There are some evidences to prove that ultrasound is subjective, as there are chances of it giving false positive results as the interpretation may vary from one evaluator to the other.
the interpretation can vary on the evaluator. There is also a higher incidence of incorrectly identifying a mass as cancerous, a false positive..
Preliminary data suggest a higher rate of
false-positive examination results with
ultrasound than with mammography
alone.100,104-106 For example, the false-
positive rate (based on solid lesion for ultrasound) ranged from 2.4% to 12.9%for
ultrasound and 0.7% to 6% for mammography
There are false positive and negative ultrasound results . Although ultrasonography is easily able to diagnose intra abdominal abscesses in cases of appendix perforation, this technique has limitations and is dependent on the user.
One major issue with ultrasound is its dependence on the operator.
However, ultrasonography is limited by the fact that it is user dependent.2,3 This means that the quality of the images obtained and their accurate interpretation depend on the experience and knowledge of the sonographer.
So these are some of the evidences proving that ultrasonography is subjective and the interpretations depend on the physician's experience and knowledge.
However, to conclude I will say that though I have given evidences of ultrasonography to be subjective (not compared to x ray) in general.
I didn't compare with x ray imaging.
Both of these modalities have their own advantage and limitations.
There is no competition between these two techniques, but it must be the physician that has to choose the better one, knowing advantages and limitations of each one, case by case.
Comparing the inter rater reliability as in this between x ray and ultrasound proved the above statement.