Compressed Sensing SEMAC MRI of Hip, Knee, and Ankle Arthroplasty Implants: A 1.5-T and 3-T Intrapatient Performance Comparison for Diagnosing Periprosthetic Abnormalities

Iman Khodarahmi, MD, PhD, Harpal S. Khanuja, MD, Steven E. Stern, PhD, John A. Carrino, MD, MPH, and Jan Fritz, MD

AJR

https://www.ajronline.org/doi/abs/10.2214/AJR.23.29380?journalCode=ajr

Background:  The utility of 3-T MRI for diagnosing joint disorders is established, but its performance for diagnosing abnormalities around arthroplasty implants is unclear. CS -SEMAC (compressed sensing slice encoding for metal artifact correction) sequences was utilized for metal artifact correction in this study.

Question: Is 3-T better than 1.5-T CS-SEMAC MRI for diagnosing periprosthetic abnormalities around hip, knee, and ankle arthroplasty implants?

Design: Prospective study

Participants: Forty-five participants (mean age ± SD, 71 ± 14 years; 26 women, 19 men) with symptomatic lower extremity arthroplasty (hip, knee, and ankle, 15 each).

Methods: Forty-five participants with symptomatic lower extremity arthroplasty prospectively underwent consecutive 1.5- and 3-T MRI with intermediate-weighted (IW) and STIR CS-SEMAC sequences. Using a Likert scale, three radiologists evaluated presence or absence of periprosthetic abnormalities, including bone marrow edema–like signal, osteolysis, stress reaction/fracture, synovitis, tendon abnormalities and collections, image quality, and visibility of anatomic structures. Statistical analysis included nonparametric comparison and interchangeability testing.

Results:  

For diagnosing periprosthetic abnormalities, 1.5-T and 3-T CS-SEMAC MRI were interchangeable.

Across all three joints, 3 T produced lower noise than 1.5 T, sharper edges, and more effective metal artifact reduction.

Agreement was moderate to substantial for image contrast and joint capsule visualization.

The bone-implant interface was more visible at 1.5 T, but periprosthetic tissues had superior visibility at 3 T.

Conclusion:  Optimized 1.5-T and 3-T CS-SEMAC MRI are interchangeable for diagnosing periprosthetic abnormalities, although metallic artifacts are larger at 3 T. With CS-SEMAC MRI, lower extremity arthroplasty implants can be scanned at 3 T rather than 1.5 T.

Senior editorial comment: This is important research as metal imaging has traditionally been performed at 1.5 T as compared to 3T scanners despite superior signal to noise ratio at 3T imaging. Fast parallel imaging again showing promise in superior imaging at high field scanner. Congratulations!

Teaching points for residents:

• 5-T and 3-T MRI systems can use faster imaging using the Compressed Sensing SEMAC (CS-SEMAC) technique in diagnosing periprosthetic abnormalities around hip, knee, and ankle arthroplasty implants.
• Both 1.5-T and 3-T CS-SEMAC MRI are interchangeable for diagnosing periprosthetic abnormalities.
• The 3-T MRI produced images with lower noise, sharper edges, and more effective metal artifact reduction.
• The bone-implant interface was more visible at 1.5 T, while periprosthetic tissues had superior visibility at 3 T.
• Despite producing larger metallic artifacts, 3-T system could be used for scanning lower extremity arthroplasty implants with CS-SEMAC MRI technique.
• These findings suggest that despite traditionally being performed at 1.5 T due to metallic artifacts, higher field (3T) scanner can be used to scan your patients with metal implants.

Two-year Skeletal Effects of Sleeve Gastrectomy in Adolescents with Obesity Assessed with Quantitative CT and MR Spectroscopy

Florian A. Huber, Vibha Singhal, Shubhangi Tuli, Imen Becetti, Ana Paola López López, Mary L. Bouxsein, Madhusmita Misra, Miriam A. Bredella

Radiology

https://pubs.rsna.org/doi/10.1148/radiol.223256#

Background: Sleeve gastrectomy (SG) is effective in the treatment of cardiometabolic complications of obesity but is associated with bone loss. Sleeve gastrectomy reduces gastric volume, thereby affecting hormone secretion, which in turn can influence bone health, with an increased risk and prevalence of fractures in adults.

Question: What are the long-term effects of SG on vertebral bone strength, density, and bone marrow adipose tissue (BMAT) in adolescents and young adults with obesity?

