Photoacoustic imaging (PAI) and thermoacoustic imaging (TAI) are two emerging biomedical imaging techniques that both utilize ultrasonic signals as an information carrier. Unique advantages of PAI and TAI are their abilities to provide high resolution functional information such as hemoglobin and blood oxygenation and tissue dielectric properties relevant to physiology and pathology. These two methods, however, may have a limited detection depth and lack of endogenous contrast. An exogenous contrast agent is often needed to effectively resolve these problems. Such agents are able to greatly enhance the imaging contrast and potentially break through the imaging depth limit. Furthermore, a receptor-targeted contrast agent could trace the molecular and cellular biological processes in tissues. Thus, photoacoustic and thermoacoustic molecular imaging can be outstanding tools for early diagnosis, precise lesion localization, and molecular typing of various diseases. The agents also could be used for therapy in conjugation with drugs or in photothermal therapy, where it functions as an enhancer for the integration of diagnosis and therapy. In this article, we present a detailed review about various exogenous contrast agents for photoacoustic and thermoacoustic molecular imaging. In addition, challenges and future directions of photoacoustic and thermoacoustic molecular imaging in the field of translational medicine are also discussed.

Delirium is a syndrome of acute brain failure that represents a change from an individual's baseline cognitive functioning characterized by deficits in attention and multiple aspects of cognition that fluctuate in severity over time. The symptomatic management of delirium's behavioral manifestations remains difficult. The alpha-2 agonists, dexmedetomidine and clonidine, are efficacious, but their potential cardiovascular adverse effects limit their utilization. Guanfacine is an oral alpha-2 agonist with a lower potential for such adverse outcomes; however, its use in delirium has not been studied. A retrospective descriptive analysis of guanfacine for managing hyperactive or mixed delirium at Tampa General Hospital from January 2020 to October 2020 was conducted. The primary outcome was the time reduction in acute sedative administration. Secondary outcomes included renewed participation in physical therapy or occupational therapy (PT/OT), decreased opioid use, and an incidence of cardiovascular adverse effects. One hundred forty-nine patients were identified as having received guanfacine for managing delirium during the study period. All experienced a reduction in acute sedative use after the initiation of guanfacine. In 93 patients receiving PT/OT and no longer participating due to behavioral agitation, 74% had a documented renewal of services within four days. Of 112 patients on opioids, 70% experienced a 25% reduction in opioid administration within four days. No patients experienced consecutive episodes of hypotension that required a change in their clinical care. Two patients experienced a single episode of consecutive bradycardia that led to the discontinuation of guanfacine. Based on our retrospective study, guanfacine is a well-tolerated medication for the management of delirium. Even in medically and critically ill patients, cardiovascular adverse events were rare with guanfacine. Patients treated with guanfacine experienced decreased acute sedative use for behavioral agitation. Additionally, patients treated with guanfacine received fewer opioids and were better able to participate in PT/OT. Future studies with prospective, randomized, placebo-controlled designs are warranted to evaluate this promising intervention for delirium further.

Transcranial magnetic stimulation (TMS) has been established as an important and effective treatment for various psychiatric disorders. However, its effectiveness has likely been limited due to the dearth of neuronavigational tools for targeting purposes, unclear ideal stimulation parameters, and a lack of knowledge regarding the physiological response of the brain to TMS in each psychiatric condition. Modern optical imaging modalities, such as functional near-infrared spectroscopy and diffuse optical tomography, are promising tools for the study of TMS optimization and functional targeting in psychiatric disorders. They possess a unique combination of high spatial and temporal resolutions, portability, real-time capability, and relatively low costs. In this mini-review, we discuss the advent of optical imaging techniques and their innovative use in several psychiatric conditions including depression, panic disorder, phobias, and eating disorders. With further investment and research in the development of these optical imaging approaches, their potential will be paramount for the advancement of TMS treatment protocols in psychiatry.