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Five MRI patterns of marrow involvement (diffuse, focal, combined diffuse and focal, variegated, and normal) are observed in patients with a marrow proliferative disorder including MM. The wide range of marrow involvement patterns in monoclonal plasma cell proliferative disorders mirrors that of their natural histories that can vary from indolent to rapidly lethal. MRI of the axial bone marrow contributes to stage these disorders, but it should not be obtained for disease detection and characterization because of its limited specificity and sensitivity. At MRI, diffuse benign hematopoietic marrow hyperplasia and marrow heterogeneities in elderly patients mimic the diffuse and variegated patterns observed in MM patients. Careful analysis of fat- and fluid-sensitive MR images and quantitative marrow assessment by using MRI and FDG-PET can contribute in differentiating these changes from those associated with neoplastic marrow infiltration, with some residual overlapping findings.

We report the observation of the soft tissue recurrence of an osteoid osteoma (OO) in a 26-year-old man initially complaining of post-traumatic pain and swelling of the right ankle. A first arthroscopic resection was performed after the misdiagnosis of "bone irregularities" observed on computed tomography (CT) and magnetic resonance imaging (MRI). The diagnosis of OO was made by histological analysis of the resection material. The patient became asymptomatic for 5 years until the symptoms progressively recurred. Follow-up MRI and CT studies demonstrated a nodular bony focus within the periarticular soft tissues of the ankle. The lesion was removed, and histological analysis confirmed the diagnosis of a whole viable OO. This observation likely resulted from the displacement of the initial lesion during the initial arthroscopic procedure. This case report highlights the possibility of recurrence of OO in the soft tissues.

Osteoid osteoma (OO), a small bone tumor relatively common in young subjects, frequently involves the hip. In addition to typical findings, we emphasize unsuspected clinical and imaging features including painless OO causing limping gait, non-visibility of totally mineralized nidus, absence of hyperostosis or adjacent edema, and recurrence at distance from the initial location. We also discuss the option of medical treatment for some cases of deep hip locations.

Fat-water swapping is an artifact specific to chemical shift encoded MRI and so-called Dixon methods. It is more frequent using the 2-point than the multi-point (> 2) Dixon method. Actually, fat-water swapping on the 2-point Dixon sequences partly triggered the development of the multi-point techniques. Fat-water swapping occurs on post-processing calculated fat- and water-only images, but not on the directly acquired in-phase and out-of-phase source images. It originates from a natural ambiguity between fat and water peaks that may cause inverted calculation between fat- and water-only voxels. Fat-water swapping artifact over large areas encompassing multiple tissues can easily be recognized, but it may be confusing when the calculation errors are limited to a single anatomic structure or a small area, especially on T2-weighted images. We report four cases with 2-point Dixon fat-water swapping artifacts mimicking musculoskeletal lesions at T2-weighted MRI and propose hints to avoid misinterpretation.

Subchondral cysts (or geodes) are common in osteoarthritis (OA), usually in association with other typical signs, i.e., joint space narrowing, subchondral bone sclerosis, and osteophytosis. However, large lesions without the typical signs of OA or lesions located outside the weight-bearing areas are unusual and may be confused for other conditions, in particular, those of tumoral origin. We report the findings in a 48-year-old man who had been complaining of left buttock pain for 3 years, getting worse over the last year, and an evolutive limited range of motion of the hip. The pain was increased by weight-bearing and was not relieved by nonsteroidal anti-inflammatory drugs. Radiographs and CT showed a large multilocular lytic lesion within the femoral head and a large lytic lesion in the left ilio-ischiatic ramus, raising the question of bifocal tumoral involvement. On MRI, the lesions had low signal intensity on T1- and high signal intensity on T2-weighted MR images, with subtle peripheral enhancement on post-contrast T1-weighted images. CT arthrography, by demonstrating a communication between the femoral head and ischiatic cysts and the joint space allowed us to definitively rule out malignant conditions and to make the diagnosis of subchondral bone cysts. Total hip arthroplasty was performed. Pathological analysis of the resected femoral head and of material obtained at curettage of the ischiatic lesion confirmed the diagnosis of degenerative geodes. This case illustrates an atypical bifocal location of giant subchondral cysts in the hip joint mimicking lytic tumors, in the absence of osteoarthritis or rheumatoid arthritis, and highlights the role of CT arthrography in identifying this condition.

