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Use of the SIAscope as an aid to the diagnosis of pigmented skin lesions
Dolianitis C, Kelly J Victorian Melanoma Service, Alfred Hospital, Melbourne
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SIAscope I skin imaging system
SIAscope II
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Infrared and colour wavebands
SIAGRAPHS SIA Algorithms Infrared and colour wavebands Sensor This results in the skin we see – a complex composite view SIA uses light …….. Detects and makes quantitative measurements of structures Presents as SIAgraphs
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Based on physics of image formation
Optical model of skin Based on physics of image formation Diffusion Stratum Corneum Absorption Epidermis Forward scatter Absorption Papillary dermis Backscatter Forward scatter Reticular dermis
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Optical model of skin B G R Stratum Corneum Epidermis Papillary dermis
Incident light Absorption Forward scatter Backscatter Diffusion Stratum Corneum Epidermis Papillary dermis Reticular dermis
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Optical model of skin B G R R Stratum Corneum B Epidermis G
Incident light Stratum Corneum Epidermis Papillary dermis Reticular dermis
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Optical model of skin Normal skin with no infiltration of pigment into the dermis, including black, sunburnt, white skin R Haemoglobin Melanin B G
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Creating SIAgraphs This calculation is performed for each of the 600,000 points in the viewfinder The colour at each point corresponds to a concentration of the component viewed This makes a concentration map across the skin Colours intended to be intuitive
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Melanin Darker brown = higher concentration of melanin
Lighter brown = less melanin
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Melanin High melanin concentration Normal melanin concentration
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Dermal Melanin Melanin involvement in dermis
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Dermal Melanin White = no dermal melanin
Green = slight dermal involvement Blue = moderate dermal involvement Red = high dermal involvement Black = maximum measurable dermal involvement
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Dermal Melanin No melanin in dermis Low melanin involvement
High melanin involvement
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Collagen Normal skin – grey / green
High collagen concentration – white E.g. fibrosis Low collagen concentration – dark “Holes” in the collagen
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Collagen Low collagen concentration High collagen concentration
Normal collagen concentration
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Blood Low blood concentration High blood concentration
Normal blood concentration
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Dermatoscopy view Melanoma exhibits suggestion of blue-grey veil, several colours Benign naevus has two colours and no suspicious features for melanoma
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Dermal melanin view White = no dermal melanin Colours indicate different depths
Melanoma exhibits dermal melanin Benign lesion has no dermal melanin
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Collagen view Whiter = more collagen
Melanoma has irregular fibrotic reaction, “increased collagen” Lesions also assessed for “collagen holes”, areas of decreased or absent collagen Benign lesion has regular collagen
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3D collagen view Shows collagen concentration Not available on Siascope version 1 used in Melbourne study Melanoma has irregularities in the collagen concentration Benign lesion has very smooth collagen concentration
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SIAGRAPHS Left hand side always shows dermatoscopy image of lesion
Right hand side image shows SIAgraph of same area of skin OR can view dermatoscopy and 5 SIAgraphs all at once
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Dermal-epidermal junction
Select an area of the lesion on the dermatoscopy image 3D view of dermal-epidermal junction shown for that area “irregularity / regularity” of dermal-epidermal can be assessed
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Melbourne SIAscope study
to investigate the role of the Siascope in differentiating melanomas from non-melanomas EXPERT SETTING Includes 88 lesions excised on suspicion of melanoma after clinical and dermatoscopic assessment
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ASSESSMENT of SIAgraphs
Total melanin , Asymmetry of pattern in 0, 1, 2 axes Dermal melanin, presence and concentration Collagen, increased, decreased, collagen hole Blood, increased (erythematous blush), decreased (blood displacement), irregular vessels Dermal-epidermal junction, regular / degree of irregularity
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DIAGNOSIS ? melanoma TOTAL 88 Melanomas 53 Dysplastic naevi Melanocytic naevi 9 Spitz / spindle cell naevi Basal cell carcinomas Lichenoid keratoses Seborrhoeic keratoses Solar keratoses Other 1
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NUMBER and THICKNESS of Melanomas
