Fast MR imaging: techniques and clinical applications

Fast MR imaging has matured in the past few years and is now of established value for several aspects of clinical MR imaging. The initial impetus for rapid imaging was to reduce scan times. Today its usefulness includes reducing motion artifacts, improved contrast per unit time, three-dimensional (3-D) imaging, real-time imaging, cine-mode imaging, and flow imaging. The focus of this review is on short-TR steady-state gradient-echo imaging. We discuss the basic sequence design of the mainstream fast techniques. Many important applications exist, including gadopentetate dimeglumine-enhanced MR imaging of the brain and spine, subsecond imaging of real-time applications, myelographic imaging of the spine, cardiac cine-mode imaging; 3-D musculoskeletal (knee) imaging, 3-D pituitary imaging; two-dimensional and 3-D body imaging; 3-D carotid and intravascular imaging, and reformatting 3-D images into arbitrary planes.     

分子成像技术的研究进展

分子成像是新时代的医学成像,它可以无创性监测活体内的细胞和分子水平的生物学过程,其中包括核医学分子显像、磁共振分子成像、超声分子成像、光学分子成像和X射线分子成像等.目前,由于多学科融合的发展,多模式融合成像技术已成功用于临床,如PET-CT和PET-MRI.随着分子探针的发展和多模式融合成像技术的成熟,越来越多的分子...     

Patellar tendons with normal imaging and pain: change in imaging and pain status over a volleyball season.

OBJECTIVE: Patellar tendon injury commonly presents as abnormal imaging with pain or abnormal imaging without pain. Normal imaging with pain has also been reported clinically, but little is known about the behavior of these tendons over time. This study investigated the behavior of tendons with normal imaging and pain over a volleyball season. DESIGN: Prospective study. SETTING: Institutional. PARTICIPANTS: One hundred and one male and female volleyball players. MAIN OUTCOME MEASUREMENTS: At the beginning and end of the season ultrasound determined imaging status and the single leg decline squat test determined pain. The imaging and pain status at follow-up of tendons with normal imaging and pain at baseline was reported and contrasted to the imaging and pain status of the other patellar tendon injuries. RESULTS: Tendons with normal imaging and pain [relative risk (RR) 15.1], abnormal imaging without pain (RR 14.6), and abnormal imaging with pain (RR 51.5) had a greater risk of having abnormal imaging with pain at the end of the season when compared with normal tendons (P < 0.01). Among tendons with normal imaging and pain at baseline, 27% had abnormal imaging without pain and 21% contained abnormal imaging with pain at the end of the season. CONCLUSIONS: Patellar tendons with normal imaging and pain at the beginning of a volleyball season are equally as likely to have abnormal imaging and pain at the end of the season as tendons with abnormal imaging without pain. Normal imaging with pain may represent a clinically relevant patellar tendon injury.     

Diffusion-weighted imaging of prostate cancer

OBJECTIVE: The purpose of this study was to assess whether T2-weighted (T2W) imaging with diffusion-weighted (DW) imaging could improve prostate cancer detection as compared with T2W imaging alone. METHODS: The subjects consisted of 37 patients with prostate cancer and 23 without cancer undergoing magnetic resonance (MR) imaging. Using a 1.5-T superconducting magnet, all patients underwent T2W and DW imaging with parallel imaging. Images were independently reviewed by 3 readers to determine the detectability of prostate cancer. The detectability of T2W imaging without and with DW imaging was assessed by means of receiver operating characteristic analysis. RESULTS: Mean areas under the receiver operating characteristic curve for T2W imaging alone and for T2W imaging with DW imaging were 0.87 and 0.93, respectively. The receiver operating characteristic analysis showed that the addition of DW imaging to conventional T2W imaging significantly improved tumor detection (P = 0.0468) compared with T2W imaging alone. CONCLUSIONS: The addition of DW imaging to conventional T2W imaging provides better detection of prostate cancer.     

