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首页> 外文学位 >MR thermometry with paramagnetic lanthanide complexes and its applications at 9.4-Tesla and development of clinical sodium (sodium-23) MRI at 3-Tesla.
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MR thermometry with paramagnetic lanthanide complexes and its applications at 9.4-Tesla and development of clinical sodium (sodium-23) MRI at 3-Tesla.

机译：具有顺磁性镧系元素配合物的MR测温技术及其在9.4-Tesla上的应用以及在3-Tesla上临床钠（sodium-23）MRI的开发。

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摘要

Magnetic resonance (MR) thermometry based on the water 1H signal provides high temporal and spatial resolution but has low temperature sensitivity (∼0.01 ppm/°C) and requires monitoring of another weaker signal for absolute temperature measurements. The use of the paramagnetic lanthanide complex, thulium 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethyl-1,4,7,10-tetraacetate (TmDOTMA-), which is ∼60 times more sensitive to temperature than the water 1H signal, is advanced to image absolute temperatures in vivo using water signal as a reference. The temperature imaging technique was developed using gradient echo and asymmetric spin echo imaging sequences on 9.4 T horizontal and vertical MR scanners. A comparison of regional temperatures measured with TmDOTMAy1 and fiber-optic probes showed that the accuracy of imaging temperature is 0.3°C. The temperature imaging technique was found to be insensitive to the main magnetic field inhomogeneities. The feasibility of imaging absolute temperature of intact rats with ∼1 mm spatial resolution in only 3 min is demonstrated with physiologically safe concentrations (∼1.4 mmol/kg dose). TmDOTMA- should prove useful for imaging absolute temperatures in deep-seated organs in numerous biomedical applications such as controlled hyperthermia.;The application of MR thermometry was taken to a new level to treat sc-implanted tumors by developing a non-invasive magnetic resonance (MR) technique that produced controlled radio-frequency (RF) hyperthermia (HT). The method used the 1H chemical shift of a different paramagnetic lanthanide complex, TmDOTA- to monitor tumor temperature non-invasively. The desired HT temperature was achieved and maintained using a feedback loop mechanism that uses a proportional-integral-derivative (PID) controller. The RF HT technique was able to heat the tumor from 33 to 45°C in ∼ 10 min and maintain the tumor temperature within +/-0.2°C of the target temperature without affecting the overall body temperature.;The in-magnet PID based RF HT was then interleaved with simultaneous 23Na and 31P MRS data collection to investigate the effects of HT on total and intracellular Na+ measured by single-quantum (SQ) and multiple-quantum-filtered (MQF) 23Na MRS, and cellular energy status (ATP/Pi), and intra- and extra-cellular pH (pH i and pHe, respectively) by 31P MRS in sc-implanted 9L-glioma in rats. Simultaneous monitoring of metabolic changes with RF HT showed a significant increase in total (12%, p ≤ 0.05) and intra-cellular (30-40%, p ≤ 0.05) sodium and a significant decrease in cellular bio-energetics (60%, p ≤ 0.05), pHi and pHe (0.2 and 0.17 pH units decrease respectively, p ≤ 0.05). The developed RF HT technique in combination with simultaneous MR measurements of sodium and cellular energetics during HT treatment show that 23Na and 31P will prove useful for monitoring therapy response during the treatment and may prove valuable in designing methods to improve therapeutic