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European radiology 31(6), 4148-4155 (2021). doi:10.1007/s00330-020-07615-w, Published by Springer, Berlin

To evaluate quantitative iodine density mapping (IDM) with spectral detector computed tomography (SDCT) as a quantitative biomarker for separation of vertebral trabecular bone metastases (BM) from healthy-appearing trabecular bone (HTB). IRB-approved retrospective single-center-study of portal venous SDCT datasets acquired between June 2016 and March 2017. Inclusion of 43 consecutive cancer patients with BM and 40 without. Target lesions and non-affected control vertebrae were defined using follow-up imaging, MRI, and/or bone scintigraphy. ID and standard deviation were determined with ROI measures by two readers in (a) bone metastases, (b) HTB of BM patients and controls, and (c) ID of various vessels. Volumetric bone mineral density (vBMD) of the lumbar spine and age were recorded. Multivariate ROC analyses und Wilcoxon test were used to determine thresholds for separation of BM and HTB. p

This study compares metal artifact (MA) reduction in imaging of total hip replacements (THR) using virtual monoenergetic images (VMI), for MA-reduction-specialized reconstructions (MAR) and conventional CT images (CI) from detector-based dual-energy computed tomography (SDCT).Twenty-seven SDCT-datasets of patients carrying THR were included. CI, MAR and VMI with different energy-levels (60-200 keV) were reconstructed from the same scans. MA width was measured. Attenuation (HU), noise (SD) and contrast-to-noise ratio (CNR) were determined in: extinction artifact, adjacent bone, muscle and bladder. Two radiologists assessed MA-reduction and image quality visually.In comparison to CI, VMI (200 keV) and MAR showed a strong artifact reduction (MA width: CI 29.9±6.8 mm, VMI 17.6±13.6 mm, p0.001; MAR 16.5±14.9 mm, p0.001; MA density: CI -412.1±204.5 HU, VMI -279.7±283.7 HU; p0.01; MAR -116.74±105.6 HU, p0.001). In strong artifacts reduction was superior by MAR. In moderate artifacts VMI was more effective. MAR showed best noise reduction and CNR in bladder and muscle (p0.05), whereas VMI were superior for depiction of bone (p0.05). Visual assessment confirmed that VMI and MAR improve artifact reduction and image quality (p0.001).MAR and VMI (200 keV) yielded significant MA reduction. Each showed distinct advantages both regarding effectiveness of artifact reduction, MAR regarding assessment of soft tissue and VMI regarding assessment of bone.• 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.

Peritoneal carcinomatosis (PC) is a prognostically relevant metastatic disease which may be difficult to depict in postoperative patients, particularly in early stages. This study aimed to determine whether PC could be diagnosed more accurately when using a combination of spectral detector CT (SDCT)-derived conventional images (CI) and iodine overlay images (IO) compared with CI only. Thirty patients with PC and 30 patients with benign peritoneal alterations (BPA) who underwent portal-venous abdominal SDCT were included. Four radiologists determined the presence/absence of PC for each patient and assessed lesion conspicuity, diagnostic certainty, and image quality using 5-point Likert scales. Subjective assessment was conducted in two sessions comprising solely CI and CI/IO between which a latency of 6 weeks was set. Iodine uptake and HU attenuation were determined ROI-based to analyze quantitative differentiation of PC/BPA. Specificity for PC was significantly higher when using CI/IO compared with using CI only (0.86 vs. 0.78, p ≤ 0.05), while sensitivity was comparable (0.79 vs. 0.81, p = 1). In postoperative patients, the increase in specificity was the highest (0.93 vs. 0.80, p ≤ 0.05). Lesion conspicuity was rated higher in CI/IO (4 (3–5)) compared with that in CI only (3 (3–4); p ≤ 0.05). Diagnostic certainty was comparable (both 4 (3–5); p = 0.5). CI/IO received the highest rating for overall image quality and assessability (CI/IO 5 (4–5) vs. CI 4 (4–4) vs. IO 4 (3–4); p ≤ 0.05). Area under the receiver operating characteristics curve (AUC) for quantitative differentiation between PC and BPA was higher for iodine (AUCIodine = 0.95, AUCHU = 0.90). Compared with CI, combination of CI/IO improves specificity in the assessment of peritoneal carcinomatosis at comparable sensitivity, particularly in postoperative patients. • Combination of iodine overlays and conventional images improves specificity when assessing patients with peritoneal carcinomatosis at comparable sensitivity. • Particularly in postsurgical patients, iodine overlays could help to avoid false-positive diagnosis of peritoneal disease. • Iodine overlays alone provided inferior image quality and assessability than conventional images, while the combination of both received the highest ratings. Iodine overlays should therefore be used in addition to and not as a substitute for conventional images.

