Cartilage can be thicker in advanced osteoarthritic knees: a tridimensional quantitative analysis of cartilage thickness at posterior aspect of femoral condyles.

To test, through tridimensional analysis, whether (1) cartilage thickness at the posterior aspect of femoral condyles differs in knees with medial femorotibial osteoarthritis (OA) compared to non-OA knees; (2) the location of the thickest cartilage at the posterior aspect of femoral condyles differs between OA and non-OA knees. CT arthrograms of knees without radiographic OA (n = 30) and with severe medial femorotibial OA (n = 30) were selected retrospectively from patients over 50 years of age. The groups did not differ in gender, age and femoral size. CT arthrograms were segmented to measure the mean cartilage thickness, the maximal cartilage thickness and its location in a region of interest at the posterior aspect of condyles. For the medial condyle, mean and maximum cartilage thicknesses were statistically significantly higher in OA knees compared to non-OA knees [1.66 vs 1.46 mm (p = 0.03) and 2.56 vs 2.14 mm (p = 0.003), respectively]. The thickest cartilage was located in the half most medial aspect of the posterior medial condyle for both groups, without significant difference between groups. For the lateral condyle, no statistically significant difference between non-OA and OA knees was found (p ≥ 0.17). Cartilage at the posterior aspect of the medial condyle, but not the lateral condyle, is statistically significantly thicker in advanced medial femorotibial OA knees compared to non-OA knees. The thickest cartilage was located in the half most medial aspect of the posterior medial condyle. These results will serve as the basis for future research to determine the histobiological processes involved in this thicker cartilage. Advances in knowledge: This study, through a quantitative tridimensional approach, shows that cartilage at the posterior aspect of the medial condyles is thicker in severe femorotibial osteoarthritic knees compared to non-OA knees. In the posterior aspect of the medial condyle, the thickest cartilage is located in the vicinity of the center of the half most medial aspect of the posterior medial condyle. These results will serve as the basis for future research to determine the histobiological processes involved in this thicker cartilage

A prospective evaluation of ultrasound as a diagnostic tool in acute microcrystalline arthritis.

The performance of ultrasound (US) in the diagnosis of acute gouty (MSU) arthritis and calcium pyrophosphate (CPP) arthritis is not yet well defined. Most studies evaluated US as the basis for diagnosing crystal arthritis in already diagnosed cases of gout and few prospective studies have been performed. One hundred nine consecutive patients who presented an acute arthritis of suspected microcrystalline arthritis were prospectively included. All underwent an US of the symptomatic joints(s) and of knees, ankles and 1(st) metatarsopalangeal (MTP) joints by a rheumatologist "blinded" to the clinical history. 92 also had standard X-rays. Crystal identification was the gold standard. Fifty-one patients had MSU, 28 CPP and 9 had both crystals by microscopic analysis. No crystals were detected in 21. One had septic arthritis. Based on US signs in the symptomatic joint, the sensitivity of US for both gout and CPP was low (60% for both). In gout, the presence of US signs in the symptomatic joint was highly predictive of the diagnosis (PPV = 92%). When US diagnosis was based on an examination of multiple joints, the sensitivity for both gout and CPP rose significantly but the specificity and the PPV decreased. In the absence of US signs in all the joints studied, CPP arthritis was unlikely (NPV = 87%) particularly in patients with no previous crisis (NPV = 94%). X-ray of the symptomatic joints was confirmed to be not useful in diagnosing gout and was equally sensitive or specific as US in CPP arthritis. Arthrocenthesis remains the key investigation for the diagnosis of microcrystalline acute arthritis. Although US can help in the diagnostic process, its diagnostic performance is only moderate. US should not be limited to the symptomatic joint. Examination of multiple joints gives a better diagnostic sensitivity but lower specificity

Computed tomography of the cervical spine: comparison of image quality between a standard-dose and a low-dose protocol using filtered back-projection and iterative reconstruction

