Objectives
Dual-energy computed tomography allows for an accurate and reliable quantification of iodine. However, data on physiological distribution of iodine concentration (IC) is still sparse. This ...study aims to establish guidance for IC in abdominal organs and important anatomical landmarks using a large cohort of individuals without radiological tumor burden.
Methods
Five hundred seventy-one oncologic, portal venous phase dual-layer spectral detector CT studies of the chest and abdomen without tumor burden at time point of imaging confirmed by > 3-month follow-up were included. ROI were placed in parenchymatous organs (
n
= 25), lymph nodes (
n
= 6), and vessels (
n
= 3) with a minimum of two measurements per landmark. ROI were placed on conventional images and pasted to iodine maps to retrieve absolute IC. Normalization to the abdominal aorta was conducted to obtain iodine perfusion ratios. Bivariate regression analysis,
t
tests, and ANOVA with Tukey-Kramer post hoc test were used for statistical analysis.
Results
Absolute IC showed a broad scatter and varied with body mass index, between different age groups and between the sexes in parenchymatous organs, lymph nodes, and vessels (range 0.0 ± 0.0 mg/ml–6.6 ± 1.3 mg/ml). Unlike absolute IC, iodine perfusion ratios did not show dependency on body mass index; however, significant differences between the sexes and age groups persisted, showing a tendency towards decreased perfusion ratios in elderly patients (e.g., liver 18–44 years/≥ 64 years: 0.50 ± 0.11/0.43 ± 0.10,
p
≤ 0.05).
Conclusions
Distribution of IC obtained from a large-scale cohort is provided. As significant differences between sexes and age groups were found, this should be taken into account when obtaining quantitative iodine concentrations and applying iodine thresholds.
Key Points
•
Absolute iodine concentration showed a broad variation and differed between body mass index, age groups, and between the sexes in parenchymatous organs, lymph nodes, and vessels.
•
The iodine perfusion ratios did not show dependency on body mass index while significant differences between sexes and age groups persisted.
•
Provided guidance values may serve as reference when aiming to differentiate healthy and abnormal tissue based on iodine perfusion ratios.
Computed tomography in suspected urolithiasis provides information about the presence, location and size of stones. Particularly stone size is a key parameter in treatment decision; however, data on ...impact of reformatation and measurement strategies is sparse. This study aimed to investigate the influence of different image reformatations, slice thicknesses and window settings on stone size measurements. Reference stone sizes of 47 kidney stones representative for clinically encountered compositions were measured manually using a digital caliper (Man-M). Afterwards stones were placed in a 3D-printed, semi-anthropomorphic phantom, and scanned using a low dose protocol (CTDI
2 mGy). Images were reconstructed using hybrid-iterative and model-based iterative reconstruction algorithms (HIR, MBIR) with different slice thicknesses. Two independent readers measured largest stone diameter on axial (2 mm and 5 mm) and multiplanar reformatations (based upon 0.67 mm reconstructions) using different window settings (soft-tissue and bone). Statistics were conducted using ANOVA ± correction for multiple comparisons. Overall stone size in CT was underestimated compared to Man-M (8.8 ± 2.9 vs. 7.7 ± 2.7 mm, p < 0.05), yet closely correlated (r = 0.70). Reconstruction algorithm and slice thickness did not significantly impact measurements (p > 0.05), while image reformatations and window settings did (p < 0.05). CT measurements using multiplanar reformatation with a bone window setting showed closest agreement with Man-M (8.7 ± 3.1 vs. 8.8 ± 2.9 mm, p < 0.05, r = 0.83). Manual CT-based stone size measurements are most accurate using multiplanar image reformatation with a bone window setting, while measurements on axial planes with different slice thicknesses underestimate true stone size. Therefore, this procedure is recommended when impacting treatment decision.
Background
Decreasing MRI scan time is a key factor to increase patient comfort and compliance as well as the productivity of MRI scanners.
Purpose/Hypothesis
Compressed sensing (CS) should ...significantly accelerate 3D scans. This study evaluated the clinical application and cost effectiveness of accelerated 3D T2 sequences of the lumbar spine.
Study Type
Prospective, cross‐sectional, observational.
Population
Twenty healthy volunteers and 10 patients.
Field Strength/Sequence
A 3D T2 TSE sequence, identical 3D sequences with three different parallel imaging and CS accelerating factors, and 2D TSE sequences as a clinical reference were obtained on a 3T scanner.
Assessment
Three readers evaluated the sequences for delineation of anatomical structures and image quality. A quantitative analysis consisting of root mean square error, structural similarity index, signal‐to‐noise ratio, and contrast‐to‐noise ratio were performed. The scan times were used to calculate cost differences for each sequence.
Statistical Tests
An analysis of variance with repeated measurements and the Friedman test were used to test for potential differences between the sequences. Post‐hoc analysis was made with the chi‐squared and Tukey–Kramer test.