Design: Prospective nonrandomized longitudinal study.

Participants: A total of 25 participants underwent SG (mean age, 18 years ± 2 [SD], 20 female), and 29 underwent dietary and exercise counseling without surgery (mean age, 18 years ± 3, 21 female).

Methods: This 2-year prospective nonrandomized longitudinal study enrolled adolescents and young adults with obesity who underwent either SG (SG group) or dietary and exercise counseling without surgery (control group) at an academic medical center from 2015 to 2020. Participants underwent quantitative CT of the lumbar spine (L1 and L2 levels) to assess bone density and strength, proton MR spectroscopy to assess BMAT (L1 and L2 levels), and MRI of the abdomen and thigh to assess body composition. Student t- and Wilcoxon signed-rank tests were used to compare 24-month changes between and within groups. Regression analysis was performed to evaluate associations between body composition, vertebral bone density, strength, and BMAT.

Results:

• Body mass index (BMI) decreased by a mean of 11.9 kg/m2 ± 5.21 [SD] after 24 months in the SG group, while it increased in the control group by a mean of 1.49 kg/m2 ± 3.10.
• Mean bone strength of the lumbar spine decreased after surgery compared with that in control subjects.
• BMAT of the lumbar spine increased after SG (mean lipid-to-water ratio increase, 0.10 ± 0.13; P = .001).
• Changes in vertebral density and strength correlated positively with changes in BMI and body composition and inversely with vertebral BMAT.

Conclusion: SG in adolescents and young adults reduced vertebral bone strength and density and increased BMAT compared with those in control participants. Adolescents and young adults with obesity had lower bone strength as assessed with quantitative CT and higher bone marrow adipose tissue as assessed with MR spectroscopy 24 months after sleeve gastrectomy compared with control participants who did not undergo surgery.

Senior editorial comment: interesting findings from this small study. The findings need further exploration from a larger study and clinical correlation for determining future fractures and quality of life among operated versus non-operated patients.

Teaching points for residents:

• Sleeve gastrectomy (SG), while effective for weight loss in obesity, is associated with bone loss due to its influence on hormone secretion.
• Imaging techniques like quantitative CT, proton MR spectroscopy, and MRI can be used to assess bone density, strength, bone marrow adipose tissue (BMAT), and body composition over time.
• In patints with SG a significant reduction in BMI post-SG, but also a decrease in vertebral bone strength and increase in bone marrow adipose tissue (BMAT), compared to the control group.
• There was a positive correlation between changes in vertebral density and strength with changes in BMI and body composition, and an inverse correlation with vertebral BMAT, showing a complex relationship between body weight, body composition, and bone health.
• The study emphasizes the need for long-term monitoring of bone health in patients who undergo SG due to the potential negative impacts on bone strength and increase in BMAT.

CT-guided Pulsed Radiofrequency Combined with Steroid Injection for Sciatica from Herniated Disk: A Randomized Trial

Alessandro Napoli , Giulia Alfieri, Alessandro De Maio, Emanuela Panella, Roberto Scipione, Giancarlo Facchini, Ugo Albisinni, Paolo Spinnato, Pier Giorgio Nardis, Roberto Tramutoli, Jacopo Lenzi, Pejman Ghanouni, Alberto Bazzocchi, Stefano Perotti, Andrew J. Schoenfeld, Carlo Catalano

Radiology

https://pubs.rsna.org/doi/full/10.1148/radiol.221478

Background: Evidence regarding effective nonsurgical management of sciatica remains limited.

Questions: Is combined pulsed radiofrequency (PRF) and transforaminal epidural steroid injection (TFESI) treatment more effective compared to TFESI alone for sciatic pain due to lumbar disk herniation?

Design: Prospective multicenter double-blind randomized clinical trial.

Participants: 351 participants

Methods: This prospective multicenter double-blind randomized clinical trial was conducted between February 2017 and September 2019 in participants with sciatica due to lumbar disk herniation lasting 12 weeks or longer that was not responsive to conservative treatment. Study participants were randomly assigned to undergo one CT-guided treatment with combined PRF and TFESI (n = 174) or TFESI alone (n = 177). The primary outcome was leg pain severity, as assessed with the numeric rating scale (NRS) (range, 0–10) at weeks 1 and 52 after treatment. Secondary outcomes included Roland-Morris Disability Questionnaire (RMDQ) score (range, 0–24) and Oswestry Disability Index (ODI) score (range, 0–100). Outcomes were analyzed according to the intention-to-treat principle via linear regression.

