Integration of dynamic parameters in the analysis of 18F-FDopa PET imaging improves the prediction of molecular features of gliomas

PURPOSE

¹⁸F-FDopa PET imaging of gliomas is routinely interpreted with standardized uptake value (SUV)-derived indices. This study aimed to determine the added value of dynamic ¹⁸F-FDopa PET parameters for predicting the molecular features of newly diagnosed gliomas.

METHODS

We retrospectively included 58 patients having undergone an ¹⁸F-FDopa PET for establishing the initial diagnosis of gliomas, whose molecular features were additionally characterized according to the WHO 2016 classification. Dynamic parameters, involving time-to-peak (TTP) values and curve slopes, were tested for the prediction of glioma types in addition to current static parameters, i.e., tumor-to-normal brain or tumor-to-striatum SUV ratios and metabolic tumor volume (MTV).

RESULTS

There were 21 IDH mutant without 1p/19q co-deletion (IDH+/1p19q-) gliomas, 16 IDH mutants with 1p/19q co-deletion (IDH+/1p19q+) gliomas, and 21 IDH wildtype (IDH-) gliomas. Dynamic parameters enabled differentiating the gliomas according to these molecular features, whereas static parameters did not. In particular, a longer TTP was the single best independent predictor for identifying (1) IDH mutation status (area under the curve (AUC) of 0.789, global accuracy of 74% for the criterion of a TTP ≥ 5.4 min) and (2) 1p/19q co-deletion status (AUC of 0.679, global accuracy of 69% for the criterion of a TTP ≥ 6.9 min). Moreover, the TTP from IDH- gliomas was significantly shorter than those from both IDH+/1p19q- and IDH+/1p19q+ (p ≤ 0.007).

CONCLUSION

Prediction of the molecular features of newly diagnosed gliomas with ¹⁸F-FDopa PET and especially of the presence or not of an IDH mutation, may be obtained with dynamic but not with current static uptake parameters.

Compared vulnerabilities to small cardiac motions between different cameras used for myocardial perfusion imaging

This phantom-based study was aimed to determine whether cardiac CZT-cameras, which provide an enhanced spatial resolution and image contrast compared to Anger cameras, are similarly affected by small cardiac motions. Translations of a left ventricular (LV) insert at half-SPECT acquisitions through six possible orthogonal directions and with 5- or 10-mm amplitude were simulated on the Discovery NM-530c and DSPECT CZT-cameras and on an Anger Symbia T2 camera equipped with an astigmatic (IQ.SPECT) or conventional parallel-hole collimator (Conv.SPECT). SPECT images were initially reconstructed as currently recommended for clinical routine. The heterogeneity in recorded activity from the 17 LV segments gradually increased between baseline and motions simulated at 5- and 10-mm amplitudes with all cameras, although being higher for Anger- than CZT-cameras at each step and resulting in a higher mean number of artifactual abnormal segments (at 10-mm amplitude, Conv.SPECT: 3.7; IQ.SPECT: 1.8, Discovery: 0.7, DSPECT: 0). However, this vulnerability to motion was markedly (1) decreased for Conv.SPECT reconstructed without the recommended Resolution Recovery algorithm and (2) increased for DSPECT reconstructed without the recommended cardiac model. CZT-cameras and especially the DSPECT appear less vulnerable to small cardiac motions than Anger-cameras although these differences are strongly dependent on reconstruction parameters.

Head-to-head comparison of image quality between brain 18F-FDG images recorded with a fully digital versus a last-generation analog PET camera

BACKGROUND

The quality of phantom images was previously shown to be higher on digital (Vereos Philips®) compared to analog PET (Ingenuity Philips®) cameras. This study aimed to determine the extent to which this difference still remains significant on normal brain ¹⁸F-FDG PET images.

METHODS

Relative noise and contrast as well as border sharpness (a spatial resolution index) of central (striata) and peripheral (occiput) gray-matter structures were compared between 10 sets of normal brain ¹⁸F-FDG PET images recorded and reconstructed on digital and analog last-generation PET cameras, together with a subjective visual analysis of image quality provided by experienced physicians.

