1. A method for compensating for table sag, the method comprising: receiving a first dimension of a table; scanning, by an energy source and a detector, a patient placed on the table to obtain a first data set; generating an image of the table by performing the scanning with the patient on the table; determining, by a processor coupled to the detector, a difference between the first dimension and a second dimension of the table in the image; and determining whether the difference can be obtained from an image generated from a scout scan of the patient.