The study was conducted in our cath lab room which was equipped with the Siemens Artis dFC Cath-Lab unit by Siemens Medical Solutions USA. A Ceiling Suspension Shield (CSS) is a lead acrylic transparent sheet of 0.5mm lead equivalence suspended on an independent handle, and it was mounted on a longitudinal ceiling rail system on the right side of the patient table, which can easily be adjustable during the procedure. CSS is intended to protect the upper half region of the cardiologist from scattered radiation emerging from the patient's body17. Various models of CSS are available in the market. The CSS model installed in our cath lab was OT90001 (Fig-1) manufactured by MAVIG GmbH X-Ray Protection and Medical Suspension Systems, Germany.
The dose rate at the cardiologist's location was assessed using a calibrated RaySafe X2 base unit with a survey sensor across different projections of the X-ray tube. RaySafe X2 systems are specially designed dosimeters for diagnostic QA (Quality Assurance). The system was manufactured by Unfors RaySafe AB, Sweden and marketed in India through Fluke Biomedical, USA. It can measure the dose ranges from 1nGy to 999Gy with 5% uncertainty. The radiation dose to the cardiologist during the procedure was measured using an analog pocket dosimeter (W-500) manufactured by Arrow-Tech, Inc.
The efficacy of CSS was checked by measuring the dose rate at the cardiologist position with and without CSS. A water equivalent phantom with 20 cm thickness was utilized to replicate the patient, resulting in realistic scattering of X-rays. The dose rate was measured using the Survey sensor of the RaySafe X2 system positioned at a reference point that is 1 meter away from the Patient entrance reference point19. This location is typically where the cardiologist stands during the procedure; hence, the dose can be considered an approximation of the cardiologist's dose. To enhance the visualization of different blood vessels, the cardiologist employed various projections of the X-ray tube. The common projections20 are Right Anterior Oblique –Cranial (RAO-CRA), Right Anterior Oblique –Caudal (RAO-CAU), Left Anterior Oblique –Cranial (LAO-CRA), and Left Anterior Oblique –Caudal (LAO-CAU) (Fig-2). For every angle of projection, the dose rate at the reference point was measured using the RaySafe X2 system .To evaluate the effect of CSS ,the reading was taken in three conditions-(i) without CSS (ii) With CSS (normal position) (iii) with CSS in a customised positions. The customised position means the position of CSS rearrange to a more covered position on scattered radiation in the selected projection. The dose to the cardiologist was measured using the pocket dosimeter that was affixed to the left side of their collar21. The dose at this level may be taken as the estimated dose to the eyes. All cardiologists wear lead aprons as a routine process during cath lab procedures. But most of them are not interested in wearing lead goggles, lead caps, or lead face shields due to their inconvenience. Therefore, the dose measurement at this level is significant. The most common cath lab treatments were percutaneous transluminal coronary angioplasty (PTCA)22 and coronary angiography (CAG)23. Coronary angioplasty is known to be the most time-consuming and radiation-intensive procedure among these. Hence, the average dose to the cardiologist is calculated using the readings taken from ten angioplasty procedures. The total radiation dose exposed to the patient is recorded from the machine-generated radiation dose structured report (RDSR).
In a busy cath lab schedule it was noticed that the staff kept the CSS at a single position throughout the procedure or forgot to position the CSS in between the field of view and the cardiologist (Fig-3). They may be exposed to a higher occupational dosage as a result of this potentially severe mistake. Fig-4 shows an incidental image taken during a cath lab procedure, adding context to the situation. In order to prevent such occurrences in our facility, we have designed and implemented a CSS sensor system that is affixed to the side of the flat detector. This system serves as an alert mechanism for cardiologists, reminding them to maintain proper positioning of the CSS during procedures.
The major component of the sensor system is an ultrasonic sensor24 module, which produces ultrasonic sound signals (USS) and detects the reflected USS signals. The electronic components utilized for constructing the alert system are detailed in Table 1, while Fig. 5 illustrates the circuit diagram. The ultrasonic sensor module comprises a transmitter and receiver responsible for transmitting and receiving ultrasonic sound signals. The IC 55525 was wired as an astable multivibrator for producing continuous square pulses to trigger the ultrasonic transmitter to produce USS. When the CSS was placed in front of the sensor, it reflected the signals. The ultrasonic receiver picked up these reflected signals and generated output pulses. The inverter circuit receives these output signals, which power the green LED. The red LED and buzzer may be turned on if the ultrasonic module is not sending out any signals. An analysis was conducted to assess the effects of the CSS sensor system in the cath lab by examining the radiation exposure for cardiologists and total air kerma during ten angioplasty procedures for LAD artery lesions.
Table − 1 Component list used for the CSS Sensor System
No
|
Component
|
Specification
|
Quantity
|
1
|
IC1
|
NE555
|
1
|
2
|
IC2
|
SN7404
|
1
|
3
|
Ultrasonic Module
|
HC-SR-04
|
1
|
4
|
LED
|
3V Red
|
1
|
5
|
LED
|
3V Green
|
1
|
6
|
Piezo buzzer
|
5V
|
1
|
7
|
Resistor
|
1K
|
1
|
8
|
Resistor
|
10 variable
|
1
|
9
|
Capacitor
|
100µF
|
1
|
10
|
Capacitor
|
10µF
|
1
|
11
|
Battery charging module
|
TP4056
|
1
|
12
|
Rechargeable Battery
|
3.2V
|
2
|
13
|
Switch
|
2pin SPST
|
2
|
14
|
Plastic case
|
(11X8X3) cm3
|
1
|