Multimodality preoperative imaging of pancreatic insulinomas

Pancreatic insulinomas are rare tumours of the islet cells of the pancreas, which account for the majority of functional neuroendocrine tumours of the pancreas. There is often a typical history of recurrent hypoglycaemic collapse and dizzy spells. Insulinomas are usually solitary, and the vast majority are intra-pancreatic in location. They are characteristically small with approximately 66% being less than 2cm at presentation. Insulinomas continue to pose a diagnostic challenge to physicians, surgeons and radiologists alike. The role of imaging is to detect and provide precise anatomical localization and staging of tumours prior to surgery. Due to their small size at clinical presentation, they are notoriously difficult to localize radiologically, and specifically designed protocols are necessary to aid detection. In this review, we describe the current "state of the art" imaging protocols that may be used in the preoperative localization of insulinomas.     

Bone marrow lesions: evaluation with fat-suppression turbo spin echo MR imaging at 0.5 T

The purpose of this study was the assessment of the diagnostic value of fat-suppression T2-weighted images for a variety of bone marrow lesions. We performed 40 studies of the axial or appendicular skeleton in 33 patients (age range 4–80 years) with neoplastic, inflammatory or traumatic lesions with a 0.5 T system (Glyroscan T5, Philips Medical Systems, Best, The Netherlands). Fat-suppression T2-weighted images [turbo spin echo (TSE) with spectral presaturation with inversion recovery (SPIR)] were obtained in addition to the routine T1-weighted SE and T2-weighted TSE sequences. Fat-suppression TSE T2-weighted images were better than standard TSE T2-weighted images in 25 studies. In 11 of them demonstration and characterization of the lesions (known from T1-weighted images) was possible only after fat suppression In the other 14 patients demonstration of the full extent of the lesion especially to the nearby soft tissues was possible only after fat suppression. In 13 studies no advantage was conferred by SPIR, whereas in two instances T2-weighted images were better. Fat-suppression T2-weighted images are diagnostically usefull in a variety of lesions of the musculoskeletal system, but their limitations should be known.Correspondence to: H. Chrysikopoulos     

MR imaging of spinal cord arteriovenous malformations at 0.5 T: study of 34 cases

Thirty-four patients with angiographically proved arteriovenous malformations of the spinal cord were studied between May 1986 and July 1987. Examinations were performed on a CGR 5000 Magniscan 0.5-T scanner with a surface coil in all cases, and multislices in both T1- and T2-weighted sequences were obtained in sagittal and axial planes. The results showed that MR can accurately diagnose all cases of intramedullary arteriovenous malformations, since transverse images were able to precisely locate the nidus within the spinal cord. Other types of spinal cord arteriovenous malformations were also studied (perimedullary fistulae and dural arteriovenous fistula), and the findings confirmed the value of MR in the characterization of these lesions as well.     