RESULTS

Compared with analog PET, digital PET provided marked improvements in image quality parameters. The median relative noise was decreased (- 22%), while gray/white-matter contrast was increased (+ 27%/+ 41% for central/peripheral gray-matter structures), with these results being consistent with visual analysis. In addition, a clear enhancement in image sharpness was further documented for digital PET owing to the possible use of a 1-mm³ voxel size (+ 24%/+ 21%).

CONCLUSIONS

On normal brain ¹⁸F-FDG images and compared with a last-generation analog PET, the fully digital PET camera offers marked improvements in image noise and contrast, as well as significant potential for further enhancing spatial resolution.

Low fibrosis biomarker levels predict cardiac resynchronization therapy response

Cardiac fibrosis is associated with heart failure and poor prognosis. Fibrosis biomarkers have been poorly evaluated as a tool to predict cardiac resynchronization therapy (CRT) response generating conflicting results. The present study assessed the predictive value of cardiac fibrosis biomarkers on CRT response. Patients underwent clinical examination, echocardiography and blood fibrosis biomarker evaluation prior to CRT implantation. At six months, a positive response to CRT was defined by a composite endpoint of no death or hospitalization for heart failure, and presence of left ventricular (LV) reverse remodeling (decrease in LV end-systolic volume ≥15%). Sixty patients were included in a multicenter study. At 6 months, 38 were positive responders to CRT and reached the response criteria (63%). Compared to non-responders, CRT responders displayed lower concentration levels of the fibrosis biomarkers procollagen type I C-terminal propeptide [PICP 135[99–166] ng/ml vs. 179[142–226]ng/ml, p = 0.001)] and procollagen type III N-terminal propeptide [PIIINP 5.50[3.66–8.96] ng/ml vs. 8.01[5.01–11.86]ng/ml, p = 0.014)] at baseline. In multivariate analysis, a PICP ≤ 163 ng/ml was associated with a positive CRT response [OR = 7.8(1.3–46.7), p = 0.023] independently of the presence of LBBB, QRS duration, LV lead position or non-ischemic cardiomyopathy. Altogether, the present findings show that a lower degree of cardiac fibrosis is associated with a positive response after CRT implantation. PICP evaluation before CRT implantation could help improve patient selection.

Low-dose dual-isotope procedure planed for myocardial perfusion CZT-SPECT and assessed through a head-to-head comparison with a conventional single-isotope protocol

PURPOSE OF THE REPORT

This study aimed at assessing an original low-dose dual-isotope procedure in which the abnormal stress Tc-99m Sestamibi SPECT is followed by rest Tl-201 SPECT, along with a head-to-head comparison with a single-isotope procedure.

METHODS AND RESULTS

One hundred two patients, referred for a low-dose stress-SPECT with Sestamibi (123 ± 20 MBq) on a CZT camera and for whom a rest Sestamibi SPECT was warranted, had an additional Tl-201 rest-SPECT (52 ± 5 MBq) between stress and rest Sestamibi SPECT recordings. Tl-201 images were processed for spill-over and scatter corrections, and uptake differences with stress Sestamibi SPECT were analyzed: (1) for rest acquisitions from Tl-201 (dual-isotope procedure) and from Sestamibi (single-isotope procedure) and (2) in segments for which a diagnosis of ischemia, infarct, or normal perfusion was achieved. Mean effective dose was 8.3 mSv for dual-isotope but would decrease to 5.7 mSv for an expected rate of 37% of patients for whom rest-SPECT is not warranted. After a further background correction of Tl-201 images, the rest-stress difference in myocardial uptake was equivalent between dual- and single-procedures for identifying ischemic segments (respective areas-under-curves: 0.83 ± 0.03 and 0.81 ± 0.03).

