Morphological imperfections of epitaxial graphene: from a hindrance to the generation of new photo-responses in the visible domain

We report the discovery of remarkable photo-physical phenomena with characteristics unique to epitaxial graphene grown on 6H-SiC (000-1). Surprisingly, the electrical resistance of graphene increases under light illumination in contrast to conventional materials where it normally decreases. The resistance shows logarithmic temperature dependences which may be attributed to an Altshuler-Aronov effect. We show that the photoresistance depends on the frequency of the irradiating light, with three lasers (red, green, and violet) used to demonstrate the phenomenon. The counterintuitive rise of the positive photoresistance may be attributed to a creation of trapped charges upon irradiation. We argue that the origin of the photoresistance is related to the texture formed by the graphene flakes. Photovoltage also exists and increases with light intensity. However, its value saturates quickly with irradiation and does not change with time. The saturation of the photovoltage may be associated with the formation of a quasi-equilibrium state of the excited electrons and holes associated with a charge redistribution between the graphene and SiC substrate. The obtained physical picture is in agreement with the photoresistance measurements: X-ray photoelectron spectrometry "XPS", atomic force microscopy "AFM", Raman spectroscopy and the magnetic dependence of photoresistance decay measurements. We also observed non-decaying photoresistance and linear magnetoresistance in magnetic fields up to 1 T. We argue that this is due to topological phases spontaneously induced by persistent current formation within the graphene flake edges by magnetic fields.

Posteromedial Corner of the Knee: The Neglected Corner

The posteromedial corner of the knee (PMC) is an important anatomic structure that is easily seen but often overlooked on magnetic resonance (MR) images. Whereas the posterolateral corner has been referred to as the "dark side of the knee" by some authors owing to widespread lack of knowledge of its complex anatomy, even less is written about the PMC; yet it is as important as the posterolateral corner in multiligament injuries of the knee. The PMC lies between the posterior margin of the longitudinal fibers of the superficial medial collateral ligament (MCL) and the medial border of the posterior cruciate ligament (PCL). The anatomy of the PMC can be complex and the literature describing it can be confusing, at times oversimplifying it and at other times adding unnecessary complexity. Its most important structures, however, can be described more simply as five major components, and can be better shown with illustrations that emphasize the anatomic distinctions. Injuries to the PMC are important to recognize, as disruption of the supporting structures can cause anteromedial rotational instability (AMRI). Isolated PMC injuries are rare; most occur in conjunction with injuries to other important stabilizing knee structures such as the anterior cruciate ligament (ACL) and PCL. Unrecognized and unaddressed injury of the PMC is one of the causes of ACL and PCL graft failures. Recognition of PMC injuries is critical, as the diagnosis will often change or require surgical management.

Madura foot: two case reports, review of the literature, and new developments with clinical correlation

"Madura foot" or pedal mycetoma is a rare destructive infection of the skin and subcutaneous tissues of the foot, progressing to involve muscle and bone. The infection can be caused by both bacteria and fungi. Infection typically follows traumatic implantation of bacteria or fungal spores, which are present in soil or on plant material. Clinically, this entity can be difficult to diagnose and can have an indolent and progressive course. Early diagnosis is important to prevent patient morbidity and mortality. We present two cases of pedal mycetoma, review the literature, review new developments in diagnosis, and discuss magnetic resonance imaging (MRI) features of this unusual entity.