Results:

• In a prospective multicenter randomized trial, 351 participants with sciatica underwent either CT-guided pulsed radiofrequency (PRF) combined with transforaminal epidural steroid injection (TFESI) (n = 174) or TFESI alone (n = 177).
• At 4, 12, and 52 weeks, there was greater leg pain reduction (P < .001) and greater disability improvement (P < .001) in the combined PRF and TFESI group compared with the TFESI alone group.
• Adverse events were reported in 6% of participants (10 of 167) for combined PRF and TFESI and in 3% of participants (six of 176) for TFESI alone.

Conclusion: In the treatment of sciatica caused by lumbar disk herniation, pulsed radiofrequency combined with transforaminal epidural steroid injection is more effective for pain relief and disability improvement than steroid injection alone.

Senior editorial comment: excellent outcomes research and these are the kind of studies needed in the domain of advanced interventions and perineural injections as these are expensive treatments. Pulsed RFA is definitely underutilized for motor or mixed neuropathy treatments.

Teaching points for residents:

• The treatment of sciatica due to lumbar disk herniation, combined pulsed radiofrequency (PRF) and transforaminal epidural steroid injection (TFESI) proved more effective for pain relief and disability improvement than steroid injection alone.
• This suggests that combined PRF and TFESI could be a potent treatment option for patients suffering from sciatica due to lumbar disk herniation, particularly those not responding to conservative treatment.

68Ga-FAPI PET/CT for Rheumatoid Arthritis: A Prospective Study

Yaping Luo, Qingqing Pan, Ziyue Zhou, Min Li, Yanping Wei, Xu Jiang, Huaxia Yang, Fang Li

Radiology

https://pubs.rsna.org/doi/full/10.1148/radiol.222052

Background:  In rheumatoid arthritis (RA), fibroblast-like synoviocyte cells, which are involved in inflammation of the articular cartilage and bone, overexpress fibroblast activation protein (FAP). This is a feature that could be leveraged to improve imaging assessment of disease.

Questions:  Does gallium 68 (68Ga)-labeled FAP inhibitor (FAPI) perform better in assessing joint disease activity of compared to fluorine 18 (18F) fluorodeoxyglucose (FDG) imaging?

Design: Prospective study.

Participants: Twenty participants with RA (15 women; mean age, 55 years ± 10 [SD]).

Methods: Twenty participants with RA were prospectively enrolled from September 2020 to December 2021 and underwent clinical and laboratory assessment of disease activity and dual-tracer PET/CT (68Ga-FAPI and 18F-FDG) imaging. Imaging-derived variables of PET joint count (the number of joints positive for RA at PET) and PET articular index (a sum of the points of the joints using a three-point scale) were correlated to clinical and laboratory variables of disease activity.

Results:

• The combined output of both PET/CT techniques helped detect 244 affected joints, all of which showed positive results at 68Ga-FAPI PET/CT.
• However, fifteen of 244 (6.1%) FAPI-avid joints in six of 20 (30%) participants were not detected at 18F-FDG PET/CT.
• The maximum standardized uptake value of the most affected joint in each participant was higher in 68Ga-FAPI than in 18F-FDG PET/CT (9.54 ± 4.92 vs 5.85 ± 2.81, respectively; P = .001).
• The maximum standardized uptake values of the joints at both 68Ga-FAPI and 18F-FDG PET/CT were positively correlated with laboratory evaluation of C-reactive protein levels (r = 0.49 [P = .03] and 0.54 [P = .01], respectively).
• The PET joint count and PET articular index scores at 68Ga-FAPI PET/CT were also positively correlated with most clinical disease activity variables and radiographic progression of joint damage (P < .05).

Conclusion: In participants with rheumatoid arthritis who underwent gallium 68 fibroblast activation protein inhibitor PET/CT, the extent of joint involvement correlated with clinical and laboratory variables of disease activity and showed a greater amount and degree of affected joints than at fluorine 18 fluorodeoxyglucose PET/CT.

Senior editorial comment: nice pilot study demonstrating that PET-CT will become more specific with newer and more targeted PET agents. One, however, needs to justify the added expense of new agents as it pertains to patient outcomes and societal efficacy.

