Mario Maas

Prospective study on diagnostic strategies in osteochondral lesions of the talus IS MRI SUPERIOR TO HELICAL CT

Our aim in this prospective study was to determine the best diagnostic method for discriminating between patients with and without osteochondral lesions of the talus, with special relevance to the value of MRI compared with the new technique of multidetector helical CT. We compared the diagnostic value of history, physical examination and standard radiography, a 4 cm heel-rise view, helical CT, MRI, and diagnostic arthroscopy for simultaneous detection or exclusion of osteochondral lesions of the talus. A consecutive series of 103 patients (104 ankles) with chronic ankle pain was included in this study. Of these, 29 with 35 osteochondral lesions were identified. Twenty-seven lesions were located in the talus. Our findings showed that helical CT, MRI and diagnostic arthroscopy were significantly better than history, physical examination and standard radiography for detecting or excluding an osteochondral lesion. Also, MRI and diagnostic arthroscopy performed better than a mortise view with a 4 cm heel-rise. We did not find a statistically significant difference between helical CT and MRI. Diagnostic arthroscopy did not perform better than helical CT and MRI for detecting or excluding an osteochondral lesion.

Oblique radiograph for the detection of bone spurs in anterior ankle impingement

Objective: The aim of this study was to develop a radiographic view to detect anteromedial talotibial osteophytes that remain undetected on standard radiographs. Design and patients: In 10 cadaver specimens the maximal size was measured of anteromedial tibial osteophytes that remain undetected on a standard lateral radiograph projection, due to the presence of the anteromedial tibial rim. The average projection of the most prominent anterolateral tibial rim over the anteromedial rim was found to be 7.3xa0mm. A 7xa0mm barium-clay osteophyte was attached to this anteromedial rim of the distal tibia. Anteromedial osteophytes become most prominent on an oblique view, in which the radiographic beam is tilted into a 45° craniocaudal direction with the leg in 30° external rotation. This oblique view was compared with the findings of arthroscopic surgery in 25 consecutive patients with anterior ankle impingement syndrome. Results: Medially located tibial and talar osteophytes remained undetected on a standard lateral projection and became visible on the oblique anteromedial impingement (AMI) radiograph. Anterolateral tibial and talar osteophytes were well detected on a standard lateral radiograph projection but were invisible on the AMI view. There was a high correlation between the location of the osteophyte and the location of symptoms and the findings at arthroscopy. Conclusion: A combination of lateral and oblique radiographs can be used to differentiate between anteromedial and anterolateral bony ankle impingement.

Measuring hindfoot alignment radiographically: the long axial view is more reliable than the hindfoot alignment view

BackgroundHindfoot malalignment is a recognized cause of foot and ankle disability. For preoperative planning and clinical follow-up, reliable radiographic assessment of hindfoot alignment is important. The long axial radiographic view and the hindfoot alignment view are commonly used for this purpose. However, their comparative reliabilities are unknown. As hindfoot varus or valgus malalignment is most pronounced during mid-stance of gait, a unilateral weight-bearing stance, in comparison with a bilateral stance, could increase measurement reliability. The purpose of this study was to compare the intra- and interobserver reliability of hindfoot alignment measurements of both radiographic views in bilateral and unilateral stance.Materials and methodsA hindfoot alignment view and a long axial view were acquired from 18 healthy volunteers in bilateral and unilateral weight-bearing stances. Hindfoot alignment was defined as the angular deviation between the tibial anatomical axis and the calcaneus longitudinal axis from the radiographs. Repeat measurements of hindfoot alignment were performed by nine orthopaedic examiners.ResultsMeasurements from the hindfoot alignment view gave intra- and interclass correlation coefficients (CCs) of 0.72 and 0.58, respectively, for bilateral stance and 0.91 and 0.49, respectively, for unilateral stance. The long axial view showed, respectively, intra- and interclass CCs of 0.93 and 0.79 for bilateral stance and 0.91 and 0.58 for unilateral stance.ConclusionThe long axial view is more reliable than the hindfoot alignment view or the angular measurement of hindfoot alignment. Although intra-observer reliability is good/excellent for both methods, only the long axial view leads to good interobserver reliability. A unilateral weight-bearing stance does not lead to greater reliability of measurement.