18F-FDG符合线路SPECT显像联合CT、B超、MRI在结直肠癌术后复发及转移中的诊断价值

目的探讨18F-FDG 符合线路 SPECT 显像联合传统显像(CT、B 超、MRI)在结直肠癌术后复发及转移中的诊断价值.资料与方法107例结直肠癌术后患者行18F-FDG 符合线路 SPECT 显像,并联合 CT、B 超、MRI 诊断结直肠癌术后复发及转移.结果107例患者最终确定复发及转移共29例.18F-FDG 符合线路 SPECT 显像与传统显像诊断均为阳性的15例患者中,传统显像检出病灶20个,符合线路 SPECT 显像检出病灶26个.传统显像检出3个符合线路 SPECT 显像未发现的转移病灶,而符合线路 SPECT 显像检出9个传统显像未发现的病灶.18F-FDG 符合线路 SPECT 显像诊断结直肠癌术后复发及转移的灵敏度、特异性和准确率分别为79.3%、89.7%和86.9%;传统显像的诊断效能分别为62.1%、88.5%和81.3%;二者联合的诊断效能分别为89.7%、92.3%和91.6%.二者联合诊断结直肠癌术后复发及转移的灵敏度和准确率明显优于传统显像(P <0.05).结论18F-FDG 符合线路 SPECT 显像联合 CT、B 超、MRI 在监测结直肠癌术后复发及转移中具有重要临床价值.     

Magnetic resonance imaging: Review of imaging techniques and overview of liver imaging

Magnetic resonance imaging (MRI) of the liver is slowly transitioning from a problem solving imaging modality to a first line imaging modality for many diseases of the liver. The well established advantages of MRI over other cross sectional imaging modalities may be the basis for this transition. Technological advancements in MRI that focus on producing high quality images and fast imaging, increasing diagnostic accuracy and developing newer function-specific contrast agents are essential in ensuring that MRI succeeds as a first line imaging modality. Newer imaging techniques, such as parallel imaging, are widely utilized to shorten scanning time. Diffusion weighted echo planar imaging, an adaptation from neuroimaging, is fast becoming a routine part of the MRI liver protocol to improve lesion detection and characterization of focal liver lesions. Contrast enhanced dynamic T1 weighted imaging is crucial in complete evaluation of diseases and the merit of this dynamic imaging relies heavily on the appropriate timing of the contrast injection. Newer techniques that include fluoro-triggered contrast enhanced MRI, an adaptation from 3D MRA imaging, are utilized to achieve good bolus timing that will allow for optimum scanning. For accurate interpretation of liver diseases, good understanding of the newer imaging techniques and familiarity with typical imaging features of liver diseases are essential. In this review, MR sequences for a time efficient liver MRI protocol utilizing newer imaging techniques are discussed and an overview of imaging features of selected common focal and diffuse liver diseases are presented.     

Cranial ultrasound in metabolic disorders presenting in the neonatal period: characteristic features and comparison with MR imaging

BACKGROUND AND PURPOSE: Brain imaging is an integral part of the diagnostic work-up for metabolic disorders, and the bedside availability of cranial ultrasonography (cUS) allows very early brain imaging in symptomatic neonates. Our aim was to investigate the role and range of abnormalities seen on cUS in neonates presenting with metabolic disorders. A secondary aim, when possible, was to address the question of whether brain MR imaging is more informative by comparing cUS to MR imaging findings. MATERIALS AND METHODS: Neonates with a metabolic disorder who had at least 1 cUS scan were eligible. cUS images were reviewed for anatomic and maturation features, cysts, calcium, and other abnormalities. When an MR imaging scan had been obtained, both sets of images were compared. RESULTS: Fifty-five infants (35 also had MR imaging) were studied. The most frequent findings were in oxidative phosphorylation disorders (21 cUS and 12 MR imaging): ventricular dilation (11 cUS and 6 MR imaging), germinolytic cysts (GLCs; 7 cUS and 5 MR imaging), and abnormal white matter (7 cUS and 6 MR imaging); in peroxisomal biogenesis disorders (13 cUS and 9 MR imaging): GLCs (10 cUS and 6 MR imaging), ventricular dilation (10 cUS and 5 MR imaging), abnormal cortical folding (8 cUS and 7 MR imaging), and lenticulostriate vasculopathy (8 cUS); in amino acid metabolism and urea cycle disorders (14 cUS and 11 MR imaging): abnormal cortical folding (9 cUS and 4 MR imaging), abnormal white matter (8 cUS and 8 MR imaging), and hypoplasia of the corpus callosum (7 cUS and 6 MR imaging); in organic acid disorders (4 cUS and 2 MR imaging): periventricular white matter echogenicity (2 cUS and 1 MR imaging); and in other disorders (3 cUS and 1 MR imaging): ventricular dilation (2 cUS and 1 MR imaging). cUS findings were consistent with MR imaging findings. cUS was better for visualizing GLCs and calcification. MR imaging was more sensitive for subtle tissue signal intensity changes in the white matter and abnormality in areas difficult to visualize with cUS, though abnormalities of cortical folding suggestive of polymicrogyria were seen on cUS. CONCLUSION: A wide range of abnormalities is seen using cUS in neonatal metabolic disorders. cUS is a reliable bedside tool for early detection of cysts, calcium, structural brain abnormalities, and white matter echogenicity, all suggestive of metabolic disorders.     

