CT in osteoarthritis: its clinical role and recent advances.

Computed tomography (CT) is a widely available imaging method and considered as one of the most reliable techniques in bone assessment. Although CT has limited tissue contrast and needs radiation exposure, it has several advantages like fast scanning time and high spatial resolution. In this regard, CT has unique roles in osteoarthritis (OA) and its variable utilities have been reported. Hence, this review highlights the clinical role of CT in OA of representative joints. In addition, CT showed the several technical advancements recently, for example, acquiring the CT image with standing, obtaining the dual-energy data, and novel photon-counting detector development. Therefore, the recent studies and potential utility of these new CT systems in OA are also discussed.

Initial Experience of Using Dual-Energy CT with an Iodine Overlay Image for Hand Psoriatic Arthritis: Comparison Study with Contrast-enhanced MR Imaging.

Purpose To determine the feasibility of dual-energy (DE) computed tomography (CT) with an iodine overlay image (IOI) for evaluation of psoriatic arthritis in the hand. Materials and Methods Approval from the institutional ethics committee and written informed consent from all patients were obtained. This prospective study included 16 patients who had psoriasis with finger joint symptoms from January 2015 to January 2016. Contrast material-enhanced (CE) DE CT and 1.5-T CE magnetic resonance (MR) imaging were performed within 1 month of each other. DE CT was performed with a tube voltage of 80 kV and 140 kV with use of a 0.4-mm tin filter. Images acquired with both modalities were evaluated by two radiologists independently by using a semiquantitative scoring system. Interreader agreement was calculated for each modality: Weighted κ values were calculated for synovitis, flexor tenosynovitis, and extensor peritendonitis, and κ values were calculated for periarticular inflammation. With consensus scores and CE MR images as the reference, the sensitivity and specificity of IOI DE CT for inflammatory lesions were calculated. Statistical analysis of discordant readings was performed by using the McNemar test. Results Interreader agreement for inflammatory lesions was excellent or good (weighted κ = 0.83 and κ = 0.75 in IOI DE CT; weighted κ = 0.81 and κ = 0.87 in CE MR imaging). The sensitivity and specificity of IOI DE CT were 0.78 and 0.87, respectively. Total agreement was 86.3%; however, there were significantly more lesions detected with IOI DE CT than with CE MR imaging alone (134 vs 20 lesions in 1120 evaluated items; P < .001). Sixty-nine percent of the abnormalities detected with IOI DE CT alone were located in distal interphalangeal joints. Conclusion IOI DE CT is a new imaging modality that may be useful for evaluating psoriatic arthritis in the hand, particularly in the detection of inflammatory lesions in small joints, and may be more useful than CE MR imaging, within the limitation that there is no histopathologic reference. © RSNA, 2017.

Comparison of Bone Evaluation and Metal Artifact between Photon-Counting CT and Five Energy-Integrating-Detector CT under Standardized Conditions Using Cadaveric Forearms.

BACKGROUND: To compare the potential of various bone evaluations by considering photon-counting CT (PCCT) and multiple energy-integrating-detector CT (EIDCT), including three dual-energy CT (DECT) scanners with standardized various parameters in both standard resolution (STD) and ultra-high-resolution (UHR) modes. METHODS: Four cadaveric forearms were scanned using PCCT and five EIDCTs, by applying STD and UHR modes. Visibility of bone architecture, image quality, and a non-displaced fracture were subjectively scored against a reference EIDCT image by using a five-point scale. Image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were also compared. To assess metal artifacts, a forearm with radial plate fixation was scanned by with and without Tin filter (Sn+ and Sn-), and virtual monoenergetic image (VMI) at 120 keV was created. Regarding Sn+ and VMI, images were only obtained from the technically available scanners. Subjective scores and the areas of streak artifacts were compared. RESULTS: PCCT demonstrated significantly lower noise (p < 0.001) and higher bone SNR and CNR (p < 0.001) than all EIDCTs in both resolution modes. However, there was no significant difference between PCCT and EIDCTs in almost all subjective scores, regardless of scan modes, except for image quality where a significant difference was observed, compared to several EIDCTs. Metal artifact analysis revealed PCCT had larger artifact in Sn- and Sn+ (p < 0.001), but fewer in VMIs than three DECTs (p < 0.001 or 0.001). CONCLUSIONS: Under standardized conditions, while PCCT had almost no subjective superiority in visualizing bone structures and fracture line when compared to EIDCTs, it outperformed in quantitative analysis related to image quality, especially in lower noise and higher tissue contrast. When using PCCT to assess cases with metal implants, it may be recommended to use VMIs to minimize the possible tendency for artifact to be pronounced.

Quantitative biomarkers for distinguishing bone metastasis and benign bone marrow lesions using turbo spin echo T1- and T2-weighted Dixon imaging at 3.0 T.

