In an ironic twist, effective imaging of skin cancers has just been accomplished by none other than the imaging modality in closest contact with the skin: ultrasound. A group from the University of Maryland School of Medicine in Baltimore and Detroit's Wayne State University conducted a study that, for the first time, looked at the utility of quantitative ultrasound elastography for identifying skin cancers.
"We in radiology have scanned almost the entire body, but ironically, extraordinarily little research has been performed on primary imaging of the skin, which should be extraodinarily accessible to imaging," said lead investigator Eliot L. Siegel, MD, at RSNA 2009 in Chicago. Dr. Siegel is the vice chair of radiology at the university.
His group's findings suggest that high-frequency ultrasound with elastography has the potential to measure the extent and depth of skin lesions as well as reduce the number of unnecessary skin biopsies by characterizing the lesions. They used high-frequency ultrasound in the range of 14 to 16 MHz with elastography to evaluate 60 patients with either benign or malignant skin lesions. They found malignant lesions are consistently less elastic than nonmalignant skin lesions. The elasticity or strain ratios of skin lesions to comparable normal skin recorded by the researchers were 3.0 or below for all benign lesions and 5.0 or higher for all malignant lesions (abstract SSJ14-04).
Ultrasound with elastography could provide detailed infomation about skin lesions without biopsy, Dr. Siegel said. "The incidence of melanoma has increased precipitously from 1935 to 2010," he added. "This makes it even more important to differentiate melanoma from other skin cancers."
According to coauthor Bahar Dasgeb, MD, a dermatology resident at Wayne State University in Detroit, current dermatology assessment of lesions is purely visual. That could change thanks to elastography. "If lesions have anything that catches the eye of the dermatologist, it's biopsied," she said. "Elastography can help determine the nature of the lesion before a potentially unnecessary biopsy is ordered."
Ultrasound hardware with a frequency between 14 and 16 MHz is relatively common and currently available clinically.
To streamline and better perfect ultrasound with elastography, technology with the ability to image at a higher frequency while maintaining the capability to determine elasticity ratios must be developed, Dr. Siegel said.
"We believe ultrasound more accurately detects skin cancer than visual inspection alone. It has tremendous potential," Dr. Siegel said.
Top, histopathology slide demonstrates proliferation of basal cells in the epidermis with palisading cells at the periphery and adjacent early stromal changes, but without the dermal invasion characteristic of basal cell carcinoma (BCC).
Bottom left, ultrasound elastography demonstrates blue area of decreased elasticity associated with BCC. The ratio of this abnormal region to adjacent epidermis was greater than 5.0 (elastic ratio of 8.26) suggesting malignancy.
Bottom right, high-resolution (16 mHz) ultrasound demonstrates corresponding area of decreased echogenicity (darker) with a well-demarcated border and an intact basement membrane. Figure courtesy of Dr. Dasgeb and Dr. Siegel.