Chances and challenges of photon-counting CT in musculoskeletal imaging.

In musculoskeletal imaging, CT is used in a wide range of indications, either alone or in a synergistic approach with MRI. While MRI is the preferred modality for the assessment of soft tissues and bone marrow, CT excels in the imaging of high-contrast structures, such as mineralized tissue. Additionally, the introduction of dual-energy CT in clinical practice two decades ago opened the door for spectral imaging applications. Recently, the advent of photon-counting detectors (PCDs) has further advanced the potential of CT, at least in theory. Compared to conventional energy-integrating detectors (EIDs), PCDs provide superior spatial resolution, reduced noise, and intrinsic spectral imaging capabilities. This review briefly describes the technical advantages of PCDs. For each technical feature, the corresponding applications in musculoskeletal imaging will be discussed, including high-spatial resolution imaging for the assessment of bone and crystal deposits, low-dose applications such as whole-body CT, as well as spectral imaging applications including the characterization of crystal deposits and imaging of metal hardware. Finally, we will highlight the potential of PCD-CT in emerging applications, underscoring the need for further preclinical and clinical validation to unleash its full clinical potential.

Morphological assessment of cartilage and osteoarthritis in clinical practice and research: Intermediate-weighted fat-suppressed sequences and beyond.

Magnetic resonance imaging (MRI) is widely regarded as the primary modality for the morphological assessment of cartilage and all other joint tissues involved in osteoarthritis. 2D fast spin echo fat-suppressed intermediate-weighted (FSE FS IW) sequences with a TE between 30 and 40ms have stood the test of time and are considered the cornerstone of MRI protocols for clinical practice and trials. These sequences offer a good balance between sensitivity and specificity and provide appropriate contrast and signal within the cartilage as well as between cartilage, articular fluid, and subchondral bone. Additionally, FS IW sequences enable the evaluation of menisci, ligaments, synovitis/effusion, and bone marrow edema-like signal changes. This review article provides a rationale for the use of FSE FS IW sequences in the morphological assessment of cartilage and osteoarthritis, along with a brief overview of other clinically available sequences for this indication. Additionally, the article highlights ongoing research efforts aimed at improving FSE FS IW sequences through 3D acquisitions with enhanced resolution, shortened examination times, and exploring the potential benefits of different magnetic field strengths. While most of the literature on cartilage imaging focuses on the knee, the concepts presented here are applicable to all joints. KEY POINTS: 1. MRI is currently considered the modality of reference for a "whole-joint" morphological assessment of osteoarthritis. 2. Fat-suppressed intermediate-weighted sequences remain the keystone of MRI protocols for the assessment of cartilage morphology, as well as other structures involved in osteoarthritis. 3. Trends for further development in the field of cartilage and joint imaging include 3D FSE imaging, faster acquisition including AI-based acceleration, and synthetic imaging providing multi-contrast sequences.

Advances in Bone Marrow Imaging: Strengths and Limitations from a Clinical Perspective.

Conventional magnetic resonance imaging (MRI) remains the modality of choice to image bone marrow. However, the last few decades have witnessed the emergence and development of novel MRI techniques, such as chemical shift imaging, diffusion-weighted imaging, dynamic contrast-enhanced MRI, and whole-body MRI, as well as spectral computed tomography and nuclear medicine techniques. We summarize the technical bases behind these methods, in relation to the common physiologic and pathologic processes involving the bone marrow. We present the strengths and limitations of these imaging methods and consider their added value compared with conventional imaging in assessing non-neoplastic disorders like septic, rheumatologic, traumatic, and metabolic conditions. The potential usefulness of these methods to differentiate between benign and malignant bone marrow lesions is discussed. Finally, we consider the limitations hampering a more widespread use of these techniques in clinical practice.

Magnetic Resonance Imaging of Accelerated Bone Remodeling.

