Compressed sensing in magnetic resonance perfusion imaging.

Perfúzní zobrazování pomocí magnetické rezonance je lékařská diagnostická metoda, která se zdá být v dnešní době velmi slibnou. Tato práce se zabývá řídkými reprezentacemi, rekonstrukcí matic s nízkou hodností a komprimovaným snímáním, které umožňuje překonání současných fyzikálních možností perfúzního zobrazování pomocí magnetické rezonance. Dále představuje několik modelů pro rekonstrukci naměřených perfúzních dat a uvádí numerické metody pro jejich softwarovou implementaci, která je důležitou součástí práce. Navržené modely jsou ověřeny na simulovaných i reálných perfúzních datech z magnetické rezonance.Magnetic resonance perfusion imaging is a today's very promising method for medicine diagnosis. This thesis deals with a sparse representation of signals, low-rank matrix recovery and compressed sensing, which allows overcoming present physical limitations of magnetic resonance perfusion imaging. Several models for reconstruction of measured perfusion data is introduced and numerical methods for their software implementation, which is an important part of the thesis, is mentioned. Proposed models are verified on simulated and real perfusion data from magnetic resonance.

Noninvasive anatomical and functional assessment of coronary artery disease.

INTRODUCTION AND OBJECTIVE: In suspected coronary artery disease (CAD), invasive coronary angiography (ICA) is traditionally the diagnostic tool of choice. However, patients often have no significant disease. Moreover, assessment of fractional flow reserve (FFR) has been shown to have prognostic implications. Recently, coronary computed tomography angiography (CTA) and cardiac magnetic resonance (CMR) myocardial perfusion imaging (CMR-Perf) have gained increasing attention through their accurate anatomical and functional assessment, respectively. We studied the added value of integrating these tests (CT+CMRint) in the diagnosis of CAD, with FFR as the reference standard. METHODS: We included 101 patients consecutively referred for outpatient assessment of CAD who underwent CTA and CMR-Perf prior to ICA with FFR assessment. Lesions were considered positive by CT+CMRint only if positive in the two tests alone. The mean follow-up was 2.9±0.6 years. RESULTS: All patients completed the study protocol without adverse effects. Forty-four patients had CAD by FFR. CTA had excellent sensitivity and negative predictive value (100%) but, as expected, its specificity and positive predictive value were lower (61% and 67%, respectively). Diagnostic accuracy by FFR was 78% for CTA, 88% for CMR-Perf and 92% for CT+CMRint. Regarding diagnostic accuracy, CT+CMRint showed statistically significant superiority (AUC=0.917, 95% CI 0.845-0.963) compared with CTA (AUC=0.807, 95% CI 0.716-0.879, p=0.0057) or CMR-Perf (AUC=0.882, 95% CI 0.802-0.938, p=0.0398) alone. Regarding prediction of revascularization, the integrated protocol maintained its superior performance. CONCLUSIONS: CT+CMRint showed superior diagnostic accuracy and could thus lead to a considerable reduction in invasive procedures for CAD diagnosis, with less risk and greater patient comfort

Diagnostic performance of 3D cardiac magnetic resonance perfusion in elderly patients for the detection of coronary artery disease as compared to fractional flow reserve

