Radiation Dose in Interventional Oncology: An Interview With Claus Schaffrath, MD

Claus Schaffrath, MD, is a physician and electrical engineer who has more than 15 years of experience in various fields of image-guided therapy, both in the hospital and medical device industries. Over the past several years he has worked with clinical key opinion leaders, industry partners, and a multidisciplinary team from the Image Guided Therapy Systems Business Innovation Unit at Philips, which focuses on building the company’s product portfolio in interventional oncology. 

IO360: Could you give us some background on the imaging modalities that are being used in interventional oncology (devices used as well as when they are used)? 

Schaffrath: The instruments in interventional oncology for a locoregional minimally invasively treatment to either a primary tumor or to a metastasis of tumors from different origins have grown and changed over the past years. What has remained as a necessary base to enable such minimally invasive treatment, however, is the need to apply adequate live image guidance – which helps to see and reach the local cancer for minimally invasive treatment. 

In interventional oncology, two main lines of treatment are currently followed to maximize the effect on the tumor tissue and minimize damage to healthy tissue as much as possible: 

1. Ablation therapy, which induces percutaneous energy to the tumor target with needles or antennae (radiofrequency, microwave, or cryoablation) with the intent to thermally destroy the malignant cells; and 
2. Embolization therapy, which is an endovascular (transarterial) super-selective approach to the tumor via its feeding vessels, which then are sealed to create cell apoptosis in the tumor tissue. This sealing can also be combined with the application of a drug (transarterial chemoembolization [TACE]) or a radioembolic substance (transarterial radioembolization [TARE] or selective internal radioembolization therapy [SIRT]). 

To see, reach, and treat a tumor with ablation therapy, computed tomography (CT), ultrasound, or live image guidance with fluoroscopy in 2D and 3D (cone-beam CT [CBCT]) in an interventional room can be used. Tumor embolization procedures and live image guidance via the vasculature is mostly performed in an interventional room under 2D and 3D fluoroscopy (CBCT). 

IO360: What dosages of radiation are typically applied when these imaging/IO procedures are being performed? 

Schaffrath: The radiation dose during tumor ablation procedures is applied to mainly see the tumor and the treatment devices. The overall patient and consecutive staff dose depends on multiple factors, such as the choice of modality, the location and size of the tumor, and the ablation method used. Ultrasound-based ablation uses no radiation, but it has its limitations because ultrasound provides in some anatomies only a limited visualization, which can be problematic when deeper-seated lesions cannot be displayed well for treatment. 

For needle procedures, which form the base for getting to the target location in ablation therapy in CT vs CBCT, several studies show that the effective radiation dose administered to the patient in the interventional room with CBCT is lower than with a standard CT scanner.^1,2 However, recently, novel dose-saving algorithms have been applied in CT, which may also have significantly lowered the applied radiation dose for CT-based ablations. In terms of the treatment efficiency, shorter treatment times with similar outcomes have been noted for CBCT compared to conventional CT tumor ablations.³ 

The main modality for tumor embolization therapy in the interventional room is the angiography/fluoroscopy system, which is capable of performing CBCT. The main radiation dose for these procedures is based on the fluoroscopy and digital subtraction angiography runs. Only a fraction of the procedural dose during these interventions is usually attributed to the 3D imaging with CBCT. In general, the benefit applied to the patient with the right indication for minimally invasive oncologic treatment is considered to significantly outweigh the radiation risks, which come via the diagnostic/interventional application of the chosen modalities. 

IO360: Has the amount of radiation applied changed over time? 

Schaffrath: In general, radiation dose applied in interventional radiology to the patient and staff with a fixed system ceiling or floor mounted can be better controlled than with a mobile c-arm device. Also, the advent of flat-panel detectors with a larger field of view compared to equally sized image intensifiers and the promotion of the ALARA principle (as low as reasonably achievable) has contributed to a significant decline in dose in interventional systems over the past 10 years. A decade ago, Philips introduced procedure protocols for its fluoroscopy devices, which allow management of system settings for specific procedures or anatomic regions. Each of these protocols comes as a factory setting, and these were established in clinical practice along the ALARA principle and can be fine tuned at the hospital to the individual preferences of contrast and adequate image quality at the lowest possible dose. 

IO360: How do imaging and the related radiation dose differ for interventional oncology procedures compared to other interventional procedures? 

