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Biomedical subjects

K M Yeon

Publications and source records attributed to K M Yeon.

At least 19 recordsLinked to original sources

MR diagnosis of cerebellar infarction due to vertebral artery dissection in children.

Posterior circulation infarction is uncommon in children. We describe the clinical presentation and radiological findings in two children with cerebellar infarction resulting from dissection of the vertebral artery. We emphasize that vertebral artery injury should be considered in a child with acute symptoms and signs of ischaemia in the posterior circulation. MRI and MRA may be helpful in the diagnosis of cerebellar infarction and vertebral artery abnormality.

Cerebellar Diseases↗

Complex bronchopulmonary foregut malformation: extralobar pulmonary sequestration associated with a duplication cyst of mixed bronchogenic and oesophageal type.

We report a 13-year-old girl with an unusual, complex bronchopulmonary foregut malformation. The malformation included extralobar pulmonary sequestration and a duplication cyst of mixed bronchogenic and oesophageal type. Preoperative CT and MRI demonstrated the cystic and solid portions of the mass and indicated an aberrant vascular supply, suggesting the possibility of bronchopulmonary foregut malformation and several other differential diagnoses. A direct communication between the cyst and the bronchus of the sequestrated lung was found on pathological examination. This unusual combination of an extralobar pulmonary sequestration and a foregut cyst points to a common embryological pathogenesis.

Adolescent↗

Gangliocytoma of the spinal cord: a case report.

We present a case of intramedullary spinal gangliocytoma in a 7-year-old girl who presented with scoliosis and progressive weakness of both legs. The tumour involved the whole spinal cord and medulla oblongata and was composed of inner cystic and outer solid components. On MRI, the solid portion of the lesion showed strong enhancement at the thoracolumbar level and mild enhancement at the cervical and medullary levels. Histological examination of the surgical specimen showed neoplastic ganglion cells arranged irregularly in benign normocellular glial background, which made a diagnosis of gangliocytoma.

Female↗

Herpes simplex encephalitis: MRI findings in two cases confirmed by polymerase chain reaction assay.

Herpes simplex virus (HSV) type I causes a fulminant necrotising meningoencephalitis distinguished from other encephalitides by its focal and often haemorrhagic nature. Specific antiviral therapy with acyclovir can significantly improve the prognosis. We present MRI findings of two cases of herpes simplex encephalitis (HSE) confirmed by PCR analysis, focusing on the serial changes after acyclovir therapy: gyral swelling, high signal intensity on T2-weighted images in the subfrontal region, temporal lobe and insula in the initial stage, then regional extension with enhancement and haemorrhage despite appropriate acyclovir therapy, and finally encephalomalacia and brain atrophy.

Acyclovir↗

Sonography of acute osteomyelitis in rabbits with pathologic correlation.

RATIONALE AND OBJECTIVES: Ultrasonography (US) has a potential role in the diagnosis of osteomyelitis. The purpose of this study was to determine the characteristic sonographic features of acute osteomyelitis and correlate them with pathologic findings. MATERIALS AND METHODS: An experimental model of acute osteomyelitis was produced in the tibiae of 20 rabbits. Daily US and plain radiography were performed for 2 weeks. The authors evaluated periosteal reaction, subperiosteal fluid collection, and soft-tissue changes seen with US. A hypoechoic band and a hyperechoic line lying along the cortex were considered positive signs of subperiosteal fluid collection and periosteal reaction, respectively. The findings of periosteal reaction were compared for US and radiography, and pathologic findings were also correlated. RESULTS: The most common sonographic finding was a hypoechoic band along the cortex (21 [75%] of 28 tibiae), usually associated with a linear periosteal reaction (20 [71%] of 28). This juxtacortical abnormal echogenicity corresponded to periosteal elevation with loose fibrovascular connective tissue and granulation, associated with subperiosteal abscess formation. The periosteal reactions were detected with US before they were seen on radiographs. The periosteum showed gradual thickening during the disease process. In 50% of infected tibiae, inflammation or abscess formation was observed in the surrounding soft tissue. CONCLUSION: US readily demonstrates juxtacortical abnormal echogenicity and soft-tissue infection related to acute osteomyelitis. The abnormal echogenicity correlated well with the pathologic findings of periosteal reaction and subperiosteal abscess.

Acute Disease↗

Cerebellopontine angle ganglioglioma: MR findings.

We present a case of cerebellopontine (CP) angle ganglioglioma in a young child with developmental delay and no trigeminal nerve symptoms. MR imaging demonstrated a mass of homogeneous low signal intensity in the left CP angle on T1-weighted images with no enhancement with gadolinium, and of relatively homogeneous high signal intensity on T2-weighted images.