Infection of costal cartilage is a rare observation. We report the case of a 43-year-old male patient without relevant history who presented with a progressive painful swelling of the left chest wall since 4 months. Computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated an abscess within the left ninth costal cartilage with surrounding reactive changes. A CT-guided biopsy was performed and the culture of the sample revealed the presence of Prevotella nigrescens. Musculoskeletal infections by Prevotella are rarely described in the literature, Prevotella oralis and Prevotella bivia being the most frequently observed pathogens. These infections usually originate from a hematogenous spread after thoracic surgery or dental procedure. In our patient, conservative treatment was chosen. A clinical improvement was noted after 1-month antibiotherapy, confirmed by short-term and 6-month imaging follow-up showing the complete disappearance of all previously observed abnormalities.

We report the case of a 55-year-old male patient who presented to the emergency department after sustaining a right ankle trauma. Swelling and tenderness of the lateral aspect of the right ankle were present on physical examination without evidence of motor or sensory deficit. Ankle radiographs were performed and showed two bony fragments, the first located postero-inferiorly to the cuboid bone while the second was adjacent to the tip of the lateral malleolus. The diagnosis of an os peroneum fracture was made with high suspicion of an associated peroneus longus tendon rupture. Computed tomography (CT) and magnetic resonance imaging (MRI) of the right ankle confirmed the diagnosis of a subtotal retracted tendinous rupture. Successful surgical repair of the injured tendon was performed. This article illustrates the imaging findings of an os peroneum fracture with its associated tendinous injury and reviews the literature.

Calcium hydroxyapatite crystal deposition is a common disorder, which sometimes causes acute pain as calcifications dissolve and migrate into adjacent soft tissue. Intraosseous calcium penetration has also been described. We illustrate the appearance of these lesions using a series of 35 cases compiled by members of the French Society of Musculoskeletal Imaging (Société d'Imagerie Musculo-Squelettique, SIMS). The first group in our series (7 cases) involved calcification-related cortical erosions of the humeral and femoral diaphyses, in particular at the pectoralis major and gluteus maximus insertions. A second group (28 cases) involved the presence of calcium material in subcortical areas. The most common site was the greater tubercle of the humerus, accompanying a calcifying tendinopathy of the supraspinatus. In addition, an extensive intramedullary diffusion of calcium deposits was observed in four of these cases, associated with cortical erosion in one case and subcortical lesions in three cases. Cortical erosions and intraosseous migration of calcifications associated with calcific tendinitis may be confused with neoplasm or infection. It is important to recognize atypical presentations of hydroxyapatite deposition to avoid unnecessary investigation or surgery.

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 (120 kVp, 275 mAs) and LD (120 kVp, 150 mAs), 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 %.

Ganglion cysts are a common cause of tarsal tunnel syndrome. As in other locations, these cysts are believed to communicate with neighboring joints. The positive diagnosis and preoperative work-up of these cysts require identification and location of the cyst pedicles so that they may be excised and the risk of recurrence decreased. This can be challenging with ultrasonography and magnetic resonance (MR) imaging. We present three cases of symptomatic ganglion cysts of the tarsal tunnel, diagnosed by MR imaging, where computed tomography (CT) arthrography with delayed acquisitions helped to confirm the diagnosis and identify precisely the topography of the communication with the subtalar joint. These cases provide new evidence of the articular origin of ganglion cysts developing in the tarsal tunnel.