放射性核素骨显像在骨折诊断中的应用

目的 探讨放射性核素骨显像在骨折诊断中的临床应用价值.方法 对48例临床疑诊骨折患者行放射性核素骨显像检查,并将骨显像检查与其它影像学检查资料进行回顾性分析.结果 所有患者均经病理或随访确诊.48例中32例放射性核素骨显像结果与其它影像资料相符;16例结果不相符中,其它影像发生漏诊10例,误诊4例,多诊2例.结论 放射性核素骨显像是诊断骨折的一种好方法,对临床早期诊断不明确病例,行核素骨扫描可提高诊断率.     

胰腺影像学检查进展

影像学技术的发展极大地促进了胰腺影像诊断水平的提高。本文回顾了螺旋CT和多层面CT、MR成像、ERCP、超声成像和介入放射学技术的进展，及其在胰腺疾病检查中的应用与常见胰腺疾病的影像学表现。多项影像学检查方法和技术的综合应用胰腺影像诊断领域的趋势。     

Fast magnetic resonance imaging of the lung.

The impact of fast MR techniques developed for MR imaging of the lung will soon be recognized as equivalent to the high-resolution technique in chest CT imaging. In this article, the difficulties in MR imaging posed by lung morphology and its physiological motion are briefly introduced. Then, fast MR imaging techniques to overcome the problems of lung imaging and recent applications of the fast MR techniques including pulmonary perfusion and ventilation imaging are discussed. Fast MR imaging opens a new exciting window to multi-functional MR imaging of the lung. We believe that fast MR functional imaging will play an important role in the assessment of pulmonary function and disease process.     

Time-multiplexed multislice inversion-recovery techniques for NMR imaging

Multislice imaging techniques effectively applicable to inversion-recovery (IR) imaging are developed and applied to human imaging. These new multislice IR imaging sequences employ the time-multiplexing (TM) technique conventionally used in the slice-by-slice saturation-recovery (SR) imaging. Two new time-multiplexed multislice (TMM) IR imaging sequences are proposed and some of the experimental results obtained with the methods are presented.     

同时多层成像技术联合肝脏MR扩散成像的应用及展望

同时多层（SMS）成像技术与多种MRI序列联合应用可明显缩短成像时间。MR扩散成像,如常规扩散加权成像（DWI）、体素内不相干运动成像（IVIM）、扩散张量成像（DTI）和扩散峰度成像（DKI）能反映组织内水分子扩散、血流灌注、组织结构复杂性等微观特征,在肝脏病变检测和辅助定性中有重要价值。SMS与MR扩散成像联合后可明显缩短成像时间,利于各种MR扩散成像在肝脏中的广泛应用。综述SMS对肝脏扩散成像扫描速度的提升效率、对影像质量和定量参数的影响,以期推动SMS成像技术在临床中的广泛应用。     

