Hemodynamic effects of monomeric nonionic contrast media in pulmonary angiography in chronic thromboembolic pulmonary hypertension.

OBJECTIVE: The purpose of this study was to investigate the hemodynamic safety of the monomeric nonionic contrast agent iomeprol for selective pulmonary angiography in chronic thromboembolic pulmonary hypertension (CTPH), and to investigate the effect of periinterventional oxygen administration. SUBJECTS AND METHODS: Selective pulmonary digital subtraction angiography was performed in 94 patients with CTPH using six bolus injections of iomeprol (posteroanterior, oblique, and lateral projections; both pulmonary arteries; iomeprol, 25 mL at 13 mL/s). Hemodynamics were obtained with Swan-Ganz catheters, and systolic pulmonary artery pressure (PAsyst) was classified into one of three groups: 30 mm Hg or less (control group), greater than 30 but less than or equal to 60 mm Hg (group 1, moderate pulmonary hypertension), and greater than 60 mm Hg (group 2, severe pulmonary hypertension). RESULTS: At baseline, values for PAsyst were 21.4 +/- 2.3 (control group, n = 8), 49.8+/- 8.5 (group 1, n = 18), and 86.5 +/- 18.9 (group 2, n = 68) mm Hg (p < 0.001). Pulmonary vascular resistance indexes (PVRI) were 222 +/- 105 (control), 703 +/- 364 (group 1), and 1,582 +/- 562 (group 2) dyne x s x cm(-5) x m2 (p < 0.001). The mean cardiac indexes were 3.1 (control), 2.8 (group 1), and 2.3 (group 2) L/min/m2 (p < 0.05). Pulmonary capillary wedge pressure (PCw) indicated healthy left heart function. Periinterventional oxygen inhalation improved oxygen saturation in all groups and slightly reduced pulmonary artery pressure and heart rate. Online measurement of pulmonary artery pressure during contrast bolus injection for angiography showed only a minor increase, predominantly in severe pulmonary hypertension (triangle up [difference] PAsyst: 1.3 +/- 1.9 [control], 2.9 +/- 3.4 [group 1], and 3.8 +/- 4.5 [group 2] mm Hg [p < 0.001]). After completion of angiography, right atrial pressure (RAP) and PAsyst were moderately increased: triangle up RAP: 1.4 (control), 2.6 (group 1, p < 0.001), and 3.0 (group 2, p < 0.001) mm Hg; triangle up PAsyst: 3.2 (control), 7.7 (group 1, p < 0.01), and 8.5 (group 2) mm Hg (p < 0.001). PVRI was significantly higher in group 2 (triangle up PVRI: 188 dyne x s x cm(-5) x m2, p < 0.001). CONCLUSION: Selective pulmonary angiography using iomeprol is safe without critical pressure peaks during selective contrast bolus injection or significant hemodynamic derangement in severe CTPH. Periinterventional oxygen inhalation improved pulmonary circulation.

Switching off HER-2/neu in a tetracycline-controlled mouse tumor model leads to apoptosis and tumor-size-dependent remission.

