Lukas Lenga

Noise-optimized virtual monoenergetic dual-energy computed tomography: optimization of kiloelectron volt settings in patients with gastrointestinal stromal tumors

PurposeThe aim of this study was to evaluate the impact of a noise-optimized virtual monoenergetic imaging (VMI+) reconstruction technique on quantitative and qualitative image analysis in patients with gastrointestinal stromal tumors (GISTs) at dual-energy computed tomography (DECT) of the abdomen.MethodsForty-five DECT datasets of 21 patients (14 men; 63.7xa0±xa09.2xa0years) with GISTs were reconstructed with the standard linearly blended (M_0.6) and VMI+ and traditional virtual monoenergetic (VMI) algorithm in 10-keV increments from 40 to 100xa0keV. Attenuation measurements were performed in GIST lesions and abdominal metastases to calculate objective signal-to-noise (SNR) and contrast-to-noise ratios (CNR). Five-point scales were used to evaluate overall image quality, lesion delineation, image sharpness, and image noise.ResultsQuantitative image parameters peaked at 40-keV VMI+ series (SNR 27.8xa0±xa013.0; CNR 26.3xa0±xa012.7), significantly superior to linearly blended (SNR 16.8xa0±xa07.3; CNR 13.6xa0±xa06.9) and all VMI series (all Pxa0<xa00.001). Qualitative image parameters were highest for 60-keV VMI+ reconstructions regarding overall image quality and image sharpness (median 5, respectively; Pxa0≤xa00.023). Qualitative assessment of lesion delineation peaked in 40 and 50-keV VMI+ series (median 5, respectively). Image noise was superior in 90 and 100-keV VMI and VMI+ reconstructions (all medians 5).ConclusionsLow-keV VMI+ reconstructions significantly increase SNR and CNR of GISTs and improve quantitative and qualitative image quality of abdominal DECT datasets compared to traditional VMI and standard linearly blended image series.

Hybrid imaging of the bowel using PET/MR enterography: Feasibility and first results

PURPOSEnTo implement a protocol for PET/MR enterography for a multimodal assessment of intestinal pathologies.nnnMATERIALS AND METHODSn19 patients with bowel malignancies, Crohns disease or fever of unknown origin (male: n=14, female: n=5, age: 57±13years) underwent PET/MR enterography with either [(18)F]FDG (n=10) or [(68)Ga]-DOTATOC (n=9) using an integrated scanner. For small bowel distension a contrast solution (1500 cm(3) of mannitol and locust bean gum) was ingested. The following sequences were acquired: (a) coronal TrueFISP; (b) coronal T2w HASTE; (c) coronal dynamic T1w VIBE; (d) axial and coronal T1w FLASH post gadolinium. All datasets were reviewed by two readers with regard to co-registration of anatomical structures based on a 3-point ordinal scale as well as overall image quality using a 4-point ordinal scale. Furthermore, visualization of intestinal and extra-intestinal pathologies was assessed.nnnRESULTSnPET/MR enterography was well tolerated by all patients. High overall MR image quality was achieved (mean score: 3.2±0.6) with good co-registration of PET and MRI (mean scores: 2.6 to 3.0). PET/MR enterography allowed for an excellent visualization of both intestinal as well as extra-intestinal pathologies.nnnCONCLUSIONnPET/MR enterography is technically feasible and offers good co-registration of bowel structures. This novel method enables a multimodal assessment of bowel lesions in malignant and inflammatory disease.

Noise-Optimized Virtual Monoenergetic Dual-Energy CT Improves Diagnostic Accuracy for the Detection of Active Arterial Bleeding of the Abdomen