OBJECTIVES: In patients of advanced age, the feasibility of myocardial ischemia testing might be limited by age-related comorbidities and falling compliance abilities. Therefore, we aimed to test the accuracy of 3D cardiac magnetic resonance (CMR) stress perfusion in the elderly population as compared to reference standard fractional flow reserve (FFR). METHODS: Fifty-six patients at age 75 years or older (mean age 79 ± 4 years, 35 male) underwent 3D CMR perfusion imaging and invasive coronary angiography with FFR in 5 centers using the same study protocol. The diagnostic accuracy of CMR was compared to a control group of 360 patients aged below 75 years (mean age 61 ± 9 years, 262 male). The percentage of myocardial ischemic burden (MIB) relative to myocardial scar burden was further analyzed using semi-automated software. RESULTS: Sensitivity, specificity, and positive and negative predictive values of 3D perfusion CMR deemed similar for both age groups in the detection of hemodynamically relevant (FFR 0.05 all). While MIB was larger in the elderly patients (15% ± 17% vs. 9% ± 13%), the diagnostic accuracy of 3D CMR perfusion was high in both elderly and non-elderly populations to predict pathological FFR (AUC: 0.906 and 0.866). CONCLUSIONS: 3D CMR perfusion has excellent diagnostic accuracy for the detection of hemodynamically relevant coronary stenosis, independent of patient age. KEY POINTS • The increasing prevalence of coronary artery disease in elderly populations is accompanied with a larger ischemic burden of the myocardium as compared to younger individuals. • 3D cardiac magnetic resonance perfusion imaging predicts pathological fractional flow reserve in elderly patients aged ≥ 75 years with high diagnostic accuracy. • Ischemia testing with 3D CMR perfusion imaging has similarly high accuracy in the elderly as in younger patients and it might be particularly useful when other non-invasive techniques are limited by aging-related comorbidities and falling compliance abilities

Impact of incomplete ventricular coverage on diagnostic performance of myocardial perfusion imaging.

In the context of myocardial perfusion imaging (MPI) with cardiac magnetic resonance (CMR), there is ongoing debate on the merits of using technically complex acquisition methods to achieve whole-heart spatial coverage, rather than conventional 3-slice acquisition. An adequately powered comparative study is difficult to achieve given the requirement for two separate stress CMR studies in each patient. The aim of this work is to draw relevant conclusions from SPECT MPI by comparing whole-heart versus simulated 3-slice coverage in a large existing dataset. SPECT data from 651 patients with suspected coronary artery disease who underwent invasive angiography were analyzed. A computational approach was designed to model 3-slice MPI by retrospective subsampling of whole- heart data. For both whole-heart and 3-slice approaches, the diagnostic performance and the stress total perfusion deficit (TPD) score-a measure of ischemia extent/severity-were quantified and compared. Diagnostic accuracy for the 3-slice and whole-heart approaches were similar (area under the curve: 0.843 vs. 0.855, respectively; P = 0.07). The majority (54%) of cases missed by 3-slice imaging had primarily apical ischemia. Whole-heart and 3-slice TPD scores were strongly correlated (R2 = 0.93, P < 0.001) but 3-slice TPD showed a small yet significant bias compared to whole-heart TPD (- 1.19%; P < 0.0001) and the 95% limits of agreement were relatively wide (- 6.65% to 4.27%). Incomplete ventricular coverage typically acquired in 3-slice CMR MPI does not significantly affect the diagnostic accuracy. However, 3-slice MPI may fail to detect severe apical ischemia and underestimate the extent/severity of perfusion defects. Our results suggest that caution is required when comparing the ischemic burden between 3-slice and whole-heart datasets, and corroborate the need to establish prognostic thresholds specific to each approach

Meta-analysis of the diagnostic performance of stress perfusion cardiovascular magnetic resonance for detection of coronary artery disease

<p>Abstract</p> <p>Aim</p> <p>Evaluation of the diagnostic accuracy of stress perfusion cardiovascular magnetic resonance for the diagnosis of significant obstructive coronary artery disease (CAD) through meta-analysis of the available data.</p> <p>Methodology</p> <p>Original articles in any language published before July 2009 were selected from available databases (MEDLINE, Cochrane Library and BioMedCentral) using the combined search terms of magnetic resonance, perfusion, and coronary angiography; with the exploded term coronary artery disease. Statistical analysis was only performed on studies that: (1) used a [greater than or equal to] 1.5 Tesla MR scanner; (2) employed invasive coronary angiography as the reference standard for diagnosing significant obstructive CAD, defined as a [greater than or equal to] 50% diameter stenosis; and (3) provided sufficient data to permit analysis.</p> <p>Results</p> <p>From the 263 citations identified, 55 relevant original articles were selected. Only 35 fulfilled all of the inclusion criteria, and of these 26 presented data on patient-based analysis. The overall patient-based analysis demonstrated a sensitivity of 89% (95% CI: 88-91%), and a specificity of 80% (95% CI: 78-83%). Adenosine stress perfusion CMR had better sensitivity than with dipyridamole (90% (88-92%) versus 86% (80-90%), P = 0.022), and a tendency to a better specificity (81% (78-84%) versus 77% (71-82%), P = 0.065).</p> <p>Conclusion</p> <p>Stress perfusion CMR is highly sensitive for detection of CAD but its specificity remains moderate.</p