Results
CS with factor 4.5 results in unchanged image quality compared to the T2 TSE for volunteers and patients (overall image impression: 4.75 vs. 4.20 P = 0.73 and 4.90 vs. 4.47 P = 0.44). The CS 4.5 scan is 167 seconds (–39%) faster than the 3D and 216.5 seconds (–45%) faster than the 2D sequences. No significant differences was found for the diagnostic certainty in the volunteers and patients between 2D TSE and 3D CS 4.5 (P = 0.89 and P = 0.43). A reduction of scan time to 148 seconds (CS 8) was still rated acceptable for most diagnosis.
Data Conclusion
CS accelerates the 3D T2 without compromising image quality. The 3D sequences offer comparable diagnostic quality to the clinical 2D standard with less scan time (–45%), potentially increasing the productivity of MRI scanners.
Level of Evidence: 1
Technical Efficacy: Stage 6 J. Magn. Reson. Imaging 2019;49:e164–e175.
Objectives
To predict the main component of pure and mixed kidney stones using dual-energy computed tomography and machine learning.
Methods
200 kidney stones with a known composition as determined ...by infrared spectroscopy were examined using a non-anthropomorphic phantom on a spectral detector computed tomography scanner. Stones were of either pure (monocrystalline,
n
= 116) or compound (dicrystalline,
n
= 84) composition. Image acquisition was repeated twice using both, normal and low-dose protocols, respectively (ND/LD). Conventional images and low and high keV virtual monoenergetic images were reconstructed. Stones were semi-automatically segmented. A shallow neural network was trained using data from ND1 acquisition split into training (70%), testing (15%) and validation-datasets (15%). Performance for ND2 and both LD acquisitions was tested. Accuracy on a per-voxel and a per-stone basis was calculated.
Results
Main components were: Whewellite (
n
= 80), weddellite (
n
= 21), Ca-phosphate (
n
= 39), cysteine (
n
= 20), struvite (
n
= 13), uric acid (
n
= 18) and xanthine stones (
n
= 9). Stone size ranged from 3 to 18 mm. Overall accuracy for predicting the main component on a per-voxel basis attained by ND testing dataset was 91.1%. On independently tested acquisitions, accuracy was 87.1–90.4%.
Conclusions
Even in compound stones, the main component can be reliably determined using dual energy CT and machine learning, irrespective of dose protocol.
Key Points
• Spectral Detector Dual Energy CT and Machine Learning allow for an accurate prediction of stone composition.
• Ex-vivo study demonstrates the dose independent assessment of pure and compound stones.
• Lowest accuracy is reported for compound stones with struvite as main component.
Objectives
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.
Methods
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.
Results
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) %.
Conclusions
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.
Key Points
•
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.
The objective of this study is to evaluate if intensified pre-scan patient preparation (IPPP) that comprises custom-made educational material on dynamic phase imaging and supervised pre-imaging ...breath-hold training in addition to standard informative conversation with verbal explanation of breath-hold commands (standard pre-scan patient preparation-SPPP) might reduce the incidence of gadoxetate disodium (Gd-EOB-DTPA)-related transient severe respiratory motion (TSM) and severity of respiratory motion (RM) during dynamic phase liver MRI.
In this bi-institutional study 100 and 110 patients who received Gd-EOB-DTPA for dynamic phase liver MRI were allocated to either IPPP or SPPP at site A and B. The control group comprised 202 patients who received gadoterate meglumine (Gd-DOTA) of which each 101 patients were allocated to IPPP or SPPP at site B. RM artefacts were scored retrospectively in dynamic phase images (1: none- 5: extensive) by five and two blinded readers at site A and B, respectively, and in the hepatobiliary phase of the Gd-EOB-DTPA-enhanced scans by two blinded readers at either site.
The incidence of TSM was 15% at site A and 22.7% at site B (p = 0.157). IPPP did not reduce the incidence of TSM in comparison to SPPP: 16.7% vs. 21.6% (p = 0.366). This finding was consistent at site A: 12% vs. 18% (p = 0.401) and site B: 20.6% vs. 25% (p = 0.590). The TSM incidence in patients with IPPP and SPPP did not differ significantly between both sites (p = 0.227; p = 0.390). IPPP did not significantly mitigate RM in comparison to SPPP in any of the Gd-EOB-DTPA-enhanced dynamic phases and the hepatobiliary phase in patients without TSM (all p≥0.072). In the Gd-DOTA control group on the other hand, IPPP significantly mitigated RM in all dynamic phases in comparison to SPPP (all p≤0.031).
We conclude that Gd-EOB-DTPA-related TSM cannot be mitigated by education and training and that Gd-EOB-DTPA-related breath-hold difficulty does not only affect the subgroup of patients with TSM or exclusively the arterial phase as previously proposed.
