Safety of Computed Tomography in Patients With Cardiac Rhythm Management Devices

[Coronary computed tomography and cardiac devices : Diagnostic results or nothing but artifacts?]

Coronary computed tomography (CT) angiography has become a major cornerstone in the diagnostic workup of cardiologic patients, particularly for evaluation of the coronary arteries and preprocedural planning of interventions for structural heart disease. Despite the possible problems that intensive electromagnetic radiation (including X‑rays) might cause when directly impacting on implanted cardiac devices, cardiac CT is a safe diagnostic test and should not be withheld from patients with devices if properly indicated. Sufficient image quality is paramount for the evaluation; hence, special attention should be paid to a low heart rate (< 60 bpm) and sufficient compliance with breathing instructions. Furthermore, pacemaker or implantable cardioverter-defibrillator (ICD) leads may cause metal artifacts, especially around the lead tip. Their dense material causes beam hardening and streak artifacts which may result in reduced image quality and limited diagnostic assessability. The prevalence of such artifacts depends not only on lead material but also on lead positioning relative to the gantry plane. Metal artifacts are more frequent in patients with unipolar leads and shock coils, which can impair the assessment of coronary arteries, mainly of the right coronary artery (RCA). Artifacts caused by left ventricular (LV) leads of cardiac resynchronization therapy (CRT) systems tend to affect assessment of the left circumflex artery (LCX). By using dual energy CT and postprocessing algorithms, the impact of artifacts can be reduced and diagnostic image quality can be achieved in most cases. Unfortunately, the actual occurrence of such artifacts or the degree of impairment of image quality cannot be reliably predicted.

Current Clinical Practice in Patients With Cardiac Implantable Electronic Devices (CIED) Undergoing Radiotherapy (RT)

Patients with cardiac implantable electronic devices (CIED) undergoing radiotherapy (RT) are more common due to ageing of the population. With newer CIEDs implementing the complementary metal-oxide semiconductor (CMOS) technology which allows the miniaturisation of CIED, it is also more susceptible to RT. Effects of RT on CIED ranges from device interference, device operational/memory errors of permanent damage. These malfunctions can cause life threatening clinical effects. Cumulative dose is not the only component of RT that causes CIED malfunction, as neutron use and dose rate effect also affects CIEDs. The management of this patient cohort in clinical practice is inconsistent due to lack of a consistent guideline from manufacturers and physician specialty societies. Our review will focus on the current clinical practice and the recent updated guidelines of managing patients with CIED undergoing RT. We aim to simplify the evidence and provide a simple and easy to use guide based on the recent guidelines.

Current clinical practice in patients with cardiac implantable electronic devices undergoing radiotherapy: a literature review

Patients with cardiac implantable electronic devices (CIED) undergoing radiotherapy (RT) are more common due to the ageing of the population. With newer CIEDs' implementing the complementary metal-oxide semiconductor (CMOS) technology which allows the miniaturization of CIED, it is also more susceptible to RT. Effects of RT on CIED ranges from device interference, device operational/memory errors of permanent damage. These malfunctions can cause life-threatening clinical effects. Cumulative dose is not the only component of RT that causes CIED malfunction, as neutron use and dose rate effect also affects CIEDs. The management of this patient cohort in clinical practice is inconsistent due to the lack of a consistent guideline from manufacturers and physician specialty societies. Our review will focus on the current clinical practice and the recently updated guidelines of managing patients with CIED undergoing RT. We aim to simplify the evidence and provide a simple and easy to use guide based on the recent guidelines.

Multitask Learning for Estimating Multitype Cardiac Indices in MRI and CT Based on Adversarial Reverse Mapping

The estimation of multitype cardiac indices from cardiac magnetic resonance imaging (MRI) and computed tomography (CT) images attracts great attention because of its clinical potential for comprehensive function assessment. However, the most exiting model can only work in one imaging modality (MRI or CT) without transferable capability. In this article, we propose the multitask learning method with the reverse inferring for estimating multitype cardiac indices in MRI and CT. Different from the existing forward inferring methods, our method builds a reverse mapping network that maps the multitype cardiac indices to cardiac images. The task dependencies are then learned and shared to multitask learning networks using an adversarial training approach. Finally, we transfer the parameters learned from MRI to CT. A series of experiments were conducted in which we first optimized the performance of our framework via ten-fold cross-validation of over 2900 cardiac MRI images. Then, the fine-tuned network was run on an independent data set with 2360 cardiac CT images. The results of all the experiments conducted on the proposed adversarial reverse mapping show excellent performance in estimating multitype cardiac indices.

Initial testing of pegfilgrastim (Neulasta Onpro) on-body injector in multiple radiological imaging environments

Purpose

An increasing number of implantable or external devices can impact whether patients can receive radiological imaging examinations. This study examines and tests the Neulasta (pegfilgrastim) Onpro on‐body injector in multiple imaging environments.

Methods

The injector was analyzed for four imaging modalities with testing protocols and strategies developed for each modality. In x‐ray and computed tomography (CT), scans with much higher exposure than clinical protocols were performed with the device attached to an anthropomorphic phantom. The device was monitored until the completion of drug delivery. For magnetic resonance imaging (MRI), the device was assessed using a hand‐held magnet and underwent the magnetically induced displacement testing in a 1.5T clinical MRI scanner room. For ultrasound, magnetic field changes were measured around an ultrasound scanner system with three transducers.