Schaffrath: For a wide range of procedures in interventional radiology, patient dose, fluoroscopy time, and number of runs have been measured to establish patient dose reference levels. For diagnostic procedures, fairly circumscriptive reference levels with limited variance could be shown; the procedural complexity, patient size, and experience of the interventionalist could be found in the literature as the biggest contributing factors of the applied patient radiation dose and consecutively staff exposure in interventional radiology.⁴ Procedures in interventional oncology are no exception to this rule. For TACE procedures, for instance, the reported dose levels are in the range of reported dose reference levels for general abdominal interventional procedures.^4,5 

IO360: How does radiation affect interventional clinicians? 

Schaffrath: The best protection against radiation dose is usually to use the ALARA principle and deliver a radiation dose to the patient that is as low as reasonably acceptable to reach an adequate image quality, and keep an adequate shielding and distance during the imaging acquisition itself. During the live image guidance with DSA and fluoroscopy runs, however, the interventionalist and staff operating the fluoroscopy system often are in close proximity to the radiation beam, and being exposed to scatter dose in those cases is difficult to prevent. 

IO360: How can clinicians better protect themselves from exposure? 

Schaffrath: The most important part of radiation protection is behavior. To apply the ALARA principle, position patient, interventionalist, and staff adequately during the procedure, and keep an adequate radiation protection with lead shielding and glasses. 

IO360: What are some new ways radiation dose is being limited or controlled for both patients and clinicians? 

Schaffrath: Two new approaches will help to significantly manage radiation exposure for patient and staff as we move forward. One is ClarityIQ, a novel dose-management technology, which aims at providing an equivalent system procedural performance, albeit at a low patient dose. Its low-dose radiation management in clinical settings has been demonstrated now for a variety of procedures, and as far as interventional oncology goes, peer-reviewed data for TACE procedures look very promising.^5,6 Additionally, innovative dose-management systems, such as Philips’ DoseAware, help to monitor, track, and provide instant feedback to increase the awareness on the current individual dose exposure during the interventional procedure, and thereby trigger and facilitate an immediate correction toward the dose level being received;⁷ however, DoseAware is not a replacement for the thermoluminescent dosimeter as a legal dose meter. 

IO360: Will there be a time when radiation is not necessary for interventional procedures? How might this be accomplished? 

Schaffrath: For all interventional procedures today based on fluoroscopy, the risk of applying radiation needs to be balanced against the procedural risk of inadequate image quality. Though radiation-free imaging, such as ultrasound or MRI, have been introduced in the interventional room before, it is hard to see how they might entirely replace fluoroscopy in the near or foreseeable future. 

This means effectively that the current trend to live up to the ALARA principle with novel technology to reduce patient and scatter dose, such as AlluraClarity, and provide individual dose awareness to all present staff during an interventional procedure via real-time monitoring, such as DoseAware, will remain critical for further shaping the safety and effectiveness profile in interventional oncology. 

Editor’s note: This article reflects the experience and opinion of Dr. Schaffrath, not Philips Healthcare. Dr. Schaffrath reports employment with Philips Healthcare.

Suggested citation: Ford J. Radiation dose in interventional oncology: an interview with Claus Schaffrath, MD. Intervent Oncol 360. 2016;4(1):E10-E13.

References 

1. Strocchi S, Colli V, Conte L. Multidetector CT fluoroscopy and cone-beam CT-guided percutaneous transthoracic biopsy: comparison based on patient doses. Radiat Prot Dosimetry. 2012;151(1):162-165.
2. Braak SJ, van Strijen MJ, van Es HW, Nievelstein RA, van Heesewijk JP. Effective dose during needle interventions: CBCT guidance compared to conventional CT guidance. J Vasc Interv Radiol. 2011;22(4):455-461. 
3. Cazzato RL, Battistuzzi JB, Catena V, et al. Cone-beam computed tomography (CBCT) versus CT in lung ablation procedure: which is faster? Cardiovasc Intervent Radiol. 2015;38(5):1231-1236. 
4. Vano E, Järvinen H, Kosunen A, et al. Patient dose in interventional radiology: a European survey. Radiat Prot Dosimetry. 2008;129(1-3):39-45. 
5. Wen X, Jiang X, Li R, Zhang J, Yang P, Shen B. Novel x-ray imaging technology allows substantial patient radiation reduction without image quality impairment in repetitive transarterial chemoembolization for hepatocellular carcinoma. Acad Radiol. 2015;22(11):1361-1367. 
6. Schernthaner RE, Duran R, Chapiro J, Wang Z, Geschwind JF, Lin M. A new angiographic imaging platform reduces radiation exposure for patients with liver cancer treated with transarterial chemoembolization. Eur Radiol. 2015;25(11):3255-3262. 
7. Müller MC, Welle K, Strauss A, et al. Real-time dosimetry reduces radiation exposure of orthopaedic surgeons. Orthop Traumatol Surg Res. 2014;100(8):947-951.