CONCLUSION

This original dual-isotope procedure provides acceptable radiation doses and consistent results, as compared with conventional single-isotope.

Assessment of Myocardial CZT SPECT Recording in a Forward-Leaning Bikerlike Position

This prospective randomized study assessed myocardial perfusion imaging with the high-sensitivity D.SPECT cadmium-zinc-telluride camera in a forward-leaning bikerlike position, which may potentially lower diaphragmatic attenuation and reduce breathing-related cardiac motion, in a manner comparable to the prone position proposed with other SPECT cameras. Methods: Patients referred for a stress-rest ^99mTc-sestamibi protocol and positioned in the biker position, with the chest leaning forward on the D.SPECT camera-head at 35° from vertical, had an additional resting D.SPECT recording in the supine position (n = 40) or in the sitting position with the back rearward at 30° from vertical (n = 40). Segments with attenuation artifacts were defined as those with less than 65% uptake but with strictly normal contractility at gated SPECT and no defect reversibility from stress images. Results: The biker position was associated with lower heart-to-detector distances than the supine or sitting positions (both P < 0.001); lower cardiac motion amplitudes, assessed on panograms, than the supine position (P < 0.001); and fewer segments with attenuation artifacts than the supine position (on average, 1.10 ± 1.01 vs. 1.90 ± 1.74, P = 0.010) or the sitting position (0.75 ± 0.93 vs. 1.38 ± 1.60, P = 0.011). Conclusion: Myocardial perfusion images from D.SPECT are enhanced for patients positioned in a forward-leaning bikerlike position comparatively to sitting or supine positions, with a notably lower rate of attenuation artifacts.

PET imaging of 68Ga-NODAGA-RGD, as compared with 18F-fluorodeoxyglucose, in experimental rodent models of engrafted glioblastoma

BACKGROUND

Tracers triggering αvβ3 integrins, such as certain RGD-containing peptides, were found promising in previous pilot studies characterizing high-grade gliomas. However, only limited comparisons have been performed with current PET tracers. This study aimed at comparing the biodistribution of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) with that of ⁶⁸Ga-NODAGA-RGD, an easily synthesized monomeric RGD compound with rapid kinetics, in two different rodent models of engrafted human glioblastoma.

METHODS

Nude rodents bearing human U87-MG glioblastoma tumor xenografts in the flank (34 tumors in mice) or in the brain (5 tumors in rats) were analyzed. Kinetics of ⁶⁸Ga-NODAGA-RGD and of ¹⁸F-FDG were compared with PET imaging in the same animals, along with additional autohistoradiographic analyses and blocking tests for ⁶⁸Ga-NODAGA-RGD.

RESULTS

Both tracers showed a primary renal route of clearance, although with faster clearance for ⁶⁸Ga-NODAGA-RGD resulting in higher activities in the kidneys and bladder. The tumor activity from ⁶⁸Ga-NODAGA-RGD, likely corresponding to true integrin binding (i.e., suppressed by co-injection of a saturating excess of unlabeled RGD), was found relatively high, but only at the 2^nd hour following injection, corresponding on average to 53% of total tumor activity. Tumor uptake of ⁶⁸Ga-NODAGA-RGD decreased progressively with time, contrary to that of ¹⁸F-FDG, although ⁶⁸Ga-NODAGA-RGD exhibited 3.4 and 3.7-fold higher tumor-to-normal brain ratios on average compared to ¹⁸F-FDG in mice and rat models, respectively. Finally, ex-vivo analyses revealed that the tumor areas with high ⁶⁸Ga-NODAGA-RGD uptake also exhibited the highest rates of cell proliferation and αv integrin expression, irrespective of cell density.

CONCLUSIONS

⁶⁸Ga-NODAGA-RGD has a high potential for PET imaging of glioblastomas, especially for areas with high integrin expression and cell proliferation, although PET recording needs to be delayed until the 2^nd hour following injection in order to provide sufficiently high integrin specificity.

