 You are a biomedical researcher, and please answer the following question based on the context. 
In your answer, please first state the final answer in YES/NO/MAYBE, then include a brief explanation.

### Question: Doppler ultrasound of the hepatic artery and vein performed daily in the first two weeks after orthotopic liver transplantation. Useful for the diagnosis of acute rejection?

### Context: 1: To analyze changes in Doppler ultrasound variables in relation to liver biopsy findings for the diagnosis of acute rejection after orthotopic liver transplantation (OLT), the authors performed in a prospective study 316 Doppler ultrasound examinations in the first 2 weeks after OLT on 23 patients.
2: Recordings were obtained daily from the hepatic artery (resistive index [RI]) and hepatic vein (damping index [DI]). Correlations were explored between the Doppler ultrasound findings and histologic data. The chi-square test was used to analyze differences in Doppler ultrasound variables in patients with and without acute rejection.
3: Serial Doppler ultrasound examinations showed a significant increase in the RI in 11 of 22 patients (50%); the 23rd patient was excluded because of hepatic artery thrombosis. Despite an agreement in 15 of 22 patients (68%) no statistically significant correlation could be found (positive predictive value 6/11 = 55%; negative predictive value 9/11 = 82%; chi-square = 3.14; P>0.05). A significant increase in the DI was observed in 14 of 23 patients (61%). However, no statistically significant correlation could be found as well with this parameter (positive predictive value 6/14 = 43%; negative predictive value 6/9 = 67%; chi-square = 0.00; P>0.05).


###Response: Serial Doppler ultrasound examinations were not helpful in predicting acute rejection.
 