1 STUDY OF RAYNAUD’S PHENOMENON BY MEANS OF INFRARED FUNCTIONAL IMAGING Arcangelo Merla 1,3 , Luigi Di Donato 1 , Giuseppina Farina 4 , Simonetta Pisarri 4 , Michele Proietti 4 , Felice Salsano 4 , Gian Luca Romani 1,2,3 1 Dipartimento di Scienze Cliniche e Bioimmagini, Universita di Chieti, V.le dei Vestini 13, I-66013 Chieti Scalo (Ch), Italy 2 ITAB, Istituto Tecnologie Avanzate Biomediche, Universita di Chieti, V.le dei Vestini 13, I-66013 Chieti Scalo (Ch), Italy 3 INFM, Sezione de LAquila, Italy 4 Dipartimento di Medicina Clinica, S.S. Clinica Immunologica e Allergologica, Universita La Sapienza , V.le del Policlinico, Roma, Italy Abstract – Infrared Functional Imaging was applied to the study of Raynaud’s Phenomenon obtaing a simultaneous assessment of the thermal properties of all five fingers of both hands of a group of patients with respect of a control group. The method is based on the use of high-resolution telethermography imaging and allows identification of objective parameters from the re-warming curves of finger immediately after a 2 min cold stress. The evaluation of the area under the temperature versus time curve, namely the temperature integral INT, provides a figure particularly effective in describing the thermal properties of the finger. 18 healthy volunteers, 20 Secondary Scleroderma and 20 Primary Raynaud’s Phenomenon patients were studied subsequently to clinical evaluation and nailfold capillaroscopy. This new approach highlighted a quite different behaviour between patients with Primary Raynaud’s Phenomenon and those with early diagnosed Systemic Sclerosis This new method, compared with other existing techniques, seems to be useful tool to discriminate between PRP and RP secondary to SSc. Keywords – Raynaud’s Phenomenon, Infrared Imaging I. INTRODUCTION Raynauds phenomenon is usually defined as an episodic vasoconstriction, in response to cold or emotion, of small arteries and arterioles of fingers, toes and, sometimes of nose’s tip and earlobes. In PRP, episodic ischaemia in response to cold exposure or to emotional stimuli is usually completely reversible: absence of tissue damage is the typical feature [1], but also mild structural changes are demonstrated [2]. On the contrary, sclerodermic RP shows irreversible tissue damage and severe structural changes in the finger vascular organisation [3]. Moreover, among a certain group of patients it is not so clear if RP is benign or if it represents the first symptom of SSc disease. Only the evaluation of the disease severity and degree of digital vascular disease will permit to distinguish between PRP and RP secondary to connective tissue diseases, especially Systemic Sclerosis. None of the physiological measurement techniques currently in use are completely exhaustive in focusing primary or secondary RP [4]. Moreover, these techniques -as nailfold capillary microscopy, cutaneous laser-Doppler flowmetry, and plethysmography- can proceed just into a partial investigation, usually assessing only one finger for each measuremento. Only infrared functional imaging (IRFI) can assess more fingers of both hands, simultaneously giving a pictorial representation of surface temperature. Thermography protocols [5-11] usually include dynamic testing, such as cold stress, in order to evaluate the capability of the patient hands to re-warm. This capability is, in some way, depicted by the pattern of the re-warming curve that also gives some information on the underlying structural diseases. Several studies have shown how the analysis of re-warming curves could differentiate between healthy subjects and RP patients [5- 11]. The direct or indirect dependence of the parameters considered in those studies on finger thermophysical properties and on blood perfusion has not been thoroughly investigated so that they may appear somewhat empirical and lacking a proper physiological meaning. Aim of this pilot study is to verify the capability of IRFI to identify objective parameters useful for discriminating PRP- from SSc patients, starting from a physiological basis, and by means of a simple thermophysical model. II. THEORY The first mechanism activated by the finger to exposure to a cold environment is vasoconstriction, which induces a rapid and consistent decrease of blood flow into distal districts, particularly in fingers. Following cold environmental temperatures, fingers blood flow drops to nutritional levels [12 - 16]. During the re-warming period following a cold stress, thermal energy is transported and exchanged at the finger level by means of different factors: 1) exchange with the environment; 2) transport by the incoming blood flow; 3) conduction from adjacent tissue layers; 4) metabolic processes. The net balance of the energy input/output determines the increase/decrease of the finger temperature. The analysis of the relative contributions of the re-warming factors suggests that the energy conducted from adjacent tissues and the metabolic processes are negligible compared to the other two [17-18]. Therefore, it may be assumed that finger temperature reflects the balance between the input power due to blood perfusion and the power lost to the environment: