefficients (ICCs) determined by two independent radiologists, were calculated. The mean T2 value was 20.8 ± 2.4 ms for the healthy labral substances and 37.7 ± 10.63 ms in the patients with SLAP lesions. The maximum T2 value in normal labrum (21.2 ms) was lower than the minimum T2 value in the patients with SLAP lesions (27.8 ms), leading to sensitivities, specificities, and positive and negative predictive values of 100% (95% CI 54.1-100.0) for all the cutoff values between 21.2 and 27.8 ms. The ICCs ranged from 0.91 to 0.99. In summary, the data suggest that evaluation and quantification of the labral (ultra)structural integrity using T2 mapping may allow discrimination between arthroscopically confirmed SLAP lesions and a healthy glenoid labrum. T2 mapping may therefore be helpful in diagnosing patients with suspected labral damage.

Long-term effects of lumacaftor/ivacaftor on paranasal sinus abnormalities in children with cystic fibrosis detected with magnetic resonance imaging

Introduction: Chronic rhinosinusitis (CRS) usually presents with nasal congestion, rhinorrhea and anosmia impacts quality of life in cystic fibrosis (CF). Especially mucopyoceles pathognomonic for CRS in CF may cause complications such as spread of infection. Previous studies using magnetic resonance imaging (MRI) demonstrated early onset and progression of CRS from infancy to school age in patients with CF, and mid-term improvements of CRS in preschool and school-age children with CF treated with lumacaftor/ivacaftor for at least 2 months. However, long-term data on treatment effects on paranasal sinus abnomalities in preschool and school-age children with CF are lacking. Methods: 39 children with CF homozygous for F508del (mean age at baseline MRI 5.9 ± 3.0 years, range 1-12 years) underwent MRI before (MRI1) and about 7 months after starting lumacaftor/ivacaftor and then annually (median 3 follow-up MRI, range 1-4) (MRI2-4). MRI were evaluated using the previously evaluated CRS-MRI score with excellent inter-reader agreement. For intraindividual analysis ANOVA mixed-effects analysis including Geisser-Greenhouse correction and Fisher's exact test, and for interindividual group analysis Mann-Whitney test were used. Results: The CRS-MRI sum score at baseline was similar in children starting lumacaftor/ivacaftor in school age and children starting therapy at preschool age (34.6 ± 5.2 vs.32.9 ± 7.8, p = 0.847). Mucopyoceles were the dominant abnormality in both, especially in maxillary sinus (65% and 55%, respectively). In children starting therapy in school age the CRS-MRI sum score decreased longitudinally from MRI1 to MRI2 (-2.1 ± 3.5, p < 0.05), MRI3 (-3.0 ± 3.7, p < 0.01) and MRI4 (-3.6 ± 4.7, p < 0.01), mainly due to a decrease in the mucopyoceles subscore (-1.0 ± 1.5, p = 0.059; -1.2 ± 2.0, p < 0.05; -1.6 ± 1.8, p < 0.01; and -2.6 ± 2.8, p = 0.417, respectively). In children starting lumacaftor/ivacaftor in preschool age, the CRS-MRI sum score remained stable under therapy over all three follow-up MRI (0.6 ± 3.3, p = 0.520; 2.4 ± 7.6, p = 0.994; 2.1 ± 10.5, p > 0.999 and -0.5 ± 0.5, p = 0.740; respectively). Conclusion: Longitudinal paranasal sinus MRI shows improvements in paranasal sinus abnormalities in children with CF starting lumacaftor/ivacaftor therapy at school age. Further, MRI detects a prevention of an increase in paranasal sinus abnormalities in children with CF starting lumacaftor/ivacaftor therapy at preschool age. Our data support the role of MRI for comprehensive non-invasive therapy and disease monitoring of paranasal sinus abnormalities in children with CF.

MRI patterns indicate treatment success and tumor relapse following radiofrequency ablation of osteoblastoma

