Coronary CT angiography in patients with implanted cardiac devices: initial experience with the metal artefact reduction technique

Multimodality imaging in patients with implantable loop recorders: Tips and tricks

An implantable loop recorder (ILR) is a leadless rectangular device used for prolonged electrocardiographic monitoring for up to 3 years. This miniaturized device, inserted subcutaneously, allows clinicians to investigate possible cardiac rhythm disturbances in patients suffering from recurrent unexplained syncope. As the age of the population increases rapidly and the number of ILR patients amplifies, the clinical significance of ILRs is undeniable. Although radioopaque and easily seen on plain chest radiographs and other imaging modalities, ILRs may represent a challenge for clinicians and radiologists to recognize their classic appearance and differentiate them from numerous other cardiac devices. This article aims to summarize current literature on ILRs, their basic function, types, and indications for implantation, but most of all, it aims to familiarize clinicians and radiologists with common imaging features of these devices, safety issues, and artifact-reducing methods. Specifically, this review discusses the typical appearance of ILRs on major diagnostic imaging modalities, including chest X-ray, mammography, ultrasonography, computed tomography, and magnetic resonance imaging (MRI). Furthermore, optimization strategies to mitigate image artifacts and safety issues regarding MRI are discussed.

Advances in metal artifact reduction in CT images: A review of traditional and novel metal artifact reduction techniques

Metal artifacts degrade CT image quality, hampering clinical assessment. Numerous metal artifact reduction methods are available to improve the image quality of CT images with metal implants. In this review, an overview of traditional methods is provided including the modification of acquisition and reconstruction parameters, projection-based metal artifact reduction techniques (MAR), dual energy CT (DECT) and the combination of these techniques. Furthermore, the additional value and challenges of novel metal artifact reduction techniques that have been introduced over the past years are discussed such as photon counting CT (PCCT) and deep learning based metal artifact reduction techniques.

[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.

A propensity score-matched comparison between Mako robotic arm-assisted system and conventional technique in total hip arthroplasty for patients with osteoarthritis secondary to developmental dysplasia of the hip

BACKGROUND

The clinical effectiveness of robotic arm-assisted systems remains unclear for total hip arthroplasty (THA) in patients suffering from osteoarthritis secondary to developmental dysplasia of the hip (DDH).

METHODS

Patients with DDH who underwent primary THA were included in this study. We conducted a propensity score-matched comparison between THAs using a robotic arm-assisted system (Mako group) versus those using the manual procedure (manual group) to compare the absolute differences in cup placement angles measured using postoperative computed tomography and those planned preoperatively.

RESULTS

A total of 217 patients with osteoarthritis due to DDH met the inclusion criteria. Eighty-four patients were matched as the Mako group and 84 as the manual group. The differences were smaller in the Mako group than the manual group in terms of both inclination and anteversion angles (1.1 ± 1.0 versus 4.2 ± 3.1, respectively; 95% CI, 2.4 to 3.8; p < 0.0001, and 1.2 ± 1.1 versus 5.8 ± 4.0, respectively; 95% CI, 3.7 to 5.5; p < 0.0001).

CONCLUSIONS

The robotic arm-assisted system may provide more accurate cup placement in THA for DDH.

Reduction of CT artifacts from cardiac implantable electronic devices using a combination of virtual monoenergetic images and post-processing algorithms

OBJECTIVES

To evaluate the reduction of artifacts from cardiac implantable electronic devices (CIEDs) by virtual monoenergetic images (VMI), metal artifact reduction (MAR) algorithms, and their combination (VMI_MAR) derived from spectral detector CT (SDCT) of the chest compared to conventional CT images (CI).

METHODS

In this retrospective study, we included 34 patients (mean age 74.6 ± 8.6 years), who underwent a SDCT of the chest and had a CIED in place. CI, MAR, VMI, and VMI_MAR (10 keV increment, range: 100-200 keV) were reconstructed. Mean and standard deviation of attenuation (HU) among hypo- and hyperdense artifacts adjacent to CIED generator and leads were determined using ROIs. Two radiologists qualitatively evaluated artifact reduction and diagnostic assessment of adjacent tissue.

RESULTS

Compared to CI, MAR and VMI_MAR ≥ 100 keV significantly increased attenuation in hypodense and significantly decreased attenuation in hyperdense artifacts at CIED generator and leads (p < 0.05). VMI ≥ 100 keV alone only significantly decreased hyperdense artifacts at the generator (p < 0.05). Qualitatively, VMI ≥ 100 keV, MAR, and VMI_MAR ≥ 100 keV provided significant reduction of hyper- and hypodense artifacts resulting from the generator and improved diagnostic assessment of surrounding structures (p < 0.05). Diagnostic assessment of structures adjoining to the leads was only improved by MAR and VMI_MAR 100 keV (p < 0.05), whereas keV values ≥ 140 with and without MAR significantly worsened diagnostic assessment (p < 0.05).

CONCLUSIONS

The combination of VMI and MAR as well as MAR as a standalone approach provides effective reduction of artifacts from CIEDs. Still, higher keV values should be applied with caution due to a loss of soft tissue and vessel contrast along the leads.

KEY POINTS

• The combination of VMI and MAR as well as MAR as a standalone approach enables effective reduction of artifacts from CIEDs. • Higher keV values of both VMI and VMI_MAR at CIED leads should be applied with caution since diagnostic assessment can be hampered by a loss of soft tissue and vessel contrast. • Recommended keV values for CIED generators are between 140 and 200 keV and for leads around 100 keV.

