Ji Kang Park

Low-dose and standard-dose unenhanced helical computed tomography for the assessment of acute renal colic: prospective comparative study.

Purpose: To compare the efficacy of low-dose and standard-dose computed tomography (CT) for the diagnosis of ureteral stones. Material and Methods: Unenhanced helical CT was performed with both a standard dose (260 mAs, pitch 1.5) and a low dose (50 mAs, pitch 1.5) in 121 patients suspected of having acute renal colic. The two studies were prospectively and independently interpreted for the presence and location of ureteral stones, abnormalities unrelated to stone disease, identification of secondary signs, i.e. hydronephrosis and perinephric stranding, and tissue rim sign. The standard-dose CT images were interpreted by one reviewer and the low-dose CT images independently by two reviewers unaware of the standard-dose CT findings. The findings of the standard and low-dose CT scans were compared with the exact McNemar test. Interobserver agreements were assessed with kappa analysis. The effective radiation doses resulting from two different protocols were calculated by means of commercially available software to which the Monte-Carlo phantom model was given. Results: The sensitivity, specificity, and accuracy of standard-dose CT for detecting ureteral stones were 99%, 93%, and 98%, respectively, whereas for the two reviewers the sensitivity of low-dose CT was 93% and 95%, specificity 86%, and accuracy 92% and 94%. We found no significant differences between standard-dose and low-dose CT in the sensitivity and specificity for diagnosing ureter stones (P>0.05 for both). However, the sensitivity of low-dose CT for detection of 19 stones less than or equal to 2 mm in diameter was 79% and 68%, respectively, for the two reviewers. Low-dose CT was comparable to standard-dose CT in visualizing hydronephrosis and the tissue rim sign. Perinephric stranding was far less clear on low-dose CT. Low-dose CT had the same diagnostic performance as standard-dose CT in diagnosing alternative diseases. Interobserver agreement between the two low-dose CT reviewers in the diagnosis of ureter stones and alternative diseases, the identification of secondary signs, and tissue rim sign were high, with kappa values ranging from 0.769 to 0.968. On standard-dose CT scans, the calculated mean effective radiation dose was 7.30 mSv for males and 10.00 mSv for females. On low-dose CT scans, the calculated mean effective radiation dose was 1.40 mSv for males and 1.97 mSv for females. Conclusion: Compared with standard scans using 260 mAs, low-dose unenhanced helical CT using a reduced tube current of 50 mAs results in a concomitant decrease in the radiation dose of 81%. Although low-dose CT was limited in its ability to depict small-sized calculi less than or equal to 2 mm, it is still comparable to standard-dose CT for the diagnosis of ureter stones and alternative disease.

Evaluation of the Somatotopic Organization of Corticospinal Tracts in the Internal Capsule and Cerebral Peduncle: Results of Diffusion-Tensor MR Tractography

Objective We have used diffusion tensor tractography (DTT) for the evaluation of the somatotopic organization of corticospinal tracts (CSTs) in the posterior limb of the internal capsule (PLIC) and cerebral peduncle (CP). Materials and Methods We imaged the brains of nine healthy right-handed subjects. We used a spin-echo echo-planar imaging (EPI) sequence with 12 diffusion-sensitized directions. DTT was calculated with an angular threshold of 35 degrees and a fractional anistropy (FA) threshold of 0.25. We determined the location of the CSTs by using two regions of interest (ROI) at expected areas of the pons and expected areas of the lateral half of the PLIC, in the left hemisphere of the brain. Fiber tracts crossing these two ROIs and the precentral gyrus (PCG) were defined as CSTs. Four new ROIs were then defined for the PCG, from the medial to lateral direction, as ROI 1 (medial) to ROI 4 (lateral). Finally, we defined each fiber tract of the CSTs between the pons and each ROI in the PCG by using two ROIs methods. Results In all subjects, the CSTs were organized along the long axis of the PLIC, and the hand fibers were located anterior to the foot fibers. The CSTs showed transverse orientation in the CP, and the hand fibers were located usually medial to the foot fibers. Conclusion Corticospinal tracts are organized along the long axis of the PLIC and the horizontal direction of the CP.

Comparison of Three Free-Breathing T2-Weighted MRI Sequences in the Evaluation of Focal Liver Lesions

OBJECTIVE The purpose of this study was to compare three free-breathing T2-weighted MRI sequences in the evaluation of focal liver lesions. MATERIALS AND METHODS Forty-nine patients with 86 focal liver lesions (56 malignant, 30 benign) underwent liver MRI with free-breathing sequences: turbo spin-echo (TSE) with navigator-triggered prospective acquisition correction (PACE), respiration-triggered TSE, and HASTE with navigator-triggered PACE. The images were retrospectively reviewed by two independent observers. Diagnostic performance was evaluated with receiver operating characteristics and sensitivity. The images were assessed quantitatively by measurement of the liver signal-to-noise ratio (SNR) and the lesion-to-liver contrast-to-noise ratio (CNR). RESULTS The PACE TSE sequence had better receiver operating characteristic curves for lesion detection and characterization than did the respiration-triggered TSE sequence, but the difference was not statistically significant (p > 0.05). The PACE TSE sequence had a significantly greater area under the curve for lesion detection (p < 0.01) and lesion characterization (p < 0.001) than did the PACE HASTE sequence. The composite sensitivity of the PACE TSE sequence for lesion detection was significantly higher than that of respiration-triggered TSE (p < 0.05) and PACE HASTE (p < 0.01). The mean signal-to-noise ratio for liver and the contrast-to-noise ratio for hepatic lesions were higher with the PACE HASTE than with the other sequences. CONCLUSION The navigator-triggered PACE technique is a valid method for T2-weighted MRI of the liver and may replace conventional respiration-triggered techniques.

