Whole-body MR/PET: applications in abdominal imaging

Over the last few decades it has been shown that novel technologies and technological progress rapidly change the working environment of radiologists and nuclear medicine physicians. Thus, new possibilities, e.g., in tumor staging and therapy monitoring, but also new challenges arise. Recently, it could be shown that the integration of magnetic resonance imaging (MRI) and positron emission tomography (PET) is technically possible. The evolvement of new dedicated hybrid MR/PET systems for whole-body imaging in humans offers new potential in multimodal imaging. Especially simultaneous measurement of PET and MRI datasets allows for insights in metabolic and functional processes, particularly in oncologic demands, but also in cardiovascular and cerebral imaging. In this work-in-progress review article, a technical summary including the method-inherent challenges are given. Furthermore, possible clinical applications and research interests are addressed.     

Clinical applications of half-Fourier (HASTE) MR sequences in abdominal imaging.

Endoscopic retrograde cholangiography remains a valuable technique in biliary disease, because therapeutic intervention, such as stone extraction and biliary drainage, can be carried out at the same time as diagnosis. Spatial resolution is superior to that of noninvasive imaging methods. HASTE MR cholangiopancreatography is as sensitive as sonography in detecting cholelithiasis. It is superior to sonography in diagnosing common bile duct stones, malignant biliary obstruction, and benign pancreatic disease. The noninvasive nature of HASTE MR imaging insures an expanding role in imaging patients with suspected pancreaticobiliary disease.     

Virtual endoscopy in abdominal MR imaging.

As illustrated in this review, the diagnostic utility of VIE is highly dependent on the individual application. Virtual intraluminal endoscopy does not alter the informational content of the data set; rather, the data is presented in a different manner. In view of the considerable time requirements still associated with the VIE rendering process, the additional diagnostic value gained by VIE must be determined for each of the potential applications. Thus VIE was shown to be of no additional value in the assessment of 3D MR angiographic data sets of the abdominal aorta and renal arteries. For MR colonography, on the other hand, in vitro experiments as well as in vivo experience have demonstrated a vast diagnostic value as a primary screen supplemented by detailed analysis of reformatted images in all three orthogonal axes. In summary, virtual intraluminal imaging is a powerful tool for exploring 3D MR data sets of various abdominal structures from a different perspective. Clearly much more work is required to determine its diagnostic utility relative to its cost.     

MR imaging evaluation of acute abdominal pain during pregnancy

MR imaging enables diagnosis of a variety of maternal diseases presenting as acute abdominal pain in pregnant patients. MR imaging is a valuable complement to ultrasound in the determination of the exact etiology of acute abdominal pain, and it is important for the radiologist to recognize the MR imaging appearance of common causes of acute abdominal pain during pregnancy. This article reviews the MR imaging technique and findings of various abnormalities causing acute abdominal pain in pregnant patients.     

MR imaging of the bowel: pediatric applications

Magnetic resonance enterography with oral contrast administration using fast T2-weighted and fat saturated, contrast-enhanced T1-weighted sequences is the most common technique for bowel evaluation. The main indication for bowel MR imaging in children has been evaluation of inflammatory bowel diseases. A less common application is appendicitis. Other potential applications include evaluation of vascular malformations and transplanted bowel.     

Coronal sonography: a review of abdominal applications

Many abdominal structures are optimally imaged in the coronal plane because of their unique shape or environment. Routine application of coronal ultrasound scanning to the spleen, kidneys, and liver is advocated. Adjunctive coronal images of the biliary tract, inferior vena cava, aorta, and retroperitoneum complement or frequently provided diagnostic information unavailable in routine views. Inadequacy of acoustic windows or limitations of tissue-beam interaction encountered in transverse and sagittal projections may be overcome with coronal scans.     

双源CT双能量扫描技术在腹部的应用

双源CT的出现和应用是CT发展史上的一次技术的飞跃,它以现有多排螺旋CT为基础,在同一扫描架上同时采用两个不同的X线发射管球和探测器来采集CT图像,按扫描时两X线管球所选择电压不同,双源CT可有如下不同的扫描模式：①心脏扫描模式：两管球使用相同电压同时扫描,     

Volumetric MR imaging of the liver and applications.

