Fluorothymidine F-18 PET in Diagnosing Patients With Intermediate or High Grade Soft Tissue Sarcoma

Inclusion Criteria: * Participants must have histological evidence of an intermediate or high grade soft tissue sarcoma (STS) of any stage * Participants must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension as \>= 1 cm with CT scan or MRI * Prior resection is allowed if there is measurable gross disease and the subject plans to have neoadjuvant radiotherapy followed by resection * Eastern Cooperative Oncology Group (ECOG) performance status =\< 4, Karnofsky performance status \>= 40% * Creatinine =\< 3 x upper limit of normal (ULM) * Blood urea nitrogen (BUN) =\< 3 x ULN * Participants should be willing and able to have both PET-CT scans * Participants should be eligible for and plan to undergo neoadjuvant radiation therapy and should be seen by a radiation oncologist prior to beginning the study; radiation at an outside facility will be allowed * Participants should be eligible for and plan to have resection with a surgeon specializing in STS at Oregon Health and Science University (OHSU) and should be seen by said surgeon prior to beginning the study * Participants should have a life expectancy that is greater than the study duration * Participants should be willing to use adequate contraception from the time of the first PET-CT scan to 2 months after radiotherapy finishes; should a woman become pregnant while participating in this study, she should inform her treating physician immediately * Women with childbearing potential must have a negative pregnancy test before each PET-CT scan * Participants should have the ability to understand and the willingness to sign a written informed consent document * Participants must sign a study specific consent form prior to registration Exclusion Criteria: * Patients with uncontrolled intercurrent illness including, but not limited to, ongoing or active infection or significant inflammation at treatment site or psychiatric illness/social situations that would limit compliance with study requirements or whose lab values do not meet the criteria above are excluded * Pregnant women are excluded from this study * Breast feeding women are excluded from this study * Patients receiving chemotherapy during the course of radiation are excluded * Patients whose weights exceed the tolerance of the table are excluded; the weight limit at OHSU is 450 pounds (lbs)