Cerebellar Neoplasms↗

Ultrasound of the adult hip.

The adult hip is a new and challenging site for evaluation with ultrasound (US). Clinically, diseases involving the hip region may be difficult to diagnose without the help of imaging. The hip region is a crossroad for numerous vascular, nervous, and muscular structures that pass between the trunk and the lower extremity. Thus, inflammatory processes and neoplasms may spread to and from the hip, buttock, thigh, pelvis, and retroperitoneum, and trauma may also effect the adjacent areas of the trunk and thigh. Because it is a crossroad, many conditions that are not specific to the hip occur in this area, including inguinal lymphadenopathy, pathology from the abdomen or the genitalia (intestinal hernia, inflammation, and infection), and even referred pain from spinal disorders. The goals of US imaging are the detection and localization of these pathological processes, the differentiation of intra-articular andextra-articular pathology, and the performance of diagnostic and therapeutic interventional procedures. This article reviews the hip anatomy, followed up by a discussion of the US evaluation and differential diagnosis of common pathology occurring in the hip area. This includes joint effusion, arthritis, loose bodies, bursitis, pseudoaneurysm, muscle and tendon diseases, as well as tumor and tumor-like lesions such as hematoma, abscess, and lymphadenopathy.

Abscess↗

MR imaging of changes of the growth plate after partial physeal removal and fat graft interposition in rabbits.

RATIONALE AND OBJECTIVES: The most important complication of skeletal injuries involving the growth plate is growth disturbance. The purpose of this study was to evaluate MR features of growth plate modification after fat graft interposition in growth plate injury and to correlate these findings with pathological findings. METHODS: A growth plate injury model was used in 12 skeletally immature rabbits. A longitudinal drill hole 5 mm in diameter was created in the central part of the growth plate in the distal femur, bilaterally. One side was filled with autologous fat, and the contralateral defect was left empty as a control. Magnetic resonance imaging was obtained 1, 3, and 6 months after surgery, and routine histological study was performed. The authors evaluated sequential changes in MR images and the histological basis of MR findings. RESULTS: In grafted femur, the signal intensity of the grafted area was lower than that of the surrounding bone on T2-weighted images at 1 month. The growth plate defect at 3 to 6 months was modified and had a proximally tapering appearance. The ratio of the growth plate defect was smaller in the grafted femur than in the control femur after surgery. Histologically, the fat-grafted area was replaced by fibrous connective tissue. In the control femur, a bony bridge was rectangular in the longitudinal direction and showed isosignal intensity with a rim of low signal intensity on T1-weighted imaging. Histologically, the defect was filled with mature fatty marrow with new bone formation in the control femur. CONCLUSIONS: The proximally pointing appearance and the low signal intensity of the grafted area on MR suggested fibrous degeneration of grafted fat that prevented solid bony bridge formation in experimentally induced growth plate injury.

Adipose Tissue↗

Metallic punctate densities in the breast after Chinese herbal treatment: mammographic findings.

PURPOSE: To describe the mammographic features of metallic punctate densities seen in women who were treated with the herb go-yak for breast abscess and to explain the cause of these findings. MATERIALS AND METHODS: Mammograms showing metallic punctate densities that appeared to be microcalcifications in 34 women were analyzed retrospectively with attention to the location, shape, distribution, and depth of the lesions. In all patients, go-yak was applied into the open wound after abscess drainage 6-42 years before mammography. In six patients, histopathologic specimens were obtained after needle localization. RESULTS: Metallic densities were in the subareolar or central breast in 24 (71%) of 34 patients. The shape was predominantly round or punctate in all patients, but rod-shaped or linear lesions were found in seven patients. The distribution and depth of lesions were variable, but they extended to the subcutaneous fat in 29 patients (85%). A high concentration of lead was found in the histopathologic specimens and herb samples. CONCLUSION: Lead deposits associated with go-yak treatment should be included in the differential diagnosis when the suspected microcalcifications are of unusually high density, are central in location, and extend into the subcutaneous fat in Asian women with a history of breast abscess.

Abscess↗

Pulmonary vasculitis: the spectrum of radiological findings.

Pulmonary vasculitis includes various disease entities with a wide range of clinical presentations and overlapping imaging features. Radiological findings of vasculitis in the angiitis-granulomatosis group are nodular and patchy opacities, whereas the principal feature of those diseases causing widespread capillaritis is diffuse air space consolidation. Aneurysms or stenoses of pulmonary arteries are seen in patients with Takayasu arteritis or Behçet's disease.

Arteritis↗

Dynamic contrast-enhanced MR imaging of bacterial abscess and VX2 carcinoma in rabbits: comparison of gadopentetate dimeglumine and a macromolecular contrast agent.

