Relationship between white matter hyperintensities volume and the circle of Willis configurations in patients with carotid artery pathology

PurposeWe aimed to assess if there is a difference of distribution and volume of white matter hyperintensities (WMH) in the brain according to the Circle of Willis (CoW) configuration in patients with carotid artery pathology.Material and methodsOne-hundred consecutive patients (79 males, 21 females; mean age 70 years; age range 46–84 years) that underwent brain MRI before carotid endarterectomy (CEA) were included. FLAIR-WMH lesion volume was performed using a semi-automated segmentation technique and the status of the circle of Willis was assessed by two neuroradiologists in consensus.ResultsWe found a prevalence of 55% of variants in the CoW configuration; 22 cases had one variants (40%); 25 cases had two variants (45.45%) and 8 cases showed 3 variants (14.55%). The configuration that was associated with the biggest WMH volume and number of lesions was the A1 + PcoA + PcoA. The PcoA variants were the most prevalent and there was no statistically significant difference in number of lesions and WMH for each vascular territory assessed and the same results were found for AcoA and A1 variants.ConclusionResults of our study suggest that the more common CoW variants are not associated with the presence of an increased WMH or number of lesions whereas uncommon configurations, in particular when 2 or more segment are missing increase the WMH volume and number of lesions. The WHM volume of the MCA territory seems to be more affected by the CoW configuration.     

Segmentation of cell nuclei in heterogeneous microscopy images: A reshapable templates approach

Histological tissue images typically exhibit very sophisticated spatial color patterns. It is of great clinical importance to extract qualitative and quantitative information from these images. As an ad hoc solution, various unsupervised approaches address the object detection and segmentation problem which are suitable for limited classes of histology images. In this paper, we propose a general purpose localization and segmentation method which utilizes reshapable templates. The method combines both pixel- and object-level features for detecting regions of interest. Segmentation is carried out in two levels including both the coarse and fine ones. A set of simple-shaped templates is used for coarse segmentation. A content based template reshaping algorithm is proposed for fine segmentation of target objects. Experimentation was done using a publicly available image data set which contains 7931 manually labeled cells of heterogeneous histology images. The experiments have demonstrated acceptable level of detection and segmentation results for the proposed approach (precision = 0.904, recall = 0.870 and Zijdenbos similarity index = 73%). Thus, the prototype software developed based on proposed method can be considered as a potential tool for pathologists in clinical process.     

Comparison of 3D bone models of the knee joint derived from CT and 3T MR imaging

PurposeTo examine whether magnetic resonance (MR) imaging can offer a viable alternative to computed tomography (CT) based 3D bone modeling.MethodsCT and MR (SPACE, TrueFISP, VIBE) images were acquired from the left knee joint of a fresh-frozen cadaver. The distal femur, proximal tibia, proximal fibula and patella were manually segmented from the MR and CT examinations. The MR bone models obtained from manual segmentations of all three sequences were compared to CT models using a similarity measure based on absolute mesh differences.ResultsThe average absolute distance between the CT and the various MR-based bone models were all below 1 mm across all bones. The VIBE sequence provided the best agreement with the CT model, followed by the SPACE, then the TrueFISP data. The most notable difference was for the proximal tibia (VIBE 0.45 mm, SPACE 0.82 mm, TrueFISP 0.83 mm).ConclusionsThe study indicates that 3D MR bone models may offer a feasible alternative to traditional CT-based modeling. A single radiological examination using the MR imaging would allow simultaneous assessment of both bones and soft-tissues, providing anatomically comprehensive joint models for clinical evaluation, without the ionizing radiation of CT imaging.     

Single source dual energy CT: What is the optimal monochromatic energy level for the analysis of the lung parenchyma?