Sclerosing bone dysplasias: review and differentiation from other causes of osteosclerosis

Sclerosing bone dysplasias are skeletal abnormalities of varying severity with a wide range of radiologic, clinical, and genetic features. Hereditary sclerosing bone dysplasias result from some disturbance in the pathways involved in osteoblast or osteoclast regulation, leading to abnormal accumulation of bone. Several genes have been discovered that, when disrupted, result in specific types of hereditary sclerosing bone dysplasia (osteopetrosis, pyknodysostosis, osteopoikilosis, osteopathia striata, progressive diaphyseal dysplasia, hereditary multiple diaphyseal sclerosis, hyperostosis corticalis generalisata), many of which exhibit similar pathologic mechanisms involving endochondral or intramembranous ossification and some of which share similar underlying genetic defects. Nonhereditary dysplasias include intramedullary osteosclerosis, melorheostosis, and overlap syndromes, whereas acquired syndromes with increased bone density, which may simulate sclerosing bone dysplasias, include osteoblastic metastases, Paget disease of bone, Erdheim-Chester disease, myelofibrosis, and sickle cell disease. Knowledge of the radiologic appearances, distribution, and associated clinical findings of hereditary and nonhereditary sclerosing bone dysplasias and acquired syndromes with increased bone density is crucial for accurate diagnosis.

The early diagnosis of sacroiliac joint infections in children

We retrospectively reviewed the medical records and imaging studies of 15 children with infections of the sacroiliac joint to determine the usefulness of specific examinations and studies to aid in the early diagnosis of this condition. The clinical presentation, physical examination findings, pertinent laboratory data, and imaging studies were reviewed. Thirteen patients (87%) were febrile at the time of presentation. One patient presented in septic shock requiring intubation and critical care management. Tenderness to palpation over the sacroiliac joint was present in all 9 patients who had this examination performed, and the flexion abduction external rotation test was positive in 10 of 12 patients (83%) who had this test done. Laboratory indicators of infection were elevated in most patients, and 6 patients (46%) had positive blood cultures, most commonly growing Staphylococcus aureus. Initial conventional radiographs were negative in all but 1 patient. Radionuclide 99-m-technetium bone scans were positive in 7 of 10 patients (70%), and magnetic resonance imaging studies were ultimately positive in 13 of 14 patients (93%). However, within the first 6 days after the onset of symptoms, only 5 of 8 bone scans (63%) and 5 of 9 magnetic resonance imaging studies (57%) were consistent with infection. We conclude that while diagnostic imaging studies are ultimately helpful in confirming the diagnosis of sacroiliac joint infections in children, studies made within 6 days of the onset of symptoms may not always confirm the diagnosis. The early diagnosis of this condition is best made on the basis of clinical and laboratory findings.

LEVEL OF EVIDENCE

Therapeutic Study, level IV (Case series [no, or historical control group]).

Infectious spondylitis

Infection of the spine is a rare but serious cause of back pain. Conventional radiographs remain the initial screening procedure. Typically two adjacent vertebral bodies and the intervening disk space are affected. Early in the course of the disease, radiographs may be normal or nondiagnostic. Magnetic resonance imaging or radionuclide bone scan will establish pathology centered in the vertebral body. Because of the ability to image soft tissues, magnetic resonance imaging is particularly helpful in detecting paravertebral and extradural abscesses. Four other conditions may mimic infectious spondylitis: degenerative disk disease associated with Modic type 1 changes, pseudoarthrosis in ankylosing spondylitis, dialysis spondyloarthropathy, and neuropathic spondyloarthropathy. Advanced imaging studies in combination with radiographs and clinical information are essential in determining the correct diagnosis.

Imaging of Intraarticular Masses

Intraarticular masses can be classified as noninfectious synovial proliferative processes (lipoma arborescens, synovial osteochondromatosis, pigmented villonodular synovitis, rheumatoid arthritis), infectious granulomatous diseases (tuberculous arthritis, coccidioidomycosis arthritis), deposition diseases (gout, amyloid arthropathy), vascular malformations (synovial hemangioma, arteriovenous malformations), malignancies (synovial chondrosarcoma, synovial sarcoma, synovial metastases), and miscellaneous (cyclops lesion). Knowledge of articular anatomy aids the radiologist in localizing masses to the joint space. Some joints have complex anatomy with contiguous or adjacent bursae, recesses, and tendinous connections from which masses may originate or into which masses may extend. Many of the diseases causing intraarticular masses have specific imaging characteristics, especially on magnetic resonance images, and knowledge of these characteristics will allow for a more confident diagnosis.