OBJECTIVE: The objective of this study was to compare enhancement patterns of a blood-pool contrast agent, Gadomer-17, with those of gadopentetate dimeglumine in bacterial abscesses and VX2 carcinoma in rabbits. MATERIALS AND METHODS: Fourteen rabbits with experimentally induced bacterial abscesses and VX2 carcinoma in both thighs underwent dynamic contrast-enhanced MR imaging with Gadomer-17 and gadopentetate dimeglumine at a 24-hr interval. The enhancement ratios (postcontrast to precontrast signal intensities) of lesions in the same animal were assessed and correlated with microvessel density. RESULTS: For Gadomer-17, the enhancement ratio of the abscesses (1.66 +/- 0.39) peaked 15 min after the injection, while that of the carcinoma (2.05 +/- 0.16) peaked at 10 min. The enhancement ratios of the carcinoma were consistently higher than those of the abscesses up to 30 min. For gadopentetate dimeglumine, peak enhancement ratio of the abscesses (2.30 +/- 0.75) was seen 5 min after the injection, while that of the carcinoma (2.32 +/- 0.51) was seen at 3 min. The enhancement ratios of the carcinomas were significantly higher at 1 min, but significantly lower at 20-30 min, compared with those of the abscesses, as a result of rapid decrease of enhancement ratios in the carcinomas. The microvessel density was 9.8 +/- 5.2 vessels per field of view for the abscesses and 36.3 +/- 9.5 vessels per field of view for the carcinoma (p < 0.001). CONCLUSION: Delayed peak enhancement and slow decay were found in both bacterial abscess and VX2 carcinoma with Gadomer-17, whereas early peak enhancement and rapid decay were found especially in VX2 carcinoma with gadopentetate dimeglumine. Enhancement ratios on MR imaging with a blood-pool contrast agent correlated well with the microvessel density in bacterial abscess and VX2 carcinoma.

Abscess↗

Transperineal ultrasonography in imperforate anus: identification of the internal fistula.

The purpose of this study was to assess the usefulness of transperineal ultrasonography in identifying the internal fistula in cases of imperforate anus. Transperineal ultrasonography was performed in 19 infants (13 neonates and 6 older infants; 13 were male and 6 were female) with imperforate anus to identify the internal fistula. Sagittal plane images were obtained through the anal dimple, and the internal connection of the rectal fistula was traced. The ultrasonographically traced internal fistula was compared with that observed on distal loopography after colostomy or with surgical findings. The internal fistula was identified as a hypoechoic linear tract, containing linear echogenicity in some cases. Of 19 patients, internal fistulas were correctly identified in 16 patients; these were rectourethral (n = 12), rectovaginal (n = 1), rectovestibular (n = 1), rectovesical (n = 1), and rectocloacal (n = 1). In three patients, internal fistulas were incorrectly defined; these cases consisted of rectovestibular (n = 2) and rectovaginal (n = 1) fistulas. Internal fistulas were correctly identified in all of the 13 male patients and in 3 of 6 female patients. Transperineal ultrasonography is an excellent diagnostic modality to define the type of the internal fistula in imperforate anus.

Anus, Imperforate↗

Complicated pleural tuberculosis in children: CT evaluation.

PURPOSE: To describe the CT features of complicated pleural tuberculosis in children and to define the use of CT in children with pleural tuberculosis. MATERIALS AND METHODS: The CT findings in 11 children with complicated pleural tuberculosis were retrospectively analysed. CT was performed to evaluate persistent pleural thickening (n = 6) or a mass-like lesion (n = 5) detected on plain radiographs. Chest radiographs and medical records were reviewed to determine whether additional information provided by CT had altered clinical management. RESULTS: On CT, more than one location was involved in five patients (45%) and in two patients (18%) the entire pleural spaces were involved. Pleural thickening was seen in all 11 patients and enhancement after administration of contrast medium occurred in ten patients (91%). Low-density fluid collections were seen in nine patients (82%) and in two, CT revealed fluid collections within calcified pleural lesions. In five patients with mass-like lesions on plain radiographs, CT showed a low-density pleural mass with peripheral enhancement in four and a calcified pleural mass with fluid collection in one. CT demonstrated parenchymal abnormalities on the same side as pleural lesions in all 11 patients and hilar or mediastinal adenopathy in four. Four patients (36%) underwent surgery because of fluid within a calcified fibrothorax (n = 3) and chest wall tuberculosis (n = 1) that were seen only on CT. CONCLUSIONS: The CT features of complicated pleural tuberculosis in children were pleural thickening, enhancement and fluid collection with associated parenchymal abnormalities and lymphadenopathy. In the evaluation of children with pleural tuberculosis, CT can be useful for demonstrating fluid within a calcified fibrothorax or chest wall involvement, which usually requires surgical intervention.