The objective of this study was to evaluate the intra-individual, longitudinal consistency of iodine measurements regarding the vascular and renal blood pool in patients that underwent repetitive spectral detector computed tomography (SDCT) examinations to evaluate their utility for oncologic imaging. Seventy-nine patients with two (n = 53) or three (n = 26) clinically indicated biphasic SDCT scans of the abdomen were retrospectively included. ROI-based measurements of Hounsfield unit (HU) attenuation in conventional images and iodine concentration were performed by an experienced radiologist in the following regions (two ROIs each): abdominal aorta, vena cava inferior, portal vein, and renal cortices. Modified variation coefficients (MVCs) were computed to assess intra-individual longitudinal between the different time points. Variation of HU attenuation and iodine concentration measurements was significantly lower in the venous than in the arterial phase images (attenuation/iodine concentration: arterial − 4.2/− 3.9, venous 0.4/1.0; p ≤ 0.05). Regarding attenuation in conventional images of the arterial phase, the median MVC was − 1.8 (− 20.5–21.3) % within the aorta and − 6.5 (− 44.0–25.0) % within the renal cortex while in the portal venous phase, it was 0.62 (− 11.1–11.7) % and − 1.6 (− 16.2–10.6) %, respectively. Regarding iodine concentration, MVC for arterial phase was − 2.5 (− 22.9–28.4) % within the aorta and − 5.8 (− 55.9–29.6) % within the renal cortex. The referring MVCs of the portal venous phase were − 0.7 (− 17.9–16.9) % and − 2.6 (− 17.6–12.5) %. Intra-individual iodine quantification of the vascular and cortical renal blood pool at different time points works most accurately in venous phase images whereas measurements conducted in arterial phase images underlay greater variability. • There is an intra-individual, physiological variation in iodine map measurements from dual-energy computed tomography. • This variation is smaller in venous phase examinations compared with arterial phase and therefore venous phase images should be preferred to minimize this intra-individual variation. • Care has to be taken, when considering iodine measurements for clinical decision-making, particularly in the context of oncologic initial or follow-up imaging.

To evaluate feasibility and diagnostic performance of multi-level calcium suppression in spectral detector computed tomography (SDCT) for assessment of bone metastasis. Retrospective IRB-approved study on 21 patients who underwent SDCT (120 kV, reference mAs 116) and MRI. Thoracic and lumbar vertebrae (n = 357) were included and categorized as normal (n = 133) or metastatic (n = 203) based on MRI (STIR, T1w, ±contrast). The multi-level virtual non-calcium (VNCa) algorithm computes dynamic soft tissue/calcium pairs allowing for computation of different suppression index levels to address inter-individual variance of prevalent calcium composition weights. We computed images with low, medium, and high calcium suppression indices and compared them with conventional images (VNCa_low/med/high and conventional images (CI)). For quantitative image analysis, regions of interest were placed in normal and metastatic bone. Two readers reviewed the datasets independently in multiple sessions. They determined the presence of vertebral metastases on a per vertebra basis using a binary scale. Statistic assessment was performed using ANOVA with Tukey HSD, Student’s T test, and ROC analysis. Attenuation of both normal and metastatic bone was lower in VNCa images than that in conventional images (e.g., CI/VNCa_low, − 46.3 to 238.8 HU/343.3–60.2 HU; p ≤ 0.05). VNCa_low+med improved separation of normal and metastatic bone in ROC analysis (AUC, CI/VNCa_low/VNCa_med = 0.74/0.95/0.98; p ≤ 0.05). In subjective analysis, both sensitivity and specificity were clearly improved in VNCa_low as compared with CI (0.85/0.84 versus 0.78/0.82). Readers showed a good inter-rater reliability (kappa = 0.65). Multi-level VNCa reconstructed from SDCT improve quantitative separation of normal and metastatic bone and subjective determination of bone metastases when using low to intermediate calcium suppression indices. • Spectral detector CT allows for multi-level calcium suppression in CT images and low and medium calcium suppression indices improved separation of normal and metastatic bone. • Thus, multi-level calcium suppression allows to optimize image contrast in regard to dedicated pathologies. • Low-level virtual non-calcium images (index 25–50) improved diagnostic performance regarding detection of metastasis.

To compare the image quality of virtual monoenergetic images and polyenergetic images reconstructed from dual-layer detector CT angiography (DLCTA). Thirty patients who underwent DLCTA of the head and neck were retrospectively identified and polyenergetic as well as virtual monoenergetic images (40 to 120 keV) were reconstructed. Signals (± SD) of the cervical and cerebral vessels as well as lateral pterygoid muscle and the air surrounding the head were measured to calculate the CNR and SNR. In addition, subjective image quality was assessed using a 5-point Likert scale. Student's t-test and Wilcoxon test were used to determine statistical significance. Compared to polyenergetic images, although noise increased with lower keV, CNR (p 0.05) of the cervical, petrous and intracranial vessels were improved in virtual monoenergetic images at 40 keV and virtual monoenergetic images at 45 keV were also rated superior regarding vascular contrast, assessment of arteries close to the skull base and small arterial branches (p < 0.0001 each). Compared to polyenergetic images, virtual monoenergetic images reconstructed from DLCTA at low keV ranging from 40 to 45 keV improve the objective and subjective image quality of extra- and intracranial vessels and facilitate assessment of vessels close to the skull base and of small arterial branches. • Virtual monoenergetic images greatly improve attenuation, while noise only slightly increases. • Virtual monoenergetic images show superior contrast-to-noise ratios compared to polyenergetic images. • Virtual monoenergetic images significantly improve image quality at low keV.