CT metal artifacts in patients with total hip replacements: for artifact reduction monoenergetic reconstructions and post-processing algorithms are both efficient but not similar

Laukamp, Kai Roman; Lennartz, Simon; Neuhaus, Victor-Frederic; Hokamp, Nils Große; Rau, Robert; Blanc, Markus Le; Abdullayev, Nuran; Mpotsaris, Anastasios; Maintz, David; Borggrefe, Jan

doi:10.1007/s00330-018-5414-2

Cited by 50 publications

(58 citation statements)

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“…In line with our results, recent studies reported that combination of VMI and MAR proved to be most effective compared to each method on its own for artifacts from different devices 15,16,22 . A recent phantom study performed with a dual-source dual-energy CT scanner revealed that artifacts caused by coils and clips could also be most effectively reduced using the combination of virtual monoenergetic imaging and dedicated metal artifact reduction algorithms 23 .…”

Section: Discussionsupporting

confidence: 92%

“…For several implants either VMI and MAR as standalone approaches have been successfully used to reduce artifacts, e.g. total hip replacements, spinal fixation hardware, contrast media, and dental implants 12,13,[22][23][24]27,28 . This aspect is highly relevant as combination of both approaches is only available in dual-energy CT systems which allow for row data-based reconstruction of virtual monoenergetic images (VMI), but clinically used are mainly conventional single-energy CT systems, thereby MAR as a standalone post processing approach has the advantage of a higher availability also in conventional CT systems 12,13 .…”

Section: Discussionmentioning

confidence: 99%

“…Mean optimal keV values for diagnostic assessment were significantly lower in combination of VMI with MAR (~170 keV) compared to VMI (~180 keV) alone. Due to their physical properties higher keV VMI reduce brain tissue contrast 26,29 , the combination of VMI and MAR enables to receive optimal artifact reduction at lower keV values, where loss of tissue contrast is lower 14,22,26,29 . To achieve optimal results, we therefore recommend using the combination VMI and MAR between 140 to 200 keV.…”

Section: Discussionmentioning

confidence: 99%

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Virtual monoenergetic images and post-processing algorithms effectively reduce CT artifacts from intracranial aneurysm treatment

Zopfs

Lennartz

Pennig

et al. 2020

Sci Rep

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To evaluate artifact reduction by virtual monoenergetic images (VMI) and metal artifact reduction algorithms (MAR) as well as the combination of both approaches (VMI MAR) compared to conventional CT images (CI) as standard of reference. In this retrospective study, 35 patients were included who underwent spectral-detector CT (SDCT) with additional MAR-reconstructions due to artifacts from coils or clips. CI, VMI, MAR and VMI MAR (range: 100-200 keV, 10 keV-increment) were reconstructed. Region-of-interest based objective analysis was performed by assessing mean and standard deviation of attenuation (HU) in hypo-and hyperdense artifacts from coils and clips. Visually, extent of artifact reduction and diagnostic assessment were rated. Compared to CI, VMI ≥ 100 keV, MAR and VMI MAR between 100-200 keV increased attenuation in hypoattenuating artifacts (CI/VMI 200keV /MAR/VMI MAR200keV , HU: −77.6 ± 81.1/−65.1 ± 103.2/−36.9 ± 27.7/−21.1 ± 26.7) and decreased attenuation in hyperattenuating artifacts (HU: 47.4 ± 32.3/42.1 ± 50.2/29.5 ± 18.9/20.8 ± 25.8). However, differences were only significant for MAR in hypodense and VMI MAR in hypo-and hyperdense artifacts (p < 0.05). Visually, hypo-and hyperdense artifacts were significantly reduced compared to CI by VMI ≥140/100keV , MAR and VMI MAR≥100keV. Diagnostic assessment of surrounding brain tissue was significantly improved in VMI ≥100keV , MAR and VMI MAR≥100keV. The combination of VMI and MAR facilitates a significant reduction of artifacts adjacent to intracranial coils and clips. Hence, if available, these techniques should be combined for optimal reduction of artifacts following intracranial aneurysm treatment. Intracranial aneurysms are a common vascular disorder with a prevalence of approximately 4%, which can be expected to increase due to an ageing population 1,2. In case of rupture they are associated with a mortality risk of up to 50% [1]. Ruptured as well as unruptured aneurysms are commonly treated with surgical clipping or endovascular coiling 3,4. Postoperative imaging is pivotal to detect postoperative complications and ensure therapy success for which computed tomography (CT) is frequently applied besides digital subtraction angiography and magnetic resonance imaging 5. However, evaluation of brain parenchyma adjacent to clips and coils is often impaired by metal artifacts. Artifacts commonly appear as hypo-and hyperdense areas surrounding the metal material. These kind of artifacts result from a combination of beam-hardening caused by absorption of low energetic photons 6,7 , photon starvation resulting from complete absorption of all photons 7,8 , and scatter artifacts that can occur due to greater attenuation differences, e.g. soft tissue and dense metal material 9. Combined, these effects can result in strong interferences that may impair depiction and interpretation of surrounding brain tissue. Therefore, evaluation of post-interventional complications, such as tissue damage, haemorrhage, infarction and oedema may be limited 10. Further, any futur...

