Yoon Joon Hwang

Uniform Image Quality Achieved by Tube Current Modulation Using SD of Attenuation in Coronary CT Angiography

OBJECTIVE The objective of our study was to evaluate whether the SD of CT attenuation values obtained from unenhanced scans of the left atrium is a reliable parameter for the individual modulation of tube current to achieve uniform image quality in coronary CT angiography (CTA). MATERIALS AND METHODS One hundred patients (59 men and 41 women) who were suspected to have coronary artery disease underwent coronary CTA using a 64-MDCT scanner. In addition to clinical studies, we also performed measurements on water phantoms. Tube current was modulated by the SD of the CT attenuation values measured from the left atrium on unenhanced images scanned at 300 mA. A modulation table was created from data obtained from the studies of water phantoms scanned at various tube currents. Other scanning parameters were identical to those used to obtain unenhanced and contrast-enhanced studies of the 100 patients. The SD values were measured from images scanned at an adjusted tube current, and the images of normal coronary and internal mammary arteries were graded. Radiation doses measured using the volume CT dose index (CTDI(vol)) were compared between the SD of the CT attenuation values and the modulation parameters suggested by the manufacturer of the scanner. RESULTS Image quality was rated as grade 3 (low mottle) on a 4-grade scale by four observers for 92-94 of the 100 patients (average, 92.5%). The mean SD value at an adjusted tube current was 12.1 H with an SD of 0.758 H (target SD = 12 H). A radiation dose reduction of 9-45% was achieved in patients grouped by weight who weighed less than 70 kg, and a reduction of up to 71% was seen in individual cases. CONCLUSION Modulating tube current using the SD of CT attenuation values from the left atrium is a highly reliable method of achieving uniform image quality in coronary CTA.

Coronary-to-bronchial artery fistula: demonstration by 64-multidetector computed tomography with retrospective electrocardiogram-gated reconstructions.

Objective: The aim of this study was to evaluate the incidence of coronary-to-bronchial artery fistula (CBF) and clinical significance in 1300 patients examined with 64-multidetector computed tomography (MDCT) coronary angiography. Methods: One thousand three hundred ten patients underwent coronary MDCT for atypical chest pain or screening. Volume-rendering and multiplanar reconstruction images were reviewed, and subsequent cineangiographies were compared. Results: Eight cases of CBF were detected-6 originated from the left circumflex artery, and 2 originated from the right coronary artery. A hypertrophied anomalous branch of left circumflex artery was observed in 1 case, and underlying bronchiectasis was noted. Seven cases had a thin-wall communicating vessel. Subsequent cineangiography revealed identical appearance with MDCT reconstruction images. Conclusions: The incidence of CBF (0.61%) in this study is similar to those of a few cineangiographic studies in the literature. Our study showed that 64-MDCT coronary angiography is an accurate and noninvasive tool for detection of CBF.

Diffusion-weighted magnetic resonance imaging in Wernicke's encephalopathy

Objective – To report diffusion‐weighted imaging (DWI) findings and postulate the pathogenic mechanism of Wernickes encephalopathy (WE). Patient – A 47‐year‐old‐woman presented with altered consciousness, ophthalmoplegia, and ataxia. DWI revealed the abnormal signal changes in periaqueductal gray matter, mamillary bodies and bilateral medial thalami. Apparent diffusion coefficient (ADC) map revealed the high signal intensity lesions in bilateral medial thalami, suggestive of vasogenic edema. The abnormal signal intensity lesions disappeared on follow‐up imaging with clinical improvement. Conclusions – Vasogenic edema plays an important role in the pathogenesis of WE and can be reversed by proper management. DWI findings in the early stage of WE may provide useful information about the prognosis.