Teaching points for residents:

• In RA patients, gallium 68 (68Ga)-labeled fibroblast activation protein inhibitor (FAPI) shows a higher extent of joint involvement, correlates well with clinical and laboratory variables of disease activity, and outperforms fluorine 18 (18F) fluorodeoxyglucose (FDG) PET imaging in terms of showing a greater amount and degree of affected joints.
• So, 68Ga-FAPI PET/CT could be a more sensitive imaging modality for assessing your patients’ RA disease activity and progression.

Percutaneous Ablation, Osteoplasty, Reinforcement, and Internal Fixation for Pain and Ambulatory Function in Periacetabular Osteolytic Malignancies

Christopher M. Dussik, Courtney Toombs, Kareme D. Alder, Kristin E. Yu, Elisa R. Berson, Izuchukwu K. Ibe, Fangyong Li, Dieter M. Lindskog, Gary E. Friedlaender, Igor Latich, Francis Y. Lee

Radiology

Background: Osteolytic neoplasms to periacetabular bone frequently cause pain and fractures. Immediate recovery is integral to lifesaving ambulatory oncologic care and maintaining quality of life. Yet, open acetabular reconstructive surgeries are associated with numerous complications that delay cancer treatments.

Question: How effective is percutaneous ablation, osteoplasty, reinforcement, and internal fixation (AORIF) for short- and long-term pain and ambulatory function for periacetabular osteolytic neoplasm?

Design: Retrospective observational study.

Participants: 50 patients (mean age, 65 years ± 14 [SD]; 25 men, 25 women) with osteolytic periacetabular metastases or myeloma.

Methods: This study evaluated clinical data from 50 patients with osteolytic periacetabular metastases or myeloma. The primary outcome of combined pain and ambulatory function index score (range, 1 [bedbound] through 10 [normal ambulation]) was assessed before and after AORIF at 2 weeks and then every 3 months up to 40 months. Secondary outcomes included Eastern Cooperative Oncology Group (ECOG) score, infection, transfusion, 30-day readmission, mortality, and conversion hip arthroplasty. Serial radiographs and CT images were obtained to assess the hip joint integrity. The paired t test or Wilcoxon signed-rank test and Kaplan-Meier analysis were used to analyze data.

Results:

• Mean combined pain and ambulatory function index scores improved from 4.5 ± 2.4 to 7.8 ± 2.1 (P < .001) and median ECOG scores from 3 (IQR, 2–4) to 1 (IQR, 1–2) (P < .001) at the first 2 weeks after AORIF.
• Of 22 nonambulatory patients, 19 became ambulatory on their first post-AORIF visit.
• Pain and functional improvement were retained beyond 1 year, up to 40 months after AORIF in surviving patients.
• No hardware failures, surgical site infections, readmissions, or delays in care were identified following AORIF.
• Of 12 patients with protrusio acetabuli, one patient required a conversion hemiarthroplasty at 24 months.

Conclusion: The ablation, osteoplasty, reinforcement, and internal fixation, or AORIF, technique was effective for short- and long-term improvement of pain and ambulatory function in patients with periacetabular osteolytic neoplasm.

Senior editorial comment: Nice study using a mixed-bag of procedures, however in an important area where no treatment can lead to significant disability and increased mortality. Further larger studies are needed to validate these findings.

Teaching points for residents:

• Treating pain and ambulatory function in patients with periacetabular osteolytic neoplasms is challenging.
• Percutaneous ablation, osteoplasty, reinforcement, and internal fixation (AORIF) technique can be an effective method for short- and long-term management of pain and improvement of ambulatory function in patients with periacetabular osteolytic neoplasms, with minimal complications. This technique could offer a less invasive alternative to open acetabular reconstructive surgeries, reducing the risk of treatment delays and complications.

Three-dimensional MR Neurography of the Brachial Plexus: Vascular Suppression with Low-dose Ferumoxytol

Emily G. Pedrick, Darryl B. Sneag, Philip G. Colucci, Mylinh Duong, Ek T. Tan

Radiology

https://pubs.rsna.org/doi/full/10.1148/radiol.221087

Background: The efficacy of ferumoxytol, an ultrasmall superparamagnetic iron oxide particle for three-dimensional (3D) MR neurography, has yet to be evaluated. A challenge in MR neurography is distinguishing nerves from adjacent vessels that exhibit similar morphology and signal intensity due to their similar relaxivity properties. Intravenous gadolinium-based contrast agents that shorten both the T1 and T2 signal of blood provide superior vascular suppression and nerve visualization to noncontrast T2-weighted three-dimensional (3D) MR neurography but require gradient waveforms for flow suppression. To increase relaxation rate (R2 = 1/T2) for vascular suppression, one solution is to administer higher concentrations of gadolinium-based contrast agents, which unfortunately would reduce T1 as well. Alternatively, a different agent with stronger relaxation rates may be used. Ferumoxytol, an ultrasmall superparamagnetic iron oxide particle, also causes T1 and T2 shortening, but its relatively strong transverse relaxivity (R2 = 1/T2 is approximately seven times that of R1 = 1/T1) provides a theoretical advantage over gadolinium-based contrast agents for suppressing blood signal