Infliximab Treatment of Familial Mediterranean Fever and Its Effect on Secondary AA Amyloidosis

We describe a patient with a long history of familial Mediterranean fever who developed proteinuria as a result of secondary AA amyloidosis. In this patient, the inflammatory process, including recurrent attacks of arthritis, abdominal pain, nephrotic syndrome secondary to amyloidosis, and high sedimentation rate, was rapidly suppressed by treatment with infliximab and there was remarkable improvement of the proteinuria.Because TNF-alpha is a proinflammatory cytokine that plays a major role in FMF and secondary amyloid, it is an appropriate target for therapy. Our case is the first case of reactive systemic amyloidosis secondary to familial Mediterranean fever, which responded favorably to infliximab.

Inflammatory arthritis secondary to metastatic gastric cancer

Metastatic spread of malignancy to the joints is rare and only a few cases of solid tumors have been reported. We describe a patient with inflammatory arthritis of the knee and ankle secondary to metastatic gastric adenocarcinoma to the joints and bone diagnosed by synovianalysis. Arthritis secondary to metastatic cancer is a poor prognostic sign. The diagnosis is based on a strong clinical suspicion, magnetic resonance imaging, and joint fluid cytology or synovial biopsy.

Imaging of Amyloid Arthropathy

Amyloidosis is a disease complex caused by the extracellular deposition of an insoluble protein called amyloid. Amyloid arthropathy results from localized amyloid deposition in and around the joints. This article discusses the types of amyloidosis associated with amyloid arthropathy and presents their characteristic imaging findings.

Gorham's disease of the radius: radiographic, scintigraphic, and MRI findings with pathologic correlation. A case report and review of the literature

A rare case of Gorham's disease affecting the radius in a 46-year-old woman is presented. It was studied by plain radiography, MRI, and scintigraphy, including three-phase radionuclide bone scan and thallium scan. Three-phase bone scan demonstrated slightly decreased activity in the affected portion of the forearm in the early phase, but showed increased activity on the blood pool and delayed imaging. A thallium scan revealed no abnormalities. Histopathologic examination revealed osteoclastic activity and scar tissue with minimal remaining vasculature.

Simultaneous occurrence of diffuse idiopathic skeletal hyperostosis and ankylosing spondylitis

To the best of our knowledge, 10 cases of Ankylosing Spondylitis (AS) and Diffuse Idiopathic Skeletal Hyperostosis (DISH) coexisting in the same patient have been reported. A new case was found in a female patient at Los Angeles Medical Center in 1993, which we report in this paper. We also review the literature (Medline 1970-1994) and analyze the features of the reported cases. In order to study the incidence of this association in our population we have reviewed 106 cases of AS for radiological features of DISH. We found only one case.

CONCLUSION

this is a rare association with an incidence of 0.94% in our patients with AS. From the known cases, patients showing this association present clinically mild AS in which radiologic findings are the basis for the diagnosis. Finally we question the validity of excluding the diagnosis of DISH in patients with radiological features of sacroiliac ankylosis.

Radionuclide imaging in forme fruste of melorheostosis

Scintigraphy was instrumental in two histologically proven cases of forme fruste melorheostosis. Radionuclide bone scans demonstrated a moderately increased uptake of radiopharmaceutical localized to the "flowing" cortical hyperostosis of melorheostosis observed radiographically. The medullary portion of the affected bones showed no increase in tracer activity. In one case, imaging with Tl-201 chloride demonstrated increased focal activity of the lesion. These scintigraphic findings can help distinguish the mildest manifestation (forme fruste) of melorheostosis from the well-ossified lesions of myositis ossificans and parosteal or periosteal osteosarcoma. The findings of MRI are also described in one patient.

