Jin Zy

In vivo high-resolution MR imaging of symptomatic and asymptomatic middle cerebral artery atherosclerotic stenosis

OBJECTIVE Recently, the technique of high-resolution magnetic resonance imaging (HR-MRI) has been developed to depict intracranial artery wall. We aimed to compare the vessel wall properties between symptomatic and asymptomatic atherosclerotic middle cerebral arteries (MCA) using HR-MRI. METHODS We studied 26 patients with symptomatic and 35 patients with asymptomatic MCA stenosis. Routine cranial MRI, magnetic resonance angiography and HR-MRI were performed on each patient. The cross-sectional images of MCA wall on HR-MRI were compared between the two groups. RESULTS The degree of MCA stenosis was similar between the two groups (67.9% vs 63.9%, P=0.327). On HR-MRI, eccentric plaques were observed in 26 (100%) symptomatic and 28 (80%) asymptomatic stenosis. In the remaining seven (20%) asymptomatic stenosis, only constrictive remodeling (vessel shrinkage) was observed. Compared with the asymptomatic group, symptomatic MCA stenosis had a larger wall area (P<0.001), greater remodeling ratio (P<0.001), higher prevalence of expansive remodeling (outward expansion of the vessel wall) (P=0.003) and lower prevalence of constrictive remodeling (P=0.008). CONCLUSIONS Different vessel wall properties on HR-MRI were observed between symptomatic and asymptomatic MCA stenosis. Further prospective studies are required to investigate whether HR-MRI is a helpful tool in stratifying stroke risk in patients with MCA atherosclerotic disease.

Adenosine-stress dynamic myocardial perfusion imaging with second-generation dual-source CT: comparison with conventional catheter coronary angiography and SPECT nuclear myocardial perfusion imaging.

OBJECTIVE The purpose of this article is to evaluate the feasibility of adenosine-stress dynamic myocardial perfusion imaging (MPI) with 128-MDCT dual-source CT for detecting myocardial ischemia in comparison with conventional catheter coronary angiography and nuclear MPI. SUBJECTS AND METHODS Thirty patients (21 men and nine women; mean [± SD] age, 59.2 ± 7.6 years) prospectively underwent a combined stress CT perfusion and CT angiography (CTA) examination. Complete time-attenuation curves of the myocardium were acquired with prospectively ECG-triggered axial images at two alternating positions. Myocardial blood flow (MBF) was quantified according to dynamic CT perfusion, and MBF values of normal and abnormal segments were compared. Findings on CT perfusion were compared with those for stress and rest SPECT. Perfusion defects according to CT were correlated to flow-obstructing stenosis detected on CTA and catheter coronary angiography. RESULTS On stress CT perfusion, 19 patients (63%) and 83 of 504 segments (16%) had perfusion abnormalities. There was a significant difference in MBF values between normal (142.9 ± 30.6 mL/100 mL/min) and hypoperfused (90.0 ± 22.8 mL/100 mL/min) segments (p < 0.001). With nuclear MPI results as a comparison, the sensitivity, specificity, positive predictive value, and negative predictive value of CT perfusion for identifying segments with perfusion defects were 0.85, 0.92, 0.55, and 0.98, respectively. On a per-vessel basis, sensitivity, specificity, positive predictive value, and negative predictive value for detecting flow-obstructing stenosis were, respectively, 1.00, 0.757, 0.541, and 1.00 for CT perfusion; 0.90, 0.514, 0.346, and 0.947 for CTA; and 0.90, 0.814, 0.581, and 0.966 for CT perfusion combined with CTA. CONCLUSION Adenosine-stress CT perfusion detects myocardial perfusion defects in good correlation with nuclear MPI. CT perfusion combined with CTA improves the diagnostic accuracy for identifying flow-obstructing stenosis compared with CTA alone.

Atherosclerosis of middle cerebral artery: Evaluation with high-resolution MR imaging at 3 T

OBJECTIVE Three-dimensional time-of-flight magnetic resonance angiography (3D TOF MRA) has been wildly used in the diagnosis of intracranial artery diseases, but it only shows the arterial lumen and does not delineate the vessel wall. The aim of this study was to assess whether high resolution cross sectional magnetic resonance imaging (HRMRI) could compensate the limitation of 3D TOF MRA in the atherosclerotic disease of middle cerebral artery (MCA). METHODS Fourty-eight suspected patients with atherosclerotic stenosis of MCA underwent 3D TOF MRA and HRMRI with a 3T scanner. The HRMRI was performed in 49 MCAs perpendicular to the M1 segment with T2-weighted imaging. Findings of HRMRI were compared with that of 3D MRA. RESULTS HRMRI displayed the artery wall clearly, and showed 37 abnormalities, including 20 plaques and 17 wall thickening. The inter-observer reproducibility was moderate for wall abnormalities with k=0.75 (95% CI 0.59-0.91), and excellent for plaques with k=0.91 (95% CI 0.80-1.03). 3D TOF MRA showed 34 stenoses at the M1 segment. Five normal MCAs on 3D TOF MRA had abnormal wall (3 plaques and 2 wall-thickening) on HRMRI. Two stenoses on 3D TOF MRA showed normal wall structure on HRMRI, indicating a possible negative remodeling phenomenon. CONCLUSIONS High-resolution MR imaging can clearly depict the wall structure of middle cerebral arteries. As a complementary method, HRMRI may compensate the limitation of 3D TOF MRA and help to detect atherosclerotic lesions not visualized by MRA.

