This invention relates generally to computed tomography (CT) imaging and more particularly, to quantification of a selected attribute of an image volume and monitoring changes of the selected attribute in a patient.
Visualization of anatomical data acquired by imaging devices generating 3D data is typically handled by volume rendering of its intensity and/or density values (Hounsfield Units (HU) in the case of Computed Tomography for instance). Many clinical applications are based on 3D visualization of the volumetric data that may include, but are not limited to, detection and sizing of lung nodules, quantification of vessel curvature, diameter and tone, cardiac vascular and function applications, and navigation of the colon for detection of polyps. These applications rely on the absolute values of the image data (intensity, density (HU), uptake (standard uptake values (SUV)), and other material properties associated with medical imaging to differentiate multi-dimensional anatomies from background tissue. Some clinical imaging applications are designed for routine screening of early cancers in the form of, for example, tumors, nodules, and polyps.
Many cancers commonly metastasize or move from their primary organ or location to involve another organ or location. The most common location for tumors to metastasize to is lymph nodes followed by lung, liver, and then bone. Frequently, metastatic disease presents as a distribution of small lesions (2-10 mm) throughout the anatomy of the body. Most common locations for metastatic lesions are in the lung and liver. The visual contrast of liver lesions on CT images is limiting to the human eye. Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) imaging have proven superior to CT for visualizing liver tumors, but contrast remains limited.
There are many treatment options for primary and secondary cancers. These may include radiation therapy, chemotherapy, hormone treatment, immune therapy, surgery and others.
To date, physicians rely significantly on the apparent anatomical size and shape of the tumor under treatment when assessing the patients response to a chosen therapy. This can be problematic in patients with “bulky disease” (meaning that the tumor burden is an overestimate of the actual presence of cancer cells) if the cancer remises, but the relative size of the tissue mass does not change. Since the inception of PET and CT/PET imaging, the size of the active portion of the tumor can be when assessed to determine patient response to therapy. The physician may desire to measure the size of the lesion(s) before and after subsequent treatments to quantify the response. In many cases of a primary cancer, it may be straightforward to quantify the volume of anatomy occupied by a lesion. Under some circumstances, a tumor can have limited contrast and/or be ill-defined, meaning that the boundaries of the tumor are difficult to identify. In the case of multiple lesions and metastatic disease, there may be hundreds of small lesions distributed throughout the body or within individual organs. However, when there are multiple lesions, it is extremely time consuming to identify and track each individual lesion. Additionally, physicians may choose to represent the sum total of the volume occupied by all of the lesions in terms of a single number called “Total Tumor Burden” (TTB). As such, when any of the tumors respond to a chosen treatment plan, the TTB will change. However, even tracking TTB over the course of a treatment regime may also require a difficult and time consuming procedure.