5.5.2.2　Detecting the rate of growth

The rate of growth has been proposed as an important feature and reliable diagnostic indicator of melanoma，compared with melanoma thickness.However，all these measurements are indirect，and there is still little direct information on the ROG of the melanomas.One roadblock is the lack of a method for noninvasive melanoma volume quantification.Because melanoma may have irregular shapes，in order to accurately quantify its volume，the whole boundary needs to be visualized.Recently，a linear transducer arraybased photoacoustic computed tomography system was applied to measure melanoma volume and the rate of growth，and nearly the entire melanoma boundary could be detected in three dimensions.With the ability to image entire melanomas in vivo，photoacoustic imaging has successfully measured both the thickness and volume of melanoma.Thus，as a significant feature of melanoma，the rate of growth can be directly calculated，which may prove to be superior to tumor thickness as a diagnostic feature（Figure 5-11）.(https://www.daowen.com)