The case of a ganglion cyst in the pulp of a fifth finger in an elderly woman initially mimicking a soft tissue tumor is described. Most typical sites of ganglion cysts are well documented at the wrist and in the vicinity of inter-phalangeal and metacarpo-phalangeal joints. In this case, ultrasonography (US) and magnetic resonance imaging (MRI) demonstrated a cystic lesion within the pulp of the fifth finger and indicated carpal osteoarthritis as the distant-and unexpected-origin of the lesion. The suggested diagnosis of ganglion cyst was confirmed by computed tomography arthrography (CT arthrography) of the wrist, which showed opacification of the cyst on delayed acquisitions after intra-articular injection into the mid-carpal joint, through the fifth flexor digitorum tendon sheath. The communications between the degenerative carpal joint, the radio-ulnar bursa, the fifth flexor digitorum tendon sheath and the pedicle of the cyst were well demonstrated.

To explain a cause of high signal intensity on T1-weighted MR images in calcified intervertebral disks associated with spinal fusion. Magnetic resonance and radiological examinations of 13 patients were reviewed, presenting one or several intervertebral disks showing a high signal intensity on T1-weighted MR images, associated both with the presence of calcifications in the disks and with peripheral fusion of the corresponding spinal segments. Fusion was due to ligament ossifications (n=8), ankylosing spondylitis (n=4), or posterior arthrodesis (n=1). Imaging files included X-rays and T1-weighted MR images in all cases, T2-weighted MR images in 12 cases, MR images with fat signal suppression in 7 cases, and a CT scan in 1 case. Histological study of a calcified disk from an anatomical specimen of an ankylosed lumbar spine resulting from ankylosing spondylitis was examined. The signal intensity of the disks was similar to that of the bone marrow or of perivertebral fat both on T1-weighted MR images and on all sequences, including those with fat signal suppression. In one of these disks, a strongly negative absorption coefficient was focally measured by CT scan, suggesting a fatty content. The histological examination of the ankylosed calcified disk revealed the presence of well-differentiated bone tissue and fatty marrow within the disk. The high signal intensity of some calcified intervertebral disks on T1-weighted MR images can result from the presence of fatty marrow, probably related to a disk ossification process in ankylosed spines.

Two cases of treated plasma cell lesions of bone are reported for which contrast-enhanced MRI had suggested necrosis, based on lack of enhancement after gadolinium injection, and in which pathologic examinations revealed the presence of extensive viable neoplastic tissue. These cases highlight the need for cautious interpretation of contrast-enhanced MRI signs of response to treatment and inactivity of lesions in the setting of plasma cell neoplasms.

A logical approach to bone marrow alterations is proposed that takes into account the high sensitivity and specificity of MR imaging for the detection of marrow fat. Marrow signal intensity on T1-weighted images is assumed to reflect the balance between fat and nonfat marrow components. Elementary patterns of marrow change include marrow depletion, infiltration, replacement and signal void. These patterns can be observed alone or in combination, and can be distributed in a focal or diffuse manner. Marrow depletion pattern shows high signal intensity reflecting increase in fat content and is frequently irrelevant clinically. Signal intensity is decreased in marrow infiltration, replacement and signal void patterns, which indicates partial or complete disappearance of fat. Focal marrow infiltration is frequently reactive to an adjacent abnormality, whereas focal marrow replacement more frequently indicates a more profound marrow alteration. The T1-weighted spin-echo sequence is satisfactory for lesion detection by virtue of its relatively high sensitivity in the detection of altered fat/nonfat marrow balance. T2-weighted sequences with saturation of the signal of fat protons or out-of-phase gradient-echo sequences improve lesion conspicuity in all situations in which the difference in fat/nonfat marrow balance between the abnormal area and the adjacent normal marrow is reduced.

