Improved visualization of hepatic tumors in magnetic resonance-guided thermoablation using T1-inversion-recovery imaging with variable inversion time.

OBJECTIVES: In magnetic resonance (MR)-guided interventions, visualization of hepatic lesions may be difficult using standard unenhanced T1-weighted gradient-echo volume-interpolated breath-hold (VIBE) sequence due to low contrast. Inversion recovery (IR) imaging may have the potential to improve visualization without the necessity to apply contrast agent. METHODS: Forty-four patients (mean age 64 years, female 33%) scheduled for MR-guided thermoablation due to liver malignancies (hepatocellular carcinoma or metastases) were prospectively included in this study between March 2020 and April 2022. Fifty-one liver lesions were intra-procedurally characterized before treatment. Unenhanced T1-VIBE was acquired as part of the standard imaging protocol. Additionally, T1-modified look-locker images were acquired with eight different inversion times (TI) between 148 and 1743 ms. Lesion-to-liver contrast (LLC) was compared between T1-VIBE and IR images for each TI. T1 relaxation times for liver lesions and liver parenchyma were calculated. RESULTS: Mean LLC in T1-VIBE sequence was 0.3 ± 0.1. In IR images, LLC was highest at TI 228 ms (1.04 ± 1.1) and significantly higher compared to T1-VIBE (p < 0.001). In subgroup analysis, lesions of colorectal carcinoma showed the highest LLC at 228 ms (1.14 ± 1.4), and hepatocellular carcinoma showed the highest LLC at 548 ms (1.06 ± 1.16). T1-relaxation times in liver lesions were higher compared to the adjacent liver parenchyma (1184 ± 456 vs. 654 ± 96 ms, p < 0.001). CONCLUSIONS: IR imaging is promising to provide improved visualization during unenhanced MR-guided liver interventions compared to standard T1-VIBE sequence when using specific TI. Low TI between 150 and 230 ms yields the highest contrast between liver parenchyma and malignant liver lesions. CLINICAL RELEVANCE STATEMENT: Improved visualization of hepatic lesions during MR-guided percutaneous interventions using inversion recovery imaging without the necessity to apply contrast agent. KEY POINTS: • Inversion recovery imaging is promising to provide improved visualization of liver lesions in unenhanced MRI. • Planning and guidance during MR-guided interventions in the liver can be performed with greater confidence without necessity to apply contrast agent. • Low TI between 150 and 230 ms yields the highest contrast between liver parenchyma and malignant liver lesions.

Cardiac MRI findings to differentiate athlete's heart from hypertrophic (HCM), arrhythmogenic right ventricular (ARVC) and dilated (DCM) cardiomyopathy.

To provide clinically relevant criteria for differentiation between the athlete's heart and similar appearing hypertrophic (HCM), dilated (DCM), and arrhythmogenic right-ventricular cardiomyopathy (ARVC) in MRI. 40 top-level athletes were prospectively examined with cardiac MR (CMR) in two university centres and compared to retrospectively recruited patients diagnosed with HCM (n = 14), ARVC (n = 18), and DCM (n = 48). Analysed MR imaging parameters in the whole study cohort included morphology, functional parameters and late gadolinium enhancement (LGE). Mean left-ventricular enddiastolic volume index (LVEDVI) was high in athletes (105 ml/m2) but significantly lower compared to DCM (132 ml/m2; p = 0.001). Mean LV ejection fraction (EF) was 61% in athletes, below normal in 7 (18%) athletes vs. EF 29% in DCM, below normal in 46 (96%) patients (p < 0.0001). Mean RV-EF was 54% in athletes vs. 60% in HCM, 46% in ARVC, and 41% in DCM (p < 0.0001). Mean interventricular myocardial thickness was 10 mm in athletes vs. 12 mm in HCM (p = 0.0005), 9 mm in ARVC, and 9 mm in DCM. LGE was present in 1 (5%) athlete, 8 (57%) HCM, 10 (56%) ARVC, and 21 (44%) DCM patients (p < 0.0001). Healthy athletes' hearts are characterized by both hypertrophy and dilation, low EF of both ventricles at rest, and increased interventricular septal thickness with a low prevalence of LGE. Differentiation of athlete's heart from other non-ischemic cardiomyopathies in MRI can be challenging due to a significant overlap of characteristics also seen in HCM, ARVC, and DCM.