ObjectiveTo determine the optimal monochromatic energy level for lung parenchyma analysis in spectral CT.MethodsAll 50 examinations (58% men, 64.8 ± 16yo) from an IRB-approved prospective study on single-source dual energy chest CT were retrospectively included and analyzed.Monochromatic images in lung window reconstructed every 5 keV from 40 to 140 keV were independently assessed by two chest radiologists. Based on the overall image quality and the depiction/conspicuity of parenchymal lesions, each reader had to designate for every patient the keV level providing the best diagnostic and image quality.Results72% of the examinations exhibited parenchymal lesions.Reader 1 picked the 55 keV monochromatic reconstruction in 52% of cases, 50 in 30% and 60 in 18%. Reader 2 chose 50 keV in 52% cases, 55 in 40%, 60 in 6% and 40 in 2%. The 50 and 55 keV levels were chosen by at least one reader in 64% and 76% of all patients, respectively.Merging 50 and 55 keV into one category results in an optimal setting selected by reader 1 in 82% of patients and by reader 2 in 92%, with a 74% concomitant agreement.ConclusionThe best image quality for lung parenchyma in spectral CT is obtained with the 50–55 keV monochromatic reconstructions.     

Clinical evaluation of whole-body oncologic PET with time-of-flight and point-spread function for the hybrid PET/MR system

PurposeHybrid positron emission tomography/magnetic resonance (PET/MR) imaging is a new multimodality imaging technology that can provide structural and functional information simultaneously. The aim of this study was to investigate the effects of the time-of-flight (TOF) and point-spread function (PSF) on small lesions observed in PET/MR images from clinical patient image sets.Materials and methodsThis study evaluated 54 small lesions in 14 patients who had undergone ¹⁸F-fluorodeoxyglucose (FDG) PET/MR. Lesions up to 30 mm in diameter were included. The PET data were reconstructed with a baseline ordered-subsets expectation-maximization (OSEM) algorithm, OSEM + PSF, OSEM + TOF and OSEM + TOF + PSF. PET image quality and small lesions were visually evaluated and scored by a 3-point scale. A quantitative analysis was then performed using the mean and maximum standardized uptake value (SUV) of the small lesions (SUV_mean and SUV_max). The lesions were divided into two groups according to the long-axis diameter and the location respectively and evaluated with each reconstruction algorithm. We also evaluated the background signal by analyzing the SUV_liver.ResultsOSEM + TOF + PSF provided the highest value and OSEM + TOF or PSF showed a higher value than OSEM for the visual assessment and quantitative analysis. The combination of TOF and PSF increased the SUV_mean by 26.6% and the SUV_max by 30.0%. The SUV_liverwas not influenced by PSF or TOF. For the OSEM + TOF + PSF model, the change in SUV_mean and SUV_max for lesions <10 mm in diameter was 31.9% and 35.8%, and 24.5% and 27.6% for lesions 10–30 mm in diameter, respectively. The abdominal lesions obtained the higher SUV than those of chest on the images with TOF and/or PSF.ConclusionApplication of TOF and PSF significantly increased the SUV of small lesions in hybrid PET/MR images, potentially improving small lesion detectability.     

Intensidad de la señal en T1 en el núcleo dentado tras la administración del agente de contraste con gadolinio macrocíclico gadoterato de meglumina: un estudio observacional