Encryption of Messages and Images Using Compressed Sensing

The article deals with compressed sensing used to encrypt data. It allows performing signal capturing, its compression and encryption at the same time. The measurement matrix is generated using a secret key and is exploited for encryption. The article shows an example of its utilization at text and image message, moreover the Arnold transform is used in colour images for increasing security

Diagnostic and Prognostic Value of Stress Cardiovascular Magnetic Resonance Imaging in Patients With Known or Suspected Coronary Artery Disease A Systematic Review and Meta-analysis

IMPORTANCE: The clinical utility of stress cardiovascular magnetic resonance imaging (CMR) in stable chest pain is still debated, and the low-risk period for adverse cardiovascular (CV) events after a negative test result is unknown.OBJECTIVE: To provide contemporary quantitative data synthesis of the diagnostic accuracy and prognostic value of stress CMR in stable chest pain.DATA SOURCES: PubMed and Embase databases, the Cochrane Database of Systematic Reviews, PROSPERO, and the ClinicalTrials.gov registry were searched for potentially relevant articles from January 1, 2000, through December 31, 2021.STUDY SELECTION: Selected studies evaluated CMR and reported estimates of diagnostic accuracy and/or raw data of adverse CV events for participants with either positive or negative stress CMR results. Prespecified combinations of keywords related to the diagnostic accuracy and prognostic value of stress CMR were used. A total of 3144 records were evaluated for title and abstract; of those, 235 articles were included in the full-text assessment of eligibility. After exclusions, 64 studies (74 470 total patients) published from October 29, 2002, through October 19, 2021, were included.DATA EXTRACTION AND SYNTHESIS: This systematic review and meta-analysis adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses.MAIN OUTCOMES AND MEASURES: Diagnostic odds ratios (DORs), sensitivity, specificity, area under the receiver operating characteristic curve (AUROC), odds ratio (OR), and annualized event rate (AER) for all-cause death, CV death, and major adverse cardiovascular events (MACEs) defined as the composite of myocardial infarction and CV death.RESULTS: A total of 33 diagnostic studies pooling 7814 individuals and 31 prognostic studies pooling 67 080 individuals (mean [SD] follow-up, 3.5 [2.1] years; range, 0.9-8.8 years; 381 357 person-years) were identified. Stress CMR yielded a DOR of 26.4 (95% CI, 10.6-65.9), a sensitivity of 81% (95% CI, 68%-89%), a specificity of 86% (95% CI, 75%-93%), and an AUROC of 0.84 (95% CI, 0.77-0.89) for the detection of functionally obstructive coronary artery disease. In the subgroup analysis, stress CMR yielded higher diagnostic accuracy in the setting of suspected coronary artery disease (DOR, 53.4; 95% CI, 27.7-103.0) or when using 3-T imaging (DOR, 33.2; 95% CI, 19.9-55.4). The presence of stress-inducible ischemia was associated with higher all-cause mortality (OR, 1.97; 95% CI, 1.69-2.31), CV mortality (OR, 6.40; 95% CI, 4.48-9.14), and MACEs (OR, 5.33; 95% CI, 4.04-7.04). The presence of late gadolinium enhancement (LGE) was associated with higher all-cause mortality (OR, 2.22; 95% CI, 1.99-2.47), CV mortality (OR, 6.03; 95% CI, 2.76-13.13), and increased risk of MACEs (OR, 5.42; 95% CI, 3.42-8.60). After a negative test result, pooled AERs for CV death were less than 1.0%.CONCLUSION AND RELEVANCE: In this study, stress CMR yielded high diagnostic accuracy and delivered robust prognostication, particularly when 3-T scanners were used. While inducible myocardial ischemia and LGE were associated with higher mortality and risk of MACEs, normal stress CMR results were associated with a lower risk of MACEs for at least 3.5 years