Is myocardial stress perfusion MR-imaging suitable to predict the long term clinical outcome after revascularization?

INTRODUCTION: Aim of our study was to evaluate, whether myocardial ischemia or myocardial infarction (MI) depicted by myocardial stress perfusion MR imaging (SP CMR) can predict the clinical outcome in patients with coronary artery disease (CAD). MATERIALS AND METHOD: 220 patients were included. Myocardial perfusion was assessed at stress and at rest, using a 2D saturation recovery gradient echo sequence (SR GRE) and myocardial viability by late gadolinium enhancement magnetic resonance images (LGE CMR). MR-images were assessed in regard of presence and extent of MI and ischemia. Patients were monitored for major adverse cardiac events (MACE) (monitoring period: 5-7 years). MACE were correlated with the initial results of SP CMR. RESULTS: Ischemia was found in 143 patients, MI in 107 patients. Number of MACE was in patients with normal SP CMR 0 (51 patients), with ischemia 21 (62 patients), with MI 14 (26 patients), with ischemia and MI 52 (81 patients). In all patients with severe MACE (MI, death) and in 63 of those with recurring symptoms LGE CMR revealed MI at baseline. CONCLUSION: Negative SP CMR indicates low risk for MACE. In patients with stress induced ischemia, MACE might occur even after myocardial revascularization. The presence of MI proved by LGE CMR is associated with a significantly increased risk for MACE.

[Cardiac magnetic resonance tomography in the diagnostics of restrictive and unclassified cardiopathies]. / Kardiale Magnetresonanztomographie in der Diagnostik der restriktiven und unklassifizierten Kardiomyopathien.

CLINICAL/METHODICAL ISSUE: Besides ischemic heart disease cardiomyopathies are common causes of heart failure and sudden cardiac death. STANDARD RADIOLOGICAL METHODS: The diagnostic spectrum in cardiomyopathies comprises non-invasive and invasive examination techniques. METHODICAL INNOVATIONS: The exact verification of certain cardiomyopathies necessitates knowledge of the latest classification of cardiomyopathies as well as dedicated examination protocols. PERFORMANCE: Modern imaging modalities, such as echocardiography and cardiac magnetic resonance imaging (MRI) have emerged as useful imaging tools in the investigation of patients suspected of having many different types of cardiomyopathies. ACHIEVEMENTS: Based on a better understanding of the underlying pathophysiology several diagnostic criteria have been defined using cardiac MRI. In particular there is an increasing importance of cardiac MRI in the description of patients with restrictive and unclassified cardiomyopathies. PRACTICAL RECOMMENDATIONS: Echocardiography still remains the modality of choice in the diagnostics of unclear left ventricular heart failure. Further diagnostic work-up should include cardiac MRI in case of any lack of clarity.

Depiction of variants of the portal confluence venous system using multidetector row CT: analysis of 916 cases.

PURPOSE: Detailed knowledge of the venous mesenteric system is important for gastrointestinal surgery, particularly for transplantation planning and surgery and for the comprehension of perioperative complications that may influence patient outcome. Data about the mesenteric venous anatomy in the literature varies substantially. The purpose of this study was to categorize venous mesenteric variants and to determine their incidence. MATERIALS AND METHODS: We included 916 patients requiring diagnostic abdominal CT in the portal venous phase. The mesenteric vein anatomy was categorized as follows: 1. the inferior mesenteric vein (IMV) enters the splenic vein (SV); 2. the IMV enters into the angle of the confluence of the SV and superior mesenteric vein (SMV) forming the portal vein (PV); 3. the IMV enters the SMV; 4. seven rare variants. We measured the diameters of the veins and distances from the confluence to the IMV origins. RESULTS: The frequency of variants was: 1. 37.6%, 2. 28.8%; 3. 19.2%. The rare variants totaled 14.4%. The average vessel diameters measured in cm: PV 1.48; SV 1.02; SMV 1.2; IMV 0.5. The mean IMV entering distances were 1.66 cm in variant 1 and 0.75 cm in variant 3. CONCLUSION: The three common variants (1, 2 and 3) are the most relevant ones. 14.4% of patients had different anatomic variants. The variability of the mesenteric venous system was higher than previously published. Knowledge of rare variants is important to avoid complications in abdominal surgery.

