Spectral Parameters of Power Doppler Ultrasound as Predictors of Malignancy Risk in Thyroid Nodules.'' 1 The authors stated that examining nodule vascularity and resistivity index (RI) and pulsatility index (PI) values by duplex power Doppler ultrasound (PDUS) is useful to differentiate between malignant and benign nodules. There are many studies about the role of PDUS in the diagnosis of malignant thyroid nodules. [2][3][4][5][6][7][8][9] Although some of these studies confirm the utility of PDUS in differentiation of thyroid nodules, others do not. The authors found that mixed vascularity with intranodular prominency (grade 3) was evident in 82% (31/38) of malignant nodules. 1 The same vascularity pattern was seen in 43% (20/47) of benign nodules. Perinodular vascularization (grade 1) was observed in 10% (4/38 nodules) and 17% (8/47 nodules) of malignant and benign nodules, respectively. 1 Sixty-seven percent of nodules with grade 1 vascularity were benign. These data show that perinodular vascularity can be seen in either malignant or benign thyroid nodules. Several studies with a similar design report that central vascular pattern supports a diagnosis of malignancy. 2,6-9 Interestingly, Bakhshaee and colleagues 1 did not report any malignant nodules with only central vascularization (grade 4). Some authors argue against the utility of vascular patterns in the diagnosis of malignant nodules. [3][4][5] An assessment of vascularization by PDUS is an operator-dependent and subjective method with controversial results. 1,2 We think that PDUS is an unreliable test for the assessment of thyroid nodules.
Bakhshaee et al. report that RI and PI values are