PURPOSEnTo evaluate diagnostic accuracy of a noise-optimized virtual monoenergetic imaging (VMI+) reconstruction technique for detection of active arterial abdominal bleeding on dual-energy (DE) CT angiography compared with standard image reconstruction.nnnMATERIALS AND METHODSnDE CT angiography data sets of 71 patients (46 men; age 63.6 y ± 13.3) with suspected arterial bleeding of the abdomen or pelvis were reconstructed with standard linearly blended (F_0.5), VMI+, and traditional virtual monoenergetic imaging (VMI) algorithms in 10-keV increments from 40 to 100 keV. Attenuation measurements were performed in the descending aorta, area of hemorrhage, and feeding artery to calculate contrast-to-noise ratios (CNRs) in patients with active arterial bleeding. Based on quantitative image quality results, the best series for each reconstruction technique were chosen to analyze the diagnostic performance of 3 blinded radiologists.nnnRESULTSnDE CT angiography showed acute arterial bleeding in 36 patients. Mean CNR was superior in 40-keV VMI+ compared with VMI series (all P < .001), which showed highest CNRs in 70-keV VMI and F_0.5 (21.6 ± 7.9, 12.9 ± 4.7, and 10.4 ± 3.6) images. Area under the curve analysis for detection of arterial bleeding showed significantly superior (P < .001) results for 40-keV VMI+ (0.963) compared with 70-keV VMI (0.775) and F_0.5 (0.817) series.nnnCONCLUSIONSnDiagnostic accuracy in patients with active arterial bleeding of the abdomen can be significantly improved using VMI+ reconstructions at 40 keV compared with standard linearly blended and traditional VMI series in DE CT angiography.

Monoenergetic Dual-energy Computed Tomographic Imaging: Cardiothoracic Applications

Monoenergetic imaging is an increasingly used reconstruction technique in postprocessing of dual-energy computed tomography (DECT). The main advantage of this technique is the ability to substantially increase image contrast of structures with uptake of iodinated contrast material. Although monoenergetic imaging was mainly used in oncological DECT applications, recent research has further demonstrated its role in vascular imaging. Using this dedicated postprocessing algorithm, image contrast of vascular structures in the thorax can be increased, a drastic reduction of contrast material is feasible, and even beam-hardening artifacts can be reduced. The aim of this review article is to explain the technical background of this technique, showcase its relevance in cardiothoracic DECT, and provide an outlook on the clinical impact of this technique beyond solely improvements in image quality.

Impact of noise-optimized virtual monoenergetic dual-energy computed tomography on image quality in patients with renal cell carcinoma

OBJECTIVEnThe aim of this study was to evaluate the impact of a noise-optimized virtual monoenergetic imaging (VMI+) reconstruction technique on image quality and lesion delineation in patients with renal cell carcinoma (RCC) undergoing abdominal dual-energy computed tomography (DECT).nnnMATERIALS AND METHODSnFifty-two patients (33 men; 61.5±13.6years) with RCC underwent contrast-enhanced DECT during the corticomedullary and nephrogenic phase of renal enhancement. DECT datasets were reconstructed with standard linearly-blended (M_0.6), as well as traditional virtual monoenergetic (VMI) and VMI+ algorithms in 10-keV increments from 40 to 100 keV. Contrast-to-noise (CNR) and tumor-to-cortex ratios for corticomedullary- and nephrogenic-phase images were objectively measured by a radiologist with 3 years of experience. Subjective image quality and RCC delineation were evaluated by three independent radiologists.nnnRESULTSnGreatest CNR values were found for 40-keV VMI+ series in both corticomedullary- (8.9±4.9) and nephrogenic-phase (7.1±4.6) images and were significantly higher compared to all other reconstructions (P<0.001). Furthermore, tumor-to-cortex ratios were highest for 40-keV nephrogenic-phase VMI+ (2.1±3.5; P≤0.016), followed by 50-keV and 60-keV VMI+ (2.0±3.2 and 1.8±2.8, respectively). Qualitative image quality scored highest for 50-keV VMI+ series in corticomedullary-phase reconstructions and 60-keV in nephrogenic-phase reconstructions (P≤0.031). Highest scores for lesion delineation were assigned for 40-keV VMI+ reconstructions (P≤0.074).nnnCONCLUSIONnLow-keV VMI+ reconstructions lead to improved image quality and lesion delineation of corticomedullary- and nephrogenic-phase DECT datasets in patients with RCC.

Optimisation of window settings for traditional and noise-optimised virtual monoenergetic imaging in dual-energy computed tomography pulmonary angiography

