Longitudinal evaluation of the occurrence of MRI-detectable bone marrow edema in osteoarthritis of the knee

BACKGROUND

Bone marrow edema (BME) is a condition detectable with magnetic resonance imaging (MRI) and is present in different stages of osteoarthritis (OA). Its pathogenesis is still not completely known.

PURPOSE

To evaluate the longitudinal occurrence and persistence of BME in early OA of the knee.

MATERIAL AND METHODS

Twenty-three patients (eight females, 15 males; mean age 55.5+/-10.3 years) were scanned with a 1.5T MR imaging unit (sagittal fat-suppressed intermediate-weighted fast spin echo; 4-mm section thickness, 1-mm intersection gap, 256 x 192 matrix, 120-mm field of view). Images were obtained in all 23 patients at two time points (TPs) and in 12 patients at three TPs. Images were evaluated by two readers independently; discrepancies in image grading were reviewed and evaluated in consensus. A four-point image-grading scale was used (absence of BME to severe BME). Four main anatomical regions were evaluated (medial femur, lateral femur, medial tibia, lateral tibia), which were subcategorized into anterior, central, and posterior regions.

RESULTS

One hundred five areas of BME in the 23 patients were found at all three TPs. In 16 areas, the BME was consistent at the same location over time, in seven locations the BME became larger, in six areas the BME became smaller, and in 16 locations it could not be detected in follow-up MRIs. In one case, the BME was smaller at TP2 but increased at TP3. In eight cases, only at the last time point could a BME be detected.

CONCLUSION

BME is not a static phenomenon but changes over time. Correlation to physical activity and local inflammatory reaction should be evaluated.

Novel fast semi-automated software to segment cartilage for knee MR acquisitions

OBJECTIVE

Validation of a new fast software technique to segment the cartilage on knee magnetic resonance (MR) acquisitions. Large studies of knee osteoarthritis (OA) will require fast and reproducible methods to quantify cartilage changes for knee MR data. In this report we document and measure the reproducibility and reader time of a software-based technique to quantify the volume and thickness of articular cartilage on knee MR images.

METHODS

The software was tested on a set of duplicate sagittal three-dimensional (3D) dual echo steady state (DESS) acquisitions from 15 (8 OA, 7 normal) subjects. The repositioning, inter-reader, and intra-reader reproducibility of the cartilage volume (VC) and thickness (ThC) were measured independently as well as the reader time for each cartilage plate. The root-mean square coefficient of variation (RMSCoV) was used as metric to quantify the reproducibility of VC and mean ThC.

RESULTS

The repositioning RMSCoV was as follows: VC=2.0% and ThC=1.2% (femur), VC=2.9% and ThC=1.6% (medial tibial plateau), VC=5.5% and ThC=2.4% (lateral tibial plateau), and VC=4.6% and ThC=2.3% (patella). RMSCoV values were higher for the inter-reader reproducibility (VC: 2.5-8.6%) (ThC: 1.9-5.2%) and lower for the intra-reader reproducibility (VC: 1.6-2.5%) (ThC: 1.2-1.9%). The method required an average of 75.4min per knee.

CONCLUSIONS

We have documented a fast reproducible semi-automated software method to segment articular cartilage on knee MR acquisitions.

Longitudinal in vivo reproducibility of cartilage volume and surface in osteoarthritis of the knee

OBJECTIVE

The aim of this study was to evaluate the longitudinal reproducibility of cartilage volume and surface area measurements in moderate osteoarthritis (OA) of the knee.

MATERIALS AND METHODS

We analysed 5 MRI (GE 1.5T, sagittal 3D SPGR) data sets of patients with osteoarthritis (OA) of the knee (Kellgren Lawrence grade I-II). Two scans were performed: one baseline scan and one follow-up scan 3 months later (96 +/- 10 days). For segmentation, 3D Slicer 2.5 software was used. Two segmentations were performed by two readers independently who were blinded to the scan dates. Tibial and femoral cartilage volume and surface were determined. Longitudinal and cross-sectional precision errors were calculated using the standard deviation (SD) and coefficient of variation (CV%=100x[SD/mean]) from the repeated measurements in each patient. The in vivo reproducibility was then calculated as the root mean square of these individual reproducibility errors.

RESULTS

The cross-sectional root mean squared coefficient of variation (RMSE-CV) was 1.2, 2.2 and 2.4% for surface area measurements (femur, medial and lateral tibia respectively) and 1.4, 1.8 and 1.3% for the corresponding cartilage volumes. Longitudinal RMSE-CV was 3.3, 3.1 and 3.7% for the surface area measurements (femur, medial and lateral tibia respectively) and 2.3, 3.3 and 2.4% for femur, medial and lateral tibia cartilage volumes.

CONCLUSION

The longitudinal in vivo reproducibility of cartilage surface and volume measurements in the knee using this segmentation method is excellent. To the best of our knowledge we measured, for the first time, the longitudinal reproducibility of cartilage volume and surface area in participants with mild to moderate OA.

[Molecular imaging: future uses in arthritides]

Molecular imaging is an upcoming field in radiology as a result of great advances in imaging technology, genetics, and biochemistry in the recent past. Early-stage imaging of molecular pathological changes in cells opens the gates to new methods in medical treatment of diseases that otherwise would only be detected in advanced stages. Methods of imaging biochemical pathways with molecular agents are currently an issue of intensive research. This article reviews current modalities of molecular imaging in arthritis that should offer future perspective on early disease detection, diagnosis, and monitoring of treatment efficiency and how they can pave the way to optimized therapy.

Evaluation of low-cost computer monitors for the detection of cervical spine injuries in the emergency room: an observer confidence-based study

BACKGROUND

To compare the diagnostic value of low-cost computer monitors and a Picture Archiving and Communication System (PACS) workstation for the evaluation of cervical spine fractures in the emergency room.

METHODS

Two groups of readers blinded to the diagnoses (2 radiologists and 3 orthopaedic surgeons) independently assessed-digital radiographs of the cervical spine (anterior-posterior, oblique and trans-oral-dens views). The radiographs of 57 patients who arrived consecutively to the emergency room in 2004 with clinical suspicion of a cervical spine injury were evaluated. The diagnostic values of these radiographs were scored on a 3-point scale (1 = diagnosis not possible/bad image quality, 2 = diagnosis uncertain, 3 = clear diagnosis of fracture or no fracture) on a PACS workstation and on two different liquid crystal display (LCD) personal computer monitors. The images were randomised to avoid memory effects. We used logistic mixed-effects models to determine the possible effects of monitor type on the evaluation of x ray images. To determine the overall effects of monitor type, this variable was used as a fixed effect, and the image number and reader group (radiologist or orthopaedic surgeon) were used as random effects on display quality. Group-specific effects were examined, with the reader group and additional fixed effects as terms. A significance level of 0.05 was established for assessing the contribution of each fixed effect to the model.

RESULTS

Overall, the diagnostic score did not differ significantly between standard personal computer monitors and the PACS workstation (both p values were 0.78).

CONCLUSION

Low-cost LCD personal computer monitors may be useful in establishing a diagnosis of cervical spine fractures in the emergency room.