A regional acceleration of bone remodeling may possibly follow biomechanical insults to the bone. This review assesses the literature and clinical arguments supporting the hypothetical association between accelerated bone remodeling and bone marrow edema (BME)-like signal intensity on magnetic resonance imaging. BME-like signal is defined as a confluent ill-delimited area of bone marrow with a moderate decrease in signal intensity on fat-sensitive sequences and a high signal intensity on fat-suppressed fluid-sensitive sequences. In addition to this confluent pattern, a linear subcortical pattern and a patchy disseminated pattern have also been recognized on fat-suppressed fluid-sensitive sequences. These particular BME-like patterns may remain occult on T1-weighted spin-echo images. We hypothesize that these BME-like patterns, with particular characteristics in terms of distribution and signal, are associated with accelerated bone remodeling. Limitations in recognizing these BME-like patterns are also discussed.

The Many Faces of Marrow Necrosis.

Depending on the age and location within the skeleton, bone marrow can be mostly fatty or hematopoietic, and both types can be affected by marrow necrosis. This review article highlights the magnetic resonance imaging findings of disorders in which marrow necrosis is the dominant feature.Fatty marrow necrosis is detected on T1-weighted images that show an early and specific finding: the reactive interface. Collapse is a frequent complication of epiphyseal necrosis and detected on fat-suppressed fluid-sensitive sequences or using conventional radiographs. Nonfatty marrow necrosis is less frequently diagnosed. It is poorly visible on T1-weighted images, and it is detected on fat-suppressed fluid-sensitive images or by the lack of enhancement after contrast injection.Pathologies historically "misnamed" as osteonecrosis but do not share the same histologic or imaging features of marrow necrosis are also highlighted.

Automated Detection of Patient Harm: Implementation and Prospective Evaluation of a Real-Time Broad-Spectrum Surveillance Application in a Hospital With Limited Resources.

OBJECTIVES: This study aimed to prospectively validate an application that automates the detection of broad categories of hospital adverse events (AEs) extracted from a basic hospital information system, and to efficiently mobilize resources to reduce the level of acquired patient harm. METHODS: Data were collected from an internally designed software, extracting results from 14 triggers indicative of patient harm, querying clinical and administrative databases including all inpatient admissions (n = 8760) from October 2019 to June 2020. Representative samples of the triggered cases were clinically validated using chart review by a consensus expert panel. The positive predictive value (PPV) of each trigger was evaluated, and the detection sensitivity of the surveillance system was estimated relative to incidence ranges in the literature. RESULTS: The system identified 394 AEs among 946 triggered cases, associated with 291 patients, yielding an overall PPV of 42%. Variability was observed among the trigger PPVs and among the estimated detection sensitivities across the harm categories, the highest being for the healthcare-associated infections. The median length of stay of patients with an AE showed to be significantly higher than the median for the overall patient population. CONCLUSIONS: This application was able to identify AEs across a broad spectrum of harm categories, in a real-time manner, while reducing the use of resources required by other harm detection methods. Such a system could serve as a promising patient safety tool for AE surveillance, allowing for timely, targeted, and resource-efficient interventions, even for hospitals with limited resources.

Osteoarthritis of the hip: is radiography still needed?

Diagnosis of hip osteoarthritis (OA) is based on clinical arguments, and medical imaging is obtained to confirm the diagnosis and rule out other possible sources of pain. Conventional radiographs are recommended as the first line imaging modality to investigate chronic hip pain. They should be obtained in a rigorous technique that includes an antero-posterior (AP) radiograph of the pelvis. The choice of the appropriate lateral view depends on the clinical indication, Lequesne's false profile being valuable in the assessment of OA. Magnetic resonance imaging (MRI) is more sensitive to detect joint effusion/synovitis, cartilage, labral, and bone marrow lesions. However, structural joint changes are frequent in asymptomatic population and neither radiographs nor MRI have shown a good correlation with pain and functional impairment. MRI seems to be more suitable than radiographs as a biomarker for clinical trials addressing early OA. The absence of a validated MR biomarker of early OA, together with issues related to machine availability and MRI protocol repeatability, prevent the widespread use of MRI in clinical trials.

Collapse-related bone changes at multidetector CT in ARCO 1-2 osteonecrotic femoral heads: correlation with clinical and MRI data.