Objective: To compare image quality of a standard-dose (SD) and a low-dose (LD) cervical spine CT protocol using filtered back-projection (FBP) and iterative reconstruction (IR). Materials and methods: Forty patients investigated by cervical spine CT were prospectively randomised into two groups: SD (120kVp, 275mAs) and LD (120kVp, 150mAs), both applying automatic tube current modulation. Data were reconstructed using both FBP and sinogram-affirmed IR. Image noise, signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were measured. Two radiologists independently and blindly assessed the following anatomical structures at C3-C4 and C6-C7 levels, using a four-point scale: intervertebral disc, content of neural foramina and dural sac, ligaments, soft tissues and vertebrae. They subsequently rated overall image quality using a ten-point scale. Results: For both protocols and at each disc level, IR significantly decreased image noise and increased SNR and CNR, compared with FBP. SNR and CNR were statistically equivalent in LD-IR and SD-FBP protocols. Regardless of the dose and disc level, the qualitative scores with IR compared with FBP, and with LD-IR compared with SD-FBP, were significantly higher or not statistically different for intervertebral discs, neural foramina and ligaments, while significantly lower or not statistically different for soft tissues and vertebrae. The overall image quality scores were significantly higher with IR compared with FBP, and with LD-IR compared with SD-FBP. Conclusion: LD-IR cervical spine CT provides better image quality for intervertebral discs, neural foramina and ligaments, and worse image quality for soft tissues and vertebrae, compared with SD-FBP, while reducing radiation dose by approximately 40

Isotropic three-dimensional T₂ mapping of knee cartilage: Development and validation.

1) To implement a higher-resolution isotropic 3D T <sub>2</sub> mapping technique that uses sequential T <sub>2</sub> -prepared segmented gradient-recalled echo (Iso3DGRE) images for knee cartilage evaluation, and 2) to validate it both in vitro and in vivo in healthy volunteers and patients with knee osteoarthritis. The Iso3DGRE sequence with an isotropic 0.6 mm spatial resolution was developed on a clinical 3T MR scanner. Numerical simulations were performed to optimize the pulse sequence parameters. A phantom study was performed to validate the T <sub>2</sub> estimation accuracy. The repeatability of the sequence was assessed in healthy volunteers (n = 7). T <sub>2</sub> values were compared with those from a clinical standard 2D multislice multiecho (MSME) T <sub>2</sub> mapping sequence in knees of healthy volunteers (n = 13) and in patients with knee osteoarthritis (OA, n = 5). The numerical simulations resulted in 100 excitations per segment and an optimal radiofrequency (RF) excitation angle of 15°. The phantom study demonstrated a good correlation of the technique with the reference standard (slope 0.9 ± 0.05, intercept 0.2 ± 1.7 msec, R <sup>2</sup> ≥ 0.99). Repeated measurements of cartilage T <sub>2</sub> values in healthy volunteers showed a coefficient of variation of 5.6%. Both Iso3DGRE and MSME techniques found significantly higher cartilage T <sub>2</sub> values (P < 0.03) in OA patients. Iso3DGRE precision was equal to that of the MSME T <sub>2</sub> mapping in healthy volunteers, and significantly higher in OA (P = 0.01). This study successfully demonstrated that high-resolution isotropic 3D T <sub>2</sub> mapping for knee cartilage characterization is feasible, accurate, repeatable, and precise. The technique allows for multiplanar reformatting and thus T <sub>2</sub> quantification in any plane of interest. 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:362-371

Three-dimensional assessment of impingement risk in geometrically parameterised hips compared with clinical measures

Abnormal bony morphology is a factor implicated in hip joint soft tissue damage and an increased lifetime risk of osteoarthritis. Standard two-dimensional radiographic measurements for diagnosis of hip deformities, such as cam deformities on the femoral neck, do not capture the full joint geometry and are not indicative of symptomatic damage. In this study, a three-dimensional geometric parameterisation system was developed to capture key variations in the femur and acetabulum of subjects with clinically diagnosed cam deformity. The parameterisation was performed for Computed Tomography scans of 20 patients (10 female, 10 male). Novel quantitative measures of cam deformity were taken and used to assess differences in morphological deformities between males and females. The parametric surfaces matched the more detailed, segmented hip bone geometry with low fitting error. The quantitative severity measures captured both the size and position of cams, and distinguished between cam and control femurs. The precision of the measures was sufficient to identify differences between subjects that could not be seen with the sole use of two-dimensional imaging. In particular, cams were found to be more superiorly located in males than in females. As well as providing a means to distinguish between subjects more clearly, the new geometric hip parameterisation facilitates the flexible and rapid generation of a range of realistic hip geometries including cams. When combined with material property models, these stratified cam shapes can be used for further assessment of the effect of the geometric variation under impingement conditions

Advanced Imaging of Glenohumeral Instability: It May Be Less Complicated than It Seems.