AbstractObjectivesTo define optimal window settings for displaying virtual monoenergetic images (VMI) of dual-energy CT pulmonary angiography (DE-CTPA).MethodsForty-five patients who underwent clinically-indicated third-generation dual-source DE-CTPA were retrospectively evaluated. Standard linearly-blended (M_0.6), 70-keV traditional VMI (M70), and 40-keV noise-optimised VMI (M40+) reconstructions were analysed. For M70 and M40+ datasets, the subjectively best window setting (width and level, B-W/L) was independently determined by two observers and subsequently related with pulmonary artery attenuation to calculate separate optimised values (O-W/L) using linear regression. Subjective evaluation of image quality (IQ) between W/L settings were assessed by two additional readers. Repeated measures of variance were performed to compare W/L settings and IQ indices between M_0.6, M70, and M40+.ResultsB-W/L and O-W/L for M70 were 460/140 and 450/140, and were 1100/380 and 1070/380 for M40+, respectively, differing from standard DE-CTPA W/L settings (450/100). Highest subjective scores were observed for M40+ regarding vascular contrast, embolism demarcation, and overall IQ (all p<0.001).ConclusionsApplication of O-W/L settings is beneficial to optimise subjective IQ of VMI reconstructions of DE-CTPA. A width slightly less than two times the pulmonary trunk attenuation and a level approximately of overall pulmonary vessel attenuation are recommended.Key Points• Application of standard window settings for VMI results in inferior image perception.n • No significant differences between B-W/L and O-W/L for M70/M40+ were observed.n • O-W/L for M70 were 450/140 and were 1070/380 for M40+.n • Improved subjective IQ characteristics were observed for VMI displayed with O-W/L.

Iodine quantification to distinguish hepatic neuroendocrine tumor metastasis from hepatocellular carcinoma at dual-source dual-energy liver CT

PURPOSEnTo investigate the value of third-generation dual-source dual-energy computed tomography (DECT) iodine quantification to distinguish hepatic neuroendocrine tumor (NET) metastasis from hepatocellular carcinoma (HCC) in non-cirrhotic liver parenchyma.nnnMATERIAL AND METHODSnForty-six patients (mean age, 64.9u202f±u202f10.1 years; 28 male and 18 female) with either hepatic NET metastasis or HCC, who had undergone liver DECT, were included in this retrospective study. For each lesion, arterial-phase attenuation values and DECT quantitative parameters, including iodine uptake, fat fraction, normalized iodine uptake (NIU), and lesion-to-liver-parenchyma ratio (LPR) were evaluated. Available cumulative data from histopathology, MRI, PET/CT, or interval imaging follow-up served as the reference standard for all liver lesions. In addition, the diagnostic accuracy of contrast-enhanced and material decomposition analysis for the differentiation of hepatic NET metastasis and HCC was assessed using receiver operating characteristics (ROC) curve analysis.nnnRESULTSnHepatic NET metastasis and HCC showed significant differences in arterial attenuation (Pu202f=u202f0.003), iodine uptake (Pu202f<u202f0.001), NIU (Pu202f<u202f0.001), and LPR (Pu202f=u202f0.003). No significant differences were found for unenhanced attenuation and fat fraction values (Pu202f=u202f0.686 and Pu202f=u202f0.892, respectively). NIU showed superior sensitivity (100%; iodine uptake, 71%), while both iodine uptake and NIU revealed superior specificity (100% and 90%, respectively) compared to LPR (sensitivity, 96%; specificity, 80%) and arterial attenuation analysis (sensitivity, 79%; specificity, 80%) (Pu202f≤u202f0.016).nnnCONCLUSIONnThird-generation DECT with assessment of iodine uptake improves the differentiation of hepatic NET metastasis and HCC in non-cirrhotic liver, with NIU showing the strongest diagnostic performance.

Dual-energy CT-based iodine quantification to differentiate abdominal malignant lymphoma from lymph node metastasis

PURPOSEnTo investigate the value of dual-energy computed tomography (DECT)-derived iodine and fat quantification in differentiating malignant abdominal lymphoma from lymph node metastasis.nnnMATERIALS AND METHODSnIn this retrospective study, 59 patients (39 men; mean age, 62.7 years) with histopathologically-confirmed diagnosis of either malignant lymphoma or lymph node metastasis were included. For each lesion, contrast-enhanced attenuation, as well as DECT-derived iodine density and fat fraction measurements were recorded. Mean attenuation and material density values were compared between malignant lymphomas and lymph node metastases. The receiver operating characteristic (ROC) curve analysis was adopted to estimate the optimal threshold for discriminating between both entities. A control group (nu202f=u202f60) was analyzed for comparison of attenuation and material density values of normal abdominal lymph nodes.nnnRESULTSnAssessment of DECT-derived iodine density and fat fraction values revealed significant differences between lymph node metastases (1.7u202f±u202f0.4u202fmg/ml and 15.5u202f±u202f7.3%) and malignant lymphomas (2.5u202f±u202f0.5u202fmg/ml and 26.7u202f±u202f12.2%) as well as normal lymph nodes (2.4u202f±u202f0.8u202fmg/ml and 24.1u202f±u202f10.8%) (Pu202f≤u202f0.013). An iodine concentration of 2.0u202fmg/ml represented the optimal threshold to discriminate between lymphoma and lymph node metastasis (sensitivity, 87%; specificity, 89%). Moreover, a significant correlation was found between iodine concentration and fat fraction for both lymphomas and lymph node metastases (Pu202f=u202f0.001).nnnCONCLUSIONnDECT enables characterization of abdominal masses as derived iodine and fat fraction values differ significantly between malignant abdominal lymphomas and lymph node metastases.

