Dear colleagues, in the next minutes I will talk about the principle of optical coherence tomography and about the main indications. So what is optical coherence tomography, in short OCT? This is a non-invasive imaging method providing three-dimensional images in real time of the skin and you can have a look at vertical images like here, the dimensions are six squares two millimeters. On the left side you see the structural OCT image where you see the small upper layer, the epidermis and then the dermis with some structures inside like neck structures or blood vessels and if the dermis is not too thick you can even see the subcutaneous fat. In the horizontal image on the right you see an area of six square six millimeter where you can look at the surface of the skin until a depth of about 500 microns and if you switch on the dynamic mode you can also see the blood vessels. It's a little bit comparable with ultrasound with a Doppler ultrasound but another kind of technique and you can quantify and look for the morphology of blood vessels in addition to the morphological view. So what are the main indications? If you have an imaging method you can look on everything of the skin also on inflammatory skin diseases or on infectious skin diseases but the main indication is non-melanoma skin cancer and especially it's perfect for diagnosing basal cell carcinomas. So I use it mainly for screening as you perhaps know in Germany we have a skin cancer screening program irregular and if I see some very small spots I do a biopsy or I use OCT instead to look if it's a basal cell carcinoma or not. If you can make diagnosis then you can also have a differential diagnosis. Is it really a BCC or is it something else? It is possible with OCT to define the subtype and also the margins and the thickness of the lesions and you can choose very fastly the perfect treatment if it's necessary to do surgery or if you can make a topical treatment and if you avoid biopsies especially if you make a non-surgical treatment then it's also very interesting to have a tool, a non-invasive tool to monitor the treatment efficacy if it's healed as a kind of aftercare. So let's start with screening. This is a very common finding that you have a small spot here on the left upper side on the back of the patient and it's completely unspecific with dermoscopy but if you look at with OCT at this lesion then you clearly see here below the epidermis deriving from the epidermis a well-demarcated tumor nodule with a dark rim around. And this is very typical for a small nodular BCC. I did a shave excision and it was confirmed by histology. On the lower part another patient with a very small spot here on the front, again unspecific and in the OCT image you clearly see here some small nests of a nodular BCC and again I did histology and it was confirmed like you see here. So if you really see BCCs then you can use it for differential diagnosis. On the upper part again a BCC, a nodular BCC with some dark cysts inside and again the dark rim which is very typical for BCCs around. And if you look at other kinds of non-melanoma skin cancer like actinic keratosis then this really looks completely different. You see in a case the severe hyperkeratosis and the epidermal-dermal junction is intact, it's not infiltrative, the dermis looks quite normal. And on the lower part there is a squamous cell carcinoma, the big thick hyperkeratosis this causes a shadow below but you see that the dermal-epidermal junction is no longer clearly identifiable so it's an infiltrative tumor. We already did several studies and there was a Cochrane review about OCT of non-melanoma skin cancer and we included patients with unclear pink patches into the studies. If you look at a projection of 1,000 people with skin lesions that are suspicious for BCCs then OCT is very useful because compared to making a diagnosis of BCCs by visual inspection and dermoscopy the addition of OCT in this group would reduce the number of false positive results and also would miss fewer BCCs. So I use it in addition to dermoscopy and it's really very helpful. So I mentioned that you can also distinguish the subtypes, in the upper part you see a nodular BCC with some roundish tumor nodules again with a dark rim. In superficial BCCs this looks like a pearl necklace with some tumor parts deriving from the epidermis again with a dark rim and in infiltrative basal cell carcinomas it looks like a shoal of fish with very small strands of tumors again with a dark rim. In most micrographic surgery it's always a question where the BCC ends and starts and I use also OCT for margin definition. You can mark the margin with a silver pen causing a shadow in the OCT image and then you can look before doing surgery if the BCC is inside the margin, the markers, or if it's outside the marker and then you have to increase the margin to avoid additional stages in most micrographic surgery. You can also define the tumor thickness and by defining this you know if it's more or less than one millimeter thick if you have to do surgery or if you have some alternatives like a shave biopsy or cryotherapy or laser therapy or topical treatment with PDT or imicrimod or what you want. If you know this is a nodular BCC and it's a thickness less than one millimeter it's not necessary to do micrographic surgery in this case because it's really clearly demarcated. For treatment monitoring it's also very helpful. This is an example of OCT before laser therapy and then also using it for aftercare. Above a superficial BCC with some very superficial nests coming down from the epidermis and if you do a topical treatment and you make an aftercare you see the image below then there is nothing. We will make a three-dimensional overview over the whole lesion in real time and this is a real nice tool. It's better than a biopsy because with the biopsy you only take a very small part out of the lesion and with the OCT you can scan the whole lesion. Here's another example of a superficial but nodular BCC less than one millimeter again and six weeks after end of treatment with imiquimod you see some keratotic cysts. I think that here the BCC is already going to keratinization but just next to this you still see some BCC parts and this is an indication that this patient and this lesion needs a second treatment cycle. So again to mention the main indication of OCT in dermatology is to detect very small I call it invisible BCCs which are not diagnosable by the naked eye or by dermoscopy. Here are again two examples of very small lesions here, very small superficial BCC or below a very small nodular BCC and if you detect those BCCs so early then the treatment is really easy and you can do it as a kind of one-stop shop. The patient is there, you make the diagnosis and this is really helpful and perfect. And you will hear more about this in special sections about BCCs and AKs and bounce disease and squamous cell carcinomas and I think OCT is really very helpful especially in those indications.

optical coherence tomography

skin cancer diagnosis

real-time imaging

basal cell carcinoma

dermatology