Tomo biopsy: What it's all about
Digital breast tomosynthesis and tomo biopsies are on the rise. Yet as is always the case when new techniques are introduced, questions arise – for example: When should tomo biopsy be performed? Are the available tomosynthesis systems equally comparable? And how will the biopsy workflow change?
When does tomo biopsy help?
Tomo-guided biopsy can be beneficial when:
• Lesions can only be seen on tomosynthesis
• Lesions visible in only one view
• Presence of subtle masses and asymmetries1
Are the available tomosynthesis systems equally suitable?
There are various tomosynthesis systems from different manufacturers available on the market. One main difference between them is the angle they offer. While every stereotactic biopsy system uses an angle of 30 degrees (+15/-15), the angle used for tomosynthesis varies between 15 degrees (+7.5/-7.5) and 50 degrees (+25/-25). What does this mean?
For tissue separation in digital breast tomosynthesis and for targeting in tomo biopsy, a high depth resolution is key. As the depth resolution increases for wider angles, you increase your biopsy precision with a wide-angle system going from 30° (stereo) to 50° (tomosynthesis).
Different tomosynthesis angles in clinical use
The MIA Radiology in East Melbourne, Australia, has two tomosynthesis systems from different manufacturers in use – a narrow-angle and a wide-angle one. At the ECR 2017, Dr. Wayne Lemish presented several cases where the difference in angle made a difference.
From left to right: 2016/2D – 2016/50° tomosynthesis – 2015/15° tomosynthesis – 2013/50° tomosynthesis
Clinical case: 51-year-old woman with a past history of fibroadenoma in the right breast
“The tomosynthesis study with a wide-angle system clearly showed an additional small circumscribed nodule deep to the right nipple. Now the question was whether this was a new nodule or a long-standing finding. So we looked at a previous tomosynthesis study, performed with a narrow-angle system 18 months earlier. Here, the nodule was very hard to detect. So we went further back and looked at a tomosynthesis study performed 18 months before that, also with a wide-angle system. Here, the nodule was visible again.”
Dr. Wayne Lemish, Melbourne, Australia
Stereotactic and tomo biopsy workflow: a comparison
One difference between the stereotactic and tomo biopsy workflow: The tomo biopsy workflow is faster – because only one acquisition is required instead of three. And having only one data set also speeds up targeting.
Tomo biopsy in a nutshell
Tomo biopsy procedures are convenient, easy, and fast to perform. This can translate into shorter workflows. And with an integrated specimen scanner it could be even faster. In addition, dose can be saved up to 50% for targeting compared to a stereotactic biopsy. Another advantage: Wide-angle tomosynthesis systems increase precision medicine – because they have a higher depth resolution than narrow-angle ones.3
New technologies in development
New methods are currently being developed that could potentially make biopsies as we know them today unnecessary:
• Liquid biopsies are based on the analysis of circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), or tumor-derived extracellular vesicles, which have been shed from tumors and their metastatic sites into the blood.4 In the future, they could be used for screening and early detection of cancer or to estimate the risk of a patient developing metastases.5
• A new imaging method in development at the University of Michigan, Virtual Biopsies, uses infrared light to recover both ultrasound images and chemical information from tissues inside the body without breaking the skin. This technique could improve traditional biopsies or, in some cases, even replace them.6
1www.sbi-online.org/Portals/0/Breast%20Imaging%20Symposium%202016/Final%20Presentations/305C%20Sumkin%20-%20Tomosynthesis%20Directed%20Biopsy_Part1.pdf [last visited: April 05, 2018]
2Simplified workflow illustration. Workflows may vary in different countries and clinics.
3Maldera et al. (2016): Digital breast tomosynthesis: Dose and image quality assessment. Physica Medica, pp. 1-12.
4www.nature.com/articles/s41698-017-0039-5 [last visited: April 4, 2018]
5www.krebsgesellschaft.de/onko-internetportal/basis-informationen-krebs/diagnosemethoden/liquid-biopsy.html [last visited: April 4, 2018]
6bme.umich.edu/virtual-biopsy/ [last visited: April 4, 2018]