Adolescent↗

Abdominal-wall myositis secondary to intra-arterial chemotherapy for femoral osteosarcoma.

With the increasing application of intra-arterial chemotherapy (IAC), new side-effects are encountered. We describe two children with proximal femoral osteosarcoma who developed focal myositis of the abdominal wall musculature after IAC. In both cases, myositis presented as abdominal pain and mimicked acute abdomen. US demonstrated asymmetrical thickening of abdominal-wall musculature in the right lower abdomen. This diagnosis should be considered when evaluating the patient with unexplained abdominal pain and a history of IAC.

Abdominal Muscles↗

Tuberculous stenosis of the left main bronchus: results of treatment with balloons and metallic stents.

PURPOSE: To assess the results of treatment with balloon dilation and metallic Z stents in patients with tuberculous stenosis of the left main bronchus. MATERIALS AND METHODS: Nineteen patients with tuberculous stenosis of the left main bronchus were treated with balloon (n = 15) and self-expanding metallic Z stents (n = 4). Respiratory status and pulmonary function tests were followed up for 2-90 months. RESULTS: In the balloon group, improvements in dyspnea occurred in 73% (11 of 15 patients) immediately, 73% after 1 month, 73% after 6 months, 64% after 1 year, 64% after 3 years, and 42% after 6 years (Kaplan-Meier method). Improvement of pulmonary function (FEV1 or FVC) was achieved in 62% (eight of 13) after 1 year. In the stent group, immediate improvements of dyspnea or pulmonary function occurred in all patients. However, fracture of the stents occurred in two patients, at 4 and 18 months, respectively. Occlusion of the lumen of the stent by granulation tissue occurred in another at 18 months. CONCLUSION: Balloon dilation can be an effective method for the treatment of tuberculous stenosis of the main bronchus. Metallic Z stents should be used cautiously because of their problems of mechanical durability and overgrowth of granulation tissue.

Adolescent↗

Short-term effects of a new intravascular nitinol stent in canine arteries.

RATIONALE AND OBJECTIVES: To evaluate the short-term effects of a new nitinol stent on canine arteries. METHODS: Eighteen nitinol mesh stents were placed in abdominal aortas, common iliac arteries, and renal arteries of six dogs. Angiography was performed to evaluate the patency rates and structural changes of arteries at 1 day, 3 weeks, 4 weeks, and 10 weeks after stent insertion. Gross and light microscopic examinations were performed after angiography. RESULTS: On angiography, the patency rate was 100%, and no thrombosis was observed. All side branches from stented segments were patent. The mean neointimal thickness over and between stent wires was 94 and 167 microns. No difference was found between the aorta and the small vessels. Histologically, the neointima was covered with endothelium and was composed of subintimal fibrosis with mild inflammation. CONCLUSIONS: The new type of nitinol mesh stent showed a high patency rate, with no thrombosis and relatively thin neointimal proliferation.

Alloys↗

Influence of instrument settings on flow signal and background noise in power Doppler US. An experimental study using a flow phantom with hyperechoic background.

OBJECTIVE: To determine the influence of various power Doppler instrument settings on intensities of flow signal and background noise in flow with a tissue-equivalent phantom. METHODS: Power Doppler images were obtained with changing wall filter level (low, medium, high, and maximum), pulse repetition frequency (PRF; 500, 700, 1000, 1500, 3000, and 6000 Hz), and Doppler gain (60%, 70%, 80%, 90%, and 100%) at different flow velocities (13.3, 26.5, and 49.8 cm/sec). To make a quantitative comparison of different settings, the authors measured the intensities of flow signal and background noise in obtained power Doppler images using the scanner and a computer program, calculated signal-to-noise difference (SND; intensity of flow signal--intensity of background noise), and evaluated the relation between SND and power Doppler settings. RESULTS: The intensities of flow signal and background noise were proportional to flow velocity and power Doppler gain but were inversely proportional to PRF and wall filter level. At constant wall filter level (medium), changes of PRF and Doppler gain to the same directions resulted in a high SND. At constant PRF (1000 Hz), changes of wall filter and Doppler gain to the same directions also resulted in a high SND. However, at constant Doppler gain (80%), a high SND was obtained with changing wall filter level and PRF to the opposite directions. CONCLUSIONS: Three Doppler instrument settings--wall filter level, pulse repetition frequency, and Doppler gain--have reciprocal influences on SND.

Blood Flow Velocity↗