LETTERS TO THE EDITOR c:::====:=::==:::::==:=:::::::::=::::!!l .. __ RESISTANCE VERSUS PULSATILITY INDEX To the Editor:-We read with interest the work of Fleischer and coworkers,t in which the authors de- scribed the use of pulsatility index (PI) as one of the parameters used in conjunction with the velocity of blood flow and the location of the blood vessels to differentiate benign versus malignant ovarian tu- mors. This study is one among several that have been conducted to evaluate areas of angiogenesis by trans- vaginal color and pulsed Doppler sonography.l-7 Pulsed Doppler waveform signals obtained from highly vascularized areas of tumoral tissue depicted by color Doppler had been analyzed primarily in terms of PP- 6 or resistance index (RI) . 2 · 7 All authors are in agreement that benign ovarian tumors have high vascular impedance to blood flow versus low vascular impedance in depicted vessels of malignant ovarian lesions. However, Fleischer and coworkers established a cut-off point of 1.00 by means of PI to discriminate high versus low vascular impedance to forward blood flow. Values above 1.00 were used to classify blood flow as benign whereas values below 1.00 were used to label vascular impedance as sug- gestive of malignancy. In Figure 4 benign sclerosing stromal tumor was illustrated and in Figure 5 a lu- teinized thecoma was demonstrated. PI value ob- tained for the first tumor was 0.71 (Fig. 4A) and for the second tumor 0.86 (Fig. SA), indicating low PI and suggesting malignancy. From the figures, peak systolic, peak end-diastolic, and mean velocities (for each PI value of these histologically proved benign tumors) can be written into the equation for resis- tance index. The RI for the first tumor would be 0.50 and for the second tumor 0.60. According to Kurjak and associates,2.s applying the RI to the same cases with cut-off value of 0.40, these tumors would be assessed as benign ovarian lesions! Thus, we would like to emphasize that if R1 is used as a parameter to quantify impedance to blood flow, such an overlap between benign and malignant tu- mors noticed with PI could be avoided or at least reduced to a minimum. To avoid pitfalls and reduce overlap of results indicating benign and malignant vascularity, blood flow velocities, vascular location, 173 and type of vascularization should be considered.9 We do believe that the parameters mentioned are necessary for accurate assessment of vascularity. ASIM K URJAK, MD, PhD MLADEN PREDA NIC, MD, MSc H f5HAM SHALAN, MD, MSc Ultrasonic Institute, Medical School, University of Zagreb, "Sveti Duh" Hospital, Zagreb, Croatia. REFERENCES 1. Fleischer A, Rodgers WH, Rao BK, et al: Assessment of ovarian tumor vascularity with transvaginal color Dopp- ler sonography. J Ultrasound Med 10:563, 1991 2. Kurjak A, Zalud I, Jurkovic 0, et al: Transvaginal color Doppler for the assessment of pelvic circulation. Acta Gynecol Obstet Scand 68:131, 1989 3. Bourne T, Campbell S, Steer C, et al: Transvaginal colour flow imaging: A possible new screening technique for ovarian cancer. Br Med J 299:1367, 1989 4. Fleischer AC, Rodgers WH, Rao BK, et a): Transvaginal color Doppler sonography of ovarian masses with pathological correlation. Ultrasound Obstet Gynecol 1: 275, 1991 5. Weiner Z, Thaler I, Beck D, et al: Differentiating malig- nant from benign ovarian tumors with transvaginal color flow imaging. Obstet Gynecol 79:159, 1992 6. Kawai M, Kano T, Kikkawa F, et al: Transvaginal Dopp- ler ultrasound with color flow imaging in the diagnosis of ovarian cancer. Obstet Gynecol 79:163, 1992 7. Hata K, Makihara K, Hata T, et al: Transvaginal color Doppler imaging for hemodynamic assessment of repro· ductive tract tumors. Int J Gynecol Obstet 36:301, 1991 8. Kurjak A, Zalud I, Alfirevic Z: Evaluation of adnexal masses with transvaginal color ultrasound. J Ultrasound Med 10:295, 1991 9. Kurjak A, Predanic M. New scoring system for predic- tion of ovarian malignancy based on transvaginal color Doppler. J Ultrasound Med (in press) ••• To the Editor:-! agree with the comments by Kurjak and coauthors concerning the impedance in benign versus malignant ovarian masses. Although a PI value of less than 1.0 was suggested in our paper as a suitable cut-off, it is clear from our data, especially