3.0T MR灌注加权成像和扩散加权成像在胰腺肿块诊断中的应用

目的 评价3.0 T MR灌注参数和ADC值在胰腺癌和胰腺肿块诊断中的应用价值.方法 选取20名正常志愿者及25例经手术病理证实的胰腺癌患者,行基于T1对比胰腺灌注扫描.测量胰腺癌组织、邻近胰腺组织、远端炎症区及正常胰腺组织的血管通透性常数(Ktrans)、血液回流常数(Kep)及细胞外血管外间质容量(Ve),并采用方差分析进行比较.15名正常志愿者及58例患者(胰腺癌30例、肿块型胰腺炎9例、实性假乳头状瘤9例及神经内分泌肿瘤10例)行DWI,采用方差分析比较不同组织的ADC值,并应用ROC曲线分析其诊断效能.结果 胰腺癌组织、邻近胰腺组织、远端炎症区及正常胰腺的Ktrans分别为(1.66±1.25)、(3.77±2.67)、(1.16±0.94)和(2.69±1.46)/min,差异有统计学意义(F=8.160,P＜0.01),其中胰腺癌组织的Ktrans低于正常胰腺组织(P=0.011)及邻近胰腺组织(P=0.002);上述部位的Kep分别为(2.53±1.55)、(5.64±2.64)、(1.70±0.91)和(4.28±1.64)/min,差异有统计学意义(F=4.544,P＜0.01),其中胰腺癌组织的Kep值均低于正常胰腺组织(P=0.035)及邻近胰腺组织(P=0.041);Ve中位数分别为0.926、0.839、0.798和0.659,差异有统计学意义(χ2=12.040,P＜0.01),胰腺癌的Ve值高于正常胰腺(P＝0.002).胰腺癌组织、肿块型胰腺炎、实性假乳头状瘤、神经内分泌肿瘤及正常胰腺的ADC值分别为(1.57±0.26)×10-3、(1.19±0.15)×10-3、(1.05±0.35)×10-3、(1.62±0.41)×10-3及(1.82±0.25)×10-3 mm2/s,差异有统计学意义(F=21.681,P＜0.01),其中肿块型胰腺炎、胰腺癌及正常胰腺的ADC值两两之间差异均有统计学意义(P＜0.01),实性假乳头状瘤的ADC值低于神经内分泌肿瘤(P＜0.01).以ADC≥1.33×10-3mm2/s从肿块型胰腺炎中鉴别诊断胰腺癌,灵敏度和特异度分别为86.7%和88.9%,阳性预测值为96.3%,阴性预测值为66.7%.以ADC值≤1.25×10-3 mm2/s作为诊断实性假乳头状瘤的临界点,灵敏度和特异度分别为77.8%和100.0%,阳性预测值100.0%,阴性预测值83.3%.结论 3.0 T MR PWI显示胰腺癌的Ktrans和Kep较低,而Ve较高;呼吸门控DWI序列的ADC值能够较好地反映正常胰腺及胰腺肿块的组织病理生理特征,有助于胰腺肿块的诊断与鉴别.

Abstract：

Objective To investigate the value of MR perfusion parameters and ADC in the diagnosis of pancreatic cancer and pancreatic mass at 3.0 T MR. Methods Twenty healthy volunteers and 25 patients with pancreatic cancers proven by pathological results underwent MR PWI at a 3.0 T scanner. A two-compartment model was used to quantify Ktrans, Kep and Ve in the pancreatic cancer, adjacent pancreatic tissue, distal inflammatory pancreatic tissue and normal pancreatic tissue. All parameters among different tissues were analyzed and compared with ANONA. Fifteen normal volunteers and 58 patients, including 30 patients with pancreatic cancer (proven histopathologically), 9 patients with pancreatitis pseudotumor (4 patients proven by histopathological results, 5 patients proven by follow-up after treatment), 9 patients with solid pseudopapillary tumor of pancreas (SPTP, proven histopathologically) and 10 patients with pancreatic neuroendocrine tumor (PET, proven by histopathology), underwent respiratory-triggered DWI on 3.0 T. ADC values of normal pancreas and all types of pancreatic lesions were statistically analyzed and compared with ANONA. ROC curve was used to analyze the diagnostic power of ADC value. Results Ktrans of pancreatic cancer, adjacent pancreatic tissue, distal inflammatory pancreatic tissue and normal pancreatic tissue were (1.66±1.25), (3.77±2.67),(1.16±0.94) and (2.69±1.46)/min respectively(F=8.160, P＜0.01). LSD test showed that Ktrans in the pancreatic cancer was statistically lower than that in normal pancreas (P=0.011)and adjacent pancreatic tissue(P=0.002). Kep of pancreatic cancer, adjacent pancreatic tissue, distal inflammatory pancreatic tissue and normal pancreatic tissue were (2.53±1.55), (5.64±2.64), (1.70±0.91) and (4.28±1.64)/min respectively(F=4.544, P＜0.01). LSD test revealed that Kep in pancreatic cancer was statistically lower than that in normal pancreatic tissue (P=0.035)and adjacent pancreatic tissue(P=0.041). The median of Ve among the pancreatic cancer, adjacent pancreatic tissue, distal inflammatory pancreatic tissue and normal pancreatic tissue were 0.926, 0.839, 0.798 and 0.659 respectively (χ2=12.040,P＜0.01). Ve in pancreatic cancer was statistically higher than that in normal pancreatic tissue (P=0.002). ADC values of the pancreatic cancer, pancreatitis pseudotumor, SPTP, PET and normal pancreas were(1.57±0.26)×10-3,(1.19±0.15)×10-3,(1.05±0.35)×10-3,(1.62±0.41)×10-3 and (1.82±0.25)×10-3 mm2/s(F=21.681, P＜0.01). LSD test showed there were significant statistical differences in ADC values among pancreatic cancer, pancreatitis pseudotumor and normal pancreatic tissue (P＜0.01). ROC curve disclosed that the sensitivity, specificity, positive predictive value and negative predictive value were 86.7%, 88.9%, 96.3% and 66.7% respectively, when ADC≥1.33×10-3 mm2/s was used as a cutoff value for differential diagnosis of PDCA from MLP. The sensitivity, specificity, positive predictive value and negative predictive value were 77.8%, 100.0%, 100.0% and 83.3% respectively when ADC≤1.25×10-3 mm2/s was used as a cutoff value for differential diagnosis of SPTP from PET. Conclusion Compared to normal pancreatic tissue, pancreatic cancer usually had a lower Ktrans, Kep and larger Ve. ADC values from respiratory-triggered DWI were well related to histopathological features of pancreatic entities and may be helpful in the differential diagnosis.     