Overexpression of the receptor tyrosine kinase HER-2/neu is associated with poor prognosis in patients with breast and ovarian cancer. Recent excitement has surrounded the therapeutic effects of HER-2-blocking therapy strategies and has rekindled interest on the molecular mechanisms of HER-2/neu in tumor biology. To study the role of HER-2/neu overexpression in vivo, we used a murine fibroblast cell line (NIH3T3-her2) conditionally expressing human HER-2/neu under control of a tetracycline-responsive promoter. Expression of HER-2 could be down-regulated below detection limit (>625-fold dilution) by exposure of NIH3T3-her2 cells to anhydrotetracycline (ATc). Subcutaneous injection of NIH3T3-her2 cells into nude mice resulted in rapid tumor growth. Mice with mean tumor volumes of 0.2, 0.8, 1.9, and 14.9 cm(3) were treated daily with 10 mg/kg ATc to switch off HER-2/neu expression, producing reductions in tumor size of 100, 98.1, 81.4, and 74.2%, respectively, by 7 days after onset of ATc administration (P = 0.005, Kruskal-Wallis test). Different long-term effects of HER-2 down-regulation were observed when mice with small (0.2 cm(3); n = 7), intermediate (0.8-1.2 cm(3); n = 10) and large (> or =1.9 cm(3); n = 11) tumors received ATc for up to 40 days. Complete remission was observed for 100, 40, and 18% of the small-, intermediate-, and large-sized tumors, respectively (P = 0.003). However, after 20-45 days of ATc administration, recurrent tumor growth was observed for all mice, even in those with previous complete remissions. The time periods for which mean tumor volume could be suppressed to volumes <0.1 cm(3) under ATc administration were 34, 22, 8, and 0 days for tumors with initial volumes of 0.2, 0.8, 1.9 and 14.9 cm(3), respectively (P = 0.005, Kruskal-Wallis test). Interestingly, HER-2 remained below the detection limit in recurrent tumor tissue, suggesting that initially HER-2-dependent tumors switched to HER-2 independence. The "second hits" leading to HER-2-independent tumor growth have not yet been identified. The rapid regression of tumors after down-regulation of HER-2 was explained by two independent mechanisms: (a) a block in cell cycle progression, as evidenced by a decrease in Ki-67 antigen expression from 40% before ATc treatment to 8.3% after 7 days of ATc treatment; and (b) induction of apoptosis as demonstrated by caspase-3 activation and by the terminal deoxynucleotidyltransferase (Tdt)-mediated nick end labeling assay (TUNEL). In conclusion, we have shown that switching off HER-2 may disturb the sensitive balance between cell proliferation and cell death, leading to apoptosis and tumor remission. Tumor remission was dependent on the volume of the tumors before down-regulation of HER-2/neu.

Endovascular aneurysm repair: Magnetic resonance monitoring of histological organization processes in the excluded aneurysm.

BACKGROUND: The purpose of the present study was to systematically analyze the histopathologic organization processes in excluded aneurysms after endovascular stenting and to develop a noninvasive monitoring method for these processes using MRI. METHODS AND RESULTS: In 36 mongrel dogs, autologous aortic aneurysms were created. Endovascular treatment was performed using covered stents. Follow-up was after 1 week, 6 weeks, and 6 months. MRI was performed with T2-weighted turbo-spin-echo sequences and T1-weighted spin-echo sequences and was repeated after contrast bolus with gadolinium. Histopathologic findings were correlated to signal intensities (SIs) of MRI images. SIs of distinct areas were analyzed and related to the SI of the reference tissue (SI ratio). The histological organization process was gradated in the following 4 classes: class 0, detritus without organization; classes I and II, connective tissue proliferation with increasing fiber synthesis; and class III, dense fibrous connective tissue. The SI ratios of T2-weighted images were significantly reduced from 4.76 in detritus (0) to 1.70 in dense fibrous connective tissue (III) as a function of histopathologic classes. SI ratios of T1-weighted images were reduced from 1.84 (0) to 1.12 (III). Contrast bolus with gadolinium-DTPA showed no change of SI ratio in detritus (0.99) but an increase from 1.12 (I) to 1.70 (III) as organization increased. CONCLUSIONS: The histological organization of excluded aneurysms can be monitored by MRI. Progressive organization is indicated by decreasing SIs in T2- and an increasing signal increase in T1-weighted images after gadolinium bolus.

Analysis of discrete and continuous distributions of ventilatory time constants from dynamic computed tomography.