Evaluation of bone mineral density of the lumbar spine using a novel phantomless dual-energy CT post-processing algorithm in comparison with dual-energy X-ray absorptiometry

BackgroundCurrent techniques for evaluation of bone mineral density (BMD) commonly require phantom calibration. The purpose of this study was to evaluate a novel algorithm for phantomless in vivo dual-energy computed tomography (DECT)-based assessment of BMD of the lumbar spine in comparison with dual-energy X-ray absorptiometry (DEXA).MethodsData from clinically indicated DECT and DEXA examinations within two months comprising the lumbar spine of 47 patients were retrospectively evaluated. By using a novel automated dedicated post-processing algorithm for DECT, the trabecular bone of lumbar vertebrae L1–L4 was selected and analysed. Linear correlation was analysed using Pearson’s product-moment correlation coefficient for the comparison of the results from DECT and DEXA.ResultsA total of 186 lumbar vertebrae in 47 patients (mean age, 58xa0years; age range, 24–85 years) were analysed, 24 men (mean age, 55xa0years; age range, 24–85 years) and 23 women (mean age, 59xa0years; age range, 31–80 years). Mean BMD of L1–L4 determined with DEXA was 0.985xa0g/cm2 and 20/47 patients (42.6%) showed an osteoporotic BMD (T score lower than –u20092.5) of at least two vertebrae. Average DECT-based BMD of L1–L4 was 86.8xa0mg/cm3. Regression analysis demonstrated a lack of correlation between DECT- and DEXA-based BMD values with a Pearson’s product-moment correlation coefficient ru2009=u20090.4205.ConclusionsDedicated post-processing of DECT data using a novel algorithm for retrospective phantomless BMD assessment of the trabecular bone of lumbar vertebrae from clinically indicated DECT examinations is feasible.

Dual-energy computed tomography in patients with cutaneous malignant melanoma: Comparison of noise-optimized and traditional virtual monoenergetic imaging

OBJECTIVEnThe aim of this study was to investigate the impact of noise-optimized virtual monoenergetic imaging (VMI+) reconstructions on quantitative and qualitative image parameters in patients with cutaneous malignant melanoma at thoracoabdominal dual-energy computed tomography (DECT).nnnMATERIALS AND METHODSnSeventy-six patients (48 men; 66.6±13.8years) with metastatic cutaneous malignant melanoma underwent DECT of the thorax and abdomen. Images were post-processed with standard linear blending (M_0.6), traditional virtual monoenergetic (VMI), and VMI+ technique. VMI and VMI+ images were reconstructed in 10-keV intervals from 40 to 100keV. Attenuation measurements were performed in cutaneous melanoma lesions, as well as in regional lymph node, subcutaneous and in-transit metastases to calculate objective signal-to-noise (SNR) and contrast-to-noise (CNR) ratios. Five-point scales were used to evaluate overall image quality and lesion delineation by three radiologists with different levels of experience.nnnRESULTSnObjective indices SNR and CNR were highest at 40-keV VMI+ series (5.6±2.6 and 12.4±3.4), significantly superior to all other reconstructions (all P<0.001). Qualitative image parameters showed highest values for 50-keV and 60-keV VMI+ reconstructions (median 5, respectively; P≤0.019) regarding overall image quality. Moreover, qualitative assessment of lesion delineation peaked in 40-keV VMI+ (median 5) and 50-keV VMI+ (median 4; P=0.055), significantly superior to all other reconstructions (all P<0.001).nnnCONCLUSIONnLow-keV noise-optimized VMI+ reconstructions substantially increase quantitative and qualitative image parameters, as well as subjective lesion delineation compared to standard image reconstruction and traditional VMI in patients with cutaneous malignant melanoma at thoracoabdominal DECT.