Question: How effective is low-dose ferumoxytol for vascular suppression and nerve visualization in 3D brachial plexus MR neurography?

Design: Prospective study

Participants: 12 volunteers (mean age, 25 years ± 3; six women) without anemia were evaluated.

Methods:

Brachial plexus MR neurography was performed 30 minutes following infusion of 25% of the standard (510 mg of iron) therapeutic ferumoxytol dose with use of a 3D short-tau inversion recovery T2-weighted fast spin-echo sequence. The 3D fast spin-echo was acquired with and without the use of additional flow suppression techniques. Two musculoskeletal radiologists qualitatively evaluated examinations for the degree of vascular suppression (0–3, none to complete), nerve visualization (0–2, none to full), and motion artifact (0–4, none to severe). Nerve-to-fat, muscle, or vessel contrast ratios were calculated with use of manually drawn regions of interests. Comparisons of the proportion of scans with adequate image quality (vascular suppression, 3; nerve visualization, 1, 2; motion artifacts, 0, 1) were made with use of the McNemar test. Comparisons of quantitative contrast ratios were performed with use of Wilcoxon signed rank tests. P < .05 was deemed statistically significant.

Results:

• All individual nerve assessments of adequate nerve visualization increased from 4%–63% to 36%–100% without and with ferumoxytol, respectively, while motion artifacts were unchanged.
• Quantitatively, nerve-to-vessel contrast ratios increased from 0.6 without to 7.6 with ferumoxytol.
• The addition of flow suppression did not change nerve-to-vessel contrast ratio quantitatively (from 7.5 to 8.4, P > .99) following ferumoxytol.

Conclusion: Low-dose ferumoxytol improved vascular suppression and nerve visualization in three-dimensional MR neurography of the brachial plexus compared to imaging without ferumoxytol.

Senior editorial comment: nice small pilot study showing improved nerve visualization following additional iron-based iv contrast. It is however, important to show whether it improves pathology visualization or diagnostic confidence of the radiologists in rendering neuropathy diagnosis compared to standard 3D STIR imaging to justify the cost of additional contrast.

Teaching points for residents:

• Brachial plexus and nerve imaging need good resolution and visualization to improve diagnostic yield.
• Ferumoxytol, an ultrasmall superparamagnetic iron oxide particle, can enhance vascular suppression and nerve visualization in the brachial plexus’s three-dimensional (3D) MR neurography.
• The unique property of ferumoxytol having a strong transverse relaxivity makes it potentially superior to gadolinium-based contrast agents for suppressing blood signal. This demonstrates the need for a detailed understanding of the properties of contrast agents to use them effectively. Provides a potential alternate to Gadolinium agents.

Focused Ultrasound and External Beam Radiation Therapy for Painful Bone Metastases: A Phase II Clinical Trial

Alessandro Napoli, Alessandro De Maio , Giulia Alfieri, Chiara Gasperini, Roberto Scipione, Laura Campanacci, Giambattista Siepe, Francesca De Felice, Benedetta Siniscalchi, Lorenzo Chiurchioni, Vincenzo Tombolini, Davide Maria Donati, Alessio Giuseppe Morganti, Pejman Ghanouni, Carlo Catalano, Alberto Bazzocchi

Radiology

https://pubs.rsna.org/doi/full/10.1148/radiol.211857

Background: Recent consensus statements and clinical trials have assessed the value of MRI-guided focused ultrasound surgery for pain palliation of bone metastases; however, a comparison with external beam radiation therapy (EBRT) has not been performed.

Question: How safe and effective is MRI-guided focused ultrasound in the treatment of bone metastases compared to EBRT?

Design: Prospective open-label nonrandomized phase II study

Participants: Among 198 participants, 100 underwent MRI-guided focused ultrasound (mean age, 63 years ± 13 [SD]; 51 women), and 98 underwent EBRT (mean age, 65 years ± 14; 52 women).

