Effect of MOSFET dosimeters' calibration method on calibration factors and radiation doses measured with the dosimeters in radiology

MOSFET dosimeters have widely been used to measure radiation doses caused by x-rays. When using the MOSFET dosimeters, calibration factors (CFs) have a direct effect on reliability of dose measurements. The aim of this paper was to study the effect of various calibration methods on the CFs of the MOSFET dosimeters. The CFs were measured on clinical digital x-ray angiography (XA) and computed tomography (CT) devices using a calibrated CT ionization chamber and a standard polymethyl methacrylate (PMMA) phantom. The measurements were conducted by having the dosimeters (1) in air, (2) on the surface of the PMMA phantom and (3) inside the phantom. A statistically significant difference was seen between the CFs measured on the XA and CT devices. The CFs measured on the CT device were 20%-165% higher than those measured with the XA device (p < 0.001) in every calibration geometry. Furthermore, the calibration geometry had a notable effect on the CFs on CT. The CFs on the surface of the phantom were 18%-25% higher than in air (p < 0.05), and the CFs inside the phantom were 32%-39% smaller than in air (p < 0.05). These results suggest that the calibration of the MOSFET dosimeters should be conducted with the same device that is used in actual dose measurements. Also, the scattering conditions and the calibration geometry should be similar in the calibration and subsequent dose measurements.

A Randomized Trial of Ultrasound- versus. Fluoroscopy-Guided Subclavian Vein Catheterization in Children with Hematologic Disease

OBJECTIVE

To compare the ultrasound- and fluoroscopy-guided subclavian vein catheterization in pediatric population with hematologic diseases.

METHODS

A randomized prospective study of subclavian vein catheterization in pediatric population with hematologic diseases was performed. After randomization, the patients were assigned to either ultrasound- or fluoroscopy-guided subclavian vein catheterization. The primary outcome was number of attempts at venous cannulation. Secondary outcomes included: catheterization success rate, fluoroscopy time, operation time, and surgical complications.

RESULTS

There were 170 children enrolled between February 2017 and July 2018. There was no difference between the two groups with regard to the demographic data. Success within 3 attempts was achieved in 82 cases (82/87, 92.0%) in the ultrasound (US) group vs. 65 cases (65/83, 78.3%) in the fluoroscopy group (P = 0.002). The average operation time was 10(7) min in US group vs. 10(6) min in fluoroscopy group (P = 0.722). There were 3 complications in the US group, while there were 6 complications in the fluoroscopy group (P = 0.321). There were 4 catheter-related thrombosis (CRTs) found in the US group during follow-up, however there was no CRT in the fluoroscopy group (P = 0.121).

CONCLUSIONS

Ultrasound-guided venous puncture is a more accurate method of subclavian vein catheterization. However, the catheter tip can be placed more precisely by fluoroscopy. Thus, combined ultrasound-and fluoroscopy-guided technology is more efficient in subclavian vein catheterization of children with hematologic disease.

Fluoroscopy-guided subclavian vein catheterization in 203 children with hematologic disease

Subclavian vein catheterization plays an important role in the treatment of children with hematologic disease. However, catheter placement is a difficult and high-risk procedure in children.Fluoroscopy-guided subclavian vein catheterization was used in 203 children (mean age, 6.99 years ± 3.722 years; range, 1-16 years) with hematologic disease. The number of vein punctures, catheterization success rate, fluoroscopy time, operation time, and surgical complications were recorded.There was a 100% success rate for fluoroscopy-guided subclavian vein catheterization. A total of 124 cases (61.1%) were successful on the first venipuncture attempt; 171 cases (84.2%) achieved success within 3 attempts. Twenty-five cases had 4 to 6 time venipunctures and the remaining 7 cases underwent ≥7 time venipunctures. All catheter tips were successfully placed at the junction of the superior vena cava and the right atrium. Fluoroscopy times ranged from 16 to 607 seconds (mean, 65.46 ± 85.864 seconds). Operation time ranged between 5 and 25 minutes (mean, 10.38 ± 4.036 minutes). Arterial punctured was happened during surgery in 2 cases. There were 2 cases of catheter-related infection, but no other complications. The mean follow-up time was 35 days; range 20 to 50 days.Fluoroscopy-guided subclavian vein catheterization in children is a safe procedure, with a high success rate, resulting in a reduced number of venipunctures, optimal catheter placement, and reduced complications.

Fluoroless catheter ablation of various right and left sided supra-ventricular tachycardias in children and adolescents

Electrophysiology study (EPS) and catheter ablation (CA) in children and adolescents carries a potentially harmful effect of radiation exposure when performed with the use of fluoroscopy. Our aim was to evaluate the feasibility, safety and effectiveness of fluoroless EPS and CA of various supra-ventricular tachycardias (SVTs) with the use of the 3D mapping system and intracardiac echocardiography (ICE). Forty-three consecutive children and adolescents (age 13 ± 3 years) underwent fluoroless EPS and CA for various supra-ventricular tachycardias. A three-dimensional (3D) mapping system NavX™ was used for guidance of diagnostic and ablation catheters in the heart. ICE was used as a fundamental imaging tool for transseptal punctures. Acute procedural success rate was 100 %. There were no procedure related complications and short-term follow up (10 ± 3 months) revealed 93 % arrhythmia free survival rate. Fluoroless CA of various SVTs in the paediatric population is feasible, safe and can be performed successfully with 3D mapping system and ICE.