Introduction and aimsContradictory results have been reported about hyperintensity of the globus pallidus and/or dentate nucleus on unenhanced T1-weighted magnetic resonance (MR) images after exposure to various gadolinium-based contrast agents. This change in signal intensity varies with different gadolinium-based contrast agents. We aimed to determine whether signal intensity in the dentate nucleus is increased in unenhanced T1-weighted images in patients who have undergone multiple studies with the macrocyclic gadolinium-based contrast agent gadoterate meglumine. We thoroughly reviewed the literature to corroborate our results.Materials and methodsWe included patients who had undergone more than 10 MR studies with gadoterate meglumine. We quantitatively analyzed the signal intensity in unenhanced T1-weighted MR images measured in regions of interest placed in the dentate nucleus and the pons, and we calculated the dentate nucleus-to-pons signal intensity ratios and the differences between the ratio in the first MR study and the last MR study. We used t-tests to evaluate whether the differences between the signal intensity ratios were different from 0. We also analyzed the subgroups of patients who had been administered < 15 and ≥15 doses of gadoterate meglumine. We used Pearson correlation to determine the relationships between the differences in the signal intensity ratios and the number of doses of gadoterate meglumine administered.ResultsThe 54 patients (26 men) had received a mean of 13.8 ± 3.47 doses (range, 10-23 doses). The difference in the dentate nucleus-pons signal intensity ratio between the first and last MR study was -0.0275 ± 0.1917 (not significantly different from 0; p = 0.2968) in the entire group, -0.0357 ± 0.2204 (not significantly different from 0; p = 0.351 in the patients who had received < 15 doses (n = 34), and -0.0135 ± 0.1332 (not significantly different from 0; p = 0.655) in those who had received ≥15 doses (n = 20). Differences in signal intensity ratios did not correlate significantly with the accumulated dose of gadoterate meglumine (P = 0.9064; ρ = -0.0164 [95%]).ConclusionsReceiving more than 10 doses of gadoterate meglumine was not associated with increased signal intensity in the dentate nucleus.     

High-resolution 3D-MRI of postmortem brain specimens fixed by formalin and gadoteridol

PurposeThe purpose of this investigation was to compare magnetization-prepared rapid gradient echo (MP-RAGE) images with T1-weighted images (T1WI) and T2-weighted images (T1W2) of postmortem brain tissue fixed by admixtures of formalin and gadoteridol. We additionally sought to explore the feasibility of using fixed brain magnetic resonance imaging (MRIs) in forensic practices.MethodsSpecimens included in the study were eight whole brains that had been removed during forensic autopsy. Brain specimens were randomly divided into three groups and MRIs were performed either (A) the day of autopsy (n = 2) on unfixed tissue, (B) after immersion fixation in 20% formalin (n = 3), or (C) after immersion fixation in 20% formalin mixed with 4 mL/L ProHance® (gadoteridol) (n = 3). T1WI, T2WI, and MP-RAGE images of all group samples were acquired with a 3T clinical MR scanner. Gray and white matter contrasts of the cortex and basal nucleus in every fixation group and image sequence were then visually compared.ResultsGray/white matter contrasts of the cortex were good in all images obtained by MP-RAGE, and T1WIs of specimens fixed by formalin and gadoteridol-mixed formalin. Additionally, gray/white matter contrast in the basal nucleus was sufficient in the MP-RAGE sequence of specimens fixed by gadoteridol-mixed formalin.ConclusionsMRI of brains immersion-fixed in formalin and gadolinium could serve as a promising tool for neuropathological assessment in forensic practices.     

Brain perfusion heterogeneity measurement based on Random Walk algorithm: Choice and influence of inner parameters

A Random Walk (RW) algorithm was designed to quantify the level of diffuse heterogeneous perfusion in brain SPECT images in patients suffering from systemic brain disease or from drug-induced therapy. The goal of the present paper is to understand the behavior of the RW method on different kinds of images (extrinsic parameters) and also to understand how to choose the right parameters of the RW (intrinsic parameters) depending on the image characteristics (i.e. SPECT images).“Extrinsic parameters” are related to the image characteristics (level/size of defect and diffuse heterogeneity) and “intrinsic” parameters are related to the parameters of the method (number (N_rw) and length of walk (L_rw), temperature (T) and slowing parameter (S)). Two successive studies were conducted to test the influence of these parameters on the RW result.In the first study, calibrated checkerboard images are used to test the influence of “extrinsic parameters” (i.e. image characteristics) on the RW result (R-value). The R-value was tested as a function of (i) the size of black & white (B&W) squares simulating the size of a cortical defect, (ii) the intensity level gaps between the B&W squares simulating the intensity of the cortical defect and (iii) intensity (=variance) of noise, simulating the diffuse heterogeneity.The second study was constructed with simulated representative brain SPECT images, to test the “intrinsic” parameters. The R-value was tested regarding the influence of four parameters: S, T, N_rw and L_rw.The third study is constructed so as to see if the classification by diffuse heterogeneity of real brain SPECT images is the same if it's made by senior clinicians or by RW algorithm.ResultsStudy 1: the RW was strongly influenced by all the characteristics of the images. Moreover, these characteristics interact with each other. The RW is influenced most by diffuse heterogeneity, then by intensity and finally by the size of a defect.Study 2: N_rw and L_rw values of 1000 give an optimal reproducibility of the measurement (mean standard deviation < 0.1), a fast computation time (time < 0.5 s/image) and have a maximum difference in terms of R-value between the two extreme images corresponding to the range of the population studied. The best S and T values for SPECT images are 3 and 15, respectively.Study 3: A significant correlation was found between RW ranking and the physicians’ consensus (ρ = 0.789; p < 0.0001).ConclusionThis study confirms that the RW method is able to measure the heterogeneity of brain SPECT images even in the presence of a large defect. However, the result of the method is strongly influenced by the “intrinsic” parameters, so the program should be calibrated for each different type of image.     