Recent improvements in MR technology have enabled the development of volumetric three-dimensional (3D) imaging methods for fat-suppressed T1-weighted images of the entire upper abdomen with pixel sizes of approximately 2 mm in all dimensions and with acquisition times of less than 25 seconds for breath-hold imaging. When performed with a timing scheme, dynamic contrast-enhanced volumetric imaging of the liver can be performed with selective imaging during the arterial phase and portal venous phase of enhancement. The volumetric data sets can be reconstructed in any oblique plane, enabling improved detection, localization, and characterization of small liver lesions. The combination of high-resolution isotropic pixels and accurate timing also permits angiographic reconstructions of the 3D images, producing MR angiography and venography that can be useful in therapeutic planning, such as for catheter-based interventions or surgical resections or transplantation. Additionally, with use of a hepatobiliary contrast agent such as mangafodipir, T1-weighted volumetric MR cholangiography can be performed in patients with nonobstructed systems for depiction of intrahepatic biliary anatomy.     

扩散张量成像数据分析方法概述

扩散张量成像(DTI)是唯一可在体显示脑白质纤维束的无创成像方法,其利用组织内水分子扩散的各向异性特征进行成像。本文以DTI基本原理为出发点,对DTI的主要研究方向和数据分析方法进行分析。     

心血管磁共振成像临床应用和新进展

近年来由于MRI的进展,现已成为医学成像技术的主要组成部分,心血管MRI已广泛、有效地应用于心脏、大血管、内脏和外周血管成像及诊治工作.本文简要叙述心血管MRI临床应用概况,如对胸主动脉疾患、缺血性心脏病、心肌病、心脏肿瘤、先心病、心包疾患和心脏瓣膜病的诊断评价等.重点讨论一些新进展,如MR心肌灌注成像和心肌存活的评价;MR冠脉造影和斑块成像;深静脉血栓和肺栓塞的MR诊断以及MR血管造影对腹主-髂股-下肢动脉狭窄性病变的诊断及效果分析.     

Perfusion MR imaging: basic principles and clinical applications

Dynamic contrast-enhanced perfusion MR imaging provides hemodynamic information that complements traditional structural imaging and is increasingly used in clinical practice to diagnose, manage, and understand brain tumors. Relative cerebral blood volume maps derived from perfusion MR imaging data provide quantifiable estimates of regional blood volume that can be used to grade gliomas, differentiate different brain tumor types, and distinguish tumors from non-neoplastic lesions. There are a few minor limitations of the dynamic contrastenhanced perfusion MR imaging technique-susceptibility artifacts, relative rather than absolute quantification of cerebral blood volume, and the inaccurate estimation of cerebral blood volume in patients in whom the blood-brain barrier has been severely disrupted or destroyed. Despite the minor potential pitfalls of the technique, inclusion of perfusion MR imaging as part of a routine evaluation of brain tumors can lead to improved diagnostic accuracy, understanding of tumor pathophysiology, and detection and quantification of tumor angiogenesis. With further work, perfusion MR imaging could be used to assess existing and novel cancer therapies that target blood vessels.     

Quality assurance methodology and applications to abdominal imaging PQI

Quality assurance has increasingly become an integral part of medicine, with tandem goals of increasing patient safety and procedural quality, improving efficiency, lowering cost, and ultimately improving patient outcomes. This article reviews quality assurance methodology, ranging from the PDSA cycle to the application of lean techniques, aimed at operational efficiency, to continually evaluate and revise the health care environment. Alignment of goals for practices, hospitals, and healthcare organizations is critical, requiring clear objectives, adequate resources, and transparent reporting. In addition, there is a significant role played by regulatory bodies and oversight organizations in determining external benchmarks of quality, practice, and individual certification and reimbursement. Finally, practical application of quality principles to practice improvement projects in abdominal imaging will be presented.     

Non-contrast MR imaging for detecting endoleak after abdominal endovascular aortic repair