OBJECTIVE: To assess the frequency of collapse-related bone changes at multi-detector CT (MDCT) in osteonecrotic femoral heads (ONFH) and to compare clinical parameters and MRI findings in Association Research Circulation Osseous (ARCO) 1-2 ONFH with or without collapse-related bone changes (CRBC) at MDCT. MATERIALS AND METHODS: This is a secondary analysis of radiographic, MRI, and MDCT examinations of ONFH of patients eligible for a prospective clinical trial. Radiographs and MRI were analyzed to perform ARCO staging. Frequency of CRBC at MDCT including cortical interruption, trabecular interruption, impaction, and resorption was determined by two readers (R1, R2) blinded to radiographic, MRI, and clinical data. Baseline clinical and imaging data of ARCO 1-2 ONFH were compared between hips with or without CRBC at MDCT. RESULTS: One hundred thirty-two hips of 77 participants were analyzed. There were 78 non-collapsed and 54 collapsed ONFH. For R1 and R2, 31/78 (40%) and 20/78 (26%) ARCO 1-2 ONFH and 54/54 (100%) and 53/54 (98%) ARCO 3-4 ONFH showed at least one CRBC at MDCT. For both readers, there was no significant difference in pain, functional impairment, size of lesion, and the presence of BME on MRI between ARCO 1-2 hips with or without CRBC at MDCT. CONCLUSION: Twenty-six to forty percent of ARCO 1-2 ONFH demonstrate at least one collapse-related bone change at CT. Their clinical and MRI findings do not differ from those without collapse-related bone changes. KEY POINTS: • Ninety-eight to one hundred percent of collapsed and 26-40% of non-collapsed osteonecrotic femoral heads presented at least one collapse-related bone change at CT (cortical or trabecular bone interruption, trabecular bone impaction, or resorption). • There was no significant difference in age, sex, pain, functional impairment, size of lesion, or frequency of marrow edema on MRI between non-collapsed hips with or without collapse-related bone changes at CT. • The significance of collapse-related bone changes at CT should be further assessed.

The Use of Medical Imaging Request Forms as Trigger Tools to Detect Intra-Hospital Adverse Events: A Pilot Study.

Aim: To evaluate the contribution of medical imaging request forms as trigger tools to detect patient adverse event (AE) occurring during hospitalization. Material and Methods: This is a retrospective study in a single institution. Between January and June 2019, the hospital information system (HIS) was fetched for request forms of radiological examinations performed for inpatients >48 hours after the admission date. The investigated request forms were: Doppler ultrasound of the upper limbs, Doppler ultrasound of the lower limbs, and the repetition of three consecutive requests of chest radiographs within 24 hrs, to detect upper or lower limb venous thrombosis, or AEs related to the respiratory system, respectively. Patients' medical charts and radiological examinations were evaluated to document the presence or absence of an AE. The frequencies of AEs in the three groups of trigger tools were compared to corresponding control groups, matched according to age, sex and length of stay. Results: Among a total of 2798 hospital admissions during the study period, there were 74 files triggered by the three types of radiological request forms. There were 6/24 AE (25%) related to upper limb venous thrombosis, 4/33 (12.1%) AE related to lower limb venous thrombosis, and 6/17 (35.3%) AE related to the respiratory system. For all the trigger tools, the frequency of AE in the study groups was significantly higher than that in the control groups. Conclusion: Medical imaging requests could be used as potential trigger tools to detect adverse events related to hospital stay.

Collapse-Related Bone Changes in Osteonecrotic Femoral Heads at Multidetector CT: Comparison between Femoral Heads with Limited and Advanced Collapse.