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Virtual monoenergetic images and post-processing algorithms effectively reduce CT artifacts from intracranial aneurysm treatment

Zopfs

Lennartz

Pennig

et al. 2020

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“…In this cohort we were able to show that VNC of TNC can reliably reduce increased liver density due to amiodarone deposition. As frequently applied in comparable studies, we used ROI-based measurements of mean attenuation [22][23][24][25]35 . Still, a volumetric assessment of attenuation covering an entire organ might be less susceptible for any measuring bias.…”

Section: Resultsmentioning

confidence: 99%

“…There is only one detector-based system available, referred to as spectral-detector CT (SDCT). This scanner uses one X-ray source and a detector with two layers; photons with higher energies are detected in the lower layer, while lower energetic photons are detected in the upper layer 21,22 . Material decomposition can be used for the identification of iodine and thereby the creation of virtual non-contrast images (VNC) that offer a way to eliminate the iodine-associated attenuation from images.…”

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confidence: 99%

Iodine accumulation of the liver in patients treated with amiodarone can be unmasked using material decomposition from multiphase spectral-detector CT

Laukamp

Lennartz

Hashmi

et al. 2020

Sci Rep

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Amiodarone accumulates in the liver, where it increases x-ray attenuation due to its iodine content. We evaluated liver attenuation in patients treated and not treated with amiodarone using true-noncontrast (TNC) and virtual-non-contrast (VNC) images acquired with spectral-detector-CT (SDCT). 142 patients, of which 21 have been treated with amiodarone, receiving SDCT-examinations (unenhancedchest CT [TNC], CT-angiography of chest and abdomen [CTA-Chest, CTA-Abdomen]) were included. TNC, CTA-Chest, CTA-Abdomen, and corresponding VNC-images (VNC-Chest, VNC-Abdomen) were reconstructed. Liver-attenuation-index (LAI) was calculated as difference between liver-and spleenattenuation. Liver-attenuation and LAI derived from TNC-images of patients receiving amiodarone were higher. Contrary to TNC, liver-attenuation and LAI were not higher in amiodarone patients in VNC-Chest and in VNC-Abdomen. To verify these initial results, a phantom scan was performed and an additional patient cohort included, both confirming that VNC is viable of accurately subtracting iodine of hepatic amiodarone-deposits. This might help to monitor liver-attenuation more accurately and thereby detect liver steatosis as a sign of liver damage earlier as well as to verify amiodarone accumulation in the liver.Amiodarone is an antiarrhythmic drug that has shown its effectiveness for several decades to treat various forms of tachyarrhythmia 1,2 . However, oral absorption and bioavailability are poor and greatly variable. Onset of therapeutic effects using oral application range between 2-21 days and after long-term treatment plasma half-life is around 100 days. Because of its lipophilic properties, iodine-containing amiodarone accumulates, among others, in hepatocytes. Here, it inhibits the enzyme phospholipase which subsequentially stops the removal of lysosomal phospholipids. Consequently, amiodarone forms a nondigestible complex with the phospholipids, resulting in phospholipidosis and extended amiodarone accumulation. Amiodarone concentrations in the liver can be up to 500-times higher than in the blood serum and release from hepatocytes is slow after treatment discontinuation 1-6 . Earlier studies found that this condition can lead to steatohepatitis and liver cirrhosis 1,7,8 .Iodinated contrast media is broadly applied in CT imaging. Due to its high physical density and k-edge effects of iodine, it increases attenuation and image contrast that improves depiction of anatomical structures (e.g. organ parenchyma and vessels) 9,10 . For intravascular injections in CT imaging almost exclusively non-ionic low-or iso-osmotic iodinated contrast media is applied. Molecular structures between agents are similar, a commonly applied agent is for example Ioversol (C 18 H 24 I 3 N 3 O 9 , molecular mass of 807.1 g/mol). It contains three iodine atoms that constitute almost 50% of its molecular mass 9-12 . Amiodarone shows several similarities to iodinated contrast media regarding the molecular structure. It is a di-iodinated benzofuran derivate, as a drug it is u...

