Nuclear magnetic resonance imaging in the assessment of unusual abdominal aortic aneurysms

Ultrasound and computed tomography (CT) have become primary methods of evaluating patients with abdominal aortic aneurysms. Arteriography may be necessary for further assessment. We have recently investigated two patients with complicated abdominal aortic aneurysms, one patient with Marfan's syndrome and the other with Behcet's disease. The initial diagnosis in both cases was made by ultrasound, but CT was inconclusive and aortography was contraindicated in both patients. Nuclear magnetic resonance (NMR) imaging was performed to see if further information could be obtained. This technique was useful in both cases, with elegant demonstration of the anatomy.     

Two-dimensional MR angiography in the evaluation of abdominal veins with gradient refocused sequences

The purpose of this study was to demonstrate the potential role of gradient refocused magnetic resonance imaging as an angiographic method in the evaluation of abdominal veins. Fifteen patients with different venous disorders were examined using first order motion refocused gradient echo sequences (fast low angle shot) in sequential section acquisition technique. Twelve patients had abdominal tumors and three idiopathic thrombosis of abdominal veins. Magnetic resonance was superior to indirect splenoportography and mesentericoportography in evaluation of the abdominal veins in 8 of 10 cases. It was also superior to ultrasound in 3 of 7 cases and to dynamic CT in 2 of 11 cases. This resulted from a higher intrinsic contrast between flowing blood and stationary tissue. It is concluded that two-dimensional gradient refocused imaging may be a valuable angiographic method in the evaluation of abdominal veins.     

3D DCE-MRA在腹部血管病变中的应用

目的 探讨3D动态增强磁共振血管造影在腹部血管病变中的检查技术及临床应用。方法 搜策18例腹部血管的3DDCE—MRA检查资料，对其影像表现进行总结分析。结果 18例3DDCE—MRA血管均显示满意，表现正常者4例，动脉硬化2例，腹主动脉瘤1例，门脉高压6例，门静脉瘤栓5例，其中2例显示门静脉海绵样变性。结论 3DDCE—MR～无损伤，成像速度快，对腹部大血管的病变能清楚显示，有重要的临床应用价值。     

Primary diagnosis of abdominal arteriovenous fistula by MR imaging

Two cases of abdominal arteriovenous (AV) fistula were imaged by magnetic resonance (MR). Magnetic resonance imaging showed abnormally increased flow with resultant dilatation of the veins draining the site of the fistula. Findings were correlated with CT, digital subtraction angiography, and arteriography. This report suggests the usefulness of MR imaging as the initial imaging technique of choice in clinically suspected cases of AV fistula. The diagnosis can be made within 30 to 45 min of imaging time and does not require administration of contrast material.     

腹部磁共振规范化扫描方案的应用初探

目的：探讨并制定上腹部规范化磁共振检查方案及其磁共振技术质控标准。方法分别选取随机组250例,平扫50例,平扫后马上增强200例,优化组250例,平扫42例,平扫后马上增强208例,从预约、准备、摆位及定位、序列的规范化、附加技术的应用、诊断信息的满足情况等五个方面共30个项目入手细化工作,并将所得影像信息进行评分及统计学分析。结果优化组评分项目达标率明显高于随机组,且各评分项目的平均值也整体高于随机组,除了D10,且两组对比,差异具有统计学意义,除了C5、D4、D6、D8、D9、D10、E3、E4、E5。各评分大项目也高于随机组,两组对比,差异具有统计学意义。优化组及随机组AA平均值、最大值、最小值分别为（27±0．097）分、30分、21分;（22．08±0．168）分、28分、15分,两组对比,差异具有统计学意义。结论实行腹部磁共振规范化扫描,优化了检查流程及图像质量,缩短了检查时间,提高了检查的成功率。     

MRI and CT features in two unusual cases of xanthogranulomatous pyelonephritis

Two unusual cases of xanthogranulomatous pyelonephritis studied by both magnetic resonance imaging and computed tomography, are presented. Extension of the disease depicted by both computed tomography and magnetic resonance imaging was compatible with the findings at surgery. Computed tomography seems to be sufficient for xanthogranulomatous pyelonephritis imaging evaluation, while magnetic resonance imaging is not recommended on a routine basis, since no additional valuable information is yielded.     

