RESUMEN
PURPOSE: To evaluate the role of "penumbra sign", diffusion-weighted imaging (DWI), and the apparent diffusion coefficient (ADC) value in differentiating tubo-ovarian abscess (TOA) from ovarian malignancy. MATERIAL AND METHODS: Thirty-six patients with 50 adnexal masses (tubo-ovarian abscess, n = 24; ovarian malignancy, n = 26), who underwent magnetic resonance imaging (MRI) with DWI, were retrospectively evaluated. "Penumbra sign" (hyperintense rim on T1W images), diffusion restriction, and mean apparent diffusion coefficient (ADC) values from cystic (c-ADC) and solid (s-ADC) components were evaluated for all the masses. RESULTS: "Penumbra sign" on T1W images was significantly more common in the TOA group (n = 21, 87.5%) than in the ovarian malignancy group (n = 2, 7.7%) (p < 0.001). Similarly, diffusion restriction in the cystic component was more frequent in the TOA group (n = 24, 100% vs. n = 2, 10.5%; p < 0.001). In contrast, diffusion restriction in the solid component was more common in the ovarian malignancy group (n = 5, 20.8% vs. n = 26, 100%; p < 0.001). The mean c-ADC value was significantly lower in TOAs (p < 0.001). A c-ADC value of 1.31 × 10-3 mm2/s may be an optimal cut-off in distinguishing TOAs from ovarian malignancies. Conversely, the mean s-ADC value was significantly lower in the ovarian malignancy group (p < 0.001). An s-ADC value of 0.869 × 10-3 mm2/s may be an optimal cut-off in differentiating ovarian malignancies from TOAs (p < 0.001). ROC curve analysis showed that c-ADC values had a higher diagnostic accuracy than s-ADC values. CONCLUSIONS: "Penumbra sign" on T1W images, diffusion characteristics, and ADC values provide important clues in addition to conventional MR imaging features in differentiating TOA from ovarian malignancy.
RESUMEN
"Penumbra sign" is a characteristic finding in magnetic resonance imaging (MRI) of Brodie's abscess, a rare variant of subacute osteomyelitis. We aimed to discuss the imaging finding penumbra sign that will help in the diagnosis of osteomyelitis and may be useful to clinicians in differential diagnosis. A 26-year-old male patient presented to the emergency department with complaints of pain and limping in the right knee that did not go away. He had a history of arthroscopic debridement and percutaneous fixation surgery due to osteochondral fragment 3 years ago. There were no additional findings in the patient's vital parameters, physical examination, and medical history. X-ray imaging revealed two screws in the distal femur and a well-defined sclerotic rim surrounding a radiolucent lesion anterior to the screws. MRI revealed a lesion in the distal femoral metaphysis with low-density fluid and hyperintense granulation tissue surrounding it. After surgical abscess drainage and local debridement, bone cement was placed in the resulting cavity. Teicoplanin treatment was started. The patient was discharged and complete recovery was achieved in the second month. The diagnosis of osteomyelitis is often missed or confused with bone tumors in non-traumatic cases presenting with persistent bone pain. MRI imaging is frequently used in differential diagnosis, and detection of characteristic imaging signs such as the penumbra sign accelerates the diagnosis. In this context, emergency department clinicians, in particular, should be cautious and not forget that early treatment can be started by recognizing these signs.
RESUMEN
Langerhans cell histiocytosis (LCH), formerly known as histiocytosis X, refers to a spectrum of diseases characterized by idiopathic proliferation of histiocytes that produce either focal (localized LCH) or systemic manifestations (Hand-Schüller-Christian disease and Letterer-Siwe disease). Localized LCH accounts for approximately 60-70 % of all LCH cases. Osseous involvement is the most common manifestation and typically involves the flat bones, along with lesions of the skull, pelvis, and ribs. Localized LCH in bone shows a wide spectrum of clinical manifestations and radiologic features that may mimic those of infections as well as benign and malignant tumors. The diagnostic imaging findings of localized LCH are also diverse and challenging. The penumbra sign is a common and characteristic magnetic resonance imaging (MRI) feature of Brodie's abscess, but is rarely seen in localized LCH. In this report, we describe a case of localized LCH misdiagnosed as Brodie's abscess in a 2-year-old child based on clinical symptoms, laboratory findings, and pre-diagnostic MRI findings (penumbra sign). Therefore, the penumbra sign is not sufficient to clearly establish the diagnosis of Brodie's abscess, and the differential diagnosis of localized LCH should be considered when a child with an osteolytic lesion presents with a penumbra sign.