**Abstract**

This communication provides an overview of the current and future applications of molecular sonography, emphasizing the principles of the technique. Molecular sonography is currently used for preclinical assessment of tumor detection and response in a variety of models. It has potential clinical applications in improved characterization of tumors based on their genomes. Clinical trials have been conducted for a variety of neoplastic, inflammatory and immunologic abnormalities.

**Keywords:** Labeled microbubbles, molecular characterization and detection, assessment of tumor response, ultrasonography

### **1. Introduction**

Molecular imaging describes a relatively new imaging technique that depicts molecular processes rather than anatomic changes that occur in diseased tissue. It affords non-invasive imaging on a cellular level based on depiction of selected molecular receptors. The premise of molecular imaging is based on the fact that molecular events precede anatomic changes, and therefore, have the potential to detect neoplastic processes early as well as potentially determine response to therapy shortly after its administration. Molecular imaging can depict genomic phenotypes, and advantage that proves key to personalizing medical therapy.

There are a variety of modalities currently used to image diseased tissue. PET, or Positron Emission Tomography, utilizes radioactive substances known as tracers to detect disease. It is noninvasive and can identify areas of high metabolic activity that may be concerning for cancer. However, PET's anatomic clarity is imprecise compared to CT/MRI and it remains quite expensive. SPECT, Single Photon Emission Tomography, implements a similar mechanism as PET but is appreciably cheaper. Additionally, the radio tracers in SPECT have much longer half-lives, extending the imaging window. However, SPECT has even lower image resolution than PET. MRI, Magnetic Resonance Imaging, does not use radiation and provides a snapshot of the patient's anatomy with excellent resolution. However, it is notably time-consuming and expensive.

Molecular sonography holds many advantages over these imaging techniques. In addition to its low cost and high spatial resolution, molecular sonography is considered easy to use and repeatable when compared to most other diagnostic modalities. Currently, it is used for evaluation of tumor models. Reports of the use of molecular sonography in human subjects have recently been published [1].

This review will describe the current uses of molecular sonography and discuss future directions for research and development.
