Germany orders 20% reduction in DRLs for radiation dose

2016 08 30 09 29 44 134 Radiation Symbol Circle 400

Stating that more progress is needed in reducing patient exposure to radiation dose, German regulatory authorities on Tuesday announced a 20% reduction in diagnostic reference levels (DRLs) for radiation from medical imaging procedures. Some experts believe the move could require some German facilities to replace aging equipment in order to meet the new standards.

Dr. Maximilian Reiser. Image courtesy of the German Radiological Society.Dr. Maximilian Reiser. Image courtesy of the German Radiological Society.

Germany's Federal Office for Radiation Protection (BfS) unveiled the new DRLs in an announcement on 23 August. The BfS stated the reduction matches an overall 20% decrease in radiation dose that's occurred in the country over the past five years due to advancements in technology for both diagnostic and interventional equipment.

The German imaging community as a whole welcomed the move, and on average, the lower levels do not come as a surprise, according to Dr. Maximilian Reiser, professor of radiology and director of clinical radiology at Ludwig Maximilian University in Munich.

"The new DRLs may support radiologists in convincing their hospital management to replace outdated equipment when the new DRLs can't be realized," he told "A further improvement would be to take patient constitution into account and to define DRLs not only for certain body regions but for specific CT protocols."

Minimizing exposure

DRLs are designed to provide a metric that imaging facilities can use to ensure the radiation dose employed in their procedures matches optimal levels. DRLs are useful by helping imaging providers to identify situations where an exam could be carried out with a lower dose, and by helping radiology staff use x-rays efficiently and reduce patient exposure, the BfS statement said. Germany last reset its DRLs for imaging procedures in 2010, according to an article in

The agency noted Germany has been relatively successful in controlling radiation dose for individual imaging procedures compared with its European neighbors, but tends to use imaging more often, with the average German citizen receiving 1.4 exposures per person per year. The statement noted CT scans of adults increased by 130% in Germany between 1996 and 2012.

In addition to reducing DRLs by 20% for x-ray procedures, the BfS is reducing DRLs for some other procedures by as much as 50%. The agency also introduced DRLs for some imaging procedures such as CT and interventional studies that previously didn't have them, such as minimally invasive x-ray-monitored heart surgery like valve replacements, or surgery on large blood vessels like aneurysms.

"Lowering the reference values is an important step that will benefit patients," said BfS President Wolfram König in the announcement. "But further improvements are needed, and we can use improved procedures to limit radiation further without reducing the quality of the information they provide. We need to exploit opportunities to reduce exposure using new technology."

An appropriate tool

Reiser is convinced that overall, DRLs are an appropriate way to improve radiation protection of patients, and they allow radiologists to select adequate protocols and methods to perform imaging and interventional procedures.

"They represent the third quartile and a typical radiation dose applied to the average patient," he stated. "The reduction of the DRLs has been made possible by the paramount improvement of technology, which was achieved recently. In CT, iterative reconstruction and automated tube current modulation as well as automated tube voltage selection allow for minimizing patient dose."

But not everybody thinks enough is being done to reduce the hazards of radiation.

"The danger remains there, but you'll never hear a word about it in public," said Inge Schmitz-Feuerhake, PhD, professor of experiment physics at the University of Bremen and a longstanding critic of government policy, in the story. Schmitz-Feuerhake said she welcomed the news that overall levels for x-ray radiation were down, in particular because they are "the most potent current source of radiation for the German population," but she called on the government to do far more.

"So many people have developed cancer, and not a word is said about them. It's good that people are waking up, but things have to move faster if we really want to do justice to our civic duty to protect."

Reiser believes Schmitz-Feuerhake's comments are not justified, however, and that she overestimates the risk of radiation exposure and underestimates the benefits. The new levels are based on what's already being achieved at the 75th percentile of German facilities -- meaning that three-quarters of imaging providers are already below the new levels.

Dr. Fabian Bamberg.Dr. Fabian Bamberg.