Aim: To assess the frequency of bone changes in resected osteonecrotic femoral head (ONFH) specimens at multidetector computed tomography (MDCT) and compare their frequencies between ONFH with limited or advanced collapse. Method: Fourteen ONFH were imaged using MDCT (n = 14) and microcomputed tomography ([µCT]; n = 8). Preoperative staging was performed using radiographs and MRI. Coronal reformats of MDCT images of the specimens were analyzed using the grid overlay method. There were 2,933 grid boxes containing cortical bone and 10,596 containing trabecular bone. Two MSK radiologists assessed in every grid box the presence of interface-related sclerosis, cortical bone interruption, trabecular bone interruption, and trabecular bone resorption. The frequency of grid boxes with bone changes at MDCT was calculated and compared between ONFH with limited (<1.5 mm) or advanced (≥1.5 mm) collapse. Results: For both readers R1 and R2, there were 1111/10596 (10.5%) and 1362/10596 (12.9%) grid boxes with interface-related bone sclerosis, 557/2933 (19%) and 413/2933 (14.1%) with cortical bone interruption, 796/10596 (7.5%) and 665/10596 (6.3%) with trabecular bone interruption, and 331/10596 (3.1%) and 595/10596 (5.6%) with trabecular bone resorption. The frequency of grid boxes with cortical interruption and trabecular bone resorption was significantly higher in ONFH with advanced than in ONFH with limited collapse. There was no significant difference in frequency of grid boxes with trabecular interruption and interface-related bone sclerosis between ONFH with advanced or limited collapse. Conclusion: Cortical interruption and trabecular resorption, but not trabecular interruption, were more frequent in osteonecrotic femoral heads with advanced than with limited collapse.

Intradural dermoid cyst with complete dermal sinus of the posterior fossa: Contribution of 3D imaging with histopathological correlation.

A 5-year-old girl who presented with two episodes of meningitis, had a patchy red area and a small skin dimple in the midline of the occiput on physical examination. Imaging revealed a well-demarcated oval intradural lesion of the posterior fossa with restricted diffusion and peripheral enhancement, raising the possibility of an abscess. The 3D volume rendering of CT images of the inner surface of bone showed chronic bone remodeling and a tiny bone defect of the outer table. This detailed anatomical evaluation has an added value to MRI characteristics to orient for a preoperative diagnosis of an intradural dermoid cyst with a dermal sinus, that was confirmed by histopathological analysis after surgical excision.

Topology of microfractures in osteonecrotic femoral heads at µCT and histology.

AIM: To assess the topology of bone and cartilage microfractures in osteonecrotic femoral heads. METHOD: Sixteen resected human femoral heads with collapsed osteonecrosis (ON, n = 11) or osteoarthritis (OA, n = 5) were imaged at µCT with 12 µ nominal resolution. Forty-seven histological sections and µCT reformats with (n = 30) or without (8 from ON and 9 from OA femoral heads) osteonecrotic lesions were obtained and divided in 2 × 2 mm segments by a superposed grid. A radiologist and a pathologist separately assessed the presence of bone and cartilage microfractures in each segment on µCT and histological images, respectively. We determined the frequency and distribution of segments with bone microfractures according to a zonal distribution. Matrix analysis was performed by using Matlab to calculate the connectivity index and long/short axis ratios of clustered segments with microfractures. RESULTS: Segments with bone microfractures but not with cartilage microfractures were found more frequently in ON than in OA femoral heads. In the 38 matched µCT and histological images from ON femoral heads, 86%/82% of segments with cortical microfracture, 91%/96% of segments with trabecular microfractures involved ON lesions at µCT/histology. At histology, 83% of segments with cartilage microfractures involved ON lesions. In the 30 paired µCT and histological images containing necrotic lesions, the frequency of segments with trabecular microfractures in the superficial layers (55% at µCT/51% at histology) was statistically significantly higher than in the deep layer (25% P < 0.0001/35%; P = 0.0006). Clustered segments with cortical/trabecular microfractures, exclusively found in osteonecrotic lesions, had a connectivity index >2.0/20.0 and mean long/short axis ratio > 2.35/2.2, respectively. CONCLUSION: Segments with bone microfractures predominate in necrotic lesions. Segments with trabecular microfractures form elongated clusters near the femoral head surface.

Value of CT to detect radiographically occult injuries of the proximal femur in elderly patients after low-energy trauma: determination of non-inferiority margins of CT in comparison with MRI.

