Pre- and intra-operative imaging for plastic surgery

Standard photography

The importance of photography in plastic surgery cannot be overstated, given that the specialty is a highly visual one with a focus on external anatomy, and its uses are innumerable. Photographs serve as a critical tool throughout a patient’s care. Photographs document a patient’s preoperative baseline anatomy and function, intra-operative critical structures and key findings, and postoperative surgical outcomes. They can capture the evolution of patients’ long-term outcomes, of a surgeon’s technique, and even of aesthetic trends in the community. Photographs become part of the medico-legal record, not only as an objective record of a patient’s pre- and postoperative status but also as a part of the consent process sur-rounding how images will be stored and used.

The role of photography is so central that the Plastic Surgery Foundation issues recommendations for standardized photo-graphy to ensure consistency and accuracy. This topic is covered at length elsewhere (see Chapter 7 ), so this chapter will only briefly review the subject. Photographs should be framed with the anatomy of interest at the center of the photo against a neutral-colored background. Ideally, the same camera and lighting set-up should be used for all photos, taking care to avoid shadowing and intrusive lighting. Standard views are recommended for different anatomic areas (e.g., faces should be photographed in anterior–posterior, right and left oblique, and right and left lateral). However, plastic surgeons may not always adhere to these standards, which can make accurate comparisons across photographs challenging.

As photography has transitioned from an analog format to a digital one, there are also a number of practical considerations for how images are now stored, modified, and shared. Images can be saved as a wide range of file formats (e.g., JPG, TIFF, RAW), each of which has its own advantages and disadvantages based on the intended use of the images. Digital photos are accompanied by metadata, which details information about the image itself such as the camera settings for the photo, the time, date, and location of the photo, and the owner of the photo. While these data can be helpful to the surgeon, they can also be used to identify individuals in otherwise anonymized photos and, in the US, must be evaluated in the context of HIPAA (Health Insurance Portability and Accountability Act of 1996) compliance. Digital photography has also facilitated the rise of social media as a tool for public engagement, both by the surgeon and the patient. Ultimately, digital photography has proven to be the most fundamental form of image guidance in plastic surgery and will continue to be a mainstay of the specialty.

Three-dimensional (3D) photography

Although photography has been a standard tool in patient assessment, there are inherent limitations in representing a three-dimensional person with a two-dimensional representation. Cross-sectional imaging – such as computed tomography (CT) and magnetic resonance imaging (MRI) – is commonly used to depict structures in three dimensions, but these techniques are poor at capturing external anatomy. Three-dimensional (3D) photography was first brought to plastic surgery in 1979, using contour maps to evaluate complex facial asymmetries that could not be easily analyzed from photographs. However, these early 3D photographs required creating contour maps using calipers and rulers, which proved to be a highly time-consuming endeavor. In recent decades, 3D photography has gained popularity as high-resolution cameras and high-speed computing become more widely available.

Modern 3D photography is rooted in stereophotogrammetry: the estimation of 3D coordinates based on two or more photographic images taken from different positions. This effect essentially recreates how humans perceive 3D images, whereby we receive slightly different images into eyes that are offset on a horizontal axis. There are three different approaches to stereophotogrammetry – active, passive, and hybrid. Active stereophotogrammetry is based on patterned light that is projected onto the surface of an object and uses two or more cameras to capture the reflections of that patterned light. This technique allows for easier identification of corresponding points between the multiple camera views and is less impacted by ambient light. Passive stereophotogrammetry does not use structured light and instead relies on natural surface markers and textures to create landmarks for stereotaxis. As a result, these systems can be impacted by ambient light that obscures detail and requires high-resolution cameras that can capture details with high fidelity. Hybrid stereophotogrammetry uses both structured light (active) and surface texturing (passive) to achieve higher precision and quality 3D surfaces.

Three 3D photography systems have widely been used in plastic surgery: 3dMD (London, UK), Vectra (Canfield Scientific – Fairfield, New Jersey) and Crisalix (Bern, Switzerland). 3dMD was one of the first systems to bring 3D photography to medicine. The company offers six different hardware systems, each of which is used for a specific application: face, head, hand, body, foot, and a modular system. A software suite is also available, which can overlay cross-sectional imaging with a 3D photograph and simulate a range of soft-tissue procedures. However, this system cannot simulate changes to underlying bony structure.

The 3dMD system has been widely used across a broad range of applications within plastic surgery. It has been shown to reliably obtain anthropometric measurements in patients with cleft lip and palate deformities and can also detect small changes in those measurements following cleft lip and palate repair. It has similarly been used to longitudinally track the degree of asymmetry in infants with deformational plagiocephaly and has reported accuracy of 0.2 mm in certain instances. In hand surgery, reports have used the system to track the soft-tissue changes in acromegaly and early signs of lymphedema.