Pseudotumor formation and serum ions after large head metal-on-metal stemmed total hip replacement. Risk factors, time course and revisions in 706 hips

IntroductionThe incidence and natural course of pseudotumors in metal-on-metal total hip arthroplasties is largely unknown. The objective of this study was to identify the true incidence and risk factors of pseudotumor formation in large head metal-on-metal total hip arthroplasties.Materials and methodsIncidence, time course and risk factors for pseudotumor formation were analysed after large femoral head MoM-THA. We defined a pseudotumor as a (semi-)solid or cystic peri-prosthetic soft-tissue mass with a diameter ≥2xa0cm that could not be attributed to infection, malignancy, bursa or scar tissue. All patients treated in our clinic with MoM-THA’s were contacted. CT scan, metal ions and X-rays were obtained. Symptoms were recorded.ResultsAfter median follow-up of 3xa0years, 706 hips were screened in 626 patients. There were 228 pseudotumors (32.3xa0%) in 219 patients (35.0xa0%). Pseudotumor formation significantly increased after prolonged follow-up. Seventy-six hips (10.8xa0%) were revised in 73 patients (11.7xa0%), independent risk factors were identified. Best cutoff point for cobalt and chromium was 4xa0μg/l (68 and 77xa0nmol/l).ConclusionsThis study confirms a high incidence of pseudotumors, dramatically increasing after prolonged follow-up. Risk factors for pseudotumors are of limited importance. Pain was the strongest predictor for pseudotumor presence; cobalt chromium and swelling were considered poor predictors. Cross-sectional imaging is the main screening tool during follow-up.

Increasing feasibility and patient comfort of MRI in children with juvenile idiopathic arthritis

BackgroundMRI is the most sensitive imaging modality in juvenile idiopathic arthritis (JIA), but has practical limitations. Optimizing the scanning protocol is, therefore, necessary to increase feasibility and patient comfort.ObjectiveTo determine the feasibility of bilateral non-contrast-enhanced open-bore MRI of knees and to assess the presence of literature-based MRI features in unsedated children with JIA.Materials and methodsChildren were classified into two clinical subgroups: active arthritis (group 1; nu2009=u200929) and inactive disease (group 2; nu2009=u200918). MRI features were evaluated using a literature-based score, comprising synovial hypertrophy, cartilage lesions, bone erosions, bone marrow changes, infrapatellar fat pad heterogeneity, effusion, tendinopathy and popliteal lymphadenopathy.ResultsThe MRI examination was successfully completed in all 47 children. No scan was excluded due to poor image quality. Synovial hypertrophy was more frequent in group 1 (36.2%), but was also seen in 19.4% of the knees in group 2. Infrapatellar fat pad heterogeneity was more prevalent in group 2 (86.1%; Pu2009=u20090.008). Reproducibility of the score was good (Cohen kappa, 0.49–0.96).ConclusionBilateral non-contrast-enhanced open-bore knee MRI is feasible in the assessment of disease activity in unsedated children with JIA. Signs differing among chidren with active and inactive disease include infrapatellar fat pad heterogeneity and synovial hypertrophy.