Objective: To assess the diagnostic performance and calculate the optimal threshold for quantitative biomarkers to differentiate bone metastasis and benign bone marrow lesions using turbo spin echo (TSE) Dixon images with a 3.0 T scanner. Materials and methods: Each 100 patients diagnosed with bone metastases and variable benign bone marrow lesions on spine MRI were included retrospectively. Images included in-phase (IP), opposed-phase (OP), water images (WI), and fat images (FI) by the TSE Dixon technique with T1WI and T2WI using a 3.0 T scanner. Regions of interest (ROI) of the lesions were manually drawn by two musculoskeletal radiologists independently, and the average signal intensity was recorded. The signal reduction rate from IP to OP (%drop) and a fat fraction (%fat) were calculated. Results: All biomarkers showed a significant difference between metastatic and benign lesions (P < 0.001). When comparing the AUCs, the %drop of T1WI had the highest AUC (0.934). Although the AUC of %fat from T2WI was significantly lower than that of other biomarkers, the %drop of T2WI was not significantly different from the %drop of T1WI (p = 0.339). The optimal threshold of %drop to differentiate metastatic and benign lesions was 22.0 in T1WI and 15.9 in T2WI. The inter-reader agreement was excellent for all biomarkers (0.82-0.86). Conclusion: While %drop of T1WI showed the highest diagnostic performance to differentiate bone metastasis from benign lesions, the %drop of T2WI showed a comparable ability using a threshold 15.9.

Comparison of the axillary lymph node between rheumatoid arthritis and psoriatic arthritis with computed tomography.

Backgrounds: There is a lack of universally available biomarker to differentiate rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Purpose: to see if the size of the axillary lymphnodes (ALNs) and the frequency of lymphadenopathy are useful biomarker to differentiate RA and PsA. Material and Methods: Forty RA and 19 PsA patients without previous biologics usage were retrospectively included. Chest CT was assessed for the presence of lymphadenopathy and the size of the largest ALN. Frequency of lymphadenopathies was statistically compared between RA and PsA. The short axis and the long axis of the largest ALN were also compared and receiver operating characteristic (ROC) curve analysis was performed. Results: Frequency of axillary lymphadenopathy was significantly higher in RA than in PsA (80% vs 31.6%, p < .001). Number of lymphadenopathies in each patient was also significantly higher in RA than in PsA (3.0 vs 1.2 per patient, p = .005). Sensitivity and specificity for differentiating RA from PsA by the presence of at least one axillary lymphadenopathy were 0.8 and 0.68, respectively.The short axis of the largest ALNs in RA was significantly longer than in PsA (6.5 ± 1.6 mm vs 4.7 ± 1.7 mm, p < .001). ROC curve analysis of the short axis showed AUC of 0.75 (p = .002) and the cutoff value of 5.1 mm with a sensitivity of 0.83 and specificity of 0.74, when differentiating RA and PsA. Conclusion: Presence of ALN lymphadenopathy and the short axis of the largest ALN may have a potential utility in differentiating RA and PsA.

Four cases of Japanese patients with psoriatic arthritis in whom effective treatments by anti-tumor necrosis factor-α drugs were evaluated by magnetic resonance imaging together with improvement of skin lesions.

Because psoriatic skin lesions of psoriatic arthritis (PsA) usually precede the onset of joint symptom, dermatologists are in an ideal position to screen and find individuals with PsA early in the disease course. There have been no reports from the dermatology field evaluating the effect of anti-tumor necrosis factor (TNF)-α drugs on joint disorders using magnetic resonance imaging (MRI) in PsA patients. The purpose of this study was to elucidate the effectiveness of MRI in the evaluation of anti-TNF-α drugs on joint disease of Japanese PsA patients. Data were collected from four adult Japanese male PsA patients. MRI of the affected hand was performed at baseline and 1-7 months after infliximab or adalimumab treatment. T1 -weighted gadolinium-enhanced images with fat suppression were acquired in the coronal, sagittal and/or axial planes. We determined the apparent improvement of synovitis, periarticular inflammation, tenosynovitis and/or bone marrow edema by MRI after anti-TNF-α treatments in all the patients together with the improvement of skin lesions. We also determined in one patient that these symptoms detected by MRI before treatment were alleviated within 1 month and had disappeared 6 months after treatment, suggesting the potentially early detection of the effect of anti-TNF-α drugs on joint disease. We present four cases of Japanese patients with PsA in whom effective treatments by anti-TNF-α drugs were evaluated by contrast-enhanced MRI. This imaging enables dermatologists and radiologists to assess and monitor early inflammatory changes, and to grant PsA patients earlier access to modern treatment such as biologics.

