Radiation Dose

Use of dose-dependent follow-up protocol and mechanism to reduce patient and staff radiation exposure in congenital and structural interventions.
Sawdy JM, et al. Cath Cardiovasc Interv 2011;78:136-42
Editorial: Cath Cardiovasc Interv 2011;78:143-4

Radiation Exposure during Radial Access (Right vs. Left)

CIRCINTERVENTIONS.111.961185

Published online before print May 17, 2011

Referenced here, more to highlight the methodology of the adult study and for actual reports of measurement dose, etc. This adult study compares right and left radial access. Radiation exposures were similar between right and left radial approached. Slightly increased exposure to the wrist in right radial approach compared to left radial approach.

Operator Radiation Exposure During Percutaneous Coronary Procedures Through the Left or Right Radial Approach

The TALENT Dosimetric Substudy

1. Alessandro Sciahbasi, MD at al.


Background—Transradial percutaneous coronary procedures may be effectively performed through the right radial approach (RRA) or the left radial approach (LRA), but data on radiation dose absorbed by operators comparing the two approaches are lacking. The aim of the present study was to evaluate radiation dose absorbed by operators during coronary procedures through the RRA and LRA.

Methods and Results—Three operators were equipped with 5 different dosimeters (left wrist, shoulder, thorax outside the lead apron, thorax under the lead apron, and thyroid) during RRA or LRA for coronary procedures. Each month, the dosimeters were analyzed to determine the radiation dose absorbed. From February to December 2009, 390 patients were randomly assigned to the RRA (185 patients; age, 66±11 years) or the LRA (185 patients; age, 66±11 years). There were no significant differences in fluoroscopy time (for RRA, 369 seconds; interquartile range, 134 to 857 seconds; for LRA, 362 seconds; interquartile range, 142 to 885 seconds; P=0.58) between the 2 groups. There were no significant differences in monthly radiation dose at the thorax (0.85±0.46 mSv for RRA and 1.12±0.78 mSv for LRA, P=0.33), at the thyroid (0.36±0.2 mSv for RRA and 0.34±0.3 mSv for LRA, P=0.87), and at the shoulder (0.73±0.44 mSv for RRA and 0.94±0.42 mSv for LRA, P=0.27). The dose at the wrist was significantly higher for the RRA (2.44±1.12 mSv) compared with the LRA (1±0.8 mSv, P=0.002). In both radial approaches, the thoracic radiation dose under the lead apron was undetectable.

Conclusions—Compared with RRA, LRA for coronary procedures is associated with similar radiation dose for operators at the body, shoulder, or thyroid level, with a possible significant advantage at the wrist. The cumulative radiation dose for both approaches is well under to the annual dose-equivalent limit.

Clinical Trial Registration—URL: http://www.clinicaltrials.gov/. Unique identifier: NCT00282646.

Radiation Safety: Adult-oriented paper and Editorial.

Cumulative Exposure to Ionizing Radiation From Diagnostic and Therapeutic Cardiac Imaging Procedures: A Population-Based Analysis Jersey Chen, Andrew J. Einstein, Reza Fazel, Harlan M. Krumholz, Yongfei Wang, Joseph S. Ross, Henry H. Ting, Nilay D. Shah, Khurram Nasir, and Brahmajee K. Nallamothu J Am Coll Cardiol 2010;56 702-711 Editorial Radiation Exposure From Cardiac Imaging Procedures: Do the Risks Outweigh the Benefits? Matthew J. Budoff and Mohit Gupta. J Am Coll Cardiol 2010;56 712-714

Radiation Safety: Dose reduction using Phillips DoseWise(R) System

Management of pediatric radiation dose using Phillips fluoroscopy systems DoseWise: perfect image, perfect sense. Stueve,D. Pediatr Radiol 2006;36(Suppl 2):216-220.

Phillips DoseWise: a set of techniques, programs and practices that ensure optimal image quality with minimum radiation.

Eleva system for fluoroscopy & Allura system for angiography incorporate DoseWise.

Smart beam management: Based on the selection of exam-type and patient-type, EPX-based program automatically selects the following:

- Radiographic exposure factors

- Focal spot size

- Spectral filtration

- Fluoroscopy type, dose and exposure rate

Radiographic Exposure Factors:

Grid-controlled Fluoroscopy (GCF) vs. Continous fluoroscopy, saves radiation. These are designed to maintain 70kV level even in very small patients.

IQX (Intelligent Exposure Control) rapidly regulates digital radiographic exposures when children are imaged.

Spectral beam filter:

"Soft radiation" (X-rays that enter patient's skin but do not have enough energy to reach image detector) are removed from the beam. Such filtration reduces dose to patient and personnel. Depending on patient size & type of exam, the filters are automatically inserted into the beam:

Copper spectral filters (0.1mm, 0.2 mm, 0.4 mm and 0.9 mm thickness)

&

Aluminum spectral filter (1 mm thickness)

Typically, 0.1 mm Cu filter reduces exposure by 50% & 0.2 mm by 70%.

Typically, 0.1 & 0.4 mm Cu filters are used in adult interventional procedures where long exposure times are common.

0.9 mm Cu filter is used for newborn & small children; and also for long EP procedures.

In cardiac & vascular procedures, 0.1 mm Cu filter & 0.4 mm Cu filter provide max. exposure of 10 R/min and 5 R/min respectively during fluoroscopy. (0.9 mm Cu filter provides 1.5 R/min max).

In standard pediatric radiology, 0.1 mm Cu filter provides best relationship best diagnostic images with lowest dose.

Customizing beam shape: 3 successive steps

1) Lead iris shape shutter (at the outlet port of X-ray tube)

2) Two Lead square shutters (positioned above 1)

3) Copper wedge filters within collimator

These shutters and wedges can be adjusted on Last-image-hold image (without using extra radiation to adjust these).

Adaptive Measuring Field (AMF):

When the field is panned through anatomic structures of varying (radio)opacity, brightness of fluoroscopic image changes. Automatic Exposure Control (AEC) - designed to maintain consistent image brightness level - would respond and increase X-ray dose to maintain brightness when very opaque object comes into the field. (Same occurs when collimator shutter are closed too small). AMF system continously monitors shutter position and uses sensors from the included areas only to set radiation output.

AEC lock-in helps to maintain image quality during panning through objects that are too dark and too light on the field. Thus, it eliminates "blooming".

Radiation-on time:

1) In-pulse radiation control (IQX) - Radiographic settings (tube voltage - kV, tube current - mA and pulse width - ms) are adjusted within the first millisecond of exposure.

2) Pulsing the beam during fluoroscopy (vs. Traditional, continous beam)

For fluoroscopy, GCF is used.

For angiography, IQX is used.

GCF (Grid-controlled Fluoroscopy):

GCF extends the in-pulse control concept to pediatric fluroscopy curves @ short pulse widths.

Production instant rise and fall of exposure (creating "square pulse"; achieved by DoseWise "Grid Switching") in stead of pulses with slight "ramp" in rise and fall (in "conventional pulse fluoroscopy") decreases radiation dose by 80-90%.

Grid switching also reduces soft radiation & motion blur.

(Two studies demonstrated GCF system reduced radiation dose between 4.6 - 17 times compared to conventional fluoroscopy: In children - Pediatr Radiol 2000;30:236-42 & In pigs - Radiol 2006;238:96-106).

Display of radiation exposure on physician's monitor display:

Air kerma dose levels

Dose Area Product (DAP) - measured from a meter located in X-ray tube collimator

Future: Display of patient entrance dose - monitored from predetermined points on patients body to warn when it approaches deterministic damage level.