Methods: Participants with painful bone metastases, excluding skull and vertebral bodies, were enrolled between January 2017 and May 2019 and underwent either MRI-guided focused ultrasound or EBRT. The primary end point was the overall response rate at 1-month following treatment, assessed via the numeric rating scale (NRS) for pain (0–10 scale, with zero meaning “no pain” and 10 meaning “the worst pain imaginable”). Secondary end points were improvements at 12-month follow-up in NRS and quality of life (QoL) measures, including the Brief Pain Inventory (BPI), QoL-Questionnaire Cancer-15 Palliative Care (QLQ-C15-PAL), and QoL-Questionnaire Bone Metastases-22 (QLQ-BM22) and analysis of adverse events. Statistical analyses, including linear regression, χ2 test, and Student t test followed the per-protocol principle.

Results

• The overall response rates at 1-month follow-up were 91% (91 of 100) and 67% (66 of 98), respectively, in the focused ultrasound and EBRT arms, and complete response rates were 43% (43 of 100) and 16% (16 of 98) (P < .001).
• The mean baseline NRS score was 7.0 ± 2.1 for focused ultrasound and 6.6 ± 2.4 for EBRT (P = .16); at 1-month follow-up, they were reduced to 3.2 ± 0.3 and 5.1 ± 0.3 (P < .001), respectively.
• QLQ-C15-PAL for physical function, appetite, nausea and vomiting, dyspnea, and QoL scores were lower in the focused ultrasound group.
• The overall adverse event rates were 15% (15 of 100) after focused ultrasound and 24% (24 of 98) after EBRT.

Conclusion: Overall pain response rates assessed with the numeric rating scale were higher for focused ultrasound than for EBRT at 1 month and 12 months. MRI-guided focused ultrasound surgery and external beam radiation therapy showed similar improvements in pain palliation and quality of life, with low adverse event rates.

Senior editorial comment: Focused US treatment is making quick inroads in several non-invasive therapeutic approaches for different diseases. Excellent study showing the same. Congratulations!

Teaching points for residents:

• Residents should understand the role of innovative technologies like MRI-guided focused ultrasound in enhancing the management of conditions such as bone metastases and can potentially reduce pain and symptoms.

MRI Quantification of Cortical Bone Porosity, Mineralization, and Morphologic Structure in Postmenopausal Osteoporosis

Brandon C. Jones, Hyunyeol Lee1, Cheng-Chieh Cheng2, Mona al Mukaddam, Hee Kwon Song, Peter J. Snyder, Nada Kamona, Chamith S. Rajapakse, Felix W. Wehrli

Radiology

https://pubs.rsna.org/doi/full/10.1148/radiol.221810

Background: Preclinical studies have suggested that solid-state MRI markers of cortical bone porosity, morphologic structure, mineralization, and osteoid density are useful measures of bone health. DXA only helps measure areal density and can neither differentiate cortical bone from trabecular bone nor distinguish between the structural and material properties that determine bone mechanical competence, which are the chief determinants of OP fracture risk. Although cortical bone microarchitecture is usually measured with high-resolution CT, advances in solid-state MRI techniques of ultrashort echo time (UTE) and zero echo time sequences enabled quantification of previously undetectable signals in tissues with solid-like MRI properties (ie, short lifetime of excited spins), similar to those from cortical bone water residing in pores (known as pore water) and water hydrogen-bonded to the osteoid (known as bound water [BW]. Furthermore, phosphorus (P) density (31P) solid-state MRI was shown to image bone mineral in human wrists and, recently, actual 31P densities were reported in the tibia. Pore water, a measure of porosity, was shown in cadaver studies to predict bone strength and density. BW, a measure of osteoid density, is related to bone’s post-yield properties. Finally, simultaneous measurement of 31P and BW can yield a noninvasive marker for degree of mineralization of bone (ie, the ratio of mineral to osteoid densities, found with the 31P-to-BW ratio).

Questions?

Are MRI markers of cortical bone porosity, morphologic structure, mineralization, and osteoid density affected in postmenopausal osteoporosis (OP)?

What are the associations between MRI markers and bone mineral density (BMD) in postmenopausal women?

Design: Prospective study.

Participants: Fifteen participants with OP (mean age, 63 years ± 5 [SD]) and 19 participants without OP (mean age, 65 years ± 6) were evaluated.