Super-paramagnetic responsive nanofibrous scaffolds under static magnetic field enhance osteogenesis for bone repair in vivo

A novel nanofibrous composite scaffold composed of super-paramagnetic γ-Fe2O3 nanoparticles (MNP), hydroxyapatite nanoparticles (nHA) and poly lactide acid (PLA) was prepared using electrospinning technique. The scaffold well responds extern static magnetic field with typical saturation magnetization value of 0.049 emu/g as well as possesses nanofibrous architecture. The scaffolds were implanted in white rabbit model of lumbar transverse defects. Permanent magnets are fixed in the rabbit cages to provide static magnetic field for the rabbits post surgery. Results show that MNP incorporated in the nanofibers endows the scaffolds super-paramagnetic responsive under the applied static magnetic field, which accelerates new bone tissue formation and remodeling in the rabbit defect. The scaffold also exhibits good compatibility of CK, Cr, ALT and ALP within normal limits in the serum within 110 days post implantation. In conclusion, the super-paramagnetic responding scaffold with applying of external magnetic field provides a novel strategy for scaffold-guided bone repair.

Middle cerebral artery intraplaque hemorrhage: Prevalence and Clinical Relevance

Little is known about the composition of middle cerebral artery (MCA) plaques and how they relate to clinical status. Using high‐resolution magnetic resonance imaging (HR‐MRI), we aimed to examine the occurrence of high signal on T1‐weighted fat‐suppressed images (HST1) of MCA plaques, which are highly suggestive of fresh or recent intraplaque hemorrhage.

Plaque Distribution of Stenotic Middle Cerebral Artery and Its Clinical Relevance

Background and Purpose— Microanatomy studies reveal that most penetrating branches of middle cerebral artery (MCA) arise from the dorsal–superior surface of the trunk. Using high-resolution MRI, we sought to explore the plaque distribution of MCA atherosclerosis and its clinical relevance in relation to the orifices of penetrating arteries. Methods— We retrospectively analyzed the imaging and clinical data of 86 patients with atherosclerotic MCA stenosis. On high-resolution MRI, plaques were categorized based on the involvement of the superior, inferior, ventral, or dorsal MCA wall. The relationship of plaque distribution and clinical presentation was analyzed. Results— A total of 92 stenotic MCAs (40 symptomatic and 52 asymptomatic) on 828 image slices were studied. Overall, of the 251 slices with identified plaques, plaques were more frequently located at the ventral (44.8%) and inferior (31.7%) wall as compared with the superior (14.3%) and dorsal wall (9.0%; P<0.001). Symptomatic MCA stenosis had more superior (P=0.016) and less inferior (P=0.023) wall plaques than asymptomatic stenosis. Within the group of symptomatic MCA stenosis, vessels with penetrating artery infarctions had more superior (P=0.001) but less ventral (P=0.038) and inferior (P=0.024) plaques than without penetrating artery infarctions. Conclusions— MCA plaques tend to locate opposite to the orifices of penetrating arterial branches. Further studies are required to investigate whether MCA plaque distribution is an independent determinant of stroke occurrence and its subtypes.

Whole-body diffusion-weighted imaging: technical improvement and preliminary results.

To optimize the free‐breathing whole‐body diffusion‐weighted imaging (WB‐DWI) protocol by using the short TI inversion‐recovery diffusion‐weighted echo‐planar imaging (STIR‐DWEPI) sequence and the built‐in body coil. Additionally, to evaluate the feasibility of tumor screening using high‐resolution three‐dimensional (3D) maximum intensity projection (MIP) images.