A soluble neuronal factor alters contractile function of ventricular myocytes without effect on troponin T isoform expression.

OBJECTIVE: The purpose of this investigation was to establish a model system to facilitate identification of the sympathetic neuronal factor(s) that promotes improved contractility in neonatal cardiac myocytes. Conditioned medium from PC12 cells with sympathetic phenotype served as the source of the neuronal factor. METHODS: Contraction frequency, amplitude and velocity of cultured neonatal rat cardiac myocytes were measured by online video analysis. Interventions included in vitro sympathetic innervation, exposure to PC12 conditioned medium, neurotransmitters and antagonists. Metabolic activity was assayed by 2-deoxyglucose uptake. Troponin T isoform expression was analyzed by SDS-polyacrylamide gel electrophoresis. RESULTS: Medium conditioned by neuronal PC12 cells induced contractility changes similar to those induced by in vitro sympathetic innervation. These effects of PC12 conditioned medium and innervation were not suppressed by adrenergic or muscarinic antagonists nor reproduced by neuropeptide Y or somatostatin. Neuronal PC12 conditioned medium but not chromaffin PC12 conditioned medium, increased metabolic activity of the myocytes as detected by [3H]-2-deoxyglucose, indicating that the effect was specific to the neuronal PC12 cells. The in vitro switch of troponin T isoform expression was not altered by exposure to PC12 conditioned medium. CONCLUSIONS: Increased contractile function induced by sympathetic innervation is reproduced by PC12 conditioned medium, but neither is mediated by sympathetic or muscarinic neurotransmitters. Troponin T isoform expression is not related to the contractility changes. This model system will allow identification of the factor(s).

Regulation of rat cardiac myocyte growth by a neuronal factor secreted by PC12 cells.

Sympathetic innervation of cardiac myocytes in vitro induces growth independent of anatomic contact between the neurons and myocytes and is not mediated by alpha- or beta-adrenergic receptor stimulation. To establish a model system that will allow purification and identification of the neuronal factor(s) responsible for mediating this regulation, we have initiated studies utilizing conditioned medium from the PC12 cell line. PC12 cells acquire a cholinergic sympathetic neuronal phenotype when exposed to nerve growth factor. Culture medium conditioned by neuronal PC12 cells, but not nonneuronal PC12 cells, induces growth in newborn rat cardiac myocytes as measured by surface area and [35S]methionine incorporation into protein and increases expression of atrionatriuretic peptide, a marker for myocyte hypertrophy. The magnitude of the growth response is dose-dependent and mimics the response to sympathetic innervation. The myocyte response to conditioned medium is not detectable after 24 h of exposure; maximal rate of protein synthesis is obtained within 48 h. Neuronally differentiated PC12 cell-conditioned medium stimulation of growth could not be mimicked by alpha- or beta-adrenergic agonists or muscarinic agonists, nor inhibited by alpha- or beta-adrenergic antagonists, nor by muscarinic antagonists. Neuropeptide Y and somatostatin, peptides known to be present in PC12 cells and sympathetic neurons, were also ineffective at reproducing the effect of neuronally differentiated PC12 cell-conditioned medium. These data indicate that neuronal cells release a soluble factor, different from neurotransmitter, which stimulates myocyte growth. They further identify the PC12 cell line as providing a convenient and abundant supply of this molecule, thus facilitating its further characterization.

Differential growth of neonatal WKY and SHR ventricular myocytes within sympathetic co-cultures.