Multicentric giant cell tumor: report of five new cases

The typical giant cell tumor (GCT) is a solitary neoplams that occurs in the epiphysis or epimetaphysis of long bones. GCT is seen with a slightly increased frequency in females, and 70% of patients are between 20 and 40 years of age at the time of presentation. Multicentric giant cell tumor (MGCT; two or more centers) is an unusual variant of GCT. Patients with MGCT are likely to be younger than those with a solitary lesion. The multicentric variety is often of a higher stage at diagnosis and is more often associated with a pathological fracture than the unifocal tumor. We are reporting five new cases of MGCT, with a total of 21 tumors seen over a period of 25 years from 1967 to 1992.

Osteosarcoma presenting as intestinal obstruction

Osteosarcoma commonly presents with osseous and pulmonary metastases. We present an unusual case of extraosseous metastatic abdominal chondroblastic osteosarcoma presenting as intestinal obstruction.

Case report 749: Primary glomus tumor of bone

We report a case of primary intraosseous glomus tumor in a 30-year-old man who was found to have an expanding, lytic lesion in the distal phalanx of his left thumb. The histological appearance was atypical in that areas of myxoid stroma resembled chondroid material. The unusual location and microscopic appearance caused diagnostic problems. Immunohistochemical studies, including strong positive staining for MSA and negative staining for keratin and S-100 protein, were helpful in establishing the correct diagnosis.

Pro-oxidative interactions of dithranol with human phagocytes promote oxidative damage to DNA of bystander leucocytes

Dithranol at therapeutic concentrations (5-40 micrograms ml-1) induced strand breaks in human leucocyte DNA in vitro in a dose-related manner. Leucocytes from individuals with chronic granulomatous disease (CGD) incurred substantially less DNA strand breaks than did normal leucocytes during exposure to dithranol indicating that activated phagocytes are involved. H-7, 4-beta-bromophenacyl bromide (BPB) and staurosporine, all inhibitors of protein kinase C, decreased both dithranol-mediated activation of the phagocyte respiratory burst and induction of DNA strand breaks. Similar effects were observed with the hydrogen peroxide scavenger catalase. These results suggest that dithranol induces DNA strand breaks, mainly as a result of pro-oxidative interactions with phagocytes.

Imaging of the sacroiliac joints

The sacroiliac joints present unique problems in diagnosis for both the clinician and the radiologist. Each of the imaging modalities presents advantages and problems. The specific clinical problems determine whether advanced imaging modalities such as scintigraphy, CT scan, or magnetic resonance imaging will complement the information on the plain radiographs.

Magnetic resonance imaging of foot and ankle trauma

MRI is a useful diagnostic tool in the assessment of traumatic lesions of the foot and ankle. It is especially useful in demonstrating acute and chronic tendon and ligament injuries. Subtle fractures, including osteochondral, nondisplaced, and stress fractures, are well shown with MRI but may be difficult to detect on radiographs. A bone scan may also be used to detect these fractures; however, with MRI the fracture extent may be determined. MRI is also useful in diagnosing complication of trauma, such as ischemic necrosis and bone and soft-tissue infections.

Trauma to the foot

Minor trauma to the foot may cause stress fracture, avulsion fracture or ligamentous and tendon injury. Plain radiographs are frequently normal. Radionuclide bone scan is a sensitive detector of early bone injury. A stress fracture may develop focal uptake or diffuse uptake throughout the bone involved. MR imaging is the most sensitive means of evaluating injury to the soft tissues. Acute edema, partial tear, complete tear, and chronic tendinitis have distinct features on T1- and T2-weighted images. Major trauma occurs most commonly as a result of falls from heights and from motor-vehicle accidents. Plain films are useful in the initial evaluation of the extent of trauma. CT is particularly useful in evaluating calcaneal fractures that involve the subtalar joint. Both MR imaging and CT scans are useful in detecting injured or entrapped tendons associated with fracture-dislocations.

