Oikawa H, al-Hallaq H A, Lewis M Z, River J N, Kovar D A, Karczmar G S
Department of Radiology, University of Chicago, Illinois 60637, USA.
Magn Reson Med. 1997 Jul;38(1):27-32. doi: 10.1002/mrm.1910380106.
A variety of treatments that modulate tumor oxygen tension are used clinically to improve the outcome of radiotherapy. High resolution, noninvasive measurements of the effects of these treatments would greatly facilitate the development of improved therapies and could guide treatment of cancer patients. Previous work demonstrated that magnetic resonance (MR) gradient echo imaging of the water proton resonance detects changes in T2* and T1 in tumors during hyperoxia that may reflect increased tumor oxygenation. This report describes the use of high resolution MR spectroscopic imaging with short repetition time (TR = 0.2 s) to improve the accuracy with which changes in T2* and T1 are measured. Mammary adenocarcinomas grown in the hind limbs of rats were studied. Carbogen inhalation was used to induce hyperoxia. A single 2-mm slice through the center of tumors and underlying muscle was imaged at 4.7 Tesla with in-plane resolution of approximately 1.2 mm and frequency resolution of 5.8 Hz. The peak integral increased by an average of 6% in tumors during carbogen inhalation suggesting a decrease in T1 (n = 8, P < 0.001). Peak height increased by an average of 15% in tumors during carbogen inhalation (n = 8, P < 0.001). The large difference between increases in peak height and peak integral demonstrates that the width of the water resonance decreased. Assuming a Lorentzian lineshape, an average increase of 12% in T2* was observed in tumors. In muscle, peak integral and peak height increased slightly (about 1.2% and 3%, respectively; P < 0.02) during carbogen inhalation but no significant change in T2* was observed. Spectroscopic imaging detects changes in the water proton resonance in tumors during hyperoxia accurately and reproducibly with high signal-to-noise ratio and allows clear separation of T1 and T2* effects. Increases in T2* may be due to decreased deoxyhemoglobin in tumor blood vessels (i.e., the BOLD effect) and may provide a clinically useful index of increases in tumor oxygenation.
临床上使用多种调节肿瘤氧张力的治疗方法来改善放射治疗的效果。对这些治疗效果进行高分辨率、非侵入性测量将极大地促进改进疗法的开发，并可为癌症患者的治疗提供指导。先前的研究表明，水质子共振的磁共振（MR）梯度回波成像可检测高氧期间肿瘤中T2和T1的变化，这可能反映肿瘤氧合增加。本报告描述了使用短重复时间（TR = 0.2 s）的高分辨率MR波谱成像来提高测量T2和T1变化的准确性。对生长在大鼠后肢的乳腺腺癌进行了研究。吸入卡波金用于诱导高氧。在4.7特斯拉下，对穿过肿瘤中心和下方肌肉的单个2毫米切片进行成像，面内分辨率约为1.2毫米，频率分辨率为5.8赫兹。吸入卡波金期间，肿瘤中的峰值积分平均增加6%，表明T1降低（n = 8，P < 0.001）。吸入卡波金期间，肿瘤中的峰值高度平均增加15%（n = 8，P < 0.001）。峰值高度和峰值积分增加的巨大差异表明水质子共振宽度减小。假设为洛伦兹线形，肿瘤中T2平均增加12%。在肌肉中，吸入卡波金期间峰值积分和峰值高度略有增加（分别约为1.2%和3%；P < 0.02），但未观察到T2有显著变化。波谱成像能够准确、可重复地检测高氧期间肿瘤中水质子共振的变化，且信噪比高，并能清晰分离T1和T2效应。T2增加可能是由于肿瘤血管中脱氧血红蛋白减少（即血氧水平依赖效应），可能为肿瘤氧合增加提供一个临床上有用的指标。