Percutaneous insertion of Zilver stent in malignant biliary obstruction

BackgroundWe evaluated the clinical efficacy and technical feasibility of the percutaneously inserted self-expandable nitinol stent (Zilver stent) for palliation of malignant biliary obstruction.MethodsSeventeen patients with malignant tumors involving the intra- or extrahepatic bile duct who presented with obstructive jaundice underwent percutaneous insertion of a self-expandable nitinol stent. We retrospectively reviewed the hospital records of patients and evaluated the technical feasibility on stent placement, complications, patient survival, and duration of stent patency.ResultsPercutaneous biliary stenting with 27 Zilver stents was performed in 17 patients with malignant biliary obstruction. Technical success was 95%. Malposition of the stent was encountered in one patient. Minor technical problems were encountered in two patients: the introducer tip was broken during stent insertion, so endoscopic removal was done. Mean follow-up period for the 17 patients was 182 days (range 29–485 days): nine patients died of progressive disease at a mean follow-up of 151 days (range 61–371days) after stent insertion and eight patients remained alive at the final follow-up of 216 days (range 29–485 days). The median survival period for all patients was 277 days. The stent occlusion rate was 26% and the mean patency period was 280 days. In five patients, seven stents were obstructed by tumor ingrowth and overgrowth. Stent patency rates were 100%, 100%, 75%, 61%, and 41% at 1, 2, 3, 6, and 12 months, respectively. A late complication, erosive bleeding of the hepatic artery by the stent, developed in one patient.ConclusionPercutaneous biliary stenting using the nitinol stent is technically feasible and safe and clinically efficacious treatment for malignant biliary obstruction, even with a minor technical problem during stent insertion.

Findings from CT, MRI, and PET/CT of a primary malignant melanoma arising in a spinal nerve root

Primary spinal malignant melanoma is an extremely rare condition. We here describe a case of a 71-year-old Asian female presenting with left upper extremity tingling sensation. Computed tomography (CT) showed a homogeneously enhanced mass occupying the left neural foramen at the C6-7 level. Magnetic resonance imaging revealed enhanced mass in intra- and extradural space compressing the spinal cord at this level. It also widened the neural foramen mimicking neurofibroma or schwannoma. Partial resection of the mass was performed. Pathologic diagnosis of the mass was malignant melanoma. Postoperative whole body positron emission tomography/CT scan demonstrated an intense 18F-FDG uptake at the residual mass site without abnormal uptake at other sites in the body.

Cytogenetic and molecular genetic study on granular cell glioblastoma: a case report.

Granular cell astrocytoma is a rare infiltrative malignant glioma with prominent granular cell change. Granular cell astrocytomas are biologically aggressive compared with conventional infiltrating astrocytomas of similar grades, but their genetic alterations are poorly known. We report a case of granular cell glioblastoma and its genetic and molecular features. Histologically, the tumor not only showed features typical of granular cell astrocytoma but also demonstrated frequent mitoses, pseudopalisading necrosis, and vascular endothelial hyperplasia, compatible with glioblastoma. Array-based comparative genomic hybridization and focused molecular genetic analyses demonstrated gain of chromosome 7; losses of chromosome 1p, 8p, 9p, 10, 13q, and 22q; amplification of epidermal growth factor receptor; and homozygous deletion of CDKN2A as well as MGMT promoter methylation. However, neither isocitrate dehydrogenase 1 mutation nor codeletion of 1p/19q was found. Our results indicate that granular cell glioblastomas, despite having its peculiar granular cell changes, share common molecular genetic features with conventional glioblastoma, especially the classical subtype.

Clinical analysis of spinal stereotactic radiosurgery in the treatment of neurogenic tumors

OBJECT In this study the authors sought to evaluate clinical outcomes after using stereotactic radiosurgery (SRS) to treat benign and malignant spinal neurogenic tumors. METHODS The authors reviewed a total of 66 procedures of spinal SRS performed between 2001 and 2013 for 110 tumors in 58 patients with spinal neurogenic tumors, which included schwannomas, neurofibromas, and malignant peripheral nerve sheath tumors (MPNSTs). The clinical and radiological findings were evaluated in patients with benign neurogenic tumors. For the 4 patients with MPNSTs, the authors reported overall survival and results of additional immunohistochemical staining to predict the survival difference among the patients. RESULTS Of the 92 benign neurogenic tumors, 65 tumors that were serially followed up using MRI after SRS showed significant change in mean tumor volume, from a mean of 12.0 ± 2.6 cm3 pre-SRS to 10.8 ± 2.5 cm3 post-SRS (p = 0.027), over an average of 44 months. The local control rate of benign neurogenic tumors was 95.4%. The 34 patients who presented with clinical symptoms of pain showed a significant symptomatic improvement. The initial mean visual analog scale (VAS) score was 6.0 and decreased dramatically to 1.0 after SRS during an average follow-up period of 10.9 months (median of 8.1 months). Although the proportions of transient swelling and loss of intramural enhancement were significantly different among the groups, there was no statistically significant correlation between those 2 factors and local tumor control (p = 0.253 and 0.067, respectively; Fishers exact text). Cross-table analysis also indicated that there was no statistically significant relationship between groups with loss of intramural enhancement and transient swelling. The median survival of neurofibromatosis Type 1 (NF1)-related and sporadic MPNSTs was 1.13 and 5.8 years, respectively. Immunohistochemical results showed that S100 was expressed in a sporadic MPNST or neurofibroma, whereas topoisomerase-IIa was expressed in NF1-related MPNSTs. CONCLUSIONS SRS is an effective treatment modality for benign neurogenic tumors, while MPNSTs showed heterogeneity in their responses to SRS.