Imaging of the ischiorectal fossa

A retrospective evaluation of 500 routine abdominal computed tomography scans revealed 21 cases of ischiorectal fossa disease in 16 patients. Pathologic processes included involvement by primary and secondary neoplasms, usually of gynecologic origin; rectal prolapse; and abscess. These abnormalities can be missed if the ischiorectal fossae are not included in routine abdominal scans. The anatomy of the ischiorectal fossae and their relationship to other pelvic organs are well demonstrated with high-resolution computed tomography scans as well as by magnetic resonance imaging.     

Magnetic resonance imaging in the initial staging of Hodgkin's disease and non-Hodgkin lymphoma

Seventy-four consecutive previously untreated patients with Hodgkin's disease (HD) and non-Hodgkin lymphomas (NHL) were evaluated with chest, abdominal and pelvic magnetic resonance (MRI) for initial staging. All patients underwent routine radiological staging procedures which included chest radiographs and lymphography (LAG). These studies were followed in most of cases by laparoscopy, during which biopsies of the liver and the spleen were taken, and bone marrow aspiration and histology. A correlation of the results of MRI with both other imaging studies and histopathologic diagnoses was performed, and discordant cases were assessed to determine the impact on clinical staging. Additional evidence of disease involvement was provided mainly in the chest, where MRI demonstrated the presence of unsuspected disease in 21% of involved patients (9 of 42). Retroperitoneal lymph nodes were correctly assessed in 97% of cases if MRI was compared with LAG. Extranodal abdominal disease was identified both in the spleen (14%) and in the liver (1%). Bone marrow abnormalities were detected in 19% of patients (14 of 74). MRI findings influenced the staging of HD and NHL patients in 11 of 74 cases (15%).     

Imaging findings of concealed intra-amniotic hemorrhage in the setting of placenta previa and placenta accreta spectrum disorder

Placental abruption is an important cause of feto-maternal hemorrhage, with significant impact on both fetal and maternal mortality. In most cases, it presents with abdominal pain and vaginal bleeding. However, vaginal bleeding may be absent with concealed intra-amniotic hemorrhage, as in cases with placenta previa, hence confounding this diagnosis. In such cases, imaging studies may be obtained to evaluate for abdominal pain in pregnancy; hence, radiologists should be aware of the ultrasound and magnetic resonance (MR) imaging appearance of intra-amniotic hemorrhage. This includes presence of markedly echogenic amniotic fluid on US. Hemorrhage signal intensity on MR imaging varies with the duration of bleeding. In acute to subacute cases, it will present as T1 isointense and T2 hypointense amniotic fluid. This case is the first report of MR imaging findings of acute concealed intra-amniotic hemorrhage.     

Usefulness of black-blood magnetic resonance angiography generated from vessel wall imaging after the stent-assisted treatment of intracranial arterial diseases

PurposeAfter stent-assisted treatment for intracranial diseases, three-dimensional time-of-flight magnetic resonance angiography is a noninvasive follow-up method, but susceptibility artifacts prevent accurate evaluations of stented arteries. Sampling perfection with application-optimized contrast using different flip angle evolution (SPACE) sequence often used for vessel wall imaging is less susceptible to susceptibility artifacts, since it is a spin-echo sequence. Hence, we evaluated the feasibility of black-blood magnetic resonance angiography generated from vessel wall imaging data obtained using the SPACE sequence in the depiction of stented arteries by comparing with three-dimensional time-of-flight magnetic resonance angiography and digital subtraction angiography.MethodsOur study group comprised 11 consecutive patients. For both three-dimensional time-of-flight magnetic resonance angiography and black-blood magnetic resonance angiography, the contrast ratio obtained from the stented artery and the normal artery proximal to the stent were calculated. And the depiction of stented arteries was visually evaluated. Additionally, the relative diameter index obtained from the stented artery and the normal artery proximal to the stent were calculated for three-dimensional time-of-flight magnetic resonance angiography, black-blood magnetic resonance angiography and digital subtraction angiography.ResultsThe contrast ratio of the stented artery was significantly lower than that of the normal artery on three-dimensional time-of-flight magnetic resonance angiography, but no significant difference was seen using black-blood magnetic resonance angiography. Regarding both the diameter index and the visual assessment score, black-blood magnetic resonance angiography was significantly better than three-dimensional time-of-flight magnetic resonance angiography. On black-blood magnetic resonance angiography, the diameter index was equal to that of digital subtraction angiography, and the flow signal was homogeneous and continuous in most the cases.     

