First-Frame-Right Fluoroscopy Imaging at Low Radiation Dose
Radiology
Article Summary
This article examines two advances in fluoroscopic imaging. Firstly, Smart Pulse Regulation, which dynamically adapts tube voltage (kV), current (mA), and exposure time (ms) within each radiation pulse, delivering accurate exposure from the first frame, and dramatically reducing or eliminating the risk of a possible under- or over-exposure of each individual frame.
Secondly, Grid-controlled fluoroscopy, which produces sharp pulses without the rising edges and falling tails seen with traditional pulse generation, to eliminate unwanted soft radiation causing excess exposure, allowing medical imaging professionals to keep radiation dose as low as reasonably achievable (ALARA).
Acknowledgements: Medical writing assistance was provided by Jessica Jinks, EMJ, London, UK.
Acknowledgements
Fluoroscopy plays a vital role in medical diagnostics by providing real-time, dynamic imaging that allows clinicians to visualise motion and position devices.
Despite its clinical value, fluoroscopy faces several persistent challenges, which include:
Introduction
Staffing shortages, due to the increasing demand for imaging studies and fewer new radiographers to replace those retiring, and a decrease in technologists with extensive fluoroscopy expertise.
Limited familiarity with exposure management may result in variability in imaging performance and suboptimal exposure parameters.
Another challenge is the need to accommodate dynamic variability. Ideally, an operator should be able to initiate an exposure at any moment without having to manually adjust or reconsider preset parameters, even when patient anatomy, motion, or projection angle changes substantially from one frame to the next.
These challenges underscore the need for technologies that can support consistent image acquisition and manage exposure automatically from the very first frame, regardless of operator expertise.
Optimising Exposure Through Pulse Control
Philips fluoroscopy systems offer two technologies that optimise exposure by controlling each pulse of radiation.
Smart Pulse Regulation
Grid-Controlled Fluoroscopy
Smart Pulse Regulation
helps ensure that every pulse has the right kV, mA, and ms exposure settings depending on the density of the irradiated region.
Grid-Controlled Fluoroscopy
helps reduce dose by creating sharp pulses that only contain radiation that contributes to image quality.
Pulsed Fluoroscopy: A Leap Forward in Dose Management
In the 1980s, radiation dose control significantly improved with the introduction of pulsed fluoroscopy. Click through to learn more.
Rather than using continuous radiation, pulsed fluoroscopy delivers short pulses and acquires an image with each pulse, reducing radiation dose while maintaining image quality.
To keep radiation dose ALARA, the pulse rate should also be as low as possible while still supporting imaging that delivers sufficient diagnostic information.
Pulsed fluoroscopy devices have become the industry standard, with pulse rates as low as 0.5 pulse per second (one pulse every 2 seconds).
The required framerate depends on the procedure and anatomy, and might even change during the procedure, for instance when a contrast agent starts flowing.
Smart Pulse Regulation
Traditional Pulse Regulation: Adapting After Acquisition
Because of changes in anatomical density during a clinical procedure, pulsed fluoroscopy requires a means to dynamically regulate exposure settings: kV, mA, and ms. Traditional pulsing technology assesses a frame exposure only after it has been fully acquired, then updates settings for the next pulse accordingly.
Traditional pulse regulation control typically requires several frames to adapt to density changes in the region of interest. This might lead to missing critical information due to over- or under-exposed images, or stabilisation lag, an inability to keep up with the ongoing dynamic process as it occurs.
One way to mitigate stabilisation lag is to increase the pulse rate, but that results in additional radiation exposure. Systems that use traditional pulse regulation are limited to regulating either mA, ms, or combined mAs-ms, as they cannot regulate kV. Instead, kV is either based on presets or, in case of an exposure series, on a short fluoroscopy run conducted specifically to determine the kV setting.
Philips Smart Pulse Regulation:
Dynamic Adjustment of Exposure Settings
Smart Pulse Regulation is a Philips-exclusive technology that dynamically adjusts the kV, mA, and ms exposure settings in each acquired frame to accommodate the density of the irradiated region during a fluoroscopy run, based on a measurement in the automatic exposure control (AEC) fields during the first milliseconds of the pulse.
By adapting kV and mA within each individual pulse, Smart Pulse Regulation dramatically reduces, or eliminates completely, the risk of a possible under- or over-exposure of each individual frame.
Smart Pulse Regulation also adapts the pulse to make sure it stays within a pre-defined exposure time, and the exposure time only needs to be extended if the maximum kV/mA is not sufficient.
Video 1: An oesophagram study shows the automatic adaption of the kV and mAs while moving down the oesophagus.
Figure 1
Figure 1 illustrates how Smart Pulse Regulation adjusts the kV as required for different parts of the oesophagus. The system also automatically adapts the mA and ms throughout the procedure, as seen in the clinical example in Video 1.
Figures 2 and 3 further illustrate the concept of Smart Pulse Regulation.
