目的： 评价应用迭代模型重建（iterative model reconstruction, IMR）技术的腰椎间盘CT低剂量扫描图像质量与MRI诊断结果进行的一致性研究。方法： 选取因怀疑腰椎间盘病变而行术前CT检查的患者共40例,且所有患者均进行过腰椎MRI检查,其中20例为低剂量组,主要扫描参数为100 kV,DoseRight指数15;20例为正常剂量对照组,扫描参数为100 kV,DoseRight指数26。扫描完成后均根据椎间隙的方向对椎间盘进行层厚为1 mm的图像重建,低剂量组图像分别以滤波反投影（Filtered back projection, FBP）和IMR（1级,软组织算法）算法重建;正常剂量组以FBP算法重建。分别对40例患者的椎间盘进行参数测定,包括椎间盘、黄韧带、椎管、腰大肌或髂腰肌CT值以及背部皮下脂肪噪声,计算各部位的信噪比（signal-to-noise ratio, SNR）及对比噪声比（contrast to-noise ratio, CNR）,同时以5分法对各椎间盘层面的图像质量进行主观评分。另外,以MRI为参考标准对2组患者的各组图像进行诊断准确率评估。结果： 低剂量组的各放射剂量指标明显低于常规剂量组[容积CT剂量指数,（5.49±1.48） mGy 比（1.06±4.42） mGy;剂量长度乘积,（182.36±51.10） mGy·cm比 （730.05±182.45） mGy·cm;有效剂量,（2.35±0.66） mSv比（9.42±2.35） mSv,P<0.05]。在低剂量组和正常剂量对照组的客观参数评价中,3组图像间的SNR和CNR存在显著差异（P<0.05）,其中低剂量组IMR图像的SNR、CNR分别优于同组FBP图像和正常剂量组FBP图像的SNR、CNR。在主观评分中,低剂量组IMR图像的软组织主观评分明显优于同组FBP图像和正常剂量组FBP图像图像,但骨骼显示方面的主观评分较差（P<0.05）。在诊断准确率评价中,低剂量IMR图像的诊断准确率（95%）明显高于同组低剂量FBP图像诊断准确率（45%）,与常规剂量FBP图像诊断准确率（90%）相仿。结论： 在腰椎间盘CT扫描中采用低剂量扫描结合IMR重建算法,能够提供优质的图像质量及较高的诊断效能,是具有广阔应用前景的新技术。

Objective: To study the CT imaging quality of low dose scanning lumbar intervertebral disc combined with IMR reconstruction and its consistency with MRI diagnosis. Methods: Forty patients suspected of lumbar intervertebral disc diseases were enrolled in the study. All patients underwent lumbar plain CT and MRI examination. Patients were divided into two groups: low-dose group (100 kV and DoseRight index 15) and conventional dose group（100 kV and Dose Right index of 26）. Images were reconstructed along the direction of the intervertebral space with 1 mm thickness. Images in the low-dose group were reconstructed by filtering back-projection (FBP) and IMR (level 1, soft tissue algorithm), while those in the conventional dose group were reconstructed by FBP algorithm. Parameters of each intervertebral disc were measured, including the CT value of intervertebral disc, yellow ligament, vertebral canal, lumbar major or iliopsoas muscle, and subcutaneous fat noise in the back. SNR (signal to noise ratio) and CNR (contrast to noise ratio) were calculated, respectively. Imaging quality was evaluated by 5-scale points. MRI was defined as the reference standard to evaluate the diag-nostic accuracy. Results: Radiation dose indices in the low dose group were significantly lower than those in the conventional dose group [CTDI_vol: （5.49±1.48） mGy vs（1.06±4.42） mGy; DLP: （182.36±51.10） mGy·cm vs （730.05±182.45） mGy·cm; Effective dose: （2.35±0.66） mSv vs （9.42±2.35） mSv, P<0.05]. The SNR and CNR of IMR images of the low-dose IMR group were superior to those of FBP images of low-dose and conventional-dose group(P<0.05). The diagnostic accuracy of low-dose IMR images (95%) was significantly higher than that of FBP images in low-dose group(45%) and was similar to that of FBP images of conventional-dose group (90%). Conclusions: Low-dose CT scan of intervertebral disc combined with IMR reconstruction algorithm can improve imaging quality and diagnostic performance.