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Preclinical validation of a novel deep learning‐based metal artifact correction algorithm for orthopedic CT imaging

Guo,

Zou,

Zhang

et al. 2023

J Applied Clin Med Phys

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PurposeTo validate a novel deep learning‐based metal artifact correction (MAC) algorithm for CT, namely, AI‐MAC, in preclinical setting with comparison to conventional MAC and virtual monochromatic imaging (VMI) technique.Materials and methodsAn experimental phantom was designed by consecutively inserting two sets of pedicle screws (size Φ 6.5 × 30‐mm and Φ 7.5 × 40‐mm) into a vertebral specimen to simulate the clinical scenario of metal implantation. The resulting MAC, VMI, and AI‐MAC images were compared with respect to the metal‐free reference image by subjective scoring, as well as by CT attenuation, image noise, signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR), and correction accuracy via adaptive segmentation of the paraspinal muscle and vertebral body.ResultsThe AI‐MAC and VMI images showed significantly higher subjective scores than the MAC image (all p < 0.05). The SNRs and CNRs on the AI‐MAC image were comparable to the reference (all p > 0.05), whereas those on the VMI were significantly lower (all p < 0.05). The paraspinal muscle segmented on the AI‐MAC image was 4.6% and 5.1% more complete to the VMI and MAC images for the Φ 6.5 × 30‐mm screws, and 5.0% and 5.1% for the Φ 7.5 × 40‐mm screws, respectively. The vertebral body segmented on the VMI was closest to the reference, with only 3.2% and 7.4% overestimation for Φ 6.5 × 30‐mm and Φ 7.5 × 40‐mm screws, respectively.ConclusionsUsing metal‐free reference as the ground truth for comparison, the AI‐MAC outperforms VMI in characterizing soft tissue, while VMI is useful in skeletal depiction.

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CT metal artifacts in patients with total hip replacements: for artifact reduction monoenergetic reconstructions and post-processing algorithms are both efficient but not similar

Abstract: • Spectral-detector computed tomography improves assessment of total hip replacements and surrounding tissue. • Virtual monoenergetic images and MAR reduce metal artifacts and enhance image quality. • Evaluation of bone, muscle and pelvic organs can be improved by SDCT.

Cited by 50 publications

References 25 publications

Virtual monoenergetic images and post-processing algorithms effectively reduce CT artifacts from intracranial aneurysm treatment

Virtual monoenergetic images and post-processing algorithms effectively reduce CT artifacts from intracranial aneurysm treatment

Iodine accumulation of the liver in patients treated with amiodarone can be unmasked using material decomposition from multiphase spectral-detector CT

Preclinical validation of a novel deep learning‐based metal artifact correction algorithm for orthopedic CT imaging

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