3.0T磁共振弥散加权成像在胰腺癌中的应用价值

目的:分析评价在3.0T磁共振非脂肪抑制憋气DWl序列在胰腺癌中的应用价值.方法-30例正常志愿者与30例经手术病理证实的胰腺癌患者,在3.0T磁共振上,术前行基于SE-EPI的非脂肪抑制憋气DWI序列,b值为0和600s/mm2,统计学比较分析正常胰腺、胰腺癌及远端炎症区的ADC值.结果:不同组织的ADC值从低到高依次为胰腺癌、正常胰腺、远端炎症,单因素方差分析显示不同组织的ADC值有明显统计学差异,F值为18.716,P值为0.0004,两两比较分析显示胰腺癌分别与正常胰腺及远端炎症的ADC值统计学有明显差异,P值分别为0.00483及0.00191.结论:在3.0T磁共振上,非脂肪抑制憋气DWI序列有助于病灶筛查,其ADC值能够较好的反映胰腺癌、正常胰腺及远端炎症的组织病理状态.     

MR imaging of intracerebral blood: diversity in the temporal pattern at 0.5 and 1.0 T

MR scans were obtained at 0.5 and 1.0 T in 40 patients with 46 intracerebral hematomas categorized as hyperacute (0-2 days), acute (3-7 days), subacute (8-14 days), and chronic (15 days to 6 years). In a retrospective review, the signal intensity of the lesions was compared with that of normal white matter of the brain on spin-density, T1-, and T2-weighted spin-echo and T1-weighted gradient-echo sequences. The classic appearance and evolution of hematomas described in the literature at 1.5 T were not found in a significant number of the cases reviewed. In the hyperacute group, only five of eight hematomas had signal intensities that were hypointense relative to brain on T2-weighted images. Two of eight hyperacute hematomas were hyperintense relative to brain on the T1-weighted spin-echo images. However, T1-weighted gradient-echo images reliably demonstrated a hypointense signal in some portion of the hematoma in 45 of 46 cases. We conclude that while there is no constant temporal pattern on spin-echo or gradient-echo sequences, there are signal-intensity changes suggestive of hemorrhage in nearly all hematomas imaged at 0.5 and 1.0 T. Although the inconsistency may be frustrating from a diagnostic standpoint, this variability may reveal important individual differences in hematomas and the brain that surrounds them, and thus be clinically significant. Before these data can be mechanistically analyzed, the reason for contrast on MR scans of hematoma must be better understood.     

