Materials and methods
The radiation dose was measured at the interventional reference point by Inch Up (19-inch, 17-inch, 14.4-inch, 13-inch) and digital zoom function (1.3×, 1.45×, 1.7×) with Interventional Angiography Systems (Azurion 7 B20/15, Philips) (Fig. 2).
Fig. 2: Devices and monitor magnification rate used for verification
a: Interventional Angiography Systems, Azurion 7 B20/15, manufactured by Philips, was used for verification. The radiation dose was measured at the interventional reference point.
b: The console is for digital zoom. It has a touch-panel format, and the magnification rate is adjusted using the console.
The same fluoroscopy conditions as those in the routine clinical practice (low 6.25 f/s)were used for imaging including that of the catheters and guide wire (Fig. 3).
Fig. 3: Image Comparison of Inch Up and Digital Zoom
In Digital Zoom, the normal size of the image is pinched-out on the monitor to the same size as that of the 19″ image from Inch Up. There are three evaluation subjects: 2.0-Fr micro catheter (Excelsior™ 1018™; Boston Scientific), 4.2-Fr catheter (CX catheter; Gadelius Medical), and guide wire (ASAHI CHIKAI; Asahi Intecc).
Visibilities of the catheters and guide wire were evaluated by five radiologists. Under a fixed evaluation environment, images that underwent a different method of processing were displayed two at a time and evaluated in five stages to obtain individual image scores.
In the analysis, Scheffe’s method was used, and results were evaluated.
Results
A greater reduction in radiation exposure was obtained with Digital Zoom compared to Inch up (Fig. 4).
Fig. 4: Differences in Dose Rate
The dose rate decreased over the range from 17-inch to 13.3-inch, with a decrease of approximately 40% at 13.3-inch.
With regard to visibility, a significant difference in the main effect was observed for all items.
A significant difference in the main effect was observed for the catheters and guide wire, even at a significance level of 1%.
However, no significant differences were observed for the main effect x personal or combined effect (Table. 1).
Table 1: Results of Analysis of Variance with Scheffe’s method
A significant difference in the main effect was observed for all items. A significant difference in the main effect was observed for the catheters and guide wire, even at a significance level of 1%.
No significant differences were observed for the main effect × personal or combined effect.
In the results of all items, the highest score was obtained at 13-inch.
In the results of all items, the highest score was obtained at 13-inch.
Discussion
Various techniques have been reported to decrease patients' radiation doses.
The fundamental and most important approach is keeping the fluoroscopy time and field of view as low as possible.
However, the latest angiographic equipment has pulse fluoroscopy as a standard feature, which is useful for reducing radiation exposure (1–4).
Nevertheless, reduction in radiation exposure to patients and interventional radiologists is being widely investigated.
According to interventional radiologists, the principal objective of angiography and fluoroscopy is not diagnosis but accurate positioning of catheters in the target arteries for treatment.
No major differences in visibility have been found between Inch Up and Digital Zoom. Therefore, it is considered that with Digital Zoom over the 19-inch to 13-inch range, catheter position adjustment is not difficult and can be performed manually.
In addition, devices such as coils used for arterial occlusion provide greater visibility compared to catheters, and their presence can be confirmed sufficiently even with digital zoom at 13-inch (Fig. 5).
Fig. 5: Differences between Inch Up and Digital Zoom in visibility of metallic coils
The coil shown here is a short Tornado coil, MWCE-185 3/2 mm, manufactured by Cook Medical, in Limerick, Ireland.
No major differences in visibility of the coil were found between Inch Up and Digital Zoom.
The 13-inch dose rate was 40% lower with Digital Zoom than with Inch Up, and therefore, it is considered that Digital Zoom will be highly useful for reducing radiation exposure to both patients and interventional radiologists.
Limitations
- This was a single-center study performed with only one type of equipment.
- Only a few catheters were used.
- Evaluations were performed with only one type of angiography equipment.
- Only a few people were evaluated.