Background Both laparoscopic surgery and computer games make similar demands on eye-hand coordination and visuospatial cognitive ability. A possible connection between both areas could be used for ...the recruitment and training of future surgery residents. Aim The goal of this study was to investigate whether gaming skills are associated with better laparoscopic performance in medical students. Methods 135 medical students (55 males, 80 females) participated in an experimental study. Students completed three laparoscopic tasks (rope pass, paper cut, and peg transfer) and played two custom-designed video games (2D and 3D game) that had been previously validated in a group of casual and professional gamers. Results There was a small significant correlation between performance on the rope pass task and the 3D game, Kendall's tau(111) = -.151, P = .019. There was also a small significant correlation between the paper cut task and points in the 2D game, Kendall's tau(102) = -.180, P = .008. Overall laparoscopic performance was also significantly correlated with both the 3D game, Kendall's tau(112) = -.134, P = .036, and points in the 2D game, Kendall's tau(113) = -.163, P = .011. However, there was no significant correlation between the peg transfer task and both games (2D and 3D game), P = n.s.. Conclusion This study provides further evidence that gaming skills may be an advantage when learning laparoscopic surgery.
Objective
Evaluation of MRI-derived cerebral
23
Na concentrations in patients with migraine in comparison with healthy controls.
Materials and methods
In this case-control study, 24 female migraine ...patients (mean age, 34 ± 11 years) were enrolled after evaluation of standardized questionnaires. Half (
n
= 12) of the cohort suffered from migraine, the other half was impaired by both migraine and tension-type headaches (TTH). The combined patient cohort was matched to 12 healthy female controls (mean age, 34 ± 11 years). All participants underwent a cerebral
23
Na-magnetic resonance imaging examination at 3.0 T, which included a T1w MP-RAGE sequence and a 3D density-adapted, radial gradient echo sequence for
23
Na imaging. Circular regions of interests were placed in predetermined anatomic regions: cerebrospinal fluid (CSF), gray and white matter, brain stem, and cerebellum. External
23
Na reference phantoms were used to calculate the total
23
Na tissue concentrations. Pearson’s correlation, Kendall Tau, and Wilcoxon rank sum test were used for statistical analysis.
Results
23
Na concentrations of all patients in the CSF were significantly higher than in healthy controls (
p
< 0.001). The CSF of both the migraine and mixed migraine/TTH group showed significantly increased sodium concentrations compared to the control group (
p
= 0.007 and
p
< 0.001). Within the patient cohort, a positive correlation between pain level and TSC in the CSF (
r
= 0.62) could be observed.
Conclusion
MRI-derived cerebral
23
Na concentrations in the CSF of migraine patients were found to be statistically significantly higher than in healthy controls.
Key Points
• Cerebral sodium MRI supports the theory of ionic imbalances and may aid in the challenging pathophysiologic understanding of migraine.
• Case-control study shows significantly higher sodium concentrations in cerebrospinal fluid of migraineurs.
• Cerebral sodium MRI may become a non-invasive imaging tool for drugs to modulate sodium, and hence migraine, on a molecular level, and influence patient management.
Implementation of DWI in the abdomen is challenging due to artifacts, particularly those arising from differences in tissue susceptibility. Two-dimensional, spatially-selective radiofrequency (RF) ...excitation pulses for single-shot echo-planar imaging (EPI) combined with a reduction in the FOV in the phase-encoding direction (i.e. zooming) leads to a decreased number of k-space acquisition lines, significantly shortening the EPI echo train and potentially susceptibility artifacts.
To assess the feasibility and image quality of a zoomed diffusion-weighted EPI (z-EPI) sequence in MR imaging of the pancreas. The approach is compared to conventional single-shot EPI (c-EPI).
23 patients who had undergone an MRI study of the abdomen were included in this retrospective study. Examinations were performed on a 3T whole-body MR system (Magnetom Skyra, Siemens) equipped with a two-channel fully dynamic parallel transmit array (TimTX TrueShape, Siemens). The acquired sequences consisted of a conventional EPI DWI of the abdomen and a zoomed EPI DWI of the pancreas. For z-EPI, the standard sinc excitation was replaced with a two-dimensional spatially-selective RF pulse using an echo-planar transmit trajectory. Images were evaluated with regard to image blur, respiratory motion artifacts, diagnostic confidence, delineation of the pancreas, and overall scan preference. Additionally ADC values of the pancreatic head, body, and tail were calculated and compared between sequences.
The pancreas was better delineated in every case (23/23) with z-EPI versus c-EPI. In every case (23/23), both readers preferred z-EPI overall to c-EPI. With z-EPI there was statistically significantly less image blur (p<0.0001) and respiratory motion artifact compared to c-EPI (p<0.0001). Diagnostic confidence was statistically significantly better with z-EPI (p<0.0001). No statistically significant differences in calculated ADC values were observed between the two sequences.
Zoomed diffusion-weighted EPI leads to substantial image quality improvements with reduction of susceptibility artifacts in pancreatic DWI.
Quantitative sodium MRI of kidney Zöllner, Frank G.; Konstandin, Simon; Lommen, Jonathan ...
NMR in biomedicine,
February 2016, Volume:
29, Issue:
2
Journal Article
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