Routine evaluation of left ventricular function using CZT-SPECT, with low injected activities and limited recording times

PURPOSE

Gamma-cameras, with Cadmium-Zinc-Telluride (CZT) detectors, allow to perform myocardial perfusion imaging (MPI) with limited injected activities and recorded times. This study aimed at determining whether the routine assessment of left ventricular (LV) function with such limited counts protocols compares well with reference values from cardiac MRI.

METHODS

The study included patients who have undergone cardiac MRI and an MPI routinely planned on a CZT camera with a low-dose protocol (120 MBq of Sestamibi for stress and 360 MBq at rest for 75 kg body weight), while targeting the recording of only 500 myocardial kcounts in order to limit the recording times (<10 minutes for stress, <4 minutes for rest). SPECT images were reconstructed with a method maintaining rather high spatial (8 mm) and temporal (16 frames/cycle) resolutions.

RESULTS

Seventy-six patients were included, and mean effective dose was 3.5 ± 1.7 mSv for the total MPI protocol. Correlations between CZT-SPECT and MRI were good to excellent for ejection fraction (r 2 = 0.77), end-diastolic (r 2 = 0.88) and end-systolic (r 2 = 0.93) volumes, and the analysis of segmental contractility correlated well between the two techniques (kappa score = 0.72 ± 0.02).

CONCLUSION

LV function, assessed on a CZT camera with low injected activities and limited recording times, correlates well with the reference assessment from cardiac MRI.

A high 18F-FDOPA uptake is associated with a slow growth rate in diffuse Grade II-III gliomas

OBJECTIVE

In diffuse Grade II-III gliomas, a high 3,4-dihydroxy-6-(¹⁸F)-fluoro-L-phenylalanine (¹⁸F-FDOPA) positron emission tomography (PET) uptake, with a standardized uptake value (SUV_max)/contralateral brain tissue ratio greater than 1.8, was previously found to be consistently associated with the presence of an isocitrate dehydrogenase (IDH) mutation, whereas this mutation is typically associated with a better prognosis. This pilot study was aimed to ascertain the prognostic value of this high ¹⁸F-FDOPA uptake in diffuse Grade II-III gliomas with regard to the velocity of diameter expansion (VDE), which represents an established landmark of better prognosis when below 4 mm per year.

METHODS

20 patients (42 ± 10 years, 10 female) with newly-diagnosed diffuse Grade II-III gliomas (17 with IDH mutation) were retrospectively included. All had a ¹⁸F-FDOPA PET, quantified with SUV_max ratio, along with a serial MRI enabling VDE determination.

RESULTS

SUV_max ratio was above 1.8 in 5 patients (25%) all of whom had a VDE <4 mm/year (100%) and IDH mutation (100%). Moreover, a SUV_max ratio above 1.8 was associated with higher rates of VDE <4 mm/year in the overall population (45 vs 0%, p = 0.04) and also in the subgroup of patients with IDH mutation (45 vs 0%, p = 0.10).

CONCLUSION

This pilot study shows that in diffuse Grade II-III gliomas, a high ¹⁸F-FDOPA uptake would be predictive of low tumour growth, with a different prognostic significance than IDH mutation. Advances in knowledge: ¹⁸F-FDOPA PET in a single session imaging could have prognostic value in initial diagnosis of diffuse Grade II-III gliomas.

Permanently Hypoxic Cell Culture Yields Rat Bone Marrow Mesenchymal Cells with Higher Therapeutic Potential in the Treatment of Chronic Myocardial Infarction

BACKGROUND

The mismatch between traditional in vitro cell culture conditions and targeted chronic hypoxic myocardial tissue could potentially hamper the therapeutic effects of implanted bone marrow mesenchymal stem cells (BMSCs). This study sought to address (i) the extent of change to BMSC biological characteristics in different in vitro culture conditions and (ii) the effectiveness of permanent hypoxic culture for cell therapy in treating chronic myocardial infarction (MI) in rats.