Current Status of Efforts on Standardizing Magnetic Resonance Imaging of Juvenile Idiopathic Arthritis: Report from the OMERACT MRI in JIA Working Group and Health-e-Child

Objective. To report on the progress of an ongoing research collaboration on magnetic resonance imaging (MRI) in juvenile idiopathic arthritis (JIA) and describe the proceedings of a meeting, held prior to Outcome Measures in Rheumatology (OMERACT) 12, bringing together the OMERACT MRI in JIA working group and the Health-e-Child radiology group. The goal of the meeting was to establish agreement on scoring definitions, locations, and scales for the assessment of MRI of patients with JIA for both large and small joints. Methods. The collaborative work process included premeeting surveys, presentations, group discussions, consensus on scoring methods, pilot scoring, conjoint review, and discussion of a future research agenda. Results. The meeting resulted in preliminary statements on the MR imaging protocol of the JIA knee and wrist and determination of the starting point for development of MRI scoring systems based on previous studies. It was also considered important to be descriptive rather than explanatory in the assessment of MRI in JIA (e.g., “thickening” instead of “hypertrophy”). Further, the group agreed that well-designed calibration sessions were warranted before any future scoring exercises were conducted. Conclusion. The combined efforts of the OMERACT MRI in JIA working group and Health-e-Child included the assessment of currently available material in the literature and determination of the basis from which to start the development of MRI scoring systems for both the knee and wrist. The future research agenda for the knee and wrist will include establishment of MRI scoring systems, an atlas of MR imaging in healthy children, and MRI protocol requisites.

Quantifying metal artefact reduction using virtual monochromatic dual-layer detector spectral CT imaging in unilateral and bilateral total hip prostheses

PURPOSEnTo quantify the impact of prosthesis material and design on the reduction of metal artefacts in total hip arthroplasties using virtual monochromatic dual-layer detector Spectral CT imaging.nnnMETHODSnThe water-filled total hip arthroplasty phantom was scanned on a novel 128-slice Philips IQon dual-layer detector Spectral CT scanner at 120-kVp and 140-kVp at a standard computed tomography dose index of 20.0mGy. Several unilateral and bilateral hip prostheses consisting of different metal alloys were inserted and combined which were surrounded by 18 hydroxyapatite calcium carbonate pellets representing bone. Images were reconstructed with iterative reconstruction and analysed at monochromatic energies ranging from 40 to 200keV. CT numbers in Hounsfield Units (HU), noise measured as the standard deviation in HU, signal-to-noise-ratios (SNRs) and contrast-to-noise-ratios (CNRs) were analysed within fixed regions-of-interests placed in and around the pellets.nnnRESULTSnIn 70 and 74keV virtual monochromatic images the CT numbers of the pellets were similar to 120-kVp and 140-kVp polychromatic results, therefore serving as reference. A separation into three categories of metal artefacts was made (no, mild/moderate and severe) where pellets were categorized based on HU deviations. At high keV values overall image contrast was reduced. For mild/moderate artefacts, the highest average CNRs were attained with virtual monochromatic 130keV images, acquired at 140-kVp. Severe metal artefacts were not reduced. In 130keV images, only mild/moderate metal artefacts were significantly reduced compared to 70 and 74keV images. Deviations in CT numbers, noise, SNRs and CNRs due to metal artefacts were decreased with respectively 64%, 57%, 62% and 63% (p<0.001) compared to unaffected pellets. Optimal keVs, based on CNRs, for different unilateral and bilateral metal hip prostheses consisting of different metal alloys varied from 74 to 150keV. The Titanium alloy resulted in less severe artefacts and were reduced more effectively compared to the Cobalt alloy.nnnCONCLUSIONSnVirtual monochromatic dual-layer Spectral CT imaging results in a significant reduction of streak artefacts produced by beam-hardening in mild and moderate artefacts by improving CT number accuracy, SNRs and CNRs, while decreasing noise values in a total hip arthroplasty phantom. An optimal monochromatic energy of 130keV was found ranging from 74keV to 150keV for different unilateral and bilateral hip prostheses consisting of different metal alloys.

