Thank you for the replies so far. This was a stress reaction in the pedicle, with no fracture. Doctor who recommended the MRI and who gave us the diagnosis is double board-certified in Physical Medicine and Rehabilitation and Sports Medicine, with a special interest in non-operative spine management. He definitely outqualifies me as to what testing to order or what the diagnosis should be, so I trust he will order a CT scan or other testing if and when he feels it is needed. One advantage he cited when he recommended the MRI was the lack of radiation exposure to a young patient.