A patient positioning system includes a vertical link member and a carriage sub-system pivotably mounted thereto. The carriage sub-system includes a carriage having a first end and a second end, a first guide movably coupled to the carriage and having a first end and a second end, a first connecting shaft pivotably coupled to the first ends of the first guide and the second guide, and a second connecting shaft pivotably coupled to the second ends of the first guide and the second guide. The system further includes a patient bed mounted to the carriage sub-system and a motor drive system including a motor drive, a belt configured to be driven by the motor drive, a rotation brake system configured to selectively engage with or disengage from the carriage, and a slab brake system configured to selectively engage with or disengage from the first and second connecting shafts.