METHODS

rat BMSCs were harvested and cultured in normoxic (21% O2, n=27) or hypoxic conditions (5% O2, n=27) until Passage 4 (P4). Cell growth tests, flow cytometry, and Bio-Plex assays were conducted to explore variations in the cell proliferation, phenotype, and cytokine expression, respectively. In the in vivo set-up, P3-BMSCs cultured in normoxia (n=6) or hypoxia (n=6) were intramyocardially injected into rat hearts that had previously experienced 1-month-old MI. The impact of cell therapy on cardiac segmental viability and hemodynamic performance was assessed 1 month later by 2-Deoxy-2[18F]fluoro-D-glucose (18F-FDG) positron emission tomography (PET) imaging and pressure-volume catheter, respectively. Additional histomorphological examinations were conducted to evaluate inflammation, fibrosis, and neovascularization.

RESULTS

Hypoxic preconditioning significantly enhanced rat BMSC clonogenic potential and proliferation without altering the multipotency. Different profiles of inflammatory, fibrotic, and angiogenic cytokine secretion were also documented, with a marked correlation observed between in vitro and in vivo proangiogenic cytokine expression and tissue neovessels. Hypoxic-preconditioned cells presented a beneficial effect on the myocardial viability of infarct segments and intrinsic contractility.

CONCLUSION

Hypoxic-preconditioned BMSCs were able to benefit myocardial perfusion and contractility, probably by modulating the inflammation and promoting angiogenesis.

Short-Term Heart Retention and Distribution of Intramyocardial Delivered Mesenchymal Cells within Necrotic or Intact Myocardium

Cell therapy with bone marrow mesenchymal stem cells (BMSCs) is a new strategy for treating ischemic heart failure, but data concerning the distribution and retention of transplanted cells remain poor. We investigated the short-term myocardial retention of BMSCs when these cells are directly injected within necrotic or intact myocardium. 111Indium-oxine-labeled autologous BMSCs were injected within either 1-month-old infarction (n = 6) or normal myocardium (n = 6) from rats. Serial in vivo pinhole scintigraphy was scheduled during 1 week in order to track the implanted cells. The myocardial retention of BMSCs was definitely higher in myocardial infarction than in normal myocardial area (estimated percent retention at 2 h: 63 ± 3% vs. 25 ± 4%, p < 0.001) and the estimated cardiac retention values were unchanged in both groups along the 7 days of follow-up. On heart sections at day 7, labeled BMSCs were still around the injection site and appeared confined to the scarred tissue corresponding either to the infarct area or to the myocardium damaged by needle insertion. BMSCs have a higher retention when they are injected in necrotic than in normal myocardial areas and these cells appear to stay around the injection site for at least a 7-day period.

Aneurysmal angiosarcoma associated with vascular graft revealed by 18F-FDG-PET imaging

We report a rare case of vascular graft-associated aneurysmal angiosarcoma by ¹⁸F-Fluorodeoxyglucose (FDG) positron emission tomography (PET). An 81-year-old male patient, with a prior history of graft interposition 1 year previously, was referred to ¹⁸F-FDG-PET because of an inflammatory syndrome of unknown origin. FDG-PET images revealed a particular pattern of intense circular uptake within the arterial wall (SUVmax = 10) in a popliteal aneurysm and, additionally, a large hypermetabolic mass centered by the graft. Remote hypermetabolisms in lung nodules and pleural thickenings were also detected. The diagnosis of angiosarcoma was ascertained through histopathological analysis of surgical samples. Development of an aneurysmal angiosarcoma at the site of a vascular graft is a rare entity, often misdiagnosed. ¹⁸F-FDG-PET appears to be useful in its detection with a PET pattern of intense circular uptake within the arterial wall. Such finding should lead to the search for distant metastasis.

