Contrast-enhanced Digital MRI For Diagnosis Of Vertebral Metastatic Tumors

Background Magnetic resonance imaging (MRI) is so sensitive to the abnormal changes ofvertebral bodies' signal that can perform an early diagnosis. The detection rate can often beincreased after injecting GD-DTPA and sometimes compounding with short time inversionrecovery (STIR). However, when facing the cases such as small, obsolete enhancement, ossify,or composing of bleed, fat and muscle tissue, situations like background masking the focus ofdisease and bad contrast between them usually occur. STIR can remove also the fat signal frombackground, but addition to more extra hardware to be requested, examination time is prolonged,picture noise is great, image quality is poor, and so on. The studies have indicated thatcontrast-enhanced digital subtraction MRI is an important technique to diagnose appendicularskeleton tumors. Besides, dynamic contrast-enhanced MRI can analyze the early changes ofabnormal signal intensity in quantity, which has confirmed by diagnosed soft tissues and skeletalmusculature tumors.Objective To evaluate the diagnostic value of contrast-enhanced digital subtraction MRIand dynamic contrast-enhanced MRI advantages compare to routine MRI and clinic meanings indiagnosis vertebral metastatic tumors.Methods The study was performed in two steps. Firstly, forty-four vertebral metastatictumors in thirty patients were scanned by routine MRI including SE T₁WI,SE T₂WI,STIR andenhanced T₁WI with an injection of Gd-DTPA(0.1mmol/kg). Digital subtraction was performedbetween pre-contrast-enhanced images and post-contrast-enhanced images. All the images ofvertebral malignant tumors were evaluated by means of signal intensity ratio (SIR) and noseratio (NR). The quality of images was also evaluated by compared subtraction MRI with routineMRI.Secondly, twenty patients were scanned by dynamic contrast-enhanced MRI. Measured andcalculated the parameters of signal intensity, and draw time-intensity cures (TICs). Then,compared with that of normal vertebrae and analyzed the characteristics.Result SIR and NR of subtraction MRI was respectively2.93, 0.98. SIR of routine MRI(enhanced T₁WI, SE T₁WI, SE T₂WI, STIR) was respectively as follows: 1.15, 1.16, 1.26, 1.69. While NR of those tests was respectively as follows: 5.25, 3.44, 4.56, 23.32. SIR and NR ofsubtraction MRI images had significant statistical differences from those of routine MRI images(P＜0.05).The parameters of vertebral metastatic tumors: peak signal intensity, signal intensityminimum signal intensity of post-peak, peak slope, initial ratio of enhancement, maximum ratioof enhancement was respectively 50.61±11.38, 46.75±10.23, 0.73±0.12, 0.33±0.08, 1.03±0.31;that of normal vertebrae were respectively 40.53±12.12, 34.72±14.06, 0.31±0.11, -0.25±0.05,0.69±0.28; and ten normal cases showed negative in initial percent of enhancement, but only twoabnormal vertebrae showed that. Above were significant statistical different. Four types of TICswere concluded: early rapid rise and early rapid descent followed by steady phase (type A),persistent rise (type B), rise phase followed by steady phase (type C), rise phase followed byrapid descent phase (type D). TICs of abnormal vertebrae were respectively 6, 5, 5, and 5 cases,most types of normal vertebrae were mainly type C, 15 cases. Type A and type B and the typewith the characteristic of early rapid descent phase were features of abnormal vertebrae; type Cwas the feature of normal one.Conclusion Contrast-enhanced digital subtraction MRI images presented clearer in details,more intensively in contrast to background, and better quality of images than routine MRIimages. Enhanced subtraction MRI could be effectively used in the diagnosis of vertebralmetastatic tumors, and performed after enhanced MRI.Dynamic contrast-enhanced MRI, which could quantitatively showed the characteristics ofearly changes of signal intensity of vertebral metastatic tumors and the significant statisticaldifferences from that of normal vertebrae, is practical in the early diagnosis of vertebralmetastatic tumors.