Clinical Application of Body Diffusion Weighted MR Imaging in the Diagnosis and Preoperative N Staging of Cervical Cancer

OBJECTIVE To evaluate the clinical impact of body diffusion weighted imaging (DWI) on the diagnosis and preoperative N staging of cervical cancer. METHODS Twenty-four patients (mean age 37.9 years old) with proved cervical cancer by cervical biopsy and 24 female patients with other suspected pelvic abnormalities received preoperative body DWI scan. Results of body DWI were compared with pathological findings. The apparent diffusion coefficient (ADC) values of normal cervix and different pathological types of cervical cancer were compared. ADC value of normal or inflammatory lymph nodes was also compared with that of metastatic ones. Students t test was used for statistical analysis. RESULTS There were 5 adenocarcinomas and 19 epitheliomas showed with biopsy results, and DWI showed 21 cervical lesions out of them (87.5%). ADC values of the normal cervix (n = 24), epithelioma (n = 19), and adenocarcinoma (n = 5) were (1.73 +/- 0.31) x 10(-3), (0.88 +/- 0.22) x 10(-3), and (1.08 +/- 0.12) x 10(-3) mm2/s, respectively. Statistical analysis showed significant difference in ADC value between normal cervical tissue and either tumor tissues (both P < 0.01). In patients had lymphadenectomy (n = 24), totally 67 lymph nodes including 16 metastatic lymph nodes were pathologically analyzed, and DWI showed 66 (98.5%) out of them. ADC values of normal/inflammatory and metastatic lymph nodes were (1.07 +/- 0.16) x 10(-3) and (0.77 +/- 0.13) x 10(-3) mm2/s (P < 0.01). Receiver operating characteristic (ROC) curve of ADC value of metastatic lymph node showed that area under curve was 0.961. CONCLUSIONS ADC value in cervical carcinoma is lower than that in normal cervix, and ADC may have predictive value in subtype discrimination. ADC value may improve the preoperative characterization of lymph node metastasis. And at least abdominal and pelvic DWI scan is suggested for N staging evaluation in such patients.

Detection and localization of active gastrointestinal bleeding with multidetector row computed tomography angiography: a 5-year prospective study in one medical center.

Goal: To prospectively assess the utility of multidetector row computed tomography angiography (MDCTA) in the diagnosis of active gastrointestinal bleeding (GIB). Background: MDCTA is a relatively recent advance in CT scanning technology enabling excellent vascular visualization and detection of various vascular abnormalities. However, there is no prospective study with a large population evaluating the role of MDCTA in the diagnosis of active GIB. Study: From January 2006 to January 2011, 113 consecutive patients with clinical signs of active GIB underwent MDCTA (16-slice, 64-slice, or dual-source). The criteria for positive CT findings included active extravasation of contrast material within bowel lumen, abnormal bowel mucosal enhancement, vascular malformation, abnormally enhancing polyp or diverticulum, or tumor. Two radiologists reviewed the images and assessed CT findings in consensus. The standards of reference included digital subtraction angiography, endoscopy, surgery, or final pathology reports. Sensitivity, specificity, positive and negative predictive values, and accuracy of MDCTA for detection of active GIB were evaluated. Results: Positive CT findings for active GIB were identified in 80 of 113 patients (70.8%), all of which were confirmed by 1 or more reference standard. Negative MDCTA results were obtained in 33 patients (29.2%). Of these, 27 patients did not require any further intervention and were discharged without incident. The overall sensitivity, specificity, positive and negative predictive values, and accuracy of MDCTA was 86.0%, 100%, 100%, 60.6%, and 88.5%, respectively. Conclusions: MDCTA is an accurate first-line screening method for detection and localization of GIB and can guide triage in patients with active GIB.

Application Of Whole Body Diffusion Weighted MR Imaging for Diagnosis and Staging of Malignant Lymphoma

OBJECTIVE To evaluate the clinical impact of whole body diffusion weighted imaging (WB-DWI) on diagnosis and staging of malignant lymphoma. METHODS Thirty-one patients with suspected lymphadenopathy were enrolled. WB-DWI was performed by using short TI inversion recovery echo-planar imaging sequence with free breathing and built-in body coil. Axial T2-weighted imaging images of the same location were used as reference. The results of WB-DWI were compared with pathological results and other imaging modalities. The mean apparent diffusion coefficient (ADC) values of different kinds of lymph nodes were compared. RESULTS WB-DWI was positive in all 18 cases with lymphoma, 5 cases with metastatic lymph nodes and 4 of 8 cases with benign lymphadenopathy. The mean ADC value of lymphomatous, metastatic and benign lymph nodes was (0.87 +/- 0.17) x 10(-3), (0.98 +/- 0.09) x 10(-3) and (1.20 +/- 0.10) x 10(-3) mm2/s. There was significant difference in ADC value between benign lymph nodes and other two groups (P < 0.01). The sensitivity, specificity and accuracy of WB-DWI in diagnosis of lymphoma were 100% (18/18), 30.8% (4/13) and 71.0% (22/31). When an ADC value of 1.08 x 10(-3) mm2/s was used as the threshold value for differentiating malignant from benign lymph nodes, the best results were obtained with sensitivity of 87.8% and specificity of 91.3%. Sixteen of eighteen cases (88.9%) of lymphoma were accurately staged in accordance with clinical staging. CONCLUSIONS WB-DWI is a sensitive, but less specific technique for diagnosis of lymphoma. It is difficult to differentiate lymphomatous from metastatic lymph nodes using WB-DWI. However, it is a valuable imaging modality for staging of patients with malignant lymphoma.