Quantitative SPM Analysis Involving an Adaptive Template May Be Easily Applied to [18F]FDG PET Images of the Rat Brain

PURPOSE

The Statistical Parametric Mapping (SPM) software is frequently used for the quantitative analysis of patients' brain images obtained from 2-deoxy-2-[¹⁸F]fluoro-D-glucose positron emission tomography ([¹⁸F]FDG PET). However, its adaptation to small animals is difficult, particularly for the initial step of spatial normalization which requires a specific brain anatomical template. This study was aimed at determining whether SPM analysis can be applied to rat, and more specifically to the lithium-pilocarpine model of epilepsy, by using an adaptive template. This template developed for PET clinical imaging is constructed from a block matching algorithm.

PROCEDURES

SPM analysis of brain [¹⁸F]FDG PET images from Sprague-Dawley rats was used with the block matching (BM) adaptive template for the detection of brain abnormalities (1) artificially inserted within the initially normal brain images of 10 rats (50 % decrease in signal intensity within 40 spheres of 0.5 to 1.0 mm in diameter) and (2) occurring at 4 h (n = 16), 48 h (n = 15), and 8 days (n = 13) after lithium-pilocarpine treatment.

RESULTS

Concordant positive clusters were documented for all inserted abnormalities, whereas no aberrant clusters were documented in remote brain areas. Positive clusters were also detected on sites known to be involved in the epileptogenesis process of the lithium-pilocarpine model (piriform and entorhinal cortex, hippocampus), with the expected time-specific changes involving an early hypermetabolism followed by a severe hypometabolism and a subsequent partial recovery.

CONCLUSION

A quantitative SPM analysis of brain [¹⁸F]FDG PET images may be applied to the monitoring of rat brain function when using an adaptive BM template.

Aortic compliance variation in long male distance triathletes: A new insight into the athlete's artery?

OBJECTIVES

To assess cardiac and vascular adaptations in long-distance male triathletes and the influence of an increased training volume on these parameters.

DESIGN

Case-control study using long-distance male triathletes (Tri) (n=12) and an age-matched cohort of sedentary volunteers (Ctrl).

METHODS

All participants gave an informed consent and underwent a Cardiovascular Magnetic Resonance imaging (CMR) exam to measure left and right ventricle functional parameters, and aortic parameters (surface, strain, compliance, pulse wave velocity). This exam was repeated in the triathletes' group after an increased training volume of at least 2h/week for six weeks.

RESULTS

Compared to control volunteers, triathletes presented at baseline a typical pattern of athlete's heart (higher end-diastolic, end-systolic and stroke volumes index, p≤0.009, and lower cardiac rate, p=0.015) but similar vascular characteristics except a trend towards an enlarged ascending aorta (surface 942±106 vs 812±127mm², p=0.058). Between the two visits, the triathletes increased their weekly training time from 9.67±2.43 (Tri1) to 12.15±3.01h (Tri2): no modifications were found regarding cardiac parameters, but compliance and distensibility of the ascending aorta increased, from 2.60 to 3.34mm²/mmHg (p=0.028) and from 3.36 to 4.40×10^-3mmHg^-1 (p=0.048) respectively.

CONCLUSIONS

Using CMR, we showed that vascular characteristics of the ascending aorta may vary along the sport season in endurance athletes. This remodelling could be considered as a physiological adaptation, but could eventually lead to an adverse vascular remodelling.

Myocardial infarct sizing by late gadolinium-enhanced MRI: Comparison of manual, full-width at half-maximum, and n-standard deviation methods

PURPOSE

To compare three widely used methods for myocardial infarct (MI) sizing on late gadolinium-enhanced (LGE) magnetic resonance (MR) images: manual delineation and two semiautomated techniques (full-width at half-maximum [FWHM] and n-standard deviation [SD]).

MATERIALS AND METHODS

3T phase-sensitive inversion-recovery (PSIR) LGE images of 114 patients after an acute MI (2-4 days and 6 months) were analyzed by two independent observers to determine both total and core infarct sizes (TIS/CIS). Manual delineation served as the reference for determination of optimal thresholds for semiautomated methods after thresholding at multiple values. Reproducibility and accuracy were expressed as overall bias ± 95% limits of agreement.