Purpose: To explore the typical magnetic resonance imaging (MRI) pattern of osteoblastoma (OB) after radiofrequency ablation (RFA) treatment and to identify signs indicating treatment success or relapse.Materials and methods: Forty-four follow-up MRI examinations of 15 patients with OB who had undergone 19 RFA procedures were analyzed retrospectively. An early follow-up group (1-4 months after RFA) and a late follow-up group (8-131 months after RFA) were established. The groups were further subdivided according to treatment success. Images were analyzed for the presence of central nidus enhancement (CNE), peripheral nidus enhancement (PNE), perifocal bone marrow edema (PBME) and fatty nidus conversion (FNC).Results: The early follow-up MRI image from every patient in the treatment success group exhibited a target-like appearance with negative CNE and positive PNE or PBME. PNE and PBME were observed in 93% and 71% of the early follow-up images, respectively. A target-like appearance was observed in 25% of the late follow-up images, and PNE and PBME were each observed in 20% of these images. FNC was not observed in the early follow-up images, but was seen in 55% of the late follow-up images. All three MRI images of the patients exhibiting clinical recurrence demonstrated strong CNE, PNE and extensive PMBE, which was in contrast to the images of the patients exhibiting treatment success.Conclusion: A target-like appearance of OB in early follow-up MRI examination indicates treatment success. PNE and PBME typically reduce over time and can lead to FNC in successfully treated patients. CNE recurrence, PNE and extensive PBME are signs of relapse.

[Radiologic diagnosis of pathologic fractures]

BACKGROUND

Pathologic fractures are fractures that occur without an adequate traumatic event due to focal benign or malignant skeletal lesions. The most common causes of pathologic fractures are cystic bone lesions, plasmocytoma or multiple myeloma, and the development of osseous metastases, which is increasing due to an aging general population and advances in cancer treatment. The differentiation of pathologic fractures from stress fractures, especially osteoporotic insufficiency fractures is crucial for correct treatment planning.

OBJECTIVES

This review intends to explain the imaging characteristics of pathologic fractures. Moreover, it explains the role of imaging when pathologic fractures are suspected. In addition, the Mirels' score and the SINS (Spinal Instability Neoplastic Score), which are powerful yet easy-to-use tools for the assessment of the fracture risk of benign or malignant bony lesions of the extremities and the vertebral column, shall be introduced.

MATERIALS AND METHODS

A PubMed literature search with the following terms was conducted: "pathologic fracture", "fatigue fracture", "insufficiency fracture", "treatment of pathologic fractures", "imaging of pathologic fractures", "fracture risk", "bone metastases", "MRI of pathologic fractures", "CT of pathologic fractures", "differentiation of pathologic and insufficiency fractures", "Mirels' score", "SINS" and "spinal instability neoplastic score".

RESULTS

The definitions of pathologic, fatigue, and insufficiency fractures are explained. Moreover, the role of imaging in the clinical workup of suspected pathologic fractures and the differentiation of pathologic fractures from fatigue or insufficiency fractures as well as common scoring systems to assess the fracture risk of pathologic fractures are described.

3-T T2 mapping magnetic resonance imaging for biochemical assessment of normal and damaged glenoid cartilage: a prospective arthroscopy-controlled study

This study evaluated the ability of T2 mapping to assess the glenoid cartilage using arthroscopy as the gold standard. Eighteen consecutive patients (mean age: 52.4 ± 14.72 years, including 12 men) with shoulder pain underwent T2 mapping at 3-T with subsequent shoulder arthroscopy. With correlation to cartilage-sensitive morphologic sequences regions-of-interest were placed in the corresponding T2 maps both in normal-appearing cartilage and focal cartilage lesions using a quadrant-wise approach. Inter-reader and intra-reader correlation coefficients (ICCs) between two independent radiologists as well as cut-off values with their sensitivities/specificities for the detection of cartilage damage were calculated. The mean T2 value for healthy cartilage was 23.0 ± 3 ms with significantly higher values in the superior quadrants compared to the inferior quadrants (p < 0.0001). In 5 patients with focal cartilage damage significantly higher T2 values of 44.7 ± 3.7 ms (P < 0.01) were observed. The maximum T2 value in normal cartilage (27.3 ms) was lower than the minimum value in damaged cartilage (40.8 ms) resulting in perfect sensitivities/specificities of 100% (95% confidence-interval 47.8-100.0) for all cut-off values between 27.3-40.8 ms. ICCs ranged between 0.63 and 0.99. In conclusion, T2 mapping can evaluate biochemical cartilage integrity and discriminates arthroscopy-proven healthy and damaged glenoid cartilage with high diagnostic performance.

Optimizing airway wall segmentation and quantification by reducing the influence of adjacent vessels and intravascular contrast material with a modified integral-based algorithm in quantitative computed tomography

Introduction

Quantitative analysis of multi-detector computed tomography (MDCT) plays an increasingly important role in assessing airway disease. Depending on the algorithms used, airway dimensions may be over- or underestimated, primarily if contrast material was used. Therefore, we tested a modified integral-based method (IBM) to address this problem.

