Oncology treatment planning is the process creating a treatment plan for treating a tumor(s) with radiation therapy (i.e., ionizing radiation), surgery, chemotherapy, etc.  Generally, for treatment planning, the subject is scanned (e.g., via a computed tomography (CT) or other scanner) and the resulting volumetric image data is used to run treatment simulations and/or create the treatment plan.  However, it is often difficult to visualize a tumor, which may be moving due to respiratory and/or cardiac motion, in the image data without contrast.  As such, a contrast-enhanced CT scan is typically performed. 
With a scanner having a z-axis detector coverage of about two and a half centimeters (2.5 cm) per rotation, a scan from the shoulders to the hips may cover about fifty centimeters (50 cm), and where each couch position is scanned over an entire breathing cycle (e.g., about four seconds (4 s) from full inhalation to full exhalation), the scan will take about eighty seconds (80 s) to perform.  Such a scan may be a low-pitch free-breathing respiratory-gated helical-CT scan in which each rotation covers the entire respiratory cycle for a number of rotations required to image the entire tumor, or a series of axial scans at different couch increments in which at each couch position the patient is scanned over the entire respiratory cycle and where the axial slices are combined together to form volumetric data covering the entire tumor. 
For such a scan, a scout or low dose scan is first performed to localize the tumor in the subject in order to determine proper positioning of the subject to scan the tumor.  In this example, a test bolus is administered to the subject in order to determine an approximated time to peak contrast uptake in the tissue of interest.  Other approaches may also be utilized to approximate the time to peak contrast uptake.  In addition, the respiratory cycle of the patient is monitored with a bellow belt or other device.  The subject is positioned based on the localization, and the monitored respiratory cycle and the approximated time to peak contrast uptake are then used to gate contrast enhanced scanning in an attempt to capture peak contrast uptake in the tissue. 
Unfortunately, it may be difficult to synchronize the timing of the scan with peak contrast uptake and enhancement of the tumor.  As such, peak contrast uptake may be missed, in part or entirely, and the subject may have to be re-scanned one or more times to capture desired contrast enhancement for treatment planning.  As a consequence, the patient may be exposed to multiple doses of contrast material and/or multiple scans and radiation exposure.