Segmentation precision of abdominal anatomy for MRI-based radiotherapy

The limited soft tissue visualization provided by computed tomography, the standard imaging modality for radiotherapy treatment planning and daily localization, has motivated studies on the use of magnetic resonance imaging (MRI) for better characterization of treatment sites, such as the prostate and head and neck. However, no studies have been conducted on MRI-based segmentation for the abdomen, a site that could greatly benefit from enhanced soft tissue targeting. We investigated the interobserver and intraobserver precision in segmentation of abdominal organs on MR images for treatment planning and localization. Manual segmentation of 8 abdominal organs was performed by 3 independent observers on MR images acquired from 14 healthy subjects. Observers repeated segmentation 4 separate times for each image set. Interobserver and intraobserver contouring precision was assessed by computing 3-dimensional overlap (Dice coefficient [DC]) and distance to agreement (Hausdorff distance [HD]) of segmented organs. The mean and standard deviation of intraobserver and interobserver DC and HD values were DC_{intraobserver} = 0.89 ± 0.12, HD_{intraobserver} = 3.6 mm ± 1.5, DC_{interobserver} = 0.89 ± 0.15, and HD_{interobserver} = 3.2 mm ± 1.4. Overall, metrics indicated good interobserver/intraobserver precision (mean DC > 0.7, mean HD < 4 mm). Results suggest that MRI offers good segmentation precision for abdominal sites. These findings support the utility of MRI for abdominal planning and localization, as emerging MRI technologies, techniques, and onboard imaging devices are beginning to enable MRI-based radiotherapy.     

Modeling of the bony pelvis from MRI using a multi-atlas AE-SDM for registration and tracking in image-guided robotic prostatectomy

A fundamental challenge in the development of image-guided surgical systems is alignment of the preoperative model to the operative view of the patient. This is achieved by finding corresponding structures in the preoperative scans and on the live surgical scene. In robot-assisted laparoscopic prostatectomy (RALP), the most readily visible structure is the bone of the pelvic rim. Magnetic resonance imaging (MRI) is the modality of choice for prostate cancer detection and staging, but extraction of bone from MRI is difficult and very time consuming to achieve manually. We present a robust and fully automated multi-atlas pipeline for bony pelvis segmentation from MRI, using a MRI appearance embedding statistical deformation model (AE-SDM). The statistical deformation model is built using the node positions of deformations obtained from hierarchical registrations of full pelvis CT images. For datasets with corresponding CT and MRI images, we can transform the MRI into CT SDM space. MRI appearance can then be used to improve the combined MRI/CT atlas to MRI registration using SDM constraints. We can use this model to segment the bony pelvis in a new MRI image where there is no CT available. A multi-atlas segmentation algorithm is introduced which incorporates MRI AE-SDMs guidance. We evaluated the method on 19 subjects with corresponding MRI and manually segmented CT datasets by performing a leave-one-out study. Several metrics are used to quantify the overlap between the automatic and manual segmentations. Compared to the manual gold standard segmentations, our robust segmentation method produced an average surface distance 1.24 ± 0.27 mm, which outperforms state-of-the-art algorithms for MRI bony pelvis segmentation. We also show that the resulting surface can be tracked in the endoscopic view in near real time using dense visual tracking methods. Results are presented on a simulation and a real clinical RALP case. Tracking is accurate to 0.13 mm over 700 frames compared to a manually segmented surface. Our method provides a realistic and robust framework for intraoperative alignment of a bony pelvis model from diagnostic quality MRI images to the endoscopic view.     