Methods

Temporally resolved cine-MDCT was performed in seven ventilated pigs in breath-hold during iodinated contrast material (CM) infusion over 60s. Identical slices in non-enhanced (NE), pulmonary-arterial (PA), systemic-arterial (SA), and venous phase (VE) were subjected to an in-house software using a standard and a modified IBM. Total diameter (TD), lumen area (LA), wall area (WA), and wall thickness (WT) were measured for ten extra- and six intrapulmonary airways.

Results

The modified IBM significantly reduced TD by 7.6%, LA by 12.7%, WA by 9.7%, and WT by 3.9% compared to standard IBM on non-enhanced CT (p<0.05). Using standard IBM, CM led to a decrease of all airway parameters compared to NE. For example, LA decreased from 80.85±49.26mm² at NE, to 75.14±47.96mm² (-7.1%) at PA (p<0.001), 74.96±48.55mm² (-7.3%) at SA (p<0.001), and to 78.95±48.94mm² (-2.4%) at VE (p = 0.200). Using modified IBM, the differences were reduced to -3.1% at PA, -2.9% at SA and -0.7% at VE (p<0.001; p<0.001; p = 1.000).

Conclusions

The modified IBM can optimize airway wall segmentation and reduce the influence of CM on quantitative CT. This allows a more precise measurement as well as potentially the comparison of enhanced with non-enhanced scans in inflammatory airway disease.

The value of chest magnetic resonance imaging compared to chest radiographs with and without additional lung ultrasound in children with complicated pneumonia

Introduction

In children with pneumonia, chest x-ray (CXR) is typically the first imaging modality used for diagnostic work-up. Repeated CXR or computed tomography (CT) are often necessary if complications such as abscesses or empyema arise, thus increasing radiation exposure. The aim of this retrospective study was to evaluate the potential of radiation-free chest magnetic resonance imaging (MRI) to detect complications at baseline and follow-up, compared to CXR with and without additional lung ultrasound (LUS).

Methods

Paired MRI and CXR scans were retrospectively reviewed by two blinded readers for presence and severity of pulmonary abscess, consolidation, bronchial wall thickening, mucus plugging and pleural effusion/empyema using a chest MRI scoring system. The scores for MRI and CXR were compared at baseline and follow-up. Furthermore, the MRI scores at baseline with and without contrast media were evaluated.

Results

33 pediatric patients (6.3±4.6 years), who had 33 paired MRI and CXR scans at baseline and 12 at follow-up were included. MRI detected significantly more lung abscess formations with a prevalence of 72.7% compared to 27.3% by CXR at baseline (p = 0.001), whereas CXR+LUS was nearly as good as MRI. MRI also showed a higher sensitivity in detecting empyema (p = 0.003). At follow-up, MRI also showed a slightly better sensitivity regarding residual abscesses. The overall severity of disease was rated higher on MRI. Contrast material did not improve detection of abscesses or empyema by MRI.

Conclusion

CXR and LUS seem to be sufficient in most cases. In cases where LUS cannot be realized or the combination of CXR+LUS might be not sufficient, MRI, as a radiation free modality, should be preferred to CT. Furthermore, the admission of contrast media is not mandatory in this context.

Diagnostic performance of 3D-multi-Echo-data-image-combination (MEDIC) for evaluating SLAP lesions of the shoulder

Background

Superior labral anterior to posterior (SLAP) lesions remain a clinical and diagnostic challenge in routine (non-arthrographic) MR examinations of the shoulder. This study prospectively evaluated the ability of 3D-Multi-Echo-Data-Image-Combination (MEDIC) compared to that of routine high resolution 2D-proton-density weighted fat-saturated (PD fs) sequence using 3 T-MRI to detect SLAP lesions using arthroscopy as gold standard.

Methods

Seventeen consecutive patients (mean age, 51.6 ± 14.8 years, 11 males) with shoulder pain underwent 3 T MRI including 3D-MEDIC and 2D-PD fs followed by arthroscopy. The presence or absence of SLAP lesions was evaluated using both sequences by two independent raters with 4 and 14 years of experience in musculoskeletal MRI, respectively. During arthroscopy, SLAP lesions were classified according to Snyder’s criteria by two certified orthopedic shoulder surgeons. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 3D-MEDIC and 2D-PD fs for detection of SLAP lesions were calculated with reference to arthroscopy as a gold standard. Interreader agreement and sequence correlation were analyzed using Cohen’s kappa coefficient.

Figure 1 demonstrates the excellent visibility of a proven SLAP lesion using the 3D-MEDIC and Fig. 2 demonstrates a false-positive case.

