Souhil Zaim

MR findings in knee osteoarthritis

Abstract. Knee osteoarthritis (OA) is a leading cause of disability. Recent advances in drug discovery techniques and improvements in understanding the pathophysiology of osteoarthritic disorders have resulted in an unprecedented number of new therapeutic agents. Of all imaging modalities, radiography has been the most widely used for the diagnosis and management of the progression of knee OA. Magnetic resonance imaging is a relatively recent technique and its applications to osteoarthritis have been limited. Compared with conventional radiography, MR imaging offers unparalleled discrimination among articular soft tissues by directly visualizing all components of the knee joint simultaneously and therefore allowing the knee joint to be evaluated as a whole organ. In this article we present the MR findings in knee OA including cartilage abnormalities, osteophytes, bone edema, subarticular cysts, bone attrition, meniscal tears, ligament abnormalities, synovial thickening, joint effusion, intra-articular loose bodies, and periarticular cysts.

Osteoarthritis, magnetic resonance imaging, and biochemical markers: a one year prospective study

Objective: To investigate the relation between biochemical markers of bone, cartilage, and synovial remodelling and the structural progression of knee osteoarthritis. Methods: 62 patients of both sexes with knee osteoarthritis were followed prospectively for one year. From magnetic resonance imaging (MRI), done at baseline and after one year, the volume and thickness of cartilage of the femur, the medial tibia, and the lateral tibia were assessed. A whole organ magnetic resonance imaging score (WORMS) of the knee was calculated for each patient at baseline and at the one year visits. This score consists in a validated, semiquantitative scoring system for whole organ assessment of the knee in osteoarthritis using MRI. Biochemical markers (serum hyaluronic acid, osteocalcin, cartilage glycoprotein 39 (YKL-40), cartilage oligomeric matrix protein (COMP), and C-telopeptide of type I collagen (CTX-I), and urine C-telopeptide of type II collagen (CTX-II)) were measured at baseline and after three months. Results: Baseline markers were not correlated with one year changes observed in cartilage volume and thickness. However, an increase in CTX-II after three months was significantly correlated with a one year decrease in mean thickness of medial tibial and lateral tibial cartilage. Patients in the highest quartile of three month changes in CTX-II experienced a mean loss of 0.07 (0.08) mm of their medial thickness, compared with a mean increase of 0.05 (0.19) mm for patients in the lowest quartile (p = 0.04) Multiple regression analysis showed that high baseline levels of hyaluronic acid are predictive of a worsening in WORMS (p = 0.004). Conclusions: These results suggest that a single measurement of serum hyaluronic acid or short term changes in urine CTX-II could identify patients at greatest risk of progression of osteoarthritis.

MRI features of cystic lesions around the knee.

Cystic lesions around the knee are a diverse group of entities, frequently encountered during routine MRI of the knee. These lesions range from benign cysts to complications of underlying diseases such as infection, arthritis, and malignancy. MRI is the technique of choice in characterizing lesions around the knee: to confirm the cystic nature of the lesion, to evaluate the anatomical relationship to the joint and surrounding tissues, and to identify associated intra-articular disorders. We will discuss the etiology, clinical presentation, MRI findings, and differential diagnosis of various cystic lesions around the knee including meniscal and popliteal (Bakers) cysts, intra-articular and extra-articular ganglia, intra-osseous cysts at the insertion of the cruciate ligaments and meniscotibial attachments, proximal tibiofibular joint cysts, degenerative cystic lesions (subchondral cyst), cystic lesions arising from the bursae (pes anserine, prepatellar, superficial and deep infrapatellar, iliotibial, tibial collateral ligament, and suprapatellar), and lesions that may mimic cysts around the knee including normal anatomical recesses. Clinicians must be aware about the MRI features and the differential diagnosis of cystic lesions around the knee to avoid misdiagnosis.

Measurement of changes in trabecular bone at fracture sites using X-ray CT and automated image registration and processing

Currently, there are no in vivo techniques for quantifying healing within fractures involving mainly trabecular bone. Methods for quantitatively assessing healing would aid the investigation of new treatment regimes, and might also be useful for predicting whether a patient may be undergoing delayed union. Using CT and automated image registration, we have developed an image processing technique for measuring changes in CT image intensity at fracture sites. The technique focuses on quantifying the formation of new mineralised tissue within fracture gaps, while ignoring loss of bone mineral due to disuse osteoporosis. Seven patients with fractures of the distal radius were examined for 12 weeks following fracture. To assess reproducibility of measurements of change in CT intensity at the fracture line, measurements were performed on two separate occasions, by each of two independent readers. Reproducibility was compared to rates of change over time, to determine detectable differences in individual progression. Scans were scored qualitatively for features of healing and scores compared to the quantitative measurements. The mean (SD) change in CT intensity was + 128 (65) Hounsfield Units (HU) over the 12 week follow‐up. Inter‐ and intra‐observer reproducibilities were both similar (±17 HU), 1/7 of the change seen during the study. In this small patient cohort, a significant increase in CT intensity was seen 2 weeks post‐fracture. Large early increases in CT intensity were associated with early visual appearance of sclerosis and blurring of the fracture line. In this preliminary, prospective study, we have developed a reproducible quantitative technique for measuring changes in CT intensity of trabecular bone at the fracture line in the distal radius. Further work is required to determine whether it can be used to identify, or monitor patients who are undergoing delayed fracture repair. The technique appears sensitive for measuring changes immediately post‐fracture, and could have a role in examining potential effects of new therapies in patient cohorts.