RESULTS

Mean infarct sizes by manual methods were 39.0%/24.4% for the acute MI group (TIS/CIS) and 29.7%/17.3% for the chronic MI group. The optimal thresholds (ie, providing the closest mean value to the manual method) were FWHM30% and 3SD for the TIS measurement and FWHM45% and 6SD for the CIS measurement (paired t-test; all P > 0.05). The best reproducibility was obtained using FWHM. For TIS measurement in the acute MI group, intra-/interobserver agreements, from Bland-Altman analysis, with FWHM30%, 3SD, and manual were -0.02 ± 7.74%/-0.74 ± 5.52%, 0.31 ± 9.78%/2.96 ± 16.62% and -2.12 ± 8.86%/0.18 ± 16.12, respectively; in the chronic MI group, the corresponding values were 0.23 ± 3.5%/-2.28 ± 15.06, -0.29 ± 10.46%/3.12 ± 13.06% and 1.68 ± 6.52%/-2.88 ± 9.62%, respectively. A similar trend for reproducibility was obtained for CIS measurement. However, semiautomated methods produced inconsistent results (variabilities of 24-46%) compared to manual delineation.

CONCLUSION

The FWHM technique was the most reproducible method for infarct sizing both in acute and chronic MI. However, both FWHM and n-SD methods showed limited accuracy compared to manual delineation. J. Magn. Reson. Imaging 2016;44:1206-1217.

Grey-Matter Metabolism in Relation with White-Matter Lesions in Older Hypertensive Patients with Subjective Memory Complaints: A Pilot Voxel-Based Analysis Study

BACKGROUND

This study aimed at assessing the changes in brain metabolism related to white-matter magnetic resonance (MR) hyperintensities of presumed vascular origin, with a voxel-based quantitative analysis of (18F)-fluorodesoxyglucose positron emission tomography (FDG-PET) imaging.

METHODS

Sixty older hypertensive patients with subjective memory complaints (75 ± 5 years, 34 women) were prospectively referred to FDG-PET and MRI brain imaging. The Statistical Parametric Mapping software was used to assess the correlation between brain distribution of FDG and white-matter hyperintensities assessed by the Fazekas score on MRI images.

RESULTS

The Fazekas score was inversely related to FDG uptake, independently of age and gender, within 14 Brodmann areas located mainly in the frontal lobe but also in certain limbic, insular and temporal areas. This relationship was also found to be largely independent of the volume of grey matter expressed in percentage of cranial volume, an index of atrophy.

CONCLUSIONS

White-matter MR hyperintensities of presumed vascular origin are cross-sectionally associated with a lower grey-matter metabolism, mainly but not only within frontal areas and independently of age, gender and grey-matter atrophy.

Joint Reconstruction of Multiple Images and Motion in MRI: Application to Free-Breathing Myocardial T₂Quantification

Exploiting redundancies between multiple images of an MRI examination can be formalized as the joint reconstruction of these images. The anatomy is preserved indeed so that specific constraints can be implemented (e.g. most of the features or spatial gradients should be in the same place in all these images) and only the contrast changes from one image to another need to be encoded. The application of this concept is particularly challenging in cardiovascular and body imaging due to the complex organ deformations, especially with the patient breathing. In this study a joint optimization framework is proposed for reconstructing multiple MR images together with a nonrigid motion model. The motion model takes into account both intra-image and inter-image motion and therefore can correct for most ghosting/blurring artifacts and misregistration between images. The framework was validated with free-breathing myocardial T2 mapping experiments from nine heart transplant patients at 1.5 T. Results showed improved image quality and excellent image alignment with the multi-image reconstruction compared to the independent reconstruction of each image. Segment-wise myocardial T2 values were in good agreement with the reference values obtained from multiple breath-holds (62.5 ± 11.1 ms against 62.2 ± 11.2 ms which was not significant with p=0.49).