Partial Electrical Reset of CT Irradiation on Implantable Cardiac Devices: Relationship between Reset and Tube Voltage, Tube Current, and Rotation Time

Abstract

SummaryThe aim of this study was to investigate the relationship between partial electrical reset (PER) and CT scan parameters (tube voltage, tube current, rotation time, and product of tube current and rotation time in mAs). A cardiac resynchronization therapy pacemaker (Insync 8040, Medtronic Inc., Tokyo) and 320 area detector CT scanner (Aquilion ONE, Toshiba medical systems, Otawara, Japan) with volume scan were used. The pacemaker was put in DDD mode. The PERs were interpreted using both the programmer's wave forms and error messages. The exposure was repeated 5 times per CT setting. The pacemaker was placed on the anterior wall and upper side of a chest phantom. Each CT scan was performed using the following parameters: tube voltage of 80, 100, 120, and 135 kV; tube current of 50-550 mA; and rotation time of 0.35-1.5 s. PERs were observed at 100, 120, and 135 kV, and more PERs were observed as the tube voltage increased. The PER tube current decreased as the rotation time was increased. In contrast, the PER tube current and rotation time product (mAs) increased as the rotation time was increased. More specifically, the radiation dose rate was the affected factor of the PERs. To avoid PER of pacemakers, CT scan parameters with lower radiation dose rates (low rather than high tube current and rotational time) is recommended. In conclusion, our results will help with CT scans of patients who have implantable cardiac devices (included pacemakers and cardioverter defibrillators).

Inhibition of the Oversensing of Cardiac Pacemakers in Chest CT

“…In the alert period, a pacemaker is programmed to sense spontaneous events (if the heart beats spontaneously without pacing) and to suppress pacing. The reports of oversensing presented at academic conferences are based on the results of X-ray irradiation in the alert period [1][2][3][4][5][6][7][8][9][10]. However, we demonstrated that the oversensing of a pacemaker is not induced by X-ray irradiation in the refractory period.…”

“…These findings lead us to conclude that they are quite useful to all X-ray examinations in the patients who implanted a pacemaker all the pacemakers have their own refractory period. There are 3 limitations in our study: the first is the dose rate of X-ray was not evaluated, because the oversensing occurs more frequently with increased dose rate [3,7]. The second is our suppression method of oversensing is not applicable to some CT units that are unable to do intermittent switching exposure during ECG gating.…”

“…case of pacemaker-related defect was ll of the refractory period of a pacem noise sampling period, and is set at the time frame fol-In 2005, the first reported in Japan claiming that a pacemaker induced a partial electric oversensing in X-ray CT [1][2][3][4][5][6][7][8]12,13]. In this study, we investigated the way to inhibit the oversensing in CT.…”

“…In 2005, the first case of the pacemaker-related defect was reported in Japan claiming that a pacemaker induced a partial electric oversensing in X-ray CT [1][2][3][4][5][6][7][8]11,12]. Ministry of Health, Labor and Welfare issued the reminder to medical institutions titling "Precautions for the use of X-ray CT and implantable cardiac pacemakers with regard to their interactions" [11,12].…”

“…As of 2011, the reports of oversensing and reset of the cardiac pacemaker still have been observed [7]. Therefore, in this article we investigated the way to inhibit the oversensing in X-ray CT.…”