Assessment of cardiac implantable electric device lead perforation using a metal artifact reduction algorithm in cardiac computed tomography

PURPOSE

CT is considered the non-invasive gold standard for evaluating cardiac implantable electronic devices (CIEDs) lead perforation, but metal artifacts caused by the lead tip affect the image quality and make a definitive diagnosis challenging. We compared the performances of the metal artifact reduction (MAR) algorithm and the conventional algorithm for identification of the right ventricular (RV) lead tip position in cardiac CT studies of patients with CIEDs.

METHOD

Forty-seven consecutive patients (26 men; age 70.3 ± 15.4 years) with CIEDs underwent cardiac CT. Using the conventional and MAR algorithm, two image reconstructions were performed for each scan. We calculated the artifact index (AI) to assess the quantitative capability of the MAR algorithm for artifact reduction and visually assessed the RV lead tip position on both images as follows: non-perforation, perforation, and equivocal.

RESULTS

The mean AIs were significantly lower with the MAR algorithm than with the conventional algorithm (96.7 ± 40.1 HU vs. 284.6 ± 134.1 HU, P < 0.001). Thirteen (27.7 %) patients were diagnosed as equivocal using the conventional algorithm but were diagnosed with perforation (2 patients) and non-perforation (11 patients) using the MAR algorithm (equivocal rate: 27.7 % vs. 0%, P < 0.001). Using the MAR algorithm, all cases were diagnosed with perforation (6 patients, 12.8 %) or non-perforation (41 patients, 87.2 %).

CONCLUSIONS

The MAR algorithm effectively reduced metal artifacts and allowed us to diagnose the presence or absence of perforation in all cases, whereas definitive diagnosis was difficult with the use of conventional algorithm in 27.7 % of cases.

The effect of the reconstruction algorithm for the pulmonary nodule detection under the metal artifact caused by a pacemaker

The aim was to compare the effects of metal artifacts from a pacemaker on pulmonary nodule detection among computed tomography (CT) images reconstructed using filtered back projection (FBP), single-energy metal artifact reduction (SEMAR), and forward-projected model-based iterative reconstruction solution (FIRST).Nine simulated nodules were placed inside a chest phantom with a pacemaker. CT images reconstructed using FBP, SEMAR, and FIRST were acquired at low and standard dose, and were evaluated by 2 independent radiologists.FIRST demonstrated the most significantly improved metal artifact and nodule detection on low dose CT (P < .0032), except at 10 mA and 5-mm thickness. At standard-dose CT, SEMAR showed the most significant metal artifact reduction (P < .00001). In terms of nodule detection, no significant differences were observed between FIRST and SEMAR (P = .161).With a pacemaker present, FIRST showed the best nodule detection ability at low-dose CT and SEMAR is comparable to FIRST at standard dose CT.

Clinical Dilemma - Cardiac Memory vs Myocardial Ischemia

Cardiac memory (CM) is a commonly unrecognized entity in which electrocardiograph (EKG) changes demonstrate T wave inversions (TWI) that appear consistent with ischemia. Inability to recognize and distinguish CM from actual ischemia can be a burden for both patients and hospitals, leading to unnecessary hospital admission, cardiac testing, and cardiac catheterization. Simple EKG analysis and meticulous interpretation of T-wave axis and morphology can help differentiate between the two. We present a case with such a dilemma, and an overview literature and physiology behind this entity.

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.

Utility of second-generation single-energy metal artifact reduction in helical lung computed tomography for patients with pulmonary arteriovenous malformation after coil embolization

PURPOSE

The quality of images acquired using single-energy metal artifact reduction (SEMAR) on helical lung computed tomography (CT) in patients with pulmonary arteriovenous malformation (PAVM) after coil embolization was retrospectively evaluated.

MATERIALS AND METHODS

CT images were reconstructed with and without SEMAR. Twenty-seven lesions [20 patients (2 males, 18 females), mean age 61.2 ± 11.0 years; number of embolization coils, 9.8 ± 5.0] on contrast-enhanced CT and 18 lesions of non-enhanced lung CT concurrently performed were evaluated. Regions of interest were positioned around the coils and mean standard deviation value was compared as noise index. Two radiologists visually evaluated metallic coil artifacts using a four-point scale: 4 = minimal; 3 = mild; 2 = strong; 1 = extensive.

RESULTS

Noise index was significantly improved with SEMAR versus without SEMAR (median [interquartile range]; 194.4 [161.6-211.9] Hounsfield units [HU] vs. 243.9 [220.4-286.0] HU; p < 0.001). Visual score was significantly improved with SEMAR versus without SEMAR (Reader 1, 3 [3] vs.1 [1]; Reader 2, 3 [3] vs.1 [1]; p < 0.001). Significant differences were similarly demonstrated on lung CT (p < 0.001).

CONCLUSION

SEMAR provided clear chest CT images in patients who underwent PAVM coil embolization.

Intracardiac foreign body resulting from a transmediastinal gunshot mimics an extracardiac foreign body: An image presentation

A transmediastinal gunshot wound (TMGW) is one of the most severe traumatic injuries, with a high mortality rate. Prompt diagnosis and emergency surgical intervention with or without cardiopulmonary bypass are usually required to save lives. We report a particular case of TMGW in which the computed tomography imaging findings indicated an extracardiac foreign body. However, intraoperative findings revealed an intracardiac foreign body, and urgent cardiopulmonary bypass was performed to remove the foreign body. We suggest that cardiopulmonary bypass should be on standby during an exploratory sternotomy for TMGW, when the trajectory of the bullet hints at a cardiac-penetrating injury according to imaging studies and the location of the bullet remains unaffected by the patient's postural changes.