Primary Extraskeletal Mesenchymal Chondrosarcoma Arising from the Pancreas

We report here on a case of primary extraskeletal mesenchymal chondrosarcoma that arose from the pancreas. A 41-year-old man was evaluated by CT to find the cause of his abdominal pain. The CT scans showed a heterogeneously enhancing necrotic mass with numerous areas of coarse calcification, and this was located in the left side of the retroperitoneal space and involved the body and tail of the pancreas. Portal venography via the celiac axis also showed invasion of the splenic vein. Following excision of the mass, it was pathologically confirmed to be primary extraskeletal mesenchymal chondrosarcoma that arose from the pancreas.

Delayed-phase CT angiography is superior to arterial-phase CT angiography at localizing occlusion sites in acute stroke patients eligible for intra-arterial reperfusion therapy.

We compared the accuracy for localizing arterial occlusion sites between delayed-phase computed tomography angiography (CTA) and arterial-phase CTA in acute stroke patients with large vessel occlusion. Institutional Review Board approval was obtained, and informed consent was waived. For patients treated with intra-arterial thrombolysis within a 6 hour window between January 2009 and November 2011, we retrospectively assessed the arterial occlusion sites of pre-treatment, delayed-phase and arterial-phase CTA and compared these with digital subtraction angiography (DSA) findings. The positive predictive value for detection of vessel occlusion for both CTA methods was derived using DSA as a reference standard. The outcomes were compared using the McNemar test. Inter-observer disagreement within each modality was assessed using the Kendall W test. Among 73 patients treated with intra-arterial thrombolysis, 24 (32.9%) underwent both arterial-phase and delayed-phase CTA, and 66 (90.4%) underwent arterial-phase CTA only. For 24 patients undergoing both arterial-phase and delayed-phase CTA, the delayed-phase CTA detected concordant occlusion sites with DSA in 21 patients, yielding a positive predictive value of 87.5%, whereas the arterial-phase CTA detected this in 14 patients, for a positive predictive value of 58.3% (p=0.013). When discordant with DSA, arterial-phase or delayed-phase CTA indicated occlusions in more proximal sites than DSA. Delayed-phase CTA more precisely localized the occlusion site than arterial-phase CTA in acute stroke patients with large vessel occlusion. Thus, delayed-phase CTA findings could guide neurointerventionists in selecting intra-arterial thrombolysis modalities.

An ROC Study of Chest Radiographs: 2K Versus 4K High-Resolution Soft-Copy Images

Computed radiography of chest with a 4K image array was recently introduced. We performed a multiobserver study to compare the diagnostic accuracy of 2K (standard) and 4K (high quality) chest radiographs displayed on a 5-mega-pixel monitor (2K monitor). One hundred cases of posteroanterior chest radiographs (a total of 200 images) were selected by two chest radiologists. Those radiographs included pneumothorax (n = 14), nodules (n = 15), interstitial disease (n = 10), or neither abnormality (n = 61). These were interpreted by four radiologists in two separate sessions. They recorded their confidence scale for the presence or absence of abnormality. Diagnostic accuracy was determined by receiver operating characteristic (ROC) analysis for each observer. ROC analysis showed no statistically significant difference between the 2K and 4K modes for the detection of any of the different abnormalities by individual readers. Our preliminary study suggests that 2K mode would be sufficient for the detection of abnormality on chest radiograph and there is no considerable validity to incline toward the 4K mode in current picture archiving and communication system environment using 2K monitor. However, we think that additional investigation using more subtle parenchymal or rib lesion should be followed.