Regional measurement of the Gd-DTPA tissue partition coefficient in canine myocardium

Quantifiable MRI perfusion studies using the contrast agent Gd-DTPA require measurement or estimation of the tissue partition coefficient (λ) for tracer kinetic modeling. Radiotracer techniques were used to obtain regional λ measurements from the left ventricles of five dogs. Measurements were analyzed to determine whether spatial heterogeneity was a major component of λ variability. No systematic variations were identified in terms of radial position, short-axis slice location, or wall position. The high λ variability seen in this study and in cited data of others may be due in part to tissue heterogeneity in interstitial volume, plasma volume, and perfusate hematocrit.     

钆贝葡胺与钆喷酸葡胺对单发脑转移瘤患者MRI T1WI增强扫描诊断价值的对比

目的 比较钆贝葡胺与钆喷酸葡胺在脑内单发转移瘤增强扫描中的价值.方法 选择81例单发脑转移瘤患者,首先行钆喷酸葡胺增强扫描,剂量0.1 mmol/kg;2 d后行钆贝葡胺增强扫描,剂量0.1 mmol/kg.结果 ①钆贝葡胺强化后,病变形态、病变边缘、强化程度及增强范围均显著优于钆喷酸葡胺,差异具有统计学意义（z=12.3232,14.43534,11.4536,12.4232,P＜0.05）;②增强扫描后,钆贝葡胺强化图像对比信噪比均显著高于钆喷酸葡胺,强化病灶/正常脑组织增强比均显著高于钆喷酸葡胺,差异具有统计学意义（t=12.3456,12.3465,11.2675,3.7865,3.8796,3.8781,P＜0.05）.结论 钆贝葡胺增强扫描对单发脑转移瘤病变形态、病变边缘、强化程度及增强范围显示更优,其图像对比信噪比及病灶/正常脑组织增强比更高.     

Study of Ocular Transport of Drugs Released from an Intravitreal Implant Using Magnetic Resonance Imaging

Ensuring optimum delivery of therapeutic agents in the eye requires detailed information about the transport mechanisms and elimination pathways available. This knowledge can guide the development of new drug delivery devices. In this study, we investigated the movement of a drug surrogate, Gd-DTPA (Magnevist®) released from a polymer-based implant in rabbit vitreous using T₁-weighted magnetic resonance imaging (MRI). Intensity values in the MRI data were converted to concentration by comparison with calibration samples. Concentration profiles approaching pseudosteady state showed gradients from the implant toward the retinal surface, suggesting that diffusion was occurring into the retinal–choroidal–scleral (RCS) membrane. Gd-DTPA concentration varied from high values near the implant to lower values distal to the implant. Such regional concentration differences throughout the vitreous may have clinical significance when attempting to treat ubiquitous eye diseases using a single positional implant. We developed a finite element mathematical model of the rabbit eye and compared the MRI experimental concentration data with simulation concentration profiles. The model utilized a diffusion coefficient of Gd-DTPA in the vitreous of 2.8×10^–6, cm², s^–1 and yielded a diffusion coefficient for Gd-DTPA through the simulated composite posterior membrane (representing the retina–choroid–sclera membrane) of 6.0×10^–8, cm², s^–1. Since the model membrane was 0.03-cm thick, this resulted in an effective membrane permeability of 2.0×10^–6, cm, s^–1. Convective movement of Gd-DTPA was shown to have minimal effect on the concentration profiles since the Peclet number was 0.09 for this system.     

犬心肌梗塞的MRI与病理对照研究

目的：研究心肌梗塞演变过程中不同时期的ＭＲＩ影像特征及其病理基础。探讨ＭＲＩ在心肌梗塞方面的应用价值。材料与方法：２５只杂种犬结扎冠状动脉左前降支后,于心肌梗塞演变过程的不同时期行ＭＲＩ平扫、电影磁共振成像和Ｇｄ－ＤＴＰＡ增强扫描。取心脏标本进行病理检查。结果：ＭＲＩ平扫不能区别梗塞心肌和非梗塞心肌。Ｃｉｎｅ－ＭＲＩ能真实反映梗塞心肌的部位、厚度及运动功能状态。心肌梗塞演变的不同时期,由于其病理基     

造影剂注入法三维肺动脉MRA用于诊断肺癌浸润肺动脉的初步临床经验

目的：介绍造影剂注入法三维肺血管MRA（3D－MRPA）技术在诊断肺癌浸润肺动脉上的应用经验,初步认识此项技术的临床价值。材料和方法：肺癌4例。Cd－DTPA0．2mmol／kg静注后,应用高性能MR扫描系统,闭气下摄取24层肺血管SPGR序列连续冠状断面像,用时27秒。再重复同样扫描,分别获得肺动脉期相与支气管动脉期相。最后,以最大强度投影法（MIP）制成3D－MRPA。结果：4例肺癌显示出3种MRPA表现：肺动脉受累、可疑肺动脉受累与肺动脉无受累。可疑肺动脉受累,病例手术证实为粘连,MRPA的原始图像显示肿瘤与血管相切密切,血管内腔通畅,但管壁轻微受压变形。结论：造影法三维MRPA可以评价肿瘤浸润肺动脉。     

Improved contrast agent bolus tracking using T1 FARM.