Snapshot imaging at 0.5 T using echo-planar techniques

Echo-planar imaging using a magnetic field strength of 0.5 T has resulted in an improvement in image quality compared with recent images published at 0.1 T. The sensitivity of the technique to main magnetic field inhomogeneity and transient eddy currents has necessitated innovations in gradient and radiofrequency coil design. These improvements are described, and new variations in the echo-planar pulse sequence which provide better contrast and allow separate imaging of water and fat distributions are presented.     

0.5 T MR单激发快速自旋回波在胆系梗阻性病变诊断中的应用

目的评估0.5 T MR单激发半傅立叶采集快速自旋回波胰胆管水成像(HASTE-MRCP)的定位及定性准确性,并与三维快速自旋回波胰胆管水成像(3D-TSE-MRCP)进行比较.方法所有95例病人均行HASTE-MRCP及结合呼吸门控的3D-TSE-MRCP检查及最大信号强度投影(MIP)(设备为Philips 0.5 T T5-NT 磁共振成像系统).分析95例患者的胆管解剖显示情况、病变显示情况并与手术结果比较.结果 HASTE-MRCP胆总管及1～3级胆管的显示率为100.0%,4～5级胆管为94.7%,胆囊为74.1%,胰管为63.2%;结石部位显示100.0%,恶性病变及术后狭窄显示率100.0%.与3D-TSE-MRCP比较,对4～5级胆管、胆囊颈及结石,尤其泥沙样结石的显示率更高,统计学上两者间差异有显著性意义(χ2 值分别为3.92、6.62、11.76 及29.93,P<0.05 或<0.01);对恶性病变及术后狭窄的显示率均为100.0%.结石主要表现为胆道内呈低信号的"充盈缺损";恶性病变则表现为截断及梗阻征象,并可显示软组织轮廓.结论 HASTE-MRCP是优秀的胰胆管超快速成像技术,在0.5 T MR 也能非常好的运用;比较结合呼吸门控的3D-TSE-MRCP ,HASTE-MRCP在重症病人成像或显示小结石及泥沙样结石上有明显优势,建议对急诊、重症及临床疑为结石的病人,首先考虑选择HASTE-MRCP技术.     

3.0T自由呼吸背景抑制弥散加权成像在胰腺癌中的应用研究

目的:在3.0T磁共振上,分析评价自由呼吸背景抑制弥散序列在胰腺癌中的应用价值。方法:20例正常志愿者行常规T1WI、频率饱和脂肪抑制T2WI、MRCP、弥散加权成像(DWI)及三维LAVE平扫,25例经手术病理证实的胰腺癌患者,术前行常规T1WI、频率饱和脂肪抑制T2WI、MRCP、DWI、三维LAVE及增强三维LAVA扫描,DWI序列基于SE-EPI序列及b值为0和600s/mm2,应用自由呼吸背景抑制技术,统计学比较分析正常胰腺、胰腺癌、邻近胰腺及远端炎症区的ADC值。结果:不同组织的ADC值从低到高依次为胰腺癌、正常胰腺、远端炎症及邻近胰腺组织,单因素方差分析显示不同组织的ADC值有明显统计学差异,F值为17.936,P值为0.0003,两两比较分析显示胰腺癌分别与正常胰腺、邻近胰腺及远端炎症的ADC值统计学有明显差异,P值分别为0.00591、0.000347及0.00211。结论:在3.0T磁共振上,自由呼吸背景抑制DWI序列有助于病灶筛查,其ADC值能够较好的反映胰腺癌、正常胰腺、邻近胰腺及远端炎症的组织病理状态。     

MR cholangiopancreatography at 0.5 T with a 3D inversion recovery turbo-spin-echo sequence