The Vectra system uses passive stereophotogrammetry by relying on the natural texture of skin to create 3D geometry. Canfield Scientific offers three different camera hardware systems based on the anatomic area of interest: front face, head and neck, or entire body. A fourth system (Vectra-CR 3D) offers a portable system that is targeted towards clinical research. Additionally, Canfield offers both a breast software suite that can automatically provide breast measurements and simulate breast augmentation outcomes and a facial software suite that can simulate a range of surgical and non-surgical facial augmentation procedures.

The Vectra system has been used to measure the volume of the hand, forearm, and upper arm in lymphedema patients and has been shown to be an efficient, contactless alternative to the traditional methods of water displacement or circumference measurement. The technique can be localized for lymphedema and can detect early localized swelling that results in functional loss. The device has also been used to reliably obtain anthropomorphic measurements in children, which can be challenging due to the time-intensive nature of measurements and the lack of patient compliance. Reports have shown that a single stereophotograph allows for measurements with less than 1 mm of error compared to direct measurements. The device has also been reported in measuring the volume of breasts and could be used as an adjunct in preoperative planning in both reconstructive and cosmetic indications.

In contrast, the Crisalix system is purely software-based and does not require any hardware. The software uses photographs taken with any consumer camera and physical distance measurements to create 3D images, and as a result, has a lower barrier to entry. However, this also means that user photos with low quality, poor lighting, or a number of other factors may result in suboptimal 3D images as a result. The company similarly offers two software suites for simulating breast augmentation and facial procedures. Additionally, Cristalix offers an option of a portable 3D sensor that can be used for capturing 3D photographs of the body that can then be used to simulate a range of cosmetic procedures.

Crisalix can predict outcomes of primary breast augmentation that have good concordance with the true postoperative results, although the software is more reliable in predicting the outcome in symmetric breasts, as compared to ptotic or tuberous breasts. Patients have found the simulated 3D results to be a useful adjunct in deciding the size and shape of breast implants. However, patients also note that the lack of tactile feedback from holding physical implants can be a drawback. Other groups have explored the use of this system in a broad range of reconstructive procedures, such as predicting the volume of breast tissue removed in mastectomy, quantifying the amount of resorption following autologous fat grafting, and creating a custom 3D-printed template based on a native breast for free flap reconstruction of the contralateral breast.

Diagnostic ultrasound (US)

The benefit of ultrasound lies in its ability to rapidly perform noninvasive diagnostics with minimal equipment. In contrast to the large and expensive scanners that are required for CT and MRI, ultrasound devices have become ever more portable, with some manufacturers offering devices that can be connected to a standard smartphone for true point-of-care diagnostics. Ultrasound offers a number of advantages such as relatively low cost, real-time acquisition of images, lack of ionizing radiation, and noninvasiveness. At its core, ultrasound relies upon the transmission of mechanical sound waves and detection of the reflections of those waves as they interact with tissues. Doppler ultrasound builds upon this by taking advantage of the Doppler effect, whereby sound that is emitted from moving objects changes its frequency, to detect blood flow and identify the location of blood vessels.

The uses of ultrasound in plastic surgery are truly innumerable and continue to grow every year. In the preoperative setting, Doppler ultrasound is routinely used to identify perforators for microsurgical reconstruction and has been reliably used in a number of flaps, including the anterolateral thigh, deep inferior epigastric, radial forearm, thora-codorsal, and freestyle flaps. Although the anatomy of perforating vessels for these flaps is well described, Doppler ultrasound provides a way to validate each patient’s unique anatomy. Ultrasound can also be combined with other techniques to aid identification of supermicrovascular structures, such as venules for lymphaticovenous anastomoses.

Outside of microsurgical reconstruction, ultrasound is an essential part of the diagnostic work-up for breast implant associated anaplastic large cell lymphoma (BIA-ALCL) in detecting late seromas and guiding fluid aspiration for cytologic analysis. It has been used to measure tissue volume changes after a wide range of procedures including fat grafting in breasts, hyaluronic injections to the face, and cryolipolysis. It can be used as an intraoperative tool to guide dissections, such as identifying fascial layers for fat grafting in the buttocks, locating the boundaries of breast implants during fat grafting, and placing analgesic blocks at the time of surgery. In hand surgery, high-resolution ultrasound can detect tendon ruptures and characterize the type and extent of vascular malformations.