SWALLOWING COMPUTED TOMOGRAPHY: DOSE ESTIMATION IN A PHANTOM STUDY CONDUCTED AT VARIOUS PATIENT RECLINING ANGLES.

Swallowing computed tomography (SCT) is a relatively new technique for the morphological and kinematic analyses of swallowing. However, no optimal scan protocols are available till date. We conducted the present SCT study to estimate the patient dose at various patient reclining positions. A RANDO phantom with a thermoluminescent dosemeter was placed on a hard Table board in a semi-reclining position at the centre and off-centre. According to predetermined scan protocols, irradiation was performed to acquire scanograms at reclining angles of 55° and 65°. The effective dose was the lowest at the centre 45° (3.8 mSv) reclining angle. Comparison between the off-centre (4.6 mSv at 55°, 6.8 mSv at 65°) and centre (4.5 mSv, 5.8 mSv) values suggested that the off-centre position is undesirable with regard to the patient dose. Accordingly, we believe that SCT methods must be revised on the basis of these factors.

Dose Estimating Application Software Modification: Additional Function of a Size-Specific Effective Dose Calculator and Auto Exposure Control.

Adequate dose management during computed tomography is important. In the present study, the dosimetric application software ImPACT was added to a functional calculator of the size-specific dose estimate and was part of the scan settings for the auto exposure control (AEC) technique. This study aimed to assess the practicality and accuracy of the modified ImPACT software for dose estimation. We compared the conversion factors identified by the software with the values reported by the American Association of Physicists in Medicine Task Group 204, and we noted similar results. Moreover, doses were calculated with the AEC technique and a fixed-tube current of 200 mA for the chest-pelvis region. The modified ImPACT software could estimate each organ dose, which was based on the modulated tube current. The ability to perform beneficial modifications indicates the flexibility of the ImPACT software. The ImPACT software can be further modified for estimation of other doses.