The qualitative and quantitative image analysis of MR imaging in patients with acute-on-chronic liver failure

PurposeTo evaluate the distinctive features of ACLF and chronic liver disease (CLD) on MR images using quantitative and qualitative analyses.MethodsTwelve patients with ACLF and 36 patients with CLD who had undergone MR images were included. MR imaging findings from both groups were assessed.ResultsGallbladder edema, esophageal varix, and ascites were significantly more prevalent in the ACLF group (all P-values < 0.05). The liver to muscle SI ratio on T2-WI was significantly higher in the ACLF group (P = 0.002).ConclusionMR imaging findings could be helpful in differentiating between patients with ACLF and those with CLD.     

Raw-data-based iterative reconstruction versus filtered back projection: image quality of low-dose chest computed tomography examinations in 87 patients

ObjectiveThe objective was to compare standard-dose chest computed tomography (CT) reconstructed with filtered back projection (FBP) versus low-dose images with FBP and raw-data-based iterative reconstruction.MethodsEighty-seven consecutive patients (46 male; mean age, 54.54±16.12; mean body mass index, 24.58±4.07) referred for initial chest CT with full-dose examinations [mean dose–length product (DLP), 183.37±44.13 mGy·cm] and follow-up chest CT with half-dose examinations (mean DLP, 91.08±23.81 mGy·cm) were included. The full-dose protocol was reconstructed with FBP; the half-dose protocol was reconstructed with FBP and sinogram-affirmed iterative reconstruction (SAFIRE). Noise and signal-to-noise ratio were compared using a paired Student’s t test; subjective image quality and lesion conspicuity were compared using Wilcoxon signed ranks test.ResultsActual radiation dose of follow-up CT was about 50% (49.26%±2.62%) of standard-dose protocol. Compared to full-dose images with FBP, there was no significant difference in half-dose images with SAFIRE in the objective noise (ascending aorta: P= .38, descending aorta: P= .70, trachea on mediastinal images: P= .37) and SNR (ascending aorta: P= .14, descending aorta: P= .72, trachea on mediastinal images: P= .06) on mediastinal images. Noise was significantly lower (P< .001) and SNR was significantly higher (P< .001) in half-dose images with SAFIRE on lung images. Noise was significantly higher (P< .001) and SNR was significantly lower (P< .001) in half-dose images with FBP. Subjective image quality was similar on both mediastinal images (P= .317) and lung images (P= .614) of half-dose SAFIRE images versus full-dose FBP images. Lesion conspicuity was also similar. Subjective image quality was significantly lower on both mediastinal images (P< .001) and lung images (P< .001) of half-dose FBP images versus full-dose FBP images. The conspicuity of some lesions was significantly lower (ground-glass opacity, P< .0001; ill-defined micronodule, P< .0001; lung cyst, P< .0001; emphysematous lesion, P= .003) on half-dose FBP versus full-dose FBP images.ConclusionCompared to full-dose CT images reconstructed with the conventional FBP algorithm, SAFIRE with three iterations could provide similar or better image quality at 50% less dose.     