In this study, an algorithm was developed to measure the distribution of pulmonary time constants (TCs) from dynamic computed tomography (CT) data sets during a sudden airway pressure step up. Simulations with synthetic data were performed to test the methodology as well as the influence of experimental noise. Furthermore the algorithm was applied to in vivo data. In five pigs sudden changes in airway pressure were imposed during dynamic CT acquisition in healthy lungs and in a saline lavage ARDS model. The fractional gas content in the imaged slice (FGC) was calculated by density measurements for each CT image. Temporal variations of the FGC were analysed assuming a model with a continuous distribution of exponentially decaying time constants. The simulations proved the feasibility of the method. The influence of experimental noise could be well evaluated. Analysis of the in vivo data showed that in healthy lungs ventilation processes can be more likely characterized by discrete TCs whereas in ARDS lungs continuous distributions of TCs are observed. The temporal behaviour of lung inflation and deflation can be characterized objectively using the described new methodology. This study indicates that continuous distributions of TCs reflect lung ventilation mechanics more accurately compared to discrete TCs.

[Hyperpolarized (3)helium gas for functional magnetic resonance imaging of the lung]. / Funktionelle MRT der Lunge unter Verwendung von hyperpolarisiertem 3Helium-Gas.

Lung imaging is traditionally done using X-ray-based methods, since MRI is limited by low proton density as well as inherent magnetic field inhomogeneities of the lung tissue. After introduction of MRI using hyperpolarized noble gases, a totally new field of MRI of the chest has rapidly evolved. These techniques reveal new functional information of the lungs, which could not be obtained before. The first part of this review describes the underlying MR technology explaining distribution of static ventilation, dynamic distribution of ventilation, lung microstructure (apparent diffusion coefficient [ADC]), measurement of oxygen partial pressure (pO(2)), and safety. The clinical potential is afterwards demonstrated in the second part. Therefore, the effort in normal lungs and the mainly focused diseases chronic obstructive pulmonary disease (COPD), smoker's lung, cystic fibrosis, asthma, lung transplantation, and pulmonary embolism are reported.

Measurements of alveolar pO2 using 19F-MRI in partial liquid ventilation.

RATIONALE AND OBJECTIVES: Partial liquid ventilation using Perfluorcarbon (PFC) is an innovative treatment of acute respiratory distress syndrome. However, the underlying mechanisms are not totally clear. The aim was to investigate the distribution of oxygen partial pressure within the PFC-filled lung (ppO2). METHODS: Nine pigs underwent partial liquid ventilation, receiving 20 mL PFC/kg bodyweight (bw). Measurements were obtained by a chemical shift selective TurboFLASH sequence at different axial lung levels. ppO2 was calculated from 19F-MRI by nonlinear curve T1-fitting technique after noise correction. RESULTS: Quantification and distribution of ppO2 was performed successfully. A narrow relationship of the inspiratory O2 fraction and ppO2, as well as a significant ventral-to-dorsal gradient of ppO2 (ventral:dependent lung = 1.9:1) were detected in all subjects and slice positions. CONCLUSIONS: In vivo measurement of local ppO2 gains new and clinical important insights into the physiology of PLV. The previously unknown ppO2 gradient within PFC fits to distribution of perfusion. Dependent lung regions appear to have limited access to O2 from central airways.

Distribution of ventilation in lung transplant recipients: evaluation by dynamic 3He-MRI with lung motion correction.

RATIONALE AND OBJECTIVES: The ability of motion corrected dynamic 3He-magnetic resonance imaging (MRI) to discriminate distributional patterns of inhaled hyperpolarized 3He between different groups of lung transplant recipients was evaluated. METHODS: An ultrafast low-angle shot 2D sequence (temporal resolution 128 ms) was used for ventilation 3He-MRI of 11 single and 6 double lung transplant recipients. After digital motion correction, signal kinetics were evaluated in a tracheal and 7 pulmonary regions of interest. Results from grafts and native lungs as well as from normal and rejected grafts were compared with each other and to reference values from healthy subjects. RESULTS: In emphysema patients, median alveolar rise time, a parameter for increase of alveolar signal, was 0.28 seconds for the graft and 0.48 seconds for the native lung, in fibrosis patients its median was 0.46 seconds for the graft and 0.21 seconds for the native lung. In double lung recipients, alveolar rise time was 0.29 seconds in normal and clinically rejected grafts. CONCLUSIONS: Dynamic ventilation 3He-MRI discriminated