Imaging of the walls of saccular cerebral aneurysms with double inversion recovery black-blood sequence.

In this study, we evaluated the wall of saccular cerebral aneurysms (SCAs) using two‐dimensional double inversion recovery black‐blood sequence (BBDI). We examined 14 patients with an unruptured SCA (USCA). The BBDI was peripheral‐pulse gated, and was acquired during the mid‐diastolic period. We evaluated whether the aneurysmal wall could be visualized with BBDI, and the wall thickness in the neck and dome portion of the aneurysm was measured in cases with acceptable imaging quality. BBDI demonstrated the USCA walls in ten patients. In four patients, the USCA walls were poorly delineated from the adjacent brain parenchyma or cerebrospinal fluid. The mean aneurysm size was 8.0 mm. The mean thickness of the aneurysmal wall in the neck portion was 0.60 ± 0.13 mm in 10 cases. The mean thickness at the dome portion was 0.46 ± 0.05 mm in five cases. In this study, BBDI revealed some portion of the USCA wall, despite the limited spatial and contrast resolution for delineation of the entire USCA wall. In our opinion, this technique may be used as an additional imaging tool for the evaluation of the aneurysmal wall. J. Magn. Reson. Imaging 2009;30:1179–1183.

Two Cases of Aberrant Right Subclavian Artery and Right Vertebral Artery that Originated from the Right Common Carotid Artery

We present here two patients that had an aberrant right subclavian artery and an anomalous origin of the right vertebral artery from the right common carotid artery. We review the previous literature and discuss herein the embryologic mechanism and clinical implications of this variation.

Distinction of reactive joint fluid from pyogenic abscess by diffusion-weighted imaging.

It is difficult to distinguish reactive joint fluid from infectious joint fluid by conventional MR images. In this presented case, we successfully distinguished these two conditions using diffusion‐weighted imaging. J. Magn. Reson. Imaging 2007.

CT imaging features of carotidynia: a case report.

Despite denial as a disease entity, carotidynia had shown relatively concordant imaging finding as an inflammatory process surrounding the carotid bifurcation area. We report serial computed tomography (CT) images of a case with carotidynia that showed the layered thickening of the carotid wall with self‐limiting disease course.

Usefulness of contrast enhanced FLAIR imaging for predicting the severity of meningitis

The aim of this study was to evaluate whether contrast enhanced fluid attenuated inversion recovery (CE-FLAIR) imaging can be used to predict the severity of meningitis based on leptomeningeal enhancement (LE) score and cerebrospinal fluid signal intensity (CSF-SI) on CE-FLAIR. We retrospectively analyzed data collected from 43 consecutive patients admitted to our hospital due to meningitis. Clinical factors including initial Glasgow Coma Scale (GCS) score, CSF glucose ratio, log CSF protein, log CSF WBC, and prognosis were evaluated. The LE score was semi-quantitatively scored, and we evaluated CSF-SI ratio at the interpeduncular or quadrigerminal cisterns on CE-FLAIR. We evaluated the differences in clinical variables, LE scores and CSF-SI ratios between the recovery and the complication group. We assessed the correlation between clinical variables, LE scores and CSF-SI ratios. The values of log CSF protein, CSF-SI ratio, and LE score were significantly higher in the complication group (p value <0.05). GCS score and CSF glucose ratio were significantly lower in the complication group (p value <0.01). The LE scores had significant negative correlation with GCS scores and CSF glucose ratios (p value <0.001). The LE score was significantly positively correlated with the value of log CSF protein and CSF-SI ratio (p value <0.01). The CSF-SI ratio was negatively correlated with GCS score and CSF glucose ratio (p value <0.01). The CSF-SI ratio was positively correlated with the value of log CSF protein (p value <0.05). Our results suggest that LE score and CSF-SI ratio are well correlated with clinical prognostic factors. We may predict the clinical severity of meningitis by using LE scores and CSF-SI ration on CE-FLAIR imaging.

Delayed Herniation of Coil Loop and Spontaneous Reposition in a Superior Cerebellar Artery Aneurysm

Herniation of coil loops into the parent artery is one of the complications of endovascular embolization with detachable coils. In this clinical setting, we cannot predict the consequence of the herniated coil loop. We report an unusual case of a superior cerebellar artery (SCA) aneurysm with delayed coil herniation into the basilar artery and spontaneous reposition into the SCA.

Precedence of Parenchymal Enhancement on CT Angiography to a Fatal Duret Hemorrhage.

We report a case of fatal duret hemorrhage (DH) in a patient with acute tentorial subdural hematoma and bilateral chronic subdural hematoma along the cerebral hemispheres. Preoperative CT angiography (CTA) revealed prominent parenchymal enhancement in the ventral pontomesencephalic area. After burr-hole drainage, a large hemorrhage developed in this area. The parenchymal enhancement in the CTA may reflect the pontomensencephalic perforating vessel injury, and may be a sign of impending DH of acute transtentorial downward herniation. Previous use of aspirin and warfarin might have potentiated the process of DH and increase the extent of the bleed.