Use of dynamic contrast enhanced time intensity curve shape analysis in MRI: theory and practice

The analysis of dynamic contrast enhanced data using the classification of the time intensity curve (TIC) shape is widely employed both in its region of interest and pixel by pixel variants. While its application in breast imaging is established and documented by a large amount of scientific works, its use for other body parts is still scattered and there is no consensus as to whether the method can be used alone to perform differential diagnosis in cancer or in inflam - matory diseases. In this review we evaluate all the literature which makes use of TIC shape analysis in tissues other than breast, discuss the results, highlight the possible shortcomings, and suggest directions for future research.

Postmortem imaging exposed: an aid in MR imaging of musculoskeletal structures

ObjectiveTo identify factors that influence the quality of postmortem magnetic resonance (MR) images of musculoskeletal (MSK) structures as described in the literature, and to evaluate the extent to which these MR images are affected.Materials and methodsFour useful studies were retrieved from a PubMed and EMBASE search, covering the literature up to 1 March 2012. Three additional studies were included after a manual search from reference lists.ResultsFour human studies and three animal studies are considered in this review. Postmortem MRI quality can be affected by storage temperature, repeated freezing and thawing and fixation. Provided there was an adequate, but above-freezing storage temperature, postmortem changes in fresh cadavers did not appear to affect the MR image quality of MSK structures up to 14xa0days after death. Image contrast, signal intensities, and relaxation times are temperature-dependent, regardless of whether the specimen was fresh or postmortem for up to 7xa0days. Bad image quality can occur owing to accelerated autolysis. Freezing and thawing did not affect image quality, unless repeated too often, or whenever a heating pad was used to speed up the thawing process. Conventional formalin-based fixation leads to swelling of soft tissue and fluid accumulation in joints, and therefore to deteriorated images, with image quality just sufficient to visualize gross anatomy.ConclusionVarious factors were identified that affect postmortem MR image quality of MSK structures. Postmortem MR image quality was good, except for images of the fixated specimen. Freezing is the preferred method of conservation for specimens that are to be subjected to postmortem MRI.

Low-dose CT imaging of a total hip arthroplasty phantom using model-based iterative reconstruction and orthopedic metal artifact reduction

ObjectiveTo compare quantitative measures of image quality, in terms of CT number accuracy, noise, signal-to-noise-ratios (SNRs), and contrast-to-noise ratios (CNRs), at different dose levels with filtered-back-projection (FBP), iterative reconstruction (IR), and model-based iterative reconstruction (MBIR) alone and in combination with orthopedic metal artifact reduction (O-MAR) in a total hip arthroplasty (THA) phantom.Materials and methodsScans were acquired from high- to low-dose (CTDIvol: 40.0, 32.0, 24.0, 16.0, 8.0, and 4.0xa0mGy) at 120- and 140-xa0kVp. Images were reconstructed using FBP, IR (iDose4 level 2, 4, and 6) and MBIR (IMR, level 1, 2, and 3) with and without O-MAR. CT number accuracy in Hounsfield Units (HU), noise or standard deviation, SNRs, and CNRs were analyzed.ResultsThe IMR technique showed lower noise levels (pu2009<u20090.01), higher SNRs (pu2009<u20090.001) and CNRs (pu2009<u20090.001) compared with FBP and iDose4 in all acquisitions from high- to low-dose with constant CT numbers. O-MAR reduced noise (pu2009<u20090.01) and improved SNRs (pu2009<u20090.01) and CNRs (pu2009<u20090.001) while improving CT number accuracy only at a low dose. At the low dose of 4.0xa0mGy, IMR level 1, 2, and 3 showed 83%, 89%, and 95% lower noise values, a factor 6.0, 9.2, and 17.9 higher SNRs, and 5.7, 8.8, and 18.2 higher CNRs compared with FBP respectively.ConclusionsBased on quantitative analysis of CT number accuracy, noise values, SNRs, and CNRs, we conclude that the combined use of IMR and O-MAR enables a reduction in radiation dose of 83% compared with FBP and iDose4 in the CT imaging of a THA phantom.