Results

For x‐ray and CT no sign of device error was identified during or after the high radiation exposure scans. Drug delivery was completed at expected timing with expected volume. For MRI the device showed significant attractive force towards the hand‐held magnet and a 50‐degree deflection angle at 50 cm from the opening of the scanner bore. No further assessment from the gradient or radiofrequency field was deemed necessary. For ultrasound the maximum magnetic field change from baseline was measured to be +11.7 μT in comparison to +74.2 μT at 4 inches from a working microwave.

Conclusions

No device performance issue was identified under the extreme test conditions in x‐ray or CT. The device was found to be MR Unsafe. Magnetic field changes around an ultrasound system met the limitation set by manufacture. Patient ultrasound scanning is considered safe as long as the transducers do not inadvertently loosen the device.

Management of radiotherapy patients with implanted cardiac pacemakers and defibrillators: A Report of the AAPM TG-203†

Managing radiotherapy patients with implanted cardiac devices (implantable cardiac pacemakers and implantable cardioverter-defibrillators) has been a great practical and procedural challenge in radiation oncology practice. Since the publication of the AAPM TG-34 in 1994, large bodies of literature and case reports have been published about different kinds of radiation effects on modern technology implantable cardiac devices and patient management before, during, and after radiotherapy. This task group report provides the framework that analyzes the potential failure modes of these devices and lays out the methodology for patient management in a comprehensive and concise way, in every step of the entire radiotherapy process.

Overranging and overbeaming measurement in area detector computed tomography: A method for simultaneous measurement in volume helical acquisition

Purpose

We propose a novel method to assess overbeaming and overranging, as well as the effect of reducing longitudinal exposure range, by using a dynamic z‐collimator in area detector computed tomography.

Methods and materials

A 500‐mm diameter cylindrical imaging plate was exposed by helical scanning in a dark room. The beam collimation of the helical acquisitions was set at 32 and 80 mm. Overbeaming and overranging with the dynamic z‐collimator were measured.

Results

The actual beam widths were approximately 39 and 88 mm at 32 and 80 mm collimation, respectively, and were relatively reduced owing to increased beam collimation. Overranging was 27.0 and 48.2 mm with a pitch of 0.83 and 1.49 at 32 mm collimation and 72.5 and 83.1 mm with a pitch of 0.87 and 0.99 at 80 mm collimation. The dynamic z‐collimator relatively reduced the overranging by 17.3% and 17.1% for the 32 and 80 mm collimation, respectively.

Conclusion

We devised a method to simultaneously measure overbeaming and overranging with only one helical acquisition. Although the dynamic z‐collimator reduced the overranging by approximately 17%, wider collimation widths and higher pitch settings would increase the exposure dose outside the scan range.

Coronary computed tomography angiography and endocardial leads - Image quality in 320-row CT using iterative reconstruction

PURPOSE

To investigate whether the presence of endocardial leads has an impact on image quality in coronary computed tomography angiography (CCTA), when current technique is employed using a 320-row computed tomography and iterative reconstruction.

MATERIALS AND METHODS

CCTA was performed in 1641 patients, from these we identified 51 patients (study group) with endocardial leads and 51 matched partners (control group) without endocardial leads. Noise was determined in the ascending aorta and the left ventricle; signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were determined in the left and right coronary artery. Subjective image quality was rated separately for the 15 segments of the coronary arteries by 2 radiologists.

RESULTS

Current CCTA technique still shows slight impairment of objective image quality in patients with endocardial leads with inferior SNR in the aorta (median 15.04 versus 16.6; p = 0.004) and inferior SNR in the left/right coronary artery (median 15.3/13.81 versus 16.1/15.41; p = 0.013/0.002). CNR of the left/right coronary artery was also inferior (median 17.4/16.46 versus 19.26/19.24; p = 0.002/<0.001). The subjective image quality was rated significantly inferior only in segment 8 (p = 0.001) compared to the control group. Artifacts by ventricular leads were found in 65% of the patients in segment 8 with non-diagnostic rating in 9 cases (18%). Atrial leads resulted in artifacts predominantly in segment 1 (45%) with non-diagnostic rating in only 2 cases (4%).

CONCLUSION

CCTA is feasible with slight restrictions for patients in the presence of implanted cardiac devices when current technique is used.

Management of patients with cardiac implantable electronic devices (CIED) undergoing radiotherapy: A consensus document from Associazione Italiana Aritmologia e Cardiostimolazione (AIAC), Associazione Italiana Radioterapia Oncologica (AIRO), Associazione Italiana Fisica Medica (AIFM)

The management of patients with a cardiac implanted electronic device (CIED) receiving radiotherapy (RT) is challenging and requires a structured multidisciplinary approach. A consensus document is presented as a result of a multidisciplinary working group involving cardiac electrophysiologists, radiation oncologists and physicists in order to stratify the risk of patients with CIED requiring RT and approaching RT sessions appropriately. When high radiation doses and beam energy higher than 6MV are used, CIED malfunctions can occur during treatment. In our document, we reviewed the different types of RT and CIED behavior in the presence of ionizing radiations and electromagnetic interferences, from the cardiologist's, radiation oncologist's and medical physicist's point of view. We also reviewed in vitro and in vivo literature data and other national published guidelines on this issue so far. On the basis of literature data and consensus of experts, a detailed approach based on risk stratification and appropriate management of RT patients with CIEDs is suggested, with important implications for clinical practice.