Adalimumab markedly improves enthesitis in patients with psoriatic arthritis: Evaluation with a magnetic resonance imaging scoring system.

Psoriatic arthritis (PsA), a seronegative arthropathy, may often result in progressive joint damage without treatment, leading to disability and impaired quality of life. Early therapeutic intervention of PsA is therefore crucial before the development of irreversible joint damage. Because psoriatic skin lesions generally precede the onset of PsA, dermatologists occupy an important position in treating patients with early PsA. This study aimed to evaluate the efficacy of adalimumab in treating joint disease in patients with PsA, using the PsA magnetic resonance imaging scoring system (PsAMRIS). Five adult Japanese male patients with active PsA were treated with adalimumab. Magnetic resonance imaging was obtained at baseline and 8-32 weeks with 2-3 time points following adalimumab treatment and assessed using PsAMRIS. Adalimumab treatment markedly improved clinical symptoms and disease activities of joint disease, which was confirmed by the reduction of PsAMRIS scores in all patients. Bone marrow edema and periarticular inflammation, reflecting the presence of enthesitis, were dramatically improved at week 8, while improvement of synovitis and flexor tenosynovitis was observed later, at week 24 or 32. However, bone erosion was not improved by adalimumab treatment during the follow-up period. These results indicate that adalimumab treatment is associated with dramatic improvement of enthesitis in patients with PsA, whereas bone erosion may be resistant to such treatment. PsAMRIS appears to be useful for the evaluation of treatment efficacy in PsA.

Factors influencing on retro-odontoid soft-tissue thickness: analysis by magnetic resonance imaging.

STUDY DESIGN: A retrospective, consecutive case series. OBJECTIVE: To analyze the relationship between retro-odontoid soft-tissue thickness and patients' age, sex, and degenerative changes of cervical spine and to investigate the effect these factors have on retro-odontoid soft-tissue thickness. SUMMARY OF BACKGROUND DATA: Thickening of the soft tissue posterior to the odontoid process can form a retro-odontoid pseudotumor causing symptoms of spinal cord compression. Rheumatoid arthritis and long-term dialysis have been reported as possible causes for this. However, there have been reports of retro-odontoid pseudotumors without coexisting diseases. METHODS: Findings from a total of 503 cases of cervical spine magnetic resonance images were reviewed, and retro-odontoid soft-tissue thickness was measured. The values were matched for age, sex, presence of degenerative changes, rheumatoid arthritis, and dialysis and were analyzed for significance. RESULTS: Retro-odontoid soft tissue thickened with age, and this was also seen in male patients and patients with degenerative changes. Significant increase in thickness was also observed in patients undergoing dialysis and further increased with prolonged dialysis. There was no significant association with presence of rheumatoid arthritis. CONCLUSION: There is association between age, sex, degenerative cervical spine changes, and dialysis with retro-odontoid soft-tissue thickness. With dialysis, retro-odontoid soft-tissue thickness increases with increasing duration. Thus, reviewing magnetic resonance image from daily practice indicates that cervical spine degeneration is associated with the development of retro-odontoid pseudotumors.

MRI of bone marrow abnormalities in hematological malignancies.

Magnetic resonance imaging (MRI) is essential for evaluating bone marrow. Bone marrow undergoes constant modification and its appearance on MRI changes in response. Knowledge of the types of changes and their origins is essential for analysis of MRI findings of bone marrow infiltration with hematological malignancies. This pictorial review describes the MRI pulse sequences used for imaging of bone marrow, and illustrates bone marrow changes due hematological malignancies, including changes following treatment.

Assessment of left ventricular ejection fraction measured by quantitative gated SPECT: correlation with left ventriculography and first-pass radionuclide angiography.

PURPOSE: The purpose of this study was to evaluate the reliability of left ventricular ejection fraction (LVEF) measured by quantitative gated SPECT (QGS). We compared the efficacy of LVEF assessment among Tc-99m tetrofosmin gated SPECT imaging, contrast left ventriculography (LVG), and first-pass radionuclide angiography (FP). PATIENTS: One-hundred and seven patients with ischemic heart disease underwent QGS and LVG simultaneously within 3 months, and 92 of the 107 patients also underwent FP at the same time. RESULTS: QGS progressively overestimated LVEF at the lower range of end-systolic volume (ESV), especially in patients with small hearts. Moreover, the QGS technique systemically tended to underestimate LVEF in comparison with LVG. However, linear regression analysis demonstrated a good correlation between the LVEF values measured by QGS and those measured by both LVG (p<0.0001) and FP (p<0.0001). CONCLUSION: Although QGS has a tendency to overestimate LVEF in patients with small hearts, and to systemically underestimate LVEF compared with LVG, this technique is still a reliable clinical tool for measurement of LVEF.