Commonly used noninvasive bioinstrumentation methods in cosmetic studies

Approximately 90% or more of the cosmetic studies performed today are designed to support claims relating to improvements of fine lines or wrinkles, uneven skin pigmentation associated with sun exposure and/or hormonal changes, skin radiance, skin roughness, skin elasticity, skin hydration and barrier function, and skin oiliness. Table 5.1 provides a listing of commonly used, noninvasive techniques that are used to help support these specific claims. A few of the instruments have been equipped with imaging capabilities in addition to measuring skin properties. For example, MoistureMeter can capture a visual image of skin hydration condition in addition to quantifying the hydration level to provide a direct visual comparison for before and after product usage effect. CutiScan captures a 3D image of skin deformation during pressure changes so a 360° view of skin microrelief response can be calculated. Worth mentioning is Antera 3D by Miravex, a handheld device that is convenient and versatile for capturing skin surface texture and skin color. It uses multispectral imaging and reflectance mapping technology to provide skin surface analysis and compare the changes for before and after product effects. For the reader who would like to learn more about these techniques or other noninvasive methods, there are a number of excellent books and articles available in the chapter’s reference list [7–14].

Ideally, an investigator would like to see agreement between the clinical grading, noninvasive bioinstrumentation measurements, and subject self‐perception questionnaires. Occasionally, investigators get good concordance between clinical grading and self‐perception questionnaires but discordance with the more “objective” noninvasive technique. There are two main reasons for this discordance. First, most bioinstrumentation devices focus on a small area of a few millimeters in diameter. In Voegeli’s 2015 sentinel paper, it is clearly demonstrated that skin hydration and barrier properties show patterns of gradient on the face [15]. Therefore, picking a location for measurement at baseline requires certain consideration and going back to the exact same location during postbaseline assessment is critical yet tricky. But more importantly, changes in a particular spot that is selected for measurement may not reflect changes on the face globally. Second, most of those devices do not directly assess the features of photodamage, such as wrinkles, pores, and pigmentation, the same way as the graders see. However, these two issues can be overcome using the combined digital photography and image analysis approach discussed in the following sections of this chapter.

Use of digital photography as a noninvasive technique for assessing skin features

Unlike bioinstrumentation devices, digital photography has the advantage of capturing the changes before and after product usage of the whole assessment area, thus allowing comprehensive global analysis similar to the assessment done by expert graders.

The challenge for clinical documentation photography is twofold: to choose the best photographic technique relative to the aims of the study and to maximize consistency of the imaging at each clinic visit throughout the trial. The key to successful photography in clinical trials is the application of standardization, which includes the control subject’s positioning, dress, lighting conditions, depth of field, background, and facial expression from visit to visit. The goal is to have images that accurately show treatment effects for use in medical and scientific journals. There is no place for misrepresenting clinical outcomes by changing viewing angles, altering lighting conditions, or having the subject apply facial makeup after using a product [16, 17].

The first step to successful photography is to create the appropriate lighting and other photographic techniques specific to the skin conditions of interest in the clinical study. A study involving a product designed to reduce the appearance of fine lines and wrinkles demands significantly different lighting than would trials involving acne, photoaging skin, skin dryness or flakiness, scars, wound healing, postinflammatory hyperpigmentation (PIH), or pseudofolliculitis barbae. In order to ensure a high degree of color consistency in photographic technique, the photographer should include color standard chips in each documentation image. Typically, these standards include small reference chips of white, 18% reflectance gray, black, red, green, and blue, as well as a millimeter scale for size confirmation. In addition, a more comprehensive color chart such as a ColorChecker^® (X‐Rite America Inc., Grand Rapids, MI, USA) should be photographed under the exact standard lighting immediately before starting each photo session to ensure the setup is correct.

Equally crucial is the careful and detailed recording of all aspects of lighting, camera, and lens settings in order to achieve maximum consistency of documentation photographs. Photographing each different photographic set‐up provides more certainty that photographs at subsequent sessions are identical to the images made at baseline visit.

Prior to photography, all makeup and jewelry must be removed, and hair kept clear of the subject’s face by use of a neutral‐color headband. Clothing should be covered by a gray or black cloth drape to prevent errors caused by color reflected from colored clothing. Subject must adopt a neutral facial expression, no smiling, frowning, or squinting during the photoshoot. Subject’s body position, such as seat height, orientation of legs, position of head and neck, will also be marked since body position often affects the positioning of the face. At each subsequent visit in the study, it is essential to use image alignment software to match postbaseline images with baseline images. Subject’s position and facial expression need to be maintained the same way as baseline images. Only under these conditions, we can be assured that changes in the skin are due to product effect and are not artifacts caused by careless photographic technique. When the study is over, the sequence of images should look almost like a time‐lapse video; the only difference from one image to another is the condition of the subject’s skin.

Standardized photobooths, such as Canfield’s VISIA CR system, Courage + Khazaka’s VisoFace, BTBP’s Clarity Pro, are designed to capture high‐quality facial images for use in clinical research. A photobooth is typically composed of an oval‐shaped plastic shell containing a digital camera and lighting system. Subject positioning is controlled by forehead and chin rests. The unit is controlled by a certain software to allow image alignment in reference to baseline images at post baseline time points. Multiple lighting modes are equipped and a series of pictures under different lighting modes can be taken quickly. This type of photo booth can be operated by individuals with little to no experience in photography.

These systems, while easy to use, have limitations in certain situations. The chin and headrests are sometimes too small for individuals with large faces, resulting in “jammed in” appearance. The chin rest also interferes with the assessment of jawlines and facial sagging. In addition, because of the close proximity of the subject’s face and the flash and camera, images can only be taken with the subject’s eyes closed. Pictures with the eyes closed do not capture effectively conditions such as dark circles and under‐eye puffiness; therefore, they are not suitable for clinical studies testing an eye treatment. Recently developed ColorFace system by Newtone attempts to alleviate some of the problems by using ear support for subject positioning which allows capturing of the lower face contour without distortion.

At SGS Stephens, Inc., we have designed fully equipped photographic studios within our clinics so that subjects can be photographed under standardized conditions from visit to visit (Figure 5.1). These studios are manned by experienced photographers who have been trained in the science of clinical research and the precision of photography. Specialized studio can be tailor designed to capture features of research interest under the best setup, e.g. cellulite condition on the back of the thighs. To understand clinical photography and be able to set up specific studio it is important to understand some terminology commonly used in clinical photography.

Review of terminology in clinical photography

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