Current MRI bolus tracking techniques, such as saturation recovery Turbo-FLASH (srTFL), suffer from signal saturation at high contrast concentrations. In this study T1 Fast Acquisition Relaxation Mapping (T1 FARM) was compared to srTFL. In phantoms, T1 FARM maps were linear with [Gd-DTPA] up to 7.0 mmol/L while srTFL images saturated above 2.0 mmol/L. In the canine left ventricle, blood concentration curves determined from T1 FARM saturated with bolus injections exceeding 0.075 mmol/kg, while srTFL curves saturated above 0.025 mmol/kg of Gd-DTPA. Also, T1 FARM improved contrast-to-noise ratio in tissue concentration curves since higher contrast concentrations could be measured without saturating.     

应用3.0T高分辨率磁共振成像活体动态观测豚鼠内耳内淋巴液

目的探讨临床用3.0T磁共振成像系统能否在活体豚鼠区分内外淋巴液。方法5只豚鼠在3.0T磁共振下行内耳容积扫描后即刻颈内静脉注射钆喷酸葡胺（3ml/kg),注射后30分钟、60分钟、90分钟、120分钟、150分钟、180分钟、210分钟、240分钟行内耳容积扫描,观测内耳内外淋巴液成像变化。结果未注射对比剂前仅能显示耳蜗及前庭轮廓,尚不能区分内外淋巴液,注射30分钟后对比剂首先进入前庭及耳蜗底转及蜗顶,注射120分钟见对比剂扩展到全内耳并有较好的显像。结论临床用3.0T磁共振成像可区分豚鼠内外淋巴液,为研究膜迷路积水提供便利。     

Computed tomography with iodine-free contrast media

The purpose of this work was to evaluate the enhancement of different concentrations of gadolinium (Gd), ytterbium (Yb) and iodine in vitro and in vivo. Comparisons were made of the enhancement (HU) of Gd, Yb and iodine in concentrations ranging from 0.1 to 30 mg/ml. In vivo dynamic CT studies were performed in ten dogs with 0.5 M Gd, Yb and iodine. Time-density curves were achieved in aorta and liver. The in vitro studies confirmed a decrease in the enhancement in this order: Gd (120 kV) > Gd (137 kV) > Yb (120 kV) > Yb (137 kV) > iodine (120 kV) > iodine (137 kV). The specific enhancement of Gd was 40.8 (120 kV), of Yb 34.2 and of iodine 29.6 HU. The enhancement of the liver decreases from 21 HU (Gd) to 19 HU (Yb) and 12 HU (iodine). Gd and Yb achieved a higher aortal enhancement than iodine (190 vs 157 HU) All contrast media were well tolerated. Equimolar concentrations of Gd and Yb show a higher in vitro contrast and enhancement than iodine. Received: 17 May 1996; Revision received: 12 September 1996; Accepted: 18 October 1996     

Gd-DTPA 增强 MRI 胸部组织序列信号变化的临床研究

目的：通过对肺癌和正常胸部组织的Ｇｄ－ＤＴＰＡ增强前后的信号强度、信噪比和相对信噪比的分析，探讨增强ＭＲ在胸部的应用价值。方法：用ＤＩＡＳＯＮＩＣ０．３５Ｔｅｓｌａ超导型ＭＲ成像仪。先常规平扫Ｔ１ＷＩ、Ｔ２ＷＩ，然后按０．１ｍｍｏｌ／ｋｇ体重，静脉内一次性注入Ｇｄ－ＤＴＰＡ（维影钆胺注射液）。立即行兴趣部位Ｔ１ＷＩ扫描。计算机测量病变及对照组织（皮下脂肪、肌肉、肺野及噪声）的信号强度，计算其信噪比（ＳＮＲ）和相对信噪比（ＣＮＲ）。结果：２９例支气管肺癌平均信号强度明显高于对照组织（Ｐ＜０．０１），增强后Ｔ１ＷＩ的ＳＮＲ明显高于平扫Ｔ１ＷＩ和Ｔ２ＷＩ；ＣＮＲ（以肌肉为对照）则高于平扫Ｔ１ＷＩ，与Ｔ２ＷＩ相似；与脂肪为参照物则与平扫Ｔ１ＷＩ、Ｔ２ＷＩ相似；以肺野为参照物则与Ｔ１ＷＩ相似，明显高于Ｔ２ＷＩ。结论：支气管肺癌增强后较对照组织有明显的强化；增强后Ｔ１ＷＩ可显著提高ＭＲ的信噪比，改善图像质量。ＭＲ造影剂在胸部有一定的应用价值