"The new references levels are based on random sample examinations drawn from all x-ray machines and CT scanners (approximately the 75th percentile) and therefore represent current practice and developments in Germany quite adequately," noted Dr. Fabian Bamberg, vice chair and professor in the Department of Diagnostic and Interventional Radiology at the University of Tübingen, in an email to

Further optimization of scan protocols by radiologists is essential, and in the case of deviations, modifications of scan parameters or technical upgrades may be requested, and these are also monitored, he added.

Like Reiser, Bamberg is not surprised by the new DRLs because radiation protection has played a major role in clinical practice for years now, and a lot of technical development and research has been successfully invested in radiation dose reduction strategies.

"This started once early scientific observations on the increasing numbers of CT examinations, with an almost exponential increase in the associated radiation dose and risk of malignancies, were published in 2007," Bamberg pointed out. "Since then, technical advances, particularly in the field of CT, including low kV acquisitions, iterative reconstruction techniques, and high-pitch scanning protocols, have lowered the amount of exposure substantially."

Importance of dose management

German radiologists are curious not only about documenting radiation dose being delivered to patients, but also about managing dose, according to Dr. Gabriele Krombach, professor and chair of radiology at Giessen University Hospital.

Dr. Gabriele Krombach.Dr. Gabriele Krombach.

"If you look back at 1895, when Wilhelm Conrad Röntgen discovered x-rays, the dose required for a given image now has decreased by more than 500%! Technical advances have allowed this," she said.

Since DRLs were introduced in Germany on 18 June 2002, the aim of authorities has been to try to force all radiologists to work according to the current technical standards, and antiquated machines have been taken out of service by this method, she continued.

"Of course, this aim has to be balanced against forcing radiologists to buy expensive new equipment. This is why the 75% percentile has been chosen. On the other hand, this law is forcing the industry to work on means for lowering x-ray exposure," Krombach stated. "Technical advances allow for decreasing the reference values again. Radiologists are also proud that dose management plays such an important role in Germany."

The full English text of the BfS announcement is as follows:

Patients gain improved protection as BfS reduces x-ray dosage levels

BfS President Wolfram König.BfS President Wolfram König.

X-rays, CT scans, and minimally invasive interventions under radiological image guidance always expose patients to radiation, and diagnostic reference values are used to minimize this exposure. BfS has now significantly reduced these, by an average of 20% and, in some cases, up to 50%.

"Lowering the reference values is an important step that will benefit patients," said BfS President Wolfram König. "But further improvements are needed, and we can use improved procedures to limit radiation further without reducing the quality of the information they provide. We need to exploit opportunities to reduce exposure using new technology."

DRLs provide guidance on radiation exposure of patients, and medical specialists are urged to remain below these average limits when using x-rays:

  • By using the diagnostic reference values to identify situations where an examination or treatment could be carried out with a lower dose
  • By using the concept of DRLs to encourage staff to use x-rays efficiently and reduce patient exposure

The BfS updates the values regularly to take account of new knowledge, procedures, and technology.

Further opportunities for improvement

This year's downward revision of the values by the BfS is mainly due to equipment improvement: Progress in medical technology has enabled a reduction in diagnostic and interventional dosage requirements by an average of 20% in the past five years.

New reference values for examinations not previously covered

Apart from reducing the existing reference values, the BfS has introduced new ones for examinations not previously included. These include certain CT examinations and high-exposure interventions that are associated with particularly high radiation levels, for example complex, minimally invasive x-ray-monitored heart surgery (such as valve replacements), surgery on large blood vessels (for example in the case of aneurysms, life-threatening swellings of the vessel walls), or on the brain (for example after a stroke).

Biggest contribution to man-made radiation exposure

Diagnostic and interventional radiological applications make up by far the largest part of man-made radiation exposure. Germany uses relatively low average doses per examination compared with its European neighbors, but uses x-rays very frequently, at an average of 1.4 exposures per person per year. Higher-dose CT scans of adults increased by 130% between 1996 and 2012, though fortunately these and radiological interventions are rarely carried out on children.

The steady growth in high-dose applications is a strong incentive to continue making medical and technological improvements, and to find ways of achieving further dosage reductions or using alternative procedures such as ultrasound and MRI.

The updated reference values can be found here.

Editor's note: The translation of the BfS statement was by Syntacta Translation & Interpreting. Click here to read the original German version.

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