Magnetic resonance imaging of aneurysms of the abdominal aorta

Experience with magnetic resonance imaging (MRI) of 10 normal control patients and 13 patients with known abdominal aortic aneurysms is presented. The aorta, renal artery origins, and iliac arteries were clearly identified in all control patients. Ten out of 13 aneurysms were optimally visualized. Three cases early in the experience were poorly seen and permitted less confident measurements. Renal artery origins were identified in 12 cases and judged to be uninvolved by the aneurysm in 11. Iliac arteries were identified in 11 cases and judged to be definitely aneurysmal in three. Sonography clearly depicted all 13 aneurysms. Correlation of the actual anteroposterior (AP) and transverse diameter aneurysm measurements with both techniques was excellent. Sonography failed to identify the renal artery origins in all cases, but could infer noninvolvement in two cases. Iliac arteries were seen in eight cases and judged definitely aneurysmal in three. According to these preliminary results, both MRI and sonography provide accurate AP and transverse outer wall measurements. MRI is superior in determining the presence of renal and/or iliac involvement. The authors recommend, however, that sonography continue to be the preliminary screening method.     

Langerhans cell histiocytosis of hypothalamus and optic chiasm: CT and MR studies

The clinical, CT, and magnetic resonance features of two cases of hypothalamic/optic chiasm involvement with Langerhans cell histiocytosis are presented. In both cases, the mass was iso- to hyperdense on noncontrast CT with uniform postcontrast enhancement, whereas with magnetic resonance (one case) the mass remained isointense to brain on both long and short repetition time sequences. The pathophysiology of hypothalamic pituitary dysfunction is briefly reviewed.     

Chemical shift artifact along the section-select axis.

Chemical shift artifact (CSA), familiar to radiologists along the frequency-encoding axis, also occurs along the section-select axis. The authors observed a case in which CSA mimicked a renal mass. Subsequent retrospective analysis of 50 abdominal magnetic resonance (MR) imaging studies was performed to assess occurrence of CSA adjacent to the upper and lower renal poles. CSA along the section-select axis was observed in 76% of cases and adjacent to 39% of all renal poles imaged. CSA along the section-select axis is common in abdominal MR imaging and may occasionally mimic disease.     

SENSE技术在磁共振腹部动态增强血管成像中的应用

目的：探讨磁共振敏感编码技术在腹部动态增强血管成像(DcE—MRA)中的应用优势。方法：将疑有腹部血管疾病的40例患者分为二组，实验组20例使用SENSE技术扫描；另外20例为对照组，直接行DCE—MRA扫描。结果：对照组20例中，13例因患者呼吸配合好，图像清晰，其中5例显示了动、静脉不同时相，8例由于扫描时间长，得到动、静脉均显影的图像。其余7例因屏气配合不好，图像出现伪影，为诊断带来了困难。实验组20例患者由于扫描时间明显缩短，均获得了清晰且不同时相的图像。结论：sENsE技术的使用大大地缩短了扫描时间，使腹部DCE—MRA可不受呼吸影响，并能获得不同时相血管强化图像，明显改善了DcE—MRA影像的质量，提高了诊断准确性。     

Endometriosis following cesarean section: ultrasonography and magnetic resonance imaging

We present three cases of endometriosis developing in the abdominal wall following cesarean section.The patients were examined by Doppler ultrasonography (US) and magnetic resonance imaging (MRI). The object is to describe the US and MRI findings of the lesion and evaluate their role in the diagnosis and management.In our opinion, a single procedure is sufficient in evaluating the lesion and in reaching the diagnosis.     

MRI findings in fetuses with an abdominal wall defect: gastroschisis, omphalocele, and cloacal exstrophy

Congenital abdominal wall defects include several entities such as gastroschisis, omphalocele, and cloacal exstrophy. It is important for perinatal management and parental counseling to understand the magnetic resonance (MR) imaging features essential for correctly diagnosing the clinical condition and predicting the prognosis of fetal patients. The purpose of this pictorial review is to demonstrate the MR imaging features of fetal cases with an abdominal wall defect and the pitfalls of image findings.     