efficiency.;Clinical 23Na magnetic resonance imaging (MRI) of the human torso using an 8-channel dual tuned 23Na and 1H transmit/receive coil for various body applications was developed, optimized and characterized at 3 T. The 23Na MR images of the human torso were acquired with 0.3 cm spatial resolution and ∼ 20 signal-to-noise ratio (SNR) in ∼15 min. These images were acquired with optimized pulse sequence and imaging parameters under specific absorption rate limit for human scans. A mathematical algorithm based on exponential signal decay was used for RF inhomogeneity correction in the 23Na images caused by the four opposing phased-array coils. Tissue sodium concentration (TSC) of 20.8 +/- 1.2 mM was calculated from the inhomogeneity corrected 23Na MR images of healthy livers (n = 6). The reproducibility of TSC measurements was evaluated in healthy volunteers and compared with the water apparent diffusion coefficient (ADC) measurements (respiratory-gated and free-breathing). Among all the liver measurements evaluated, TSC values from the 23 Na MR images were the most reproducible parameter with a minimal inter-volunteer (4.2%) and intra-volunteer variability (4.4%) even without cardiac or respiratory gating. It is likely that this developed 23Na MRI technique can yield useful information to study normal and abnormal physiology because of the immense physiological significance of trans-membrane sodium gradient. The ability to perform 23Na MRI of the torso in clinical settings will prove useful to non-invasively detect and diagnose a number of diseases in various body organs and will greatly aid in monitoring therapy response.
机译：基于水1H信号的磁共振（MR）测温法可提供较高的时间和空间分辨率，但具有较低的温度敏感性（〜0.01 ppm /°C），并且需要监视另一个较弱的信号以进行绝对温度测量。使用顺磁性镧系元素络合物1,4,7,10-四氮杂十二环dec-1,4,7,10-四甲基-1,4,7,10-四乙酸th（TmDOTMA-），其敏感性高约60倍温度高于水1H信号的温度，然后以水信号为参考将其成像到体内的绝对温度。使用9.4 T水平和垂直MR扫描仪上的梯度回波和非对称自旋回波成像序列开发了温度成像技术。用TmDOTMAy1和光纤探头测得的区域温度的比较表明，成像温度的准确度<0.3°C。发现温度成像技术对主磁场的不均匀性不敏感。用生理上安全的浓度（约1.4 mmol / kg剂量）证明了在3分钟内以约1 mm的空间分辨率对完整大鼠的绝对温度成像的可行性。 TmDOTMA-应该被证明可用于在许多生物医学应用（例如控制体温过高）中对深部器官的绝对温度进行成像; MR测温的应用已通过发展非侵入性磁共振技术达到了治疗SC植入肿瘤的新水平（ MR）技术可产生受控的射频（RF）热疗（HT）。该方法使用了另一种顺磁性镧系元素TmDOTA-的1H化学位移来无创地监测肿瘤温度。使用使用比例积分微分（PID）控制器的反馈回路机制可以达到并保持所需的HT温度。 RF HT技术能够在约10分钟内将肿瘤从33°C加热到45°C，并使肿瘤温度保持在目标温度的+/- 0.2°C之内，而不会影响整体体温。然后将RF HT与同时的23Na和31P MRS数据收集进行交错，以研究HT对通过单量子（SQ）和多量子滤波（MQF）23Na MRS测量的总和细胞内Na +的影响以及细胞能量状态（ATP） / Pi），以及31P MRS在大鼠皮下植入的9L神经胶质瘤中的细胞内和细胞外pH（分别为pH i和pHe）。用RF HT同时监测代谢变化显示，钠和细胞内钠的总量（12％，p≤0.05）显着增加（30-40％，p≤0.05），而细胞生物能显着下降（60％， p≤0.05），pHi和pHe（pH单位分别降低0.2和0.17，p≤0.05）。发达的RF HT技术与HT治疗期间同时进行钠和细胞能量的MR测量相结合，表明23Na和31P将被证明对监测治疗过程中的治疗反应有用，并且在设计提高治疗效率的方法中可能被证明有价值。使用8通道双调谐23Na和1H发射/接收线圈对人体进行共振成像（MRI），在3 T时对其进行了优化和表征。在0.3 cm处采集了人体的23Na MR图像约15分钟内获得空间分辨率和约20的信噪比（SNR）。这些图像是在人体扫描的特定吸收率限制下以优化的脉冲序列和成像参数采集的。基于指数信号衰减的数学算法用于校正由四个相对的相控阵线圈引起的23Na图像中的RF不均匀性。根据健康肝脏的不均匀性校正后的23Na MR图像计算得出的组织钠浓度（TSC）为20.8 +/- 1.2 mM（n = 6）。在健康志愿者中评估了TSC测量值的可重复性，并与水表观扩散系数（ADC）测量值（呼吸门和自由呼吸）进行了比较。在所有评估的肝脏测量结果中，即使没有心脏或呼吸门控，来自23个Na MR图像的TSC值也是可重复性最高的参数，具有最小的志愿者间（4.2％）和志愿者内变异（4.4％）。由于跨膜钠梯度的巨大生理意义，这种发达的23Na MRI技术可能会为研究正常和异常生理学提供有用的信息。在临床环境中对躯干进行23Na MRI的能力将证明对非侵入性检测和诊断各种人体器官中的多种疾病非常有用，并且将大大有助于监测治疗反应。

著录项

  • 作者

    James, Judy Rose.;

  • 作者单位

    Purdue University.;

  • 授予单位 Purdue University.;
  • 学科 Engineering Biomedical.;Health Sciences Radiology.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 150 p.
  • 总页数 150
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

  • 入库时间 2022-08-17 11:37:52

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