Pancreatic acinar cell carcinoma with subcutaneous and intraosseous fat necrosis

On rare occasions, excessive lipase production by functioning pancreatic acinar cell carcinoma results in subcutaneous and intraosseous fat necrosis. A patient with subcutaneous nodules and osteolytic lesions from metastatic fat necrosis associated with this malignancy is reported. Prompt recognition of the syndrome led to complete resection of the otherwise asymptomatic neoplasm of the exocrine pancreas.

Classification of ankle fractures: an algorithm

In 1950, Lauge-Hansen devised a classification of ankle fractures based on the position of the foot and the deforming force at the time of injury. This has been widely accepted by orthopedists, but is not in general use by radiologists. An algorithm based on his classification that allows rapid assessment of the mechanism of injury in 90%-95% of cases has been devised by the authors. Identification of the fractures and classification of the type of injury allows diagnosis of the otherwise occult ligamentous injuries. On the basis of location and appearance of the fibular fracture, the four types of injuries are immediately identified: pronation-abduction, pronation-lateral rotation, supination-adduction, and supination-lateral rotation. Subsequent assessment for medial malleolar fracture and then posterior malleolar fracture defines the stage of completeness of the injury and localizes the sites of ligamentous disruption.

Calcific tendinitis of the neck

When a calcific deposit in the shoulder, hip or elbow ruptures, it results in severe pain and tenderness. Few clinicians are aware that the longus colli muscle of the neck is also subject to acute tendinitis. When it occurs, the pain and spasm mimic infectious spondylitis or meningitis. Four patients are presented with acute tendinitis of the longus colli muscle and the classic radiographic findings of soft-tissue swelling and amorphous calcium deposits in the tendon.

Migrating bone shards in dissecting Charcot joints

Extensive periarticular calcification is characteristic of Charcot joints. Fragmentation of the articular margins of bone contributes to the bony detritus, but the majority forms de novo in the joint capsule. Occasionally the calcific debris is seen far removed from the joint. Dissection of a chronically distended joint along muscle planes is most commonly associated with the inflammatory joint disease of rheumatoid arthritis. Its occurrence in Charcot joints is documented by arthrography, which demonstrates continuity of the joint space and the distant calcifications.

The radiology of bone and soft tissue sarcomas

Solitary lesions of bone often have characteristic radiographic patterns that suggest the diagnosis of a specific bone tumor. Differentiation of tumor from infection, however, frequently may be impossible, and the majority of bone lesions require biopsy for histologic confirmation of the type of tumor or for identification of the infectious organism. Soft tissue masses, unlike bone tumors, most commonly look alike. They too require biopsy, but in this case to distinguish a benign mass from a soft tissue sarcoma. Special radiographic techniques such as isotopic and CAT scans or angiography add information about the morphology and response of adjacent bone, but fail to differentiate one category of disease from another or to establish a histologic diagnosis of the type of tumor.

Dysphagia and Forestier disease

Forestier disease (ankylosing hyperostosis) is a well-recognized and common disease entity. Although these patients rarely have complaints related to their spine, they are seen by the otorhinolaryngologist because of dysphagia, since the osteophytic spurs may impinge on the posterior pharyngeal wall. Since the plain roentgenogram and barium swallow is so specific, biopsy examination of the pharyngeal mass is not necessary.

Periostitis and pseudoperiostitis

Increased metabolic activity with the periosteum is demonstrated radiographically by the presence of a linear shadow of bone paralleling the cortex, most commonly reflecting increased osteoblastic activity and thus representing periosteal new bone. This is frequently seen in psoriatic arthritis and Reiter's syndrome. A similar picture occurs with increased osteoclastic activity and reflects rapid demineralization, simulating periostitis. This change must be recognized as a reflection of osteoporosis, lest the condition be misdiagnosed as inflammatory disease.