The sensitive and specific detection of premalignant and malignant lesions is a crucial and indispensable prerequisite for optimal treatment outcome and prognosis. Surgical biopsy, which is currently the primary diagnostic tool, often causes patient anxiety and discomfort, undesirable side effects, and sampling errors. For example, multiple prostate biopsies miss up to 30% of cancer present at the time of biopsy.^{1, 2, 3} An urgent need exists to develop cost-effective, minimally invasive imaging technologies to identify premalignancy and malignancy with high sensitivity and specificity.⁴ Optical imaging tools such as reflectance confocal microscopy, optical coherence tomography (OCT), and optical coherence microscopy (OCM) are promising diagnostic tools for detecting cancer at an early stage.⁵ Optical imaging is particularly useful for in vivo applications because it uses near-infrared wavelengths $\left(770\text{to}1300\mathrm{nm}\right)$ that avoid predominant absorption in tissue.⁶

Multiphoton microscopy (MPM) is an important tool for high-resolution, noninvasive imaging of thick biological tissues.^{1, 2, 3, 4, 5} MPM utilizes femtosecond lasers to excite nonlinear contrast signals that include two-photon excited fluorescence (TPEF) and second-harmonic generation (SHG). TPEF can be detected from intrinsic sources (e.g., cofactors, proteins) and exogenous fluorophores, while strong SHG signals can be obtained from noncentrosymmetric molecules such as collagen, a common extracellular matrix protein. Thus, MPM can image and distinguish cellular and extracellular matrix structures simultaneously. MPM systems have been mostly developed using free-space optics and microscope platforms. However, for in vivo imaging and clinical applications, a fiber-optic MPM endoscope is desirable where light can be delivered through a flexible fiber and images can be acquired using a miniature probe.^{6, 7, 8, 9} Delivering femtosecond pulses through fibers and designing miniature scanning probes are two challenges in MPM endoscopy.

In the United States, approximately 1.5 million new cancer cases were expected to be diagnosed in 2010, excluding most carcinomas in situ (noninvasive cancers) as well as basal and squamous cell skin cancers.¹ Over half a million Americans were expected to die of cancer, more than 1,500 people a day in the year 2010.¹ Cancer is the second most common cause of death in the US, exceeded only by heart disease.¹ The 5-year relative survival rate for all cancers diagnosed between 1999 and 2005 was 68%, up from 50% in 1975 to 1977. The improvement in survival reflects progress in diagnosing certain cancers earlier and improvements in treatment. More than 85% of cancers originate in the epithelium, and epithelial cancers are preceded by a curable pre-cancerous stage, when 95% of cases completely recover.² Cancer detection is further complicated by field cancerization or multicentric lesions. Current diagnostic techniques require repeated surgical biopsies of lesions that frequently turn out to be benign, yet they often also detect malignant change too late for curative treatment. Of all oral cancer cases documented by the National Cancer Institute, advanced lesions outnumbered localized lesions at the time of diagnosis by more than 2:1. These statistics mean that at least some lesions were ignored or missed by patients, healthcare professionals, or both. It is partly due to an incomplete understanding or awareness that even small asymptomatic lesions can have significant malignant potential and partly due to the lack of effective diagnostic modalities. Five-year survival rate is only 16% for patients with oral cancer metastasis, but 75% for those with localized disease at the time of diagnosis.^{1, 2} The current approach to detecting malignant change in existing oral lesions that are potentially pre-dysplastic or dysplastic is regular surveillance combined with biopsy or surgical excision. However, these techniques are invasive, often poorly tolerated by patients, may miss additional lesions or areas of more severe pathology, and unsuitable for regular screening of high risk sectors of the population.

Selective adsorption of specific salivary biopolymers on the enamel surface leads to the formation of an acquired salivary pellicle.¹ The adsorbed protein layer can be considered a dynamic biofilm that regulates and modulates interactions at the interface between the tooth surface and oral cavity.^{1, 2, 3, 4, 5} The pellicle serves as a lubricant, protecting the dentition against abrasion and attrition.¹ In addition, the salivary pellicle may protect against demineralization of dental hard tissues caused by acid attack.^{1, 2, 3, 4, 5} The adsorbed pellicular phosphoproteins and mucins reduce enamel surface solubility, acting as a perm-selective membrane and regulating not only the diffusion of calcium and phosphate ions, but also the acidic agents.^{1, 2, 3, 4, 5} In addition to its protective functions of lubricating, inhibiting demineralization, and working as a diffusion barrier against chemical attacks of the enamel, the pellicle can act as a reservoir of agents promoting remineralization. The maturation age of the pellicle, when it can effectively inhibit erosive activity, remains unclear.

We created an auto-para viewer, an autofluorescence imaging device, to localize the parathyroid glands during thyroidectomy using an inexpensive Raspberry Pi. A special emission filter in the auto-para viewer was designed to pass 1/100 of visible light and nearly all infrared light longer than 808 nm. With this emission filter, we simultaneously acquired an autofluorescence image of the parathyroid and a visible light image of the surrounding surgical field. The auto-para viewer displayed four times brighter autofluorescence of the parathyroid glands compared to the background tissues without operating room light. Additionally, it showed two times brighter autofluorescence than the background tissues simultaneously showing the surgical field illuminated by the visible light from the operating room light. The NOIR camera, using the auto-para viewer, could reduce the camera's exposure time so the parathyroid glands to be viewed in real-time, which is expected to prevent unintentional damage to the parathyroid gland during thyroidectomy.

Optical coherence tomography (OCT) is a nondestructive imaging technique offering high temporal and spatial resolution, which makes it a natural choice for assessing tissue mechanical properties. We have developed methods to mechanically analyze the compliance of the rabbit trachea in vivo using tissue deformations induced by tidal breathing, offering a unique tool to assess the behavior of the airways during their normal function. Four-hundred images were acquired during tidal breathing with a custom-built endoscopic OCT system. The surface of the tissue was extracted from a set of these images via image processing algorithms, filtered with a bandpass filter set at respiration frequency to remove cardiac and probe motion, and compared to ventilatory pressure to calculate wall compliance. These algorithms were tested on elastic phantoms to establish reliability and reproducibility. The mean tracheal wall compliance (in five animals) was 1.3±0.3×10⁻⁵ (mm Pa)⁻¹. Unlike previous work evaluating airway mechanics, this new method is applicable in vivo, noncontact, and loads the trachea in a physiological manner. The technique may have applications in assessing airway mechanics in diseases such as asthma that are characterized by significant airway remodeling.