Glenohumeral joint instability is usually an intimidating topic for most radiologists due to both the complexity of related anatomical and biomechanical considerations and the increasing number of classifications and acronyms reported in the literature in association with this condition. In this short review, we aim to demystify glenohumeral instability by first focusing on the relevant anatomy and pathophysiology. Second, we will review what the important imaging findings are and how to describe them for the clinician in the most relevant yet simple way. The role of the radiologist in assessing glenohumeral instability lesions is to properly describe the stabilizing structures involved (bone, soft-tissue stabilizers, and their periosteal insertion) to localize them and to attempt to characterize them as acute or chronic. Impaction fractures on the glenoid and humeral sides are important to specify, locate, and quantify. In particular, the description of soft-tissue stabilizers should include the status of the periosteal insertion of the capsulo-labro-ligamentous complex. Finally, any associated cartilaginous or rotator cuff tendon lesion should be reported to the clinician

Subjective Evaluation of the In-Line Phase-Sensitive Imaging Systems in Breast Cancer Screening and Diagnosis

Breast x-ray imaging remains the gold standard screening tool despite the various imaging modalities. The phase-sensitive breast imaging is an evolving technology that may provide higher diagnostic accuracy and potentially reduce the patient radiation dose. Many studies evaluate the performance of the In-line phase-sensitive breast imaging to improve this imaging modality further. Whereas radiologists are the end-users of this imaging technology, the primary goal of this dissertation project is to investigate the performance of human observers in varying conditions for further improvement of the in-line phase-sensitive x-ray imaging system. A CDMAM phantom and an ACR mammography phantom are used in the observer performance study to compare the high-energy in-line phase-sensitive system with a mid-energy system as an alternative approach to balancing the attenuation-based image contrast with the accuracy of single-projection PAD-base phase-retrieval. Additionally, a series of ROC studies are designed by a contrast-detail phantom to evaluate the diagnostic accuracy of digital breast tomosynthesis (DBT) and the phase-sensitive prototype imaging system (PBT). The area under the ROC curves (AUC) and partial area under the ROC curves (pAUC) are estimated as a figure of merits in the two systems, delivering the equivalent radiation doses. A two-alternative-forced choice (2AFC) study is also designed to determine the preferred image in identifying the suspicious lesions within a heterogeneous pattern acquired by the DBT and PBT systems under an equivalent radiation dose. The observer performance studies show that the mid-energy system has a potential advantage in providing a relatively higher image quality while the radiation dose is reduced in the mid-energy system compared with a high-energy system. The ROC study shows that the diagnostic accuracy of observers is more significant in the prototype PBT system than in a commercial DBT system, delivering the same radiation dose. The 2AFC study also revealed that observers prefer the PBT system in detecting and distinguishing the conspicuity of tumors in the images with structural noise, and the results were statistically significant. The dissertation also introduces a mathematical approach for estimating the half-value-layer (HVL) from measured or simulated x-ray spectra. The HVL measurement is expected to be less accurate or experimentally challenging in some clinical equipment or when a quick beam quality evaluation is needed. Additionally, the impact of varying thicknesses of external filtration is subjectively and objectively investigated to evaluate the feasibility of reducing the image acquisition time in a mid-energy system without compromising the observer's performance and detectability. The preliminary results from phase-contrast images suggest that an in-line phase-sensitive system operated at 59 kV shows a comparable image quality with the x-ray beams filtered by 1.3 mm and 2.5 mm-thick aluminum filters. This finding could help shorten the exposure time by 34% in the mid-energy system, where image blurring is a concern due to patient movement in a longer image acquisition time. In summary, and as expected, the subjective analyses of the in-line phase-sensitive imaging system align with the previous findings. However, the PBT imaging system may benefit from further improvement in image processing algorithms and optimizing the system with the most appropriate x-ray beam quality, considering the acquisition time, breast glandular composition, breast thickness, and different x-ray energies. Keywords: Phase-sensitive X-ray Imaging, Breast Imaging, Image Quality, Human Observer Performance Stud