Assessment of image display of contrast enhanced T1W images with fat suppression

The effects of imaging conditions and measures for their improvement were examined with regard to recognition of the effects of contrast on images when T1-weighted imaging with selective fat suppression was applied. METHOD: Luminance at the target region was examined before and after contrast imaging using phantoms assuming pre- and post-imaging conditions. A clinical examination was performed on tumors revealed by breast examination, including those surrounded by mammary gland and by fat tissue. RESULTS: When fat suppression was used and imaging contrast was enhanced, the luminance level of fat tumors with the same structure as the prepared phantoms appeared to be high both before and after contrast imaging, and the effects of contrast were not distinguishable. This observation is attributable to the fact that the imaging conditions before and after contrast imaging were substantially different. To make a comparison between pre- and post-contrast images, it is considered necessary to perform imaging with fixed receiver gain and to apply the same imaging method for pre- and post-contrast images by adjusting post-contrast imaging conditions to those of pre-contrast imaging.     

Imaging in interventional oncology

Medical imaging in interventional oncology is used differently than in diagnostic radiology and prioritizes different imaging features. Whereas diagnostic imaging prioritizes the highest-quality imaging, interventional imaging prioritizes real-time imaging with lower radiation dose in addition to high-quality imaging. In general, medical imaging plays five key roles in image-guided therapy, and interventional oncology, in particular. These roles are (a) preprocedure planning, (b) intraprocedural targeting, (c) intraprocedural monitoring, (d) intraprocedural control, and (e) postprocedure assessment. Although many of these roles are still relatively basic in interventional oncology, as research and development in medical imaging focuses on interventional needs, it is likely that the role of medical imaging in intervention will become even more integral and more widely applied. In this review, the current status of medical imaging for intervention in oncology will be described and directions for future development will be examined.     

盆腔异位肾肾动态显像前后位像GFR测定值的差异比较

目的比较分析盆腔异位肾肾动态显像前、后位像肾小球滤过率（GFR）测定值的差异。方法回顾性分析10例盆腔异位肾患者的肾动态显像GFR测定结果,分别进行前位异位单肾处理和后位双肾处理,将后位像处理所获正常肾脏GFR与前位像处理所获异位肾GFR相加,获得总肾GFR,并与后位像处理所获双肾GFR和双血浆法GFR测定结果进行比较和相关性分析,并进行了相应随访。采用配对t检验法和双变量相关分析检验法对数据进行统计学分析。结果10例盆腔异位肾患者前位像处理所获异位肾GFR[（27．48±12．24）ml／（min·1．73m^2）]较后位像处理所获异位肾GFR[（10．71±4．74）ml／（min·1．73m^2）]高出46％,二者间差异有统计学意义（t=5．481,P〈0．01）。前位像处理所获总GFR与双血浆法GFR差异无统计学意义（t=-2．238,P〉0．05）,二者的相关性较好（r=0．704,P〈0．05）;后位像处理所获总GFR与双血浆法GFR差异有统计学意义（t=4．629,P〈0．01）,二者的相关性较差（r=0．576,P〉0．05）。结论在肾动态显像中,前位像处理所获GFR较后位像更能真实地反映盆腔异位。肾的功能状况。     

MR fluid-attenuated inversion recovery imaging as routine brain T2-weighted imaging

We tried to investigate if magnetic resonance (MR) fluid-attenuated inversion recovery (FLAIR) imaging can be used as a routine brain screening examination instead of spin-echo T2-weighted imaging. Three hundred and ninety-four patients with clinically suspected brain diseases were randomly selected and examined with both brain MR FLAIR and T2-weighted imaging on the axial plane. These two imaging techniques were evaluated by two neuroradiologists as to which imaging was better for routine brain T2-weighted imaging. In 123 of 394 cases (31%), FLAIR imaging was superior to spin-echo T2-weighted imaging. Especially in cases with inflammatory diseases, traumatic diseases and demyelinating diseases, FLAIR imaging was particularly useful. Small lesions bordering cerebrospinal fluid (CSF) are often detected only by FLAIR imaging. In 259 cases (66%), including 147 normal cases (37%), they were equally evaluated. Only in 12 cases (3%) was conventional T2-weighted imaging superior to FLAIR imaging. Cerebrovascular lesions like cerebral aneurysm and Moyamoya disease could not be detected on FLAIR images because these structures were obscured by a low signal from the CSF. Also, because old infarctions tend to appear as low signal intensity on FLAIR images, the condition was sometimes hard to detect. Finally, FLAIR imaging could be used as routine brain T2-weighted imaging instead of conventional spin-echo T2-weighted imaging if these vascular lesions were watched.     