Our aim was to investigate the possibility of ruling out endoleak after endovascular aortic repair (EVAR) of abdominal aortic aneurysm (AAA) using non-contrast MRI. Twenty-three patients (20 males, aged 73 ± 8 years) with an EVAR-treated AAA underwent 1.5-T MRI using axial, coronal and sagittal oblique true-FISP sequences. Two blinded and independent readers with 4 (R1) and 2 (R2) years of experience evaluated these images considering an area of even less than 5 mm in diameter with a signal intensity higher than that of normal muscles visible in the excluded aneurysmal sac as a sign of potential endoleak. The final assessment, mainly based on MR angiography and previous examinations, served as reference standard. Out of 23 patients, 13 (57 %) were negative for endoleak at final assessment, while the remaining 10 (43 %) were positive, with the following type distribution: Ia (n = 4), Ib (n = 2), II (n = 3), and III (n = 1). Sensitivity was 10/10 (100 %; CI 95 % 69–100 %), specificity 7/13 (54 %; 25–81 %), accuracy 17/23 (74 %; 52–90 %), PPV 10/16 (63 %; 35–85 %) and NPV 7/7 (100 %; 59–100 %) for R1; 9/10 (90 %; 56–100 %), 8/13 (62 %; 32–86 %), 17/23 (74 %; 52–90 %), 9/14 (64 %; 35–87 %), and 8/9 (89 %; 52–100 %) for R2, respectively. Inter-reader Cohen κ was 0.810. A negative non-contrast true-FISP MR study can be used to rule out endoleak after EVAR of AAA. This hypothesis may contribute to the reduction of ionizing radiation exposure and contrast material administration for monitoring patients with an EVAR-treated AAA.     

儿童腹盆腔横纹肌肉瘤的CT与MR影像学分析

目的:探讨儿童腹盆腔横纹肌肉瘤(RMS)的CT与MR影像学特征.方法:对经手术病理证实的10例腹盆腔RMS患儿的CT与MR影像资料进行总结分析.其中行CT平扫10例,增强扫描6例;行MR平扫3例,增强扫描3例.结果:CT平扫均见腹盆腔内较大软组织肿物,密度欠均匀,部分有坏死区,邻近组织受压推移甚至侵犯、淋巴结及远处转移;增强后病灶不均匀轻中度强化,以周边强化明显,动脉期病灶内可见较多增粗、扭曲的供血动脉影,延迟期斑片状持续性强化.MR检查T1WI序列示腹盆腔内等低混杂信号巨大肿物,T2WI序列上以稍高信号为主;增强后呈不均匀持续性强化.结论:儿童腹盆腔RMS是一种少见的间充质源性恶性肿瘤,CT与MR影像学表现能为其诊断及鉴别提供有用的信息.     

MR imaging in the triage of pregnant patients with acute abdominal and pelvic pain

Purpose  To retrospectively assess the performance of MR imaging in the evaluation and triage of pregnant patients presenting with acute abdominal or pelvic pain. Method and materials  MRI studies of pregnant patients who were referred for acute abdominal pain between 2001 and 2007 were included. MR images were retrospectively reviewed and compared with surgical and pathologic findings and clinical follow-up data. Analysis of imaging findings included evaluation of the visceral organs, bowel and mesentery, appendix (for presence of appendicitis), ovaries (detection and adnexal masses were evaluated), focal inflammation, presence of abscesses, and any other abnormal findings. Results  A total of 118 pregnant patients were included. MR findings were inconclusive in 2 patients and were positive for acute appendicitis in 11 patients (n = 9 confirmed by surgery, n = 2 improved without surgery). One patient with inconclusive MR had surgically confirmed appendicitis; the other patient with inconclusive MR had surgically confirmed adnexal torsion. Other surgical/interventional diagnoses suggested by MR imaging were adnexal torsion (n = 4), abscess (n = 4), acute cholecystitis (n = 1), and gastric volvulus (n = 1). Two patients with MR diagnosis of torsion improved without surgery. One patient with MR diagnosis of abscess had biliary cystadenoma at surgery. The rest of the MR diagnoses above were confirmed surgically or interventionally. MR imaging was normal in 67 patients and demonstrated medically treatable etiology in 28 patients: adnexal lesions (n = 9), urinary pathology (n = 6), cholelithiasis (n = 4), degenerating fibroid (n = 3), DVT (n = 2), hernia (n = 1), colitis (n = 1), thick terminal ileum (n = 1), rectus hematoma (n = 1). Three of these patients had negative surgical exploration and one had adnexal mass excision during pregnancy. Other patients were discharged with medical treatment. The sensitivity, specificity, accuracy, positive predictive values (ppv), and negative predictive values (npv) of MR imaging for acute appendicitis, and surgical/ interventional diagnoses were 90.0% vs. 88.9%, 98.1% vs. 95.0%, 97.5% vs. 94.1%, 81.8% vs. 76.2%, 99.1% vs. 97.9%, respectively. Conclusion  MR imaging is an excellent modality for diagnosis of acute appendicitis and exclusion of diseases requiring surgical/interventional treatment. Therefore MR imaging is useful for triage of pregnant patients with acute abdominal and pelvic pain.