Exposures and exposure series are usually acquired at higher exposure settings than those which are used for fluoroscopy viewing. Traditional pulse regulation requires a fluoroscopy run before exposure to determine the appropriate settings, adding both radiation dose and an extra workflow step.
Figure 3
With Smart Pulse Regulation, exposure settings are adapted to the changed density within the first millisecond of the pulse, where traditional pulse regulation requires several pulses to stabilise.
Figure 2
Smart Pulse Regulation regulates the kV within each individual pulse, choosing a value within the energy range of the tube. Smart Pulse Regulation also adjusts the mA, and in case of extremely dense anatomy, the ms can be adjusted, to deliver a higher dose through a longer pulse duration.
This fluoroscopy run is not required with Smart Pulse Regulation, because it automatically adjusts the kV within the exposure itself, starting from a standard value. This helps ensure that each exposure is right from the start, regardless of changes in density, and eliminates the need for the extra workflow step.
Smart Pulse Regulation in Action
The value of Smart Pulse Regulation is evident in clinical practice. For example, during oesophagrams, the exposure starts at the mouth (i.e., base of the skull), where a moderate kV may be sufficient, and passes through the neck, shoulder, chest, and upper abdominal areas, which require increasing higher kVs, ending at the stomach where a varying kV is needed (respectively lower, higher, lower, and again higher due to variations in anatomical makeup).
A second example of the clinical value of Smart Pulse Regulation is paediatric micturating cystourethrograms (MCUG). Radiation protection is of particular concern for paediatric fluoroscopy studies, because children are more radiosensitive than adults.
In MCUGs, ultra-low frame rates can be used to visualise the contrast agent while it sits idle in the bladder. The flow of the contrast agent only needs to be visualised at a higher temporal resolution when the patient starts micturating.
Smart Pulse Regulation allows a frame rate as low as 0.5 fps, which limits the amount of radiation that the patient is exposed to before micturating.
In addition, the CombiDiagnost R90 system used in this study is able to change the pulse rate within an exposure run for this purpose. There is no need to delay the procedure by stopping exposure, adjusting the pulse rate, and restarting exposure.
Image Quality and Radiation Exposure
While they seek to limit radiation exposure as much as possible, they also understand that high image quality is essential to confident diagnoses.
In both paediatric and adult exams, the interplay of dose and image quality is always top of mind among medical imaging professionals.
Grid-Controlled Fluoroscopy
Traditional Pulse Generation: Useless Radiation Creates Unnecessary Patient Dose
With traditional pulse generation, the high-voltage generator creates the X-ray pulses.
However, long power cables from generator to X-ray tube behave like big capacitors, strongly affecting the form of the electric signal they transport. Therefore, pulses are not precisely rectangular, but rounded, with rising edges (ramping) and falling tails (trailing). This results in low-energy X-rays, often called soft radiation (Figure 4A).
Figure 4A
Traditional pulse generation: Un-sharp, high, and long pulses, with ramping and trailing, creating extra dose for the patient through soft radiation.
Philips Grid-Controlled Fluoroscopy: Lower Dose Through Sharp Pulses
Grid-Controlled Fluoroscopy creates pulses directly inside the X-ray tube with Philips grid-switching technology. This technology, which produces sharp pulses without the rising edges and falling tails seen with traditional pulse generation, eliminates the unwanted soft radiation (Figure 4B).
Figure 4B
Grid-Controlled Fluoroscopy: Sharper, smaller, and shorter pulses without ramping or trailing of soft radiation, delivering only dose that contributes to the image.
In addition, Grid-Controlled Fluoroscopy is able to create smaller, shorter pulses with lower current but higher voltage. These optimised voltage control curves are tailored specifically to the needs of paediatric fluoroscopy, and result in a substantially lower dose rate.
For paediatric examinations, Philips Grid-Controlled Fluoroscopy enables a dose rate reduction up to 68% compared to traditional pulse generation, depending on patient type and clinical application.a,b
aDose rate determined according to IEC 60601-2-54, 203.5.2.4.5.102, System set up: detector format 43 x 43 cm (17 17"), patient type children, 0.1 mm Cu + 1 mm Al filter, reduced dose and pulsed slow fluoroscopy mode with 2 pulses/s, Phantom: 5 cm (2 in) PMMA.
bRelative difference of two reference air kerma rates between a system with Grid-Controlled Fluoroscopy and system with traditional pulse generation.
Learn More About Philips Fluoroscopy Solutions
Philips CombiDiagnost R90 and ProxiDiagnost N90 are fluoroscopy solutions that offer Smart Pulse Regulation and Grid-Controlled Fluoroscopy. For more on Smart Pulse Regulation and clinical image examples, see the recent Philips white paper.¹
Koninklijke Philips N.V. Fluoroscopy with smart pulse regulation. 2026. Available at: https://www.documents.philips.com/assets/20260302/4b2fd758c75e46a4992db401011a40aa.pdf. Last accessed: 18 September 2026.