骶骨功能不全性骨折的^99mTc-MDP SPECT/CT影像特征

Imaging features of ^99mTc-MDP SPECT/CT in patients with sacrum insufficiency fracture

目的:分析和总结骶骨功能不全性骨折(Insufficiency fracture,IF)的99mTc-MDP全身骨显像及骨盆SPECT/CT断层融合显像的影像学特征,探讨SPECT/CT的诊断增益价值。方法:回顾性分析21例经影像检查或临床观察、随访明确诊断为骶骨IF的临床及影像资料,分析两种影像检查在骶骨IF上的影像特征,对比二者的诊断准确性。结果:全身骨显像诊断15例(71.4%)骶骨IF骨折中,4例(26.7%)表现为单侧骶骨翼与骶髂关节平行走行的显像剂分布异常浓聚灶,其中有2例累及S2~S3骶骨体部;11例(73.3%)表现为双侧骶骨翼浓聚区形成的2条与骶髂关节平行的纵行带,其中8例(53.3%)同时累及S1~S4骶骨体部浓聚区形成的与骶髂关节垂直的水平带连接组成,表现为7例(46.7%)呈典型"蝶"形、"H"形,1例呈"弓"形。骨盆SPECT/CT断层融合显像上诊断骶骨IF 20例(95.2%),12例(60%)骶骨IF表现为双侧显像剂分布异常浓聚,9例(45%)在CT上可见双侧骶骨翼骨折,其中8例(40%)同时累及S1~S4骶骨体部,表现为双侧骶骨翼处走行与骶髂关节平行的低密度不规则"锯齿"状骨折透亮线影和/或硬化带、不均匀骨痂形成,骶骨翼边缘伴或不伴骨皮质不连续、轻微错位,骶骨体部横行骨折线走行与骶髂关节垂直;8例(40%)为单侧骶骨翼骨折,6例(30%)CT上显示为骶骨翼上走行与骶髂关节平行的模糊不规则低密度骨折线和硬化带,向前累及骶骨翼边缘伴骨皮质断裂、轻微错位,4例(20%)累及S2~S3骶骨体部骨折线走行垂直于骶髂关节。全身骨显像与骨盆SPECT/CT断层融合显像诊断骶骨IF的准确率分别为71.43%(15/21)和95.2%(20/21),骨盆SPECT/CT断层融合显像诊断骶骨IF准确率高于全身骨显像,差异具有统计学意义(P<0.05)。结论:全身骨显像上骶骨典型的"H"形、"蝶"形或"弓"形的显像剂异常浓聚可较容易诊断骶骨IF,但在不典型骶骨IF时,骨盆SPECT/CT断层融合显像能提高骶骨IF的诊断准确率,具有明显的增益价值。

Objective:To investigate the added value of SPECT/CT by analyzing the imaging features of 99mTc-MDP whole-body bone scan and pelvic SPECT imaging performed in conjunction with low-dose CT fusion imaging in sacral insufficiency fractures(IF).Methods:The clinical and imaging data of 21 patients diagnosed with IF in sacrum by imaging or clinical observation and follow-up were analyzed retrospectively,and the accuracy of the two imaging methods in diagnosing IF in sacrum were compared.Results:Of the 15 cases(71.4%)of sacral IF fractures diagnosed by whole-body bone scanning,4 cases(26.7%)showed abnormal concentration distribution of imaging agents in the single side of the sacrum wing parallel to the sacroiliac joint,with involvement of the sacral body S2~S3 in two.Eleven cases(73.3%)showed imaging agent distribution of anomaly concentrated area in bilateral sacral wings,including 7 cases of typical"butterfly"shape,"H"shape,1 case of"bow"form.Twenty cases(95.2%)of sacral IF fractures were diagnosed by pelvic SPECT/CT fusion imaging.There were 12 cases(60%)of bilateral sacral alar fractures,include 9(45%)bilateral sacral alar fractures on CT scan.The irregular low density"sawtooth"fracture bright line and/or hardening belt were only shown in 8(40%)sacral fracture,longitudinal walking line in dual lateral sacral wings,with or without cortical discontinuity in sacral alar margin.Eight cases(40%)were unilateral sacral alar fractures,including 4 cases(20%)of fracture lines in the sacral body perpendicular to the sacroiliac joint.The imaging agent distribution of anomaly concentrated area was only shown in afflicted part of 2(10%)sacral IF patients,but no obvious fracture line was observed on CT of the same machine,focal bone hyperplasia and sclerosis were only showed in 1 case(5%).The accuracy of whole-body bone scan and pelvic SPECT/CT fusion imaging in diagnosing IF of the sacrum were 71.43%(15/21)and 95.2%(20/21),respectively.The accuracy of pelvic SPECT/CT fusion imaging in diagnosing IF of the sacrum was higher than that of whole-body bone scanning,and the difference was statistically significant(P<0.05).Conclusion:IF in sacrum can be diagnosed easily with the typical"H"shape,"sphenoid"shape or"arch"shape of the unusually concentrated imaging agent,but in the case of atypical sacral IF,SPECT/CT fusion imaging of the pelvis can improve the diagnosis accuracy of IF and has added value.