PURPOSE: To determine the margins of non-inferiority of the sensitivity of CT and the sample size needed to test the non-inferiority of CT in comparison with MRI. MATERIALS AND METHODS: During a 2-year period, elderly patients with suspected radiographically occult post-traumatic bone injuries were investigated by CT and MRI in two institutions. Four radiologists analyzed separately the CT and MRI examinations to detect post-traumatic femoral injuries. Their sensitivities at CT (SeCT) and MRI (SeMRI) were calculated with the reference being a best valuable comparator (consensus reading of the MRI and clinical follow-up). ROC analysis followed by an exact test (Newcombe's approach) was performed to assess the 95% confidence interval (CI) for the difference SeCT-SeMRI for each reader. A sample size calculation was performed based on our observed results by using a one-sided McNemar's test. RESULTS: Twenty-nine out of 102 study participants had a post-traumatic femoral injury. SeCT ranged between 83 and 93% and SeMRI ranged between 97 and 100%. The 95% CIs for (SeCT-SeMRI) were [- 5.3%, + 0.8%], (pR1 = 0.1250), [- 4.5%; + 1.2%] (pR2 = 0.2188), [- 3.4%; + 1.1%] (pR3 = 0.2500) to [- 3.8%; + 1.6%] (pR4 = 0.3750) according to readers, with a lowest limit for 95% CIs superior to a non-inferiority margin of (- 6%) for all readers. A population of 440 patients should be analyzed to test the non-inferiority of CT in comparison with MRI. CONCLUSION: CT and MRI are sensitive for the detection of radiographically occult femoral fractures in elderly patients after low-energy trauma. The choice between both these modalities is a compromise between the most available and the most sensitive technique. KEY POINTS: • The sensitivity of four separate readers to detect radiographically occult post-traumatic femoral injuries in elderly patients after low-energy trauma ranged between 83 and 93% at CT and between 97 and 100% at MRI according to a best valuable comparator including MRI and clinical follow-up. • CT is a valuable alternative method to MRI for the detection of post-traumatic femoral injuries in elderlies after low-energy trauma if a 6% loss in sensitivity can be accepted in comparison with MRI. • The choice between CT and MRI is a compromise between the most available and the most sensitive technique.

Conventional Radiography of the Hip Revisited: Correlation with Advanced Imaging.

This review proposes a structured approach to analyzing conventional radiographs of adult hips by focusing on alterations of radiological bone density, femoral head contours, and the joint space. Conventional radiography enables detecting subtle changes in cortical contours and joint space width due to its high spatial resolution. It is limited to the detection of cortical changes in areas to which the x-ray beam is tangent. It has reduced sensitivity for the detection of trabecular bone and medullary changes. Radiographic findings in common hip disorders, such as osteoarthritis, osteonecrosis, transient osteoporosis, and subchondral insufficiency fractures, are correlated to changes on MR imaging and computed tomography.

Depressive symptoms among surrogate decision makers in Lebanese ICUs.

Surrogate decision making is advocated to protect the vulnerable patient. Family members of patients in intensive care units (ICUs) are prone to develop depressive symptoms which may undermine their decisional capacity. Lebanon is a multicultural country where paternalism still dominates the physician-patient relationship and ethics are far from being the subject of research and studies. This multicenter observational study in the Greater Beirut area attempts to estimate the prevalence of depressive symptoms among surrogates deciding on behalf of ICU patients and to correlate their severity with sociodemographic factors. During the period March-May 2011, direct interviews were conducted and the Patient Health Questionnaire-9 (PHQ-9) was administered to 56 family members who had given consent, regarding therapeutic options, on behalf of ICU patients in seven university hospitals. We looked for relationships, in these surrogates, between severity of depression and age, sex, marital status, level of education, religion and status as the patient's spouse. The prevalence of major depression among surrogates was 61% using a cutoff of 10 on the PHQ-9 scale. Among the surrogates with depression, 15% had untreated moderate-to-severe depression. Severity of depression and suicidal ideation were not related to any of the studied factors. Depressive symptoms are prevalent among family members deciding on behalf of ICU patients, rendering them vulnerable. Appropriate measures should be taken to identify and treat them.