In vivo measurement of volumetric strain in the human brain induced by arterial pulsation and harmonic waves

Motion‐sensitive phase contrast magnetic resonance imaging and magnetic resonance elastography are applied for the measurement of volumetric strain and tissue compressibility in human brain. Volumetric strain calculated by the divergence operator using a biphasic effective‐medium model is related to dilatation and compression of fluid spaces during harmonic stimulation of the head or during intracranial passage of the arterial pulse wave. In six volunteers, phase contrast magnetic resonance imaging showed that the central cerebrum expands at arterial pulse wave to strain values of (2.8 ± 1.9)·10^?4. The evolution of volumetric strain agrees well with the magnitude of the harmonic divergence measured in eight volunteers by magnetic resonance elastography using external activation of 25 Hz vibration frequency. Intracranial volumetric strain was proven sensitive to venous pressure altered by abdominal muscle contraction. In eight volunteers, an increase in volumetric strain due to abdominal muscle contraction of approximately 45% was observed (P = 0.0001). The corresponding compression modulus in the range of 9.5–13.5 kPa demonstrated that the compressibility of brain tissue at 25 Hz stimulation is much higher than that of water. This pilot study provides the background for compression‐sensitive magnetic resonance imaging with or without external head stimulation. Volumetric strain may be sensitive to fluid flow abnormalities or pressure imbalances between vasculature and parenchyma as seen in hydrocephalus. Magn Reson Med 70:671–683, 2013. © 2012 Wiley Periodicals, Inc.     

Coronal nuclear magnetic resonance (NMR) imaging of the abdomen at 0.5 tesla

Coronal nuclear magnetic resonance (NMR) abdominal imaging was performed on a normal volunteer. The scan technique and anatomic features are described. Coronal abdominal scanning optimizes vascular imaging in the abdomen and is helpful in defining the anatomic relationships of a variety of structures.     

Abdominal aortic aneurysm. Detection of multilevel vascular pathology by time-resolved multiphase 3D gadolinium MR angiography: initial report.

OBJECTIVE: To evaluate multiphasic 3D gadolinium-enhanced magnetic resonance angiography (3D-Gd-MRA) for detection of vascular pathology at multiple levels of the aorta and iliac arteries. METHODS: In 18 patients with abdominal aortic aneurysm (n = 13), dissection (n = 3), or both (n = 2), multiphase 3D-Gd-MRA was performed acquiring five consecutive (6.8 seconds) 3D data sets in a single breath-hold. In each of the five time-resolved phases, vessel visibility of the abdominal aortic branches and iliac arteries was assessed. The extent of vessel involvement by the aneurysm or dissection seen on multiphase 3D-Gd-MRA was compared with standard imaging and surgical findings. Digital subtraction angiography was available for comparison in 4 cases, CT angiography in 10 cases. RESULTS: Due to the delayed filling of the aortic aneurysm, the proximal aortic branches and the aneurysm neck demonstrated an inversely related enhancement compared with the distal abdominal and iliac vessels (P < 0.001). Review of all five phases of multiphase 3D-Gd-MRA allowed optimal visualization of each vessel segment without any artifacts due to parenchymal or venous overlay. In dissections, review of three phases was required (P < 0.001) for diagnostic evaluation of the true and false lumens. Substantially more vessel involvement was detected on multiphase 3D-Gd-MRA; this was surgically confirmed in 10 of 11 cases and affected therapy management in 11 of 18 cases. CONCLUSIONS: Multiphase 3D-Gd-MRA is a convenient, robust, and safe technique for presurgical anatomic mapping of complex aortic aneurysms and dissections.     

Magnetic resonance of acute appendicitis: pearls and pitfalls

Acute appendicitis is the most common surgical abdominal emergency. Although the clinical diagnosis can be made accurately in typical cases, imaging plays an important role in improving diagnostic accuracy of this condition, especially when the clinical diagnosis is uncertain. Magnetic resonance imaging is an emerging promising technique for the diagnosis of acute appendicitis, especially in patients with nondiagnostic ultrasound and in patients where radiation is a clinical concern. In the following review, the role of magnetic resonance in the diagnosis of appendicitis will be discussed.