Methods:

In this single-center study, postmenopausal women were prospectively recruited from January 2019 to October 2020 into two groups: participants with OP who had not undergone treatment, defined as having any dual-energy x-ray absorptiometry (DXA) T-score of −2.5 or less, and age-matched control participants without OP (hereafter, non-OP). Participants underwent MRI in the midtibia, along with DXA in the hip and spine, and peripheral quantitative CT in the midtibia. Specifically, MRI measures of cortical bone porosity (pore water and total water), osteoid density (bound water [BW]), morphologic structure (cortical bone thickness), and mineralization (phosphorous [P] density [31P] and 31P-to-BW concentration ratio) were quantified at 3.0 T. MRI measures were compared between OP and non-OP groups and correlations with BMD were assessed.

Results

• The OP group had elevated pore water and total water densities and had lower cortical bone thickness and 31P density than the non-OP group, respectively, although there was no evidence of a difference in BW or 31P-to-BW concentration ratio.
• Pore and total water densities were inversely associated with DXA and peripheral quantitative CT BMD, whereas cortical bone thickness and 31P density were positively associated with DXA and peripheral quantitative CT BMD. BW, 31P density, and 31P-to-BW concentration ratio were positively associated with DXA, but not with peripheral quantitative CT.
• An MRI marker of cortical porosity, pore water, explained 70% (r2 = 0.70) of the variation in bone mineral density (BMD) in the same tibia location, indicating that variations in BMD reflect differences in pore volume fraction.

Conclusion: Solid-state MRI markers of cortical bone porosity, morphologic structure, and mineralization were associated with bone mineral density in postmenopausal women, and they helped detect impairments in bone quality associated with postmenopausal osteoporosis.

Senior editorial comment: Very small study and correlations done with DEXA. Needs further validation in a larger cohort and with patient outcomes to justify MRI expense.

Teaching points for residents:

• Using MRI, osteoporotic women showed elevated pore water and total water densities and had lower cortical bone thickness and phosphorus density than non-osteoporotic women.
• These MRI measures were found to be associated with bone mineral density, as assessed by DXA and peripheral quantitative CT. For example, pore and total water densities were inversely associated with bone mineral density.
• There is a potential benefit of using MRI markers to differentiate between structural and material properties of the bone, which could be instrumental in determining fracture risk, a crucial aspect of osteoporosis management.
• MRI can be added to different imaging modalities, like, DXA, and peripheral quantitative CT, which can offer complementary information about bone health.

Twin Robotic Gantry-Free Cone-Beam CT in Acute Elbow Trauma

Andreas Steven Kunz , Jonas Schmalzl, Henner Huflage, Karsten Sebastian Luetkens, Theresa Sophie Patzer, Philipp Josef Kuhl, Philipp Gruschwitz, Bernhard Petritsch, Rainer Schmitt, Thorsten Alexander Bley, Jan-Peter Grunz

Radiology

https://pubmed.ncbi.nlm.nih.gov/36346312/

Background: Posttraumatic CT imaging of the elbow can be challenging when patient mobility is limited. Gantry-free cone-beam CT (CBCT) with a twin robotic radiography system offers greater degrees of positioning freedom for three-dimensional elbow scans over gantry-based multidetector CT (MDCT), but studies analyzing their clinical value remain lacking.

Question: What is the diagnostic performance of gantry-free CBCT compared to two-dimensional radiography in adults and children with acute elbow trauma?

Design: Retrospective study

Participants: Elbow examinations of 23 adults and children (mean age ± SD, 49 years ± 23; seven women) were included with individual assessment of humerus, radius, and ulna (69 bones; 36 fractured).

Methods:

In a retrospective study, consecutive patients with elbow trauma and positioning difficulty in a gantry-based MDCT who underwent three-dimensional elbow imaging with a gantry-free CBCT after radiography were enrolled between January 2021 and April 2022 at a tertiary care university hospital. Imaging data sets were independently analyzed for fracture presence, articular involvement, and multi-fragment injuries by three radiologists. Diagnostic performance was calculated individually with surgical reports serving as the reference standard. Differences between radiography and CBCT were compared with the McNemar test. Diagnostic confidence was estimated subjectively by each reader, and results were compared with the Wilcoxon signed-rank test.