Sympathetic innervation is known to increase heart size in the immature animal, yet the mechanism for this growth remains to be established. This comparative study stereologically quantified the volume of cultured neonatal ventricular myocytes with and without in vitro sympathetic innervation to isolate the mechanisms regulating cardiac growth. Since ventricular myocyte size at birth differs between the spontaneously hypertensive rat (SHR) and the normotensive Wistar-Kyoto (WKY), we questioned whether SHR myocytes respond differently than WKY myocytes to innervation. Four groups of ventricular myocytes from each strain were compared: myocytes grown alone, myocytes innervated by cultured sympathetic neurons, innervated myocytes exposed to adrenoceptor blockade, and non-innervated myocytes in co-culture dishes. Volumes for the myocyte, nucleus, cytoplasm, mitochondria, sarcomeres and other cellular organelles were assessed within each population and between populations. Relative volumes were determined for the mitochondria, sarcomeres, and other cellular components within the cytoplasm. Innervated WKY myocytes were 38% larger than control myocytes (P < 0.0004). This growth was not blocked by adrenoceptor blockade (P = 0.89 vs. innervated) and was present in the non-innervated myocytes distant from the neurons in the co-cultures (P = 0.39 vs. innervated). SHR myocytes were 36% larger than WKY myocytes (P < 0.009) but did not increase with innervation (P = 0.48). SHR myocyte size was also unaffected by adrenoceptor blockade (P = 0.39) or presence of the neurons in the culture dish (P = 0.53). Neonatal WKY ventricular myocyte growth can be provoked in vitro by sympathetic innervation via regulatory mechanisms independent of neuroeffector transmission or anatomic contact, whereas volume of neonatal SHR myocytes is unaltered by sympathetic coculture. These findings are significant for understanding normal as well as aberrant cardiomyocyte growth.

Application of stereological analysis of cell volume to isolated myocytes in culture with and without adrenergic innervation.

A three-dimensional analysis to evaluate structural changes in cultured cardiac myocytes following adrenergic innervation was performed using stereological techniques formerly limited to cells in tissue and organs. Cell volumes were calculated for two groups of cells at 96 hours in culture: isolated myocytes and myocytes innervated with adrenergic neurons. Relative and absolute volumes of the nucleus, cytoplasm, and cell were quantified by systematically sampling sections throughout the cell and by point count sampling techniques. Volumetric estimates were similarly determined for the mitochondria, sarcomeres, and other cellular components in the cytoplasm. Data were analyzed with ANOVA and randomized block design to control for variation among the cultures. Adrenergic innervation produced a 44% increase in cell volume, X +/- SEM, (3,344 +/- 196 microns3 to 4,816 +/- 400 microns3, P = 0.007). The absolute volume of mitochondria significantly increased after innervation (521 +/- 42 microns3 to 744 +/- 54 microns3, P less than 0.01). Absolute sarcomere volume did not change significantly (750 +/- 92 microns3 to 642 +/- 1061 microns3, P = 0.14). Other cellular components, defined as all cytoplasmic components except mitochondria and sarcomeres, significantly increased with innervation (1,739 +/- 166 microns3 to 3,097 +/- 338 microns3, P = 0.02). The relative volume of the nucleus and the cytoplasm in the cell remained unchanged following innervation. However, the relative volume of mitochondria decreased by 6%, the percent of the cytoplasm occupied by the sarcomeres decreased by 44%, and the volume occupied by the other cellular components increased by 22%. These findings support the use of stereological analysis as a means to quantify cell volumes of cultured myocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

A method for assessing the physiologic significance of coronary obstructions in man at cardiac surgery.

The functional significance of coronary narrowings of intermediate severity is often difficult to assess from preoperative coronary arteriograms. To complement the anatomic data obtained by arteriography, a method for measuring phasic coronary velocity and reactive hyperemia in man at cardiac surgery has been developed. The method uses a single-crystal Doppler probe coupled to surface coronary vessels with a small suction pad. The validity of the measurements has been documented in a series of in vitro and animal experiments. Because physiologically significant coronary narrowings invariably attenuate reactive hyperemic responses, this approach can be used to determine the functional importance of coronary obstruction before placement of coronary bypass grafts. Initial experience in 50 patients indicates that the measurements can be obtained safely and that the functional significance of coronary obstructions can be readily assessed.