LEVEL I MELANOMA Superficial spreading melanomas 16 Lentigo malignas LEVEL II MELANOMA Superficial spreading melanomas , 0.40, 0.45, 0.45, 0.45, 0.45, 0.60, 0.60, 0.62, 0.65 LEVEL III MELANOMA Superficial spreading melanomas , 0.35, 0.55, 0.55, 0.70, 0.80, 0.85 Nodular melanomas , 1.75 LEVEL IV MELANOMAS Superficial spreading melanomas , 2.30, 2.70, 4.20 LEVEL V MELANOMAS Lentigo maligna melanoma
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Melanomas 29 level I melanomas 24 invasive melanomas
mean thickness of 1.22mm Median thickness 0.62 mm Group of early melanomas Median level level I melanoma
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Feature Sensitivity Specificity Erythematous blush 100% (94-100)
88 lesions excised on suspicion of melanoma: Sensitivity, Specificity (95% confidence intervals) FEATURES WITH HIGH SENSITIVITY Feature Sensitivity Specificity Erythematous blush 100% (94-100) 11% (5-19) Total asymmetry 94% (87 – 98) 34% (24 – 45)
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Feature Sensitivity Specificity Blood comma 30 % (21-41) 94% (87-98)
88 lesions excised on suspicion of melanoma: Sensitivity, Specificity (95% confidence intervals) FEATURES WITH HIGH SPECIFICITY Feature Sensitivity Specificity Blood comma 30 % (21-41) 94% (87-98) Blood displacement 6% (2-13) 77% (67-85) Collagen hole 21% (13-31) 74% (64-83)
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Feature Sensitivity Specificity 75% (65-83) 80% (70-87) 91% (83-96)
88 lesions excised on suspicion of melanoma: Sensitivity, Specificity (95% confidence intervals) COMBINATION OF FEATURES needed to achieve good sensitivity / specificity Feature Sensitivity Specificity Erythematous blush and Total asymmetry without blood displacement with either of collagen hole, blood comma or irregular dermal epidermal junction 75% (65-83) 80% (70-87) Erythematous blush and total asymmetry with any of dermal melanin, collagen holes, blood comma or irregular dermal epidermal junction 91% (83-96) 49% (38-60)
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EXPERT SETTING 88 lesions excised on suspicion of melanoma
Significant differences found between melanomas and non-melanomas with Siascope using combination of features These results are independent of history, clinical, dermatoscopy and photographic assessment Combination of clinical and dermatoscopy with Siascope would be expected to improve results
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The “less expert setting”
larger group of mainly pigmented skin lesions 88 lesions excised on suspicion of melanoma after clinical and dermatoscopic assessment AND another 129 lesions Total of 217 lesions
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The “Less expert” setting Lesion Number
Total 217 Melanomas 53 Seborrhoeic keratoses 47 Dysplastic naevi 43 Compound / Junctional naevi 25 SCC 10 Haemangioma 7 Solar keratoses 5
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The “less expert” setting FEATURES WITH HIGH SENSITIVITY
Specificity Erythematous blush 100 % 24% Total asymmetry 94% 50%
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The “less expert” setting FEATURES WITH HIGH SPECIFICITY
Sensitivity Specificity Blood comma 30% 96% Collagen hole 21% 87% Blood displacement 6% 85% Irregular dermal epidermal junction 55% 71% Dermal melanin 57% 69%
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The “less expert” setting COMBINATION OF FEATURES gave best sensitivity / specificity
Erythematous blush and total asymmetry with any of dermal melanin, collagen hole, blood comma or irregular dermal epidermal junction 91% 82% Total asymmetry and erythematous blush with either collagen hole or blood comma or irregular dermal-epidermal junction 81% 88%
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Comparison ‘expert’ to ‘less expert’ setting
EXPERT SETTING Sensitivity / Specificity LESS EXPERT Sensitivity/ Specificity Erythematous blush and Total asymmetry without blood displacement with either of collagen hole, blood comma or irregular dermal epidermal junction 75% / 80% 75% / 92% Erythematous blush and total asymmetry with at least one of dermal melanin, collagen hole, blood comma or irregular dermal-epidermal junction 91% / 49% 91% / 82%
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Comments Some features objective, e.g. dermal melanin
Some features subjective, e.g. irregularity of dermal epidermal junction Experience with the technique may affect results NOT an automated diagnosis Need to assess the reliability of assessment by the same observer and reproducibility of results between different observers
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Comments Recall bias (one person collecting images, following up pathology results and doing analysis) This study - retrospective analysis, needs to be repeated in a prospective fashion with observer blinded to histopathology results Histopathological correlation of Siascope features Comparison of features displayed by melanomas of different thickness / level of invasion
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Conclusion Results independent of history, clinical features and dermatoscopic features Combination of Siascope features were found to have good sensitivity and specificity in the diagnosis of melanoma Combination of Siascope assessment with clinical and/or dermatoscopic assessment would improve sensitivity and specificity Image collection funded by Astron Clinica, Cambridge, UK
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