This pilot study will determine changes over time in tumor volume/motion & patient anatomy, as well as dose distributions to normal organs. The study will inform medical decision-making about need for (and timing of) re-calibration of radiation dosimetry plans. Weekly CT and/or serial MR scans will be employed for those patients receiving 7-8 wks of radiation therapy. The study will enroll 30 patients in each stratum: Non small cell lung cancer (NSCLC), Head & Neck, gastrointestinal (GI) and Gynecologic tumor.