Thursday, July 18, 2019

Reflectance Confocal Microscopy (RCM)- The latest Imaging Advancement for Dermatologists


DR. MANU JAIN, Optical Imaging Specialist at Memorial Sloan Kettering Cancer Centre (MSKCC) Department of Dermatology provides great insight on the advantages of Reflectance Confocal Microscopy (RCM) for the diagnosis of skin cancers, in vivo.

RCM is a form of in vivo microscopy— “histopathology-like” diagnosis without doing a biopsy.  It offers several advantages over conventional light microscopy, including imaging of tissue in vivo and ability to provide bedside diagnosis. In addition to its applications in dermatology it can also be applied for oral cancers.  Meanwhile, we call this application ‘optical biopsy’.   Microscopy is actually what's paving the way for digital imaging in dermatology. Before this it was the naked eye and magnifying lens.

THE POWER OF LIGHT
As ultrasound is recognized for being non-invasive and radiation free, so is optical imaging – gathering cellular and nuclear epidermal and superficial dermal information through the use of LIGHT and laser.  It penetrates the skin to reach an estimated 200 micron in depth - good enough in dermatology to diagnose skin cancers like melanoma, basal cell carcinoma, and squamous cell carcinoma. Because most tumors that appear originates at the dermo-epidermal junction (around a hundred-micron depth from skin surface). In addition to morphological and cellular details, RCM also provides information on the dynamic phenomenon of the blood flow very clearly. 

Dr. Jain joined MSK four years ago, but this technology has been used primarily for research  prior to her joining in the USA. The engineering team at MSK (headed by Dr. Milind Rajadhyaksha) helped design this machine in collaboration with Caliber ID (Rochester, NY) 20+ years ago.  Few years ago, RCM acquired a category I current procedural terminology (CPT) reimbursement codes (96931–96936) by the US Centers for Medicare and Medicaid Services (CMS) [1]. However, there are limited expert readers of RCM in the US. To bridge this gap, Dr. Jain teaches and trains her residents in the dermatology and dermatopathology. She is has started her own annual CME accredited confocal courses at Memorial Sloan Kettering Cancer Center. She is also the Vice-president of recently formed American Confocal Group.

This innovation relies solely on reflectiveness of various tissue structures in the skin, illuminating and magnifying images by relying on the light planes. “Your skin is like a mirror and when you shine light on the mirror, whatever absorbs all the light becomes dark and whatever reflects all the light appears bright”.

"I think it could be interesting to explore the option of combining confocal microscopy with ultrasound because ultrasound can give us the doppler information and also the depth is a very good with ultrasound… which we miss with confocal microscopy.  So that would be really great. Like they have done with confocal and optical coherence tomography."

 Her professional focus is to teach RCM to dermatologists and dermatopathologists.  For the large institutions, it’s fairly affordable and cost-effective as it takes only 15 minutes or 20 minutes to do one lesion.  That means a patient gets scanned and diagnosed at the same time. This saves a lot of time for the patient at the end of the day because the patient doesn't have to wait for the biopsy report for week.

According to Dr. Jain's original bedside diagnosis study,, RCM has shown remarkable sensitivity (~90%) and specificity (~70%) in hands of a novice, within a short interval of 16 months [2] , for skin cancers..  Several studies reported RCM imaging to achieve sensitivity of 70–92% and specificity 84–88% for melanocytic lesions [3] and sensitivity of 100–92% and specificity 85–97% for non-melanocytic skin lesions . . "As an example, we’re examining a patient's new mole with confocal microscopy and if we are suspicious that it might be melanoma, we can use dermoscopy and confocal together to improve the accuracy of diagnosis. 

Although the sensitivity of RCM has not much changed over dermoscopy but the specificity is two times superior—translating into marked decrease in benign biopsies. 

RCM TECHNOLOGY DEVELOPMENT
Thanks to the developmental expertise of Dr. Milind Rajadhyaksha (member of the faculty of Memorial Sloan Kettering Cancer Center), the IN VIVO CONFOCAL MICROSCOPY is fast becoming the new standard in dermal non-invasive imaging.  Originally conceptualized with his mentors at MD Anderson (renowned physicist Dr. Robert Webb and dermatologist/laser pioneer Dr. Rox Anderson), the team sought better ways to detect skin cancers while reducing the need for biopsies in real time at the bed-side.  At the time, biopsy and pathology were the standard approach for detecting and diagnosing skin lesions.  The demand for advancing diagnostic imaging was a call from the 5 million+ new cases diagnosed in the US each year and another million cases detected in Europe, UK, Australia, other regions of the world.

Milind (as he prefers to be called) described how the RCM works in simplified terms: “We start with a bright light source… in our case it's a laser.  We focus the laser down to a very tiny spot inside the skin and we move the spot around in 2 dimensions so we create essentially a plane of illumination by moving that spot. Imagine having a flashlight which you point at a wall and now you move the flashlight back and forth, sideways and up and down until you can illuminate the entire wall.  Similarly, we ‘paint’ a single plane within tissue with focused laser spot and we collect light from each location that the spot illuminates and that we can use that to produce an image. You can essentially create an image or a picture of a single layer of cells or layer of tissue within skin.”

Milind states having built the original laboratory bench top portion in the early 1990’s and continued the expansion of the technology with MSKCC since 2005. He has been involved with advancing both the IN vivo (means directly on the patient) and the EX vivo microscope (referring to any fresh tissue that has been removed from the patient, ie. biopsy) to do faster imaging over large areas. Besides looking at skin cancers, this technology is set up over a mic top with a probe that can allow for imaging inside the oral cavity looking for oral cancers. “We've done a lot of work in imaging to guide treatment, surgeries and to guide laser ablations at Memorial for more than a decade.”

References:
1) Current Procedural Terminology, Professional Edition. Chicago IL: American Medical Association; 2016. The preliminary physician fee schedule for 2017 is available at https://www.cms.gov/Medicare/Medicare-Fee-for-Service-Payment/PhysicianFeeSched/PFS-Federal-Regulation-Notices-Items/CMS-1654-P.html


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