The objective of this study was to assess the diagnostic value of magnetic resonance cholangiopancreatography (MRCP) at 0.5 T. The MRCP technique was performed in 28 patients with symptomatology referrable to the biliary system. A three-dimensional (3D) inversion recovery turbo-spin-echo (TSE) sequence was used to create 3D reconstructions of the bile ducts. Dilation of the biliary tree or pancreatic duct in 23 patients due to tumor, calculi, or strictures was depicted with excellent contrast resolution. The approximate level of obstruction and all calculi were accurately predicted by MRCP. In another 3 patients no cause was found for the biliary dilatation. In the last 2 cases no abnormalities were found by either MRCP or endoscopic retrograde cholangiopancreatography (ERCP). The MRCP technique at 0.5 T is an accurate method for the assessment of pathology of the biliary tree. Received 23 August 1996; Revision received 31 January 1997; Accepted 5 February 1997     

MR imaging of the larynx at 1.5 T

The normal magnetic resonance (MR) anatomy of the larynx at high field strength (1.5 T) was studied in 2 normal excised larynges and 62 subjects without laryngopharyngeal disease. The two normal excised larynges were imaged using a 1.5 T MR scanner with a 3 in diameter circular surface coil and a GE 9800 CT scanner. The larynges were sectioned transversely and the MR and CT images compared to gross and histologic sections. Unossified hyaline cartilage was intermediate in signal intensity on T1-weighted and proton density images and low in intensity on T2-weighted images. The signal intensity from ossified cartilage was determined by the amount of fatty marrow and was high in intensity on T1-weighted and proton density images and low to intermediate in intensity on T2-weighted images. A chemical shift artifact from high intensity fatty marrow obscured the calcified or ossified cortex of the major laryngeal cartilages along the frequency encoding axis. The epiglottic cartilage demonstrated an intermediate signal intensity on T1-weighted images and higher intensity on proton density and T2-weighted images. The intralaryngeal muscles were well demonstrated as low intensity structures. The conus elasticus and the vocal ligaments were not recognized as distinct structures. However, the quadrangular membrane and a previously undescribed membrane separating the preepiglottic and paralaryngeal spaces were shown on MR as low intensity linear structures. In the 62 subjects, MR at 1.5 T proved excellent for demonstrating the anatomical details of the major laryngeal cartilages, extra- and intralaryngeal muscles, ligaments, and soft tissues including the vocal cords, false vocal cords, laryngeal ventricles, aryepiglottic folds, preepiglottic space, and paralaryngeal spaces. Visibility and intensity of muscles, ligaments, and soft tissues did not depend on age or sex. The intensity pattern of the thyroid and cricoid cartilages demonstrated wide variations in the same sex and age groups, depending on the degree of ossification. However, they did show more high intensity foci in older men than in younger women. Magnetic resonance showed better contrast resolution and finer detail than CT scans in the same subjects. Magnetic resonance imaging at 1.5 T, with either a saddle-shaped neck surface coil or a 3 in diameter circular surface coil, provides high contrast and high spatial resolution images and could be useful for the diagnosis of lesions of the larynx.(ABSTRACT TRUNCATED AT 400 WORDS)     

Comparison of MR sequences in early cerebral infarction at 0.5 T

Purpose: To compare the diagnostic values of fluid-attenuated inversion recovery (FLAIR) and gradient spin-echo (GRASE) with those of conventional spin-echo (SE) and fast SE T2-weighted sequences in the evaluation of acute cerebrovascular lesions at 0.5 T.Material and Methods: Twenty-two consecutive patients with the clinical diagnosis of acute cerebrovascular accident were examined by MR imaging within the first 48 h of ictus. MR examination included 5-mm axial conventional SE and turbo SE (TSE) T2-weighted, dual-echo GRASE and FLAIR sequences. The patients also had pre- and postcontrast T1-weighted axial images. Two examiners evaluated the images and scored the conspicuity of the acute lesions.Results: Regardless of location, FLAIR provided the best lesion conspicuity in the detection of acute infarcts, followed by the GRASE sequence. In the posterior fossa, TSE and SE demonstrated the lesions better than GRASE and FLAIR techniques. In the detection of hemorrhagic elements within the ischemic region, TSE demonstrated statistically significant superiority over other sequences.Conclusion: In the detection of acute ischemic lesions in locations other than the posterior fossa, FLAIR provided the best lesion conspicuity among four T2-weighted sequences, including SE, TSE, GRASE and FLAIR. However, for the posterior fossa examination, preference of SE or TSE T2-weighted sequences is suggested.     