Results: 

• In a retrospective study, elbow fractures in 23 adults and children with positioning difficulty in gantry-based CT were diagnosed with similar or higher sensitivity by three readers with gantry-free cone-beam CT (CBCT) (range, 94%–100%) than two-dimensional radiography (range, 72%–81%).
• Gantry-free CBCT of the elbow region was performed with low radiation dose (median dose-length product, 70.9 mGy · cm; median volume CT dose index, 4.4 mGy), even in patients with limited joint mobility.

Conclusion: In acute elbow injuries, gantry-free cone-beam CT enabled improved detection of fractures, articular involvement, and multi-fragmentary patterns compared with two-dimensional radiography. Gantry-free cone-beam CT with a twin robotic radiography system allows for excellent diagnostic performance for the diagnosis of fractures and fracture-related findings in elbow joint examinations with low radiation dose.

Senior editorial comment: This is an excellent system and probably more cost-effective with superior resolution to diagnose musculoskeletal injuries and pathologies. Well-done! Congratulations!

Teaching points for residents:

• A gantry-free CBCT with a twin robotic radiography system allows excellent diagnostic performance for the diagnosis of fractures and fracture-related findings in elbow joint examinations with a low radiation dose, and can be a more effective and possibly cost-efficient solution for diagnosing musculoskeletal injuries and pathologies.

Synovial Oxygenation at Photoacoustic Imaging to Assess Rheumatoid Arthritis Disease Activity

Meng Yang*, Chenyang Zhao*, Ming Wang, Qian Wang, Rui Zhang, Wei Bai, Jian Liu, Shangzhu Zhang, Dong Xu, Sirui Liu, Xuelan Li, Zhenhong Qi, Fang Yang, Lei Zhu, Xujin He, Xinping Tian, Xiaofeng Zeng, Jianchu Li, Yuxin Jiang

Radiology

https://pubs.rsna.org/doi/10.1148/radiol.212257

Background:  Synovial hypoxia is a hallmark of rheumatoid arthritis (RA). Photoacoustic (PA) imaging, based on the use of laser-generated US, can detect the oxygenation status of tissue in individuals with RA. However, large studies are lacking, with few investigating the correlation between oxygenation status and disease activity.

Questions: What is the correlation between PA imaging–measured oxygen saturation (SO2) and disease activity?

Design: Prospective observational cohort study

Participants: A total of 118 participants with RA (median age, 55 years [IQR, 41–62 years]; 92 women) and 15 healthy control participants (median age, 37 years [IQR, 33–41 years]; 11 women) were included.

Methods: Multimodal PA US imaging examinations were performed on small joints of consecutive participants with RA, who were treated at two outpatient rheumatology clinics from 2019 to 2021, and healthy controls. The SO2 values of the synovium were measured with dual-wavelength PA imaging and classified into three categories—hyperoxia, intermediate oxygenation status, or hypoxia—based on the signal coloration and clustering analysis of the SO2 values. The correlations of oxygenation status with power Doppler US (PDUS) scoring and clinical disease activity index were evaluated with one-way analysis of variance and the Kruskal-Wallis test with Bonferroni correction.

Results:

• In this prospective study of 118 participants with rheumatoid arthritis (RA) and 15 control participants, the oxygen saturation values of the synovium measured with photoacoustic imaging were classified as hyperoxia, intermediate oxygenation status, or hypoxia.
• In participants with RA, hypoxia in thickened synovium had less local Doppler US–depicted vascularization than hyperoxic synovium (mean Doppler US grades, 2.7 vs 1.1; P < .001).
• Hypoxic joints had higher clinical disease activity than those with an intermediate oxygenation status (clinical disease activity index, 11.0 vs 26.0; P = .001)

Conclusion: Photoacoustic imaging–detected hypoxia in thickened synovium correlated with less vascularization and higher disease activity in participants with rheumatoid arthritis.

Senior editorial comment: Novel evaluation of RA and inflammation. Very few controls is a significant limitation of the study.

Teaching points for residents:

• Synovial hypoxia (low oxygen levels in the synovial tissue) is a key feature of RA.
• Photo Acoustic imaging, which utilizes laser-generated ultrasound, can assess the oxygenation status of tissue, including the synovium.
• In RA patients, hypoxic (low oxygen level) synovium showed less local Doppler US–depicted vascularization compared to hyperoxic (high oxygen level) synovium.
• Hypoxic joints likely have higher clinical disease activity than those with an intermediate oxygenation status.
• Hypoxia detected in thickened synovium via PA imaging is associated with less vascularization and higher disease activity in RA patients.
• PA imaging can be used as a diagnostic tool for assessing disease activity in RA.