A review of molecular imaging studies reaching the clinical stage

The practice of molecular imaging in the clinics is examined across various imaging modalities to assess the current status of clinical molecular imaging. The various physiologic and scientific bases of clinical molecular imaging are surveyed to assess the possibilities and opportunities for the deployment of the different imaging modalities in the near future. The requisites for successful candidate(s) of clinical molecular imaging are reviewed for future development.     

肿瘤受体显像

肿瘤受体显像研究包括放射性标记配体的制备、配体与受体的体外分析及体内受体显像,肿瘤受体配体可用18F、123I(或131I)、111In与99Tcm标记,通过放射性受体结合分析、放射性自显影与受体特性分析,对其体外性能进行研究。神经多肽受体显像、类固醇受体显像与σ受体显像等已应用于多种肿瘤的诊断、分期、治疗方案选择与预后评价,其中神经多肽受体显像得到了较广泛的研究与应用。     

Localization of prostate cancer using 3T MRI: comparison of T2-weighted and dynamic contrast-enhanced imaging

OBJECTIVE: To compare dynamic contrast-enhanced imaging and T2-weighted imaging using a 3T MR unit for the localization of prostate cancer. METHODS: Twenty consecutive patients with biopsy-proven prostate cancer underwent both T2-weighted imaging and dynamic contrast-enhanced imaging. At T2-weighted imaging and dynamic contrast-enhanced imaging, the presence or absence of prostate cancer confined within the prostate without extracapsular or adjacent organ invasion was evaluated in the peripheral zones of base, mid-gland, and apex on each side. Final decisions on prostate cancer localization were made by consensus between two radiologists. Degrees of depiction of tumor borders were graded as poor, fair, or excellent. RESULTS: Prostate cancer was pathologically detected in 64 (53%) of 120 peripheral zone areas. The sensitivity, specificity, and accuracy for prostate cancer detection were 55%, 88% and 70% for T2-weighted imaging and 73%, 77%, and 75% for dynamic contrast-enhanced imaging, respectively. Three cancer areas were detected only by T2-weighted imaging, 15 only by dynamic contrast-enhanced imaging, and 34 by both T2-weighted imaging and dynamic contrast-enhanced imaging. A fair or excellent degree at depicting tumor border was achieved in 67% by T2-weighted imaging and in 90% by dynamic contrast-enhanced imaging (P<0.05). CONCLUSIONS: Dynamic contrast-enhanced imaging at 3T MRI is superior to T2-weighted imaging for the detection and depiction of prostate cancer and thus is likely to be more useful for preoperative staging.     

Contributions of newer MR imaging strategies for congenital heart disease.

Magnetic resonance (MR) imaging is a valuable noninvasive adjunct in the evaluation of congenital heart disease (CHD). With its multiplanar image acquisition, good spatial resolution, and large-field-of-view image display, MR imaging can allow appreciation of vascular connections not readily apparent at echocardiography or angiography. Evaluation of CHD with MR imaging has two components: definition of cardiovascular anatomy and characterization of blood flow. However, the variety of MR imaging options is large and often confusing. Besides spin-echo and gradient-echo imaging, MR imaging techniques for evaluation of CHD include MR angiography, cine MR imaging, and flow quantification. An understanding of the potential MR imaging options enables formulation and more efficient application of MR imaging strategies. When performed well, MR imaging greatly enhances surgical planning and can even obviate cardiac catheterization. MR imaging is also an excellent modality for serial evaluation of surgical results and complications in cases of CHD.