Mottled MR appearance of a hyperacute intracerebral hemorrhage at 0.5 T

A hypertensive patient was examined by CT and magnetic resonance (0.5 T) within 3 h from stroke onset. Computed tomography revealed a thalamocapsular hemorrhage. Hematoma was isointense to the white matter on T1-weighted and hyperintense on T2-weighted spin echo images. The T2-weighted gradient echo images showed a mixture of hypointense and hyperintense signal. This latter aspect has not previously been reported and is probably related to abundant intracellular deoxyhemoglobin in clotted areas rich in red blood cells.     

Inversion-recovery echo-planar imaging (IR-EPI) at 0.5 T

Echo-planar imaging is used in combination with a spin preparation phase to produce a T1-weighted image. The small additional time penalty in this procedure does not detract significantly from the ultrahigh-speed imaging capability of EPI, allowing a rapid real-time optimization of tissue parameters in the image display. Results obtained on a head demonstrate this technique.     

MR imaging of pancreatic diseases

This article presents current MR imaging techniques for the pancreas, and review a spectrum of MR imaging features of various pancreatic diseases. These include: 1) congenital anomalies such as anomalous union of pancreatobiliary ducts, divisum, and annular pancreas, 2) inflammatory diseases, including acute or chronic pancreatitis with complications, groove pancreatitis, and autoimmune pancreatitis, tumor-forming pancreatitis, 3) pancreatic neoplasms, including adenocarcinoma, islet cell tumors, and cystic neoplasms (microcystic adenoma, mucinous cystic neoplasms, and intraductal mucin-producing pancreatic tumor). Particular attention is paid to technical advances in MR imaging of the pancreas such as fat-suppression, MR pancreatography (single- or multi-slice HASTE), and thin-section 3D multiphasic contrast-enhanced dynamic sequences. Imaging characteristics that may lead to a specific diagnosis or narrow the differential diagnosis are also discussed.     

胰腺疾病的MRI诊断

随着MBI成像技术的迅速发展和MBI的广泛应用，利用MBI诊断胰腺疾病正引起人们的普遍关注。现代MRI技术包括屏气T1加权成像及其脂肪抑制、T2加权成像及其脂肪抑制、MBI动态增强扫描、MR胰胆管成像和MR血管成像。这些脉冲序列各自有不同的组织对比机制，而且是互相补充的，它们的综合应用，可以较全面地评价胰腺及胰腺病变，从而明显改善了MBI对胰腺疾病的检测和诊断。本文着重介绍胰腺的MR成像技术，正常解剖、先天性异常和常见疾病的NR诊断价值。     

Adrenal tissue characterization with 0.5-T MR imaging: Value of T2*-weighted images

The authors investigated the value of magnetic resonance (MR) imaging at 0.5 T for distinguishing adrenal adenomas from adrenal metastases. The series included 23 adrenal adenomas (18 nonhyperfunctioning, five hyperfunctioning) and 23 adrenal metastases from various organs. Adrenal tumor–liver signal intensity ratios on T1-, T2-, and T2*-weighted images were calculated for adrenal tissue characterization. Adrenal adenomas were more precisely distinguished from adrenal metastases on T2*-weighted images (21 of 23, 91%) than on T2-weighted images (15 of 23, 65%). T1-weighted images were not useful for this distinction. In conclusion, T2*-weighted images were better than routine T2-weighted images for distinguishing adrenal adenomas from adrenal metastases. It can be postulated that the total signal intensity of adrenal adenomas, which contain some fat components, decreased on T2*-weighted images because of an out-of-phase effect.