Gadoxetic acid-enhanced high temporal-resolution hepatic arterial-phase imaging with view-sharing technique: Impact on the LI-RADS category

PurposeTo evaluate the value of view-sharing multi-hepatic arterial-phase (mHAP) imaging for diagnosis of hypervascular hepatocellular carcinoma (HCC).Materials and methodsForty-seven consecutive patients with HCC underwent gadoxetic acid-enhanced magnetic resonance (MR) imaging before angiographic and lipiodol CT. Hepatic arterial-phase images were obtained at 5 consecutive phases with shared central k-space of 25%, followed by portal venous, late (2 and 3 min), and hepatobiliary phase imaging. One-hundred-eight HCC nodules (size: 5–88 mm, mean size: 18.2 mm) confirmed on angiographic CT and lipiodol CT were evaluated for LI-RADS category and compared with single arterial-phase and mHAP findings regarding wash out, capsule, corona enhancement, and image quality.ResultsTwenty-four HCCs (22.2%) (size: 6–19 mm, mean size: 12.3 mm) were categorized as LR-3 based on the single arterial-phase. Capsule appearance (25.9%) and washout (57.4%) were most frequently observed in late phase (2 min). Corona enhancement was observed in 73.1% of all HCCs on mHAP. For the 24 HCCs of LR-3, corona enhancement was observed in 75% on mHAP and contributed to upgrade category. No significant difference was found in the frequency of corona enhancement between mHAP and angiographic CT (P = 0.11). Image quality was valued as good or excellent in all cases.ConclusionView-sharing mHAP was feasible without compromising image quality and contributed to the improvement in diagnostic confidence for hypervascular HCC in gadoxetic acid-enhance MR imaging.     

Metal artifact reduction by dual-layer computed tomography using virtual monoenergetic images

ObjectiveThe aim of the study was to investigate the performance and diagnostic value of metal artifact reduction in virtual monoenergetic images generated from dual-layer computed tomography (DLCT).Methods35 patients that received a DLCT at the University Hospital Cologne and had an orthopedic implant in the examined region were included in this study. For each DLCT virtual monoenergetic images of different energy levels (64 keV, 70 keV, 105 keV, 140 keV, 200 keV and an optimized photon energy) were reconstructed and analyzed by three blinded observers. Images were analyzed with regard to subjective criteria (extent of artifacts, diagnostic image quality) and objective criteria (width and density of artifacts).Results21 patients had implants in the spine, 8 in the pelvis and 6 patients in the extremities. Diagnostic image quality improved significantly at high photon energies from a Likert-score of 4.3 (±0.83) to 2.3 (±1.02) and artifacts decreased significantly from a score of 4.3 (±0.66) to 2.6 (±2.57). The average optimized photon energy was 149.2 ± 39.4 keV. The density as well as the width of the most pronounced artifacts decreased from−374.6 ± 251.89 HU to −12.5 ± 205.84 HU and from 14.5 ± 8.74 mm to 6.4 ± 10.76 mm, respectively.ConclusionUsing virtual monoenergetic images valuable improvements of diagnostic image quality can be achieved by reduction of artifacts associated with metal implants. As preset for virtual monoenergetic images, 140 keV appear to provide optimal artifact reduction. In 20% of the patients, individually optimized keV can lead to a further improvement of image quality compared to 140 keV.     

Optimized Bayes variational regularization prior for 3D PET images

A new prior for variational Maximum a Posteriori regularization is proposed to be used in a 3D One-Step-Late (OSL) reconstruction algorithm accounting also for the Point Spread Function (PSF) of the PET system.The new regularization prior strongly smoothes background regions, while preserving transitions. A detectability index is proposed to optimize the prior.The new algorithm has been compared with different reconstruction algorithms such as 3D-OSEM + PSF, 3D-OSEM + PSF + post-filtering and 3D-OSL with a Gauss-Total Variation (GTV) prior.The proposed regularization allows controlling noise, while maintaining good signal recovery; compared to the other algorithms it demonstrates a very good compromise between an improved quantitation and good image quality.     