Automating measurement of subtle changes in articular cartilage from MRI of the knee by combining 3D image registration and segmentation

In osteoarthritis, articular cartilage loses integrity and becomes thinned. This usually occurs at sites which bear weight during normal use. Measurement of such loss from MRI scans, requires precise and reproducible techniques, which can overcome the difficulties of patient repositioning within the scanner. In this study, we combine a previously described technique for segmentation of cartilage from MRI of the knee, with a technique for 3D image registration that matches localized regions of interest at followup and baseline. Two patients, who had recently undergone meniscal surgery, and developed lesions during the 12 month followup period were examined. Image registration matched regions of interest (ROI) between baseline and followup, and changes within the cartilage lesions were estimate to be about a 16% reduction in cartilage volume within each ROI. This was more than 5 times the reproducibility of the measurement, but only represented a change of between 1 and 2% in total femoral cartilage volume. Changes in total cartilage volume may be insensitive for quantifying changes in cartilage morphology. A combined used of automated image segmentation, with 3D image registration could be a useful tool for the precise and sensitive measurement of localized changes in cartilage from MRI of the knee.

Assessment of Knee Cartilage

The evaluation of articular cartilage has gained increasing attention in the scientific community as injuries and degenerative changes in the articular cartilage are a significant cause of morbidity and impaired quality of life (Yelin and Callahan 1995), with an increasing impact in our aging society. The fundamental component of osteoarthritis is degradation and subsequent loss of articular cartilage.

Gastroenteropancreatic neuroendocrine tumors: multimodality imaging features with pathological correlation

Neuroendocrine tumors of the gastrointestinal tract are rare entities. Functioning neuroendocrine tumors tend to present early because of hormoneinduced clinical symptoms, but detection of the primary lesion may be difficult owing to their small size. Neuroendocrine tumors are typically hypervascular and show enhancement after contrast administration on computed tomography (CT) or magnetic resonance imaging (MRI). Large nonfunctioning tumors may be found in asymptomatic patients. In such cases, the synchronous presence of hypervascular hepatic metastases should be explored. This pictorial review illustrates imaging features of functioning and nonfunctioning neuroendocrine tumors arising in the gastrointestinal tract and the pancreas. Modalities included are CT, MRI, ultrasonography, and nuclear medicine. Characteristic histological specimens of these lesions are presented.

High Kellgren-Lawrence Grade and Bone Marrow Lesions Predict Worsening Rates of Radiographic Joint Space Narrowing; The SEKOIA Study.

Objective. Determinants of radiographic progression in osteoarthritis (OA) are poorly understood. We investigated which features on baseline magnetic resonance imaging (MRI) acted as predictors of change in joint space width (JSW). Methods. A total of 559 men and women over the age of 50 years with clinical knee OA [Kellgren-Lawrence (KL) grade 2–3] were recruited to the placebo arm of the SEKOIA study (98 centers; 18 countries). Minimal tibiofemoral joint space and KL grade on plain radiograph of the knee were assessed at baseline and at yearly followup up to 3 years. In a subset, serial knee MRI examinations were performed. Individuals with a bone marrow lesion (BML) ≥ grade 2 at the tibiofemoral joint at baseline were classified as BML-positive. Relationships between change in JSW and risk factors were assessed using linear regression. Results. The mean age of study participants was 62.8 (SD 7.5) years and 73% were female; 38.6% had BML. Mean baseline JSW was 3.65 mm. This reduced by 0.18 (0.30) mm/year in men and 0.13 (0.23) mm/year in women. Those with BML had a significantly higher rate of annualized change in JSW; this relationship remained robust after adjustment for age, sex, and baseline KL grade [β = −0.10 (95% CI −0.18, −0.02) mm/yr]. Age, sex, baseline KL grade, and other MRI findings did not influence the rate of change in JSW. Conclusion. The rate of change in JSW was similar in men and women. BML on knee MRI predicted the rate of radiographic change in JSW. This relationship was independent of age, sex, and baseline KL grade.

What semi-quantitative scoring instrument for knee OA MRI should you use?

Multiple techniques have been used to assess synovial morphology and change on MRI in OA. Broadly speaking these methods are divided into quantitative and semi-quantitative methods. Quantitative measurements use computer-aided image processing to assess joint quantification (cartilage morphometry, bone volume, bone marrow lesion volume, meniscal position and volume, synovial volume, etc). In contrast to quantitative measures, semi-quantitative image analysis is typically much more observer dependent and generates grades or scales rather than truly continuous output. Multiple methods for semi-quantitative multi-feature assessment of the knee using conventional MRI acquisitions exist. These instruments provide for broad assessment of the whole joint and derive from knowledge from reading as to what joint features are morphologically abnormal. They are labour- and expertise-intensive compared to more automated methodologies. As a consequence of their reader dependence, precision and reliability results have not been as favourable for these instruments as their quantitative cousins. These instruments are generally based on past perceptions of what should be considered an important feature and therefore can bias future research. This said they do provide an important tool especially when quantitative methodologies are lacking or have their own inherent limitations.

3D segmentation and quantification of magnetic resonance data: application to the osteonecrosis of the femoral head

The general objective of our study is the development of a clinically robust three-dimensional segmentation and quantification technique of Magnetic Resonance (MR) data, for the objective and quantitative evaluation of the osteonecrosis (ON) of the femoral head. This method will help evaluate the effects of joint preserving treatments for femoral head osteonecrosis from MR data. The disease is characterized by tissue changes (death of bone and marrow cells) within the weight-bearing portion of the femoral head. Due to the fuzzy appearance of lesion tissues and their different intensity patterns in various MR sequences, we proposed a semi-automatic multispectral segmentation of MR data introducing data constraints (anatomical and geometrical) and using a classical K-means unsupervised clustering algorithm. The method was applied on ON patient data. Results of volumetric measurements and configuration of various tissues obtained with the semi- automatic method were compared with quantitative results delineated by a trained radiologist.