Objective. To correlate the MR appearance of the proximal femur marrow with clinical and blood parameters. Design and patients. The proportion of the femoral neck surface area occupied by red marrow was determined on T1-weighted magnetic resonance (MR) images of the hip in a series of 120 subjects, aged from 15 to 75 years, with ten females and ten males per decade, and correlated with clinical data. This parameter and the bulk T1 values of femoral red marrow were determined in 30 other subjects 25–46 years of age and correlated with their blood parameters. Results. In the series of 120 subjects, the proportion of red marrow surface area decreased with age (P

Hyperechoic microfoci are sometimes visualized in normal joints. We hypothesized that these microfoci may correspond to gas microbubbles produced by a vacuum phenomenon. The purpose of our study was to demonstrate the possibility of generating intraarticular hyperechoic microbubbles by creating a vacuum phenomenon through traction on a metacarpophalangeal joint. We applied manual traction to the second metacarpophalangeal (MCP) joint of 22 volunteer subjects to separate articular surfaces with the aim of producing a vacuum. For one subject, the production of a vacuum was verified on a radiograph performed during the traction maneuver. For all subjects, ultrasonographic examination of the MCP joints was performed before, during, and after traction maneuvers. Two radiologists evaluated the presence of intraarticular hyperechoic microfoci and measured the widening of the joint space during traction. In the first subject, the widening of the joint space and the production of an intraarticular gas-like cavity by traction was confirmed on the radiograph. In 10 out of the 22 volunteers, the widening of the joint space was immediately followed by the appearance of a large intraarticular hyperechoic band, which disappeared when the traction was stopped, followed by the appearance of hyperechoic microfoci that persisted several minutes. The widening of the joint during the traction maneuver was greater in the group where hyperechoic foci were produced than in the group with no hyperechoic foci (mean 2.5 vs. 1.2 mm and 2.2 vs. 0.8 mm, respectively, for observers 1 and 2; P

OBJECTIVE: The aim of this study was to describe and compare the magnetic resonance (MR) and histological appearance of subchondral vertebral lesions that are idiopathic or that develop with vertebral fractures. MATERIALS AND METHODS: T1- and T2-weighted spin-echo images and radiographs were obtained in 81 cadaveric spine specimens. All subchondral vertebral lesions that were considered to be idiopathic or associated with vertebral end plate fractures were selected. Lesions due to growth disturbance were excluded. Radiographs and MR images were analyzed in consensus by two radiologists, and sampled specimens were analyzed by a pathologist. RESULTS: Eleven idiopathic and ten fracture-associated vertebral lesions were available. On T1-weighted images, all lesion signal intensity was low and homogeneous. On T2-weighted images, all idiopathic lesions showed a heterogeneous signal with a central low or intermediate signal component and a peripheral high or intermediate component. All but one fracture-related lesions showed a homogeneous intermediate to high signal intensity. Histological analysis of idiopathic lesions showed a central acellular fibrous connective tissue in all cases surrounded by loose connective tissue in nine cases. Herniated disk material and cartilage metaplasia were found in one lesion only. Fracture-associated lesions contained herniated disk material, necrotic tissue, and loose connective tissue with a peripheral component of loose fibrovascular connective tissue in four cases only. CONCLUSION: MR and histological appearance of idiopathic and fracture-associated subchondral vertebral lesions differ, suggesting that they might have a different origin.

OBJECTIVE: To determine the frequency and topography of cartilage lesions involving the femoro-tibial joints in patients with normal knee radiographs and without a remembered history of trauma. DESIGN AND PATIENTS: A radiologist retrospectively reviewed the dual-detector spiral CT knee arthrograms performed in 209 consecutive patients (mean age 37.6 years) with normal knee radiographs. Images were analyzed for the presence, grade (Noyes classification system) and location of cartilage lesions, the location being designated by dividing each articular surface into a grid of 16 parts. RESULTS: Fifty-three percent of knees had cartilage lesions of grade 2A or higher that involved articular surfaces to a variable extent: lateral tibial plateau (31%), medial femoral condyle (27%), medial tibial plateau (14%) and lateral femoral condyle (5%). Areas of the posterior half of the lateral tibial plateau and of the inner half of the medial femoral condyle were statistically more frequently involved than their counterparts (P

The bone marrow is a complex organ that contains fat and nonfat cells, the proportions of which vary greatly with age and in the different bones of the skeleton. Magnetic resonance (MR) imaging provides information on the composition of the medullary cavity of any given bone and on the distribution of red and yellow marrow in the skeleton. This article deals with the wide spectrum of appearances of the normal bone marrow at MR imaging.