Quantification accuracy of neuro-oncology PET data as a function of emission scan duration in PET/MR compared to PET/CT

ObjectivesTo evaluate and compare the effect of reduced acquisition time, as a surrogate of injected activity, on the PET quantification accuracy in PET/CT and PET/MR imaging.MethodsTwenty min ¹⁸F-FDG phantom measurements and 10 min ¹⁸F-FET brain scans were acquired in a Biograph-True-Point-True-View PET/CT (n = 8) and a Biograph mMR PET/MR (n = 16). Listmode data were repeatedly split into frames of 1 min to 10 min length and reconstructed using two different reconstruction settings of a 3D-OSEM algorithm: with post-filtering (“OSEM”), and without post-filtering but with resolution recovery (“PSF”). Recovery coefficients (RC_max, RC_A50) and standard uptake values (SUV_max, SUV_A50) were evaluated.ResultsRC_max (phantom) and SUV_max (patients) increased significantly when reducing the frame duration. Significantly lower deviations were observed for RC_A50 and SUV_A50, respectively, making them more appropriate to compare PET studies at different number of counts. No statistical significant differences were observed when using post-filtering and reducing the frame time to 4 min (RC_A50, reference 20 min, phantom) and to 3 min (SUV_A50, reference 10 min, patients).ConclusionsFor hybrid aminoacid brain imaging, frame duration (or injected activity) can potentially be reduced to 30% of the standard used in clinical routine without significant changes on the quantification accuracy of the PET images if adequate reconstruction settings and quantitative measures are used. Frame times below 4 min in the NEMA phantom are not advisable to obtain quantitative and reproducible measures.     

Abbreviated breast magnetic resonance protocol: Value of high-resolution temporal dynamic sequence to improve lesion characterization

PurposeTo evaluate the added value of ULTRAFAST-MR sequence to an abbreviated FAST protocol in comparison with FULL protocol to distinguish benign from malignant lesions in a population of women, regardless of breast MR imaging indication.Materials and methodsFrom March 10th to September 22th, 2014, we retrospectively included a total of 70 consecutive patients with 106 histologically proven lesions (58 malignant and 48 benign) who underwent breast MR imaging for preoperative breast staging (n = 38), high-risk screening (n = 7), problem solving (n = 18), and nipple discharge (n = 4) with 12 time resolved imaging of contrast kinetics (TRICKS) acquisitions during contrast inflow interleaved in a regular high-resolution dynamic MRI protocol (FULL protocol). Two readers scored MR exams as either positive or negative and described significant lesions according to Bi-RADS lexicon with a TRICKS images (ULTRAFAST), an abbreviated protocol (FAST) and all images (FULL protocol). Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for each protocol and compared with McNemar’s test.ResultsFor all readers, the combined FAST–ULTRAFAST protocol significantly improved the reading with a specificity of 83.3% and 70.8% in comparison with FAST protocol or FULL protocol, respectively, without change in sensitivity. By adding ULTRAFAST protocol to FAST protocol, readers 1 and 2 were able to correctly change the diagnosis in 22.9% (11/48) and 10.4% (5/48) of benign lesions, without missing any malignancy, respectively. Both interpretation and image acquisition times for combined FAST-ULTRAFAST protocol and FAST protocol were shorter compared to FULL protocol (p < 0.001).ConclusionCompared to FULL protocol, adding ULTRAFAST to FAST protocol improves specificity, mainly in correctly reclassifying benign masses and reducing interpretation and acquisition time, without decreasing sensitivity.     

Altered spontaneous brain activity pattern in cognitively normal young adults carrying mutations of APP,presenilin-1/2 and APOE ε4

