| Objective; Pheochromocytoma are rare tumors derived from adrenal medulla, sympathetic ganglion and other tissues, some of which can synthesize secrete catecholamine and cause hypertension and dys-metabolism symptoms. Incidence of pheochromocytma was reported to be0.005-0.1%in autopsy. Most of pheochromocytomas are benign which can be cured by operation. However, about10percents (5-26%) of pheochromocytomas are malignant. There was no specific manifestation for malignant pheochromocytomas clinically and routine radiological imaging. It is difficult to make malignancy diagnose even pathologically without evidence of capsular or vascular invasion. Definite diagnosis of malignant pheochromocytomas was based on metastasis to lymph node, liver, lung, spine, et al. So it is usually made by radiologist other than pathologist. However, treatment of malignant pheochromocytoma in such stage is rather difficult, and not all malignant pheochromocytoma metastasize at onset. So it not sufficient for clinical use to made malignancy diagnosis by evidence of metastasis. Full evaluation of pheochromocytoma is very important before operation, especially for prognosis. DWI was appreciated in differentiation of adrenal tumors for its indirect reflecting cell microstructures and function. MR dynamic enhanced imaging was new sequence indirect reflecting tissues perfusion. Quantity and semi-quantity evaluation of ADCs and dynamic contrast-enhanced imaging of pheochromocytomas were employed to determine whether it is useful for differentiating malignant pheochromocytomas from benign ones.Methods:Sixty-three tumors in59patients were examed, and19patients were excluded for under-quality image, no pathology results and mistake diagnosis. Forty patients (26are male,14are female) were included in this study, ageing from13to61(42.3+2.6). Symptoms are headache, palpitation, and sweating. Serine and urine catecholamine and VMA in some cases was above normal level. Siemens3.0T Verio with phase contrast array was employed. Patients was supine and covered from diaphragm to kidney, and elongated to pelvic if ectopic pheochromocytoma was suspected. DWI in addition to T2-weighted sequences, chemical shift imaging techniques, and dynamic contrast-enhanced MR imaging. In each patient, precontrast single-shot spin-echo echo-planar DWI was performed with b values of0and800seconds/mm’. In each patient,3-dimensional fat-saturated Tl-weighted dynamic contrast enhanced MR imaging (VIBE) was performed at baseline (precontrast), during the arterial phase, and1,2,3, and5minutes after contrast injection. Diagnosis was based on pathologic findings in surgical specimens and more than one years’ followup. Independent samples t test was used to compare ADCs of benign and malignant pheochromocytomas. Receiver operating characteristic curve analysis was used to test the ability of ADCs in differentiating malignant from benign pheochromocytomas. Differences in dynamic contrastenhanced patterns between malignant and benign pheochromocytomas were analyzed. The definite diagnosis was based on pathology and more than half year" follow-up. All images were read by two radiologist without knowing each other, and a high rank radiologist for definite describing diagnosis, and average result was accepted for measurement. Location, size, signal and contrast enhancement was analyzed in Siemens Syngo workstation, ADC map was generated and round or oval ROI was used for measurement of ADC and signal intensity (SI) of enhanced image. SI-time curve w: as drawn with software. Diagnosis was based on pathology and follow up; definite diagnosis of malignancy was based on metastasis at diagnosis or follow up. Pearson×4, independent t test ROC curve was used to do analysis with SPSS13.0. P<0.05was accepted as significant. Threshold was analyzed with sensitivity, specificity, and Youden index.Results:Pathologic diagnoses revealed that10pheochromocytomas with metastasis in lymph node with2ones invading renal vein, the other3without metastasis and invasion manifested by metastasis to lymph node and lung in follow up. So13cases were considered malignancy in this group. Another27patients (three from both adrenal glands of the same patient) were benign. Eight of13malignant pheochromocytomas were found in adrenal glands and the others are ectopic. Incidence of malignancy ectopic (5/13) was high than that in adrenal gland (8/29), but have no significance (Pearson×2=0.497; P=0.481). Size of13malignant pheochromocytomas arranged from3.6cm to12.4cm (6.1±1.7) while size of benign ones from1.7cm to9.6cm (5.4±1.7), which have no statistic significance (P=0.062) in independent t test. Signals of tumors are homogenous in9cases (1.7cm-5.1cm), non-homogenous in18cases (2.2cm-10.6cm), and cystic or necrotic in15cases(4.7cm-12.4cm). Tumor is homogeneously or non-homogeneously hypertension in T2WI, hypotension in T1WI, non signal cancellation in chemical shift imaging, and hyper T1WI signal intensity in5cases. Diffusion of tumor is homogeneously or non-homogeneously restricted. Tumor was enhanced homogeneously or non-homogeneously after contrast injection。With b values of0and800seconds/mm2,(mean±SD) ADC of malignant pheochromocytomas ([1.175±0.132]×10-3mm2/s) was larger than that of benign ones ([0.918±0.124]×10-3mm2/s), and the difference was significant (P<0.001). Apparent diffusion coefficients obtained with b values of0and800seconds/mm2were effective for distinguishing malignant from benign pheochromocytomas (area under the receiver operating characteristic curve,0.906):A threshold value of1.016×10-3mm2/s permitted distinction with high sensitivity (93.3%) and specificity (77.8%). In contrast-enhanced SI-time curve, malignant pheochromocytomas got peak signal intensity earlier (at arterial phase) than benign ones (1minute after contrast injection), and then wash out gradually. Conclusion:In our study, ADCs in DWimaging with b values of0and800seconds/mm2and dynamic contrast-enhanced pattern of malignant pheochromocytomas were significantly different from that of benign ones, suggesting that DW imaging and dynamic contrastenhanced MR imaging may be useful in preoperative characterization and prognosis of pheochromocytomas, especially for those without obvious metastasis and vascular invasion. |
PDF Full Text Request