Results

Arthroscopy revealed SLAP lesions in 11/17 patients. Using 3D-MEDIC, SLAP lesions were diagnosed in 14/17 patients by reader 1 and in 13/17 patients by reader 2. Using 2D-PD fs, SLAP lesions were diagnosed in 11/17 patients by reader 1 and 12/17 patients for reader 2. Sensitivity, specificity, PPV, and NPV of 3D-MEDIC were 100.0, 50.0, 78.6, and 100.0% for reader 1; and 100.0, 66.7, 84.6, and 100% for reader 2, respectively. Sensitivity, specificity, PPV, and NPV of 2D-PD fs were 90.9, 83.3, 90.9, and 83.3% for reader 1 and 100.0, 83.3, 91.7, and 100.0% for reader 2. The combination of 2D-PD fs and 3D-MEDIC increased specificity from 50.0 to 83.3% for reader 1 and from 66.7 to 100.0% for reader 2. Interreader agreement was almost perfect with a Cohen’s kappa of 0.82 for 3D-MEDIC and 0.87 for PD fs.

Conclusions

With its high sensitivity and NPV, 3D-MEDIC is a valuable tool for the evaluation of SLAP lesions. As the combination with routine 2D-PD fs further increases specificity, we recommend incorporation of 3D-MEDIC as an additional sequence in conventional shoulder protocols in patients with non-specific shoulder pain.

[MR and CT arthrography in cartilage imaging : Indications and implementation]

BACKGROUND

The imaging of chondral pathologies is an essential part in the work-up of acute and chronic joint diseases. Besides conventional MR imaging, CT and MR arthrography are well-established methods in evaluating articular cartilage. The application of these techniques requires knowledge of indications and safe injection procedures by the performing radiologist.

PURPOSE

Our goal is to describe the techniques of cross-sectional arthrographies of different joints, give an overview of general and joint-specific considerations for practical application as well as provide typical indications for cartilage imaging.

MATERIALS AND METHODS

A selective PubMed literature search concerning "arthrography", "CT arthrography", "MR arthrography", "arthrography cartilage", "arthrography wrist", "arthrography elbow", "arthrography shoulder", "arthrography hip", "arthrography knee", "arthrography ankle", "arthrography complications", "arthrography imaging guidance" "osteochondral lesion", "cartilage imaging" and "cartilage lesion" was performed.

RESULTS AND CONCLUSION

CT and MR arthrography are valuable and safe tools in cartilage imaging. They are useful to verify and specify chondral pathologies, usually after conventional MR imaging, and have an important role in evaluating the stability and therefore in therapeutic decision making of osteochondral lesions. CT arthrography is not only a substitute technique in case of MR contraindications, it can be advantageous in small joints (wrist, elbow, ankle) compared to MR arthrography due to its higher image resolution. Fluoroscopic guided joint puncture is still the most commonly used image guidance method, but the role of ultrasound is steadily increasing. Joint traction in MR arthrography is a promising technique to improve cartilage visualization, though it is not yet used in clinical routine imaging.

Towards synchrotron phase-contrast lung imaging in patients - a proof-of-concept study on porcine lungs in a human-scale chest phantom

In-line free propagation phase-contrast synchrotron tomography of the lungs has been shown to provide superior image quality compared with attenuation-based computed tomography (CT) in small-animal studies. The present study was performed to prove the applicability on a human-patient scale using a chest phantom with ventilated fresh porcine lungs. Local areas of interest were imaged with a pixel size of 100 µm, yielding a high-resolution depiction of anatomical hallmarks of healthy lungs and artificial lung nodules. Details like fine spiculations into surrounding alveolar spaces were shown on a micrometre scale. Minor differences in artificial lung nodule density were detected by phase retrieval. Since we only applied a fraction of the X-ray dose used for clinical high-resolution CT scans, it is believed that this approach may become applicable to the detailed assessment of focal lung lesions in patients in the future.

Imaging of the Knee Following Repair of Focal Articular Cartilage Lesions

Focal chondral or osteochondral lesions of the knee are common lesions involving either the cartilage layers or the cartilage layers and the subchondral bone. Despite their heterogeneous clinical presentation, they are important risk factors for the premature development of osteoarthritis. Therefore, early detection of osteochondral lesions and focal cartilage defects is crucial. In symptomatic (osteo-)chondral lesions, numerous therapeutic strategies, ranging from conservative treatment to surgical procedures such as marrow stimulation, osteochondral autograft transplantation, or autologous chondrocyte implantation are available. Musculoskeletal radiologists should be familiar with these surgical procedures, the evaluation of the postoperative findings as well as the possible complications when interpreting postoperative imaging studies. This review article describes the different surgical approaches to focal osteochondral lesions of the knee with emphasis on postoperative imaging findings and the pitfalls possibly encountered by the radiologist.