ObjectiveTo explore genetic effects of amyloid precursor protein (APP), presenilin-1/2 and apolipoprotein E (APOE) ε4 on brain structural and functional alterations in cognitively normal young adults.Materials and methodsEighty healthy adults (mean age 24.0 ± 2.5 years; n = 18, APP/presenilin-1/2 group; n = 31, APOE ε4 group; n = 31, control group [without above-mentioned gene mutation]) underwent high-resolution T1-weighted 3D anatomical imaging, resting-state functional MR imaging and neuropsychological assessments. We used voxel-based morphometry and regional homogeneity (ReHo) algorithms to investigate brain structural and functional changes among three groups, and performed correlation analyses between the brain regions with statistically significant difference and neuropsychological results.ResultsNo brain structural changes were found, however, ReHo values were increased in right parietal-frontal lobes in APOE ε4 group, and decreased in the left middle temporal gyrus in APP/presenilin-1/2 group compared with controls (all P < 0.05). Compared with APOE ε4 group, decreased ReHo values of bilateral temporal lobes were shown in APP/presenilin-1/2 group (P < 0.05). ReHo values of right superior frontal gyrus in APOE ε4 group positively correlated with neuropsychological tests scores(P < 0.05).ConclusionCognitively normal young adults carrying APOE ε4 or APP/presenilin-1/2 had different spontaneous brain activity patterns without cerebral structural differences.     

Automated identification of anatomical landmarks on 3D bone models reconstructed from CT scan images

Identification of anatomical landmarks on skeletal tissue reconstructed from CT/MR images is indispensable in patient-specific preoperative planning (tumour referencing, deformity evaluation, resection planning, and implant alignment and anchoring) as well as intra-operative navigation (bone registration and instruments referencing). Interactive localisation of landmarks on patient-specific anatomical models is time-consuming and may lack in repeatability and accuracy. We present a computer graphics-based method for automatic localisation and identification (labelling) of anatomical landmarks on a 3D model of bone reconstructed from CT images of a patient. The model surface is segmented into different landmark regions (peak, ridge, pit and ravine) based on surface curvature. These regions are labelled automatically by an iterative process using a spatial adjacency relationship matrix between the landmarks. The methodology has been implemented in a software program and its results (automatically identified landmarks) are compared with those manually palpated by three experienced orthopaedic surgeons, on three 3D reconstructed bone models. The variability in location of landmarks was found to be in the range of 2.15–5.98 mm by manual method (inter surgeon) and 1.92–4.88 mm by our program. Both methods performed well in identifying sharp features. Overall, the performance of the automated methodology was better or similar to the manual method and its results were reproducible. It is expected to have a variety of applications in surgery planning and intra-operative navigation.     

Evaluating the effect of rectal distension on prostate multiparametric MRI image quality

PurposeTo evaluate the effect of rectal distension on the quality of anatomical and functional prostate multiparametric (mp) MRI.Materials and methodsMultiparametric (mp) 3T-MRI images of 173 patients were independently evaluated by two radiologists in this retrospective study. Planimetry rectal volumes were derived and a subjective assessment of rectal distension was made using a 5-point Likert scale (1 = no stool/gas, 5 = large amount of stool/gas). Image quality of diffusion-weighted imaging (DWI) was evaluated using a 5-point Likert scale. DWI was further scored for distortion and artefact. T2W images were evaluated for image sharpness and the presence of motion artefact. The stability of the dynamic contrast-enhancement acquisition was assessed by recording the number of corrupt data points during the wash-out phase.ResultsThere was a strong correlation between subjective scoring of rectal loading and objectively measured rectal volume (r = 0.82), p < 0.001. A significant correlation was shown between increased rectal distension and both reduced DW image quality (r = −0.628, p < 0.001), and increased DW image distortion (r = 0.814, p < 0.001). There was also a significant trend for rectal distension to increase artefact at DWI (r = 0.154, p = 0.042). Increased rectal distension led to increased motion artefact on T2 (p = 0.0096), but did not have a significant effect on T2-sharpness (p = 0.0638). There was no relationship between rectal distension and DCE image quality (p = 0.693). 63 patients underwent lesion-targeted biopsy post MRI, there was a trend to higher positive predictive values in patients with minor rectal distension (34/38, 89.5%) compared to those with moderate/marked distension (18/25, 72%), p = 0.09.ConclusionRectal distension has a significant negative effect on the quality of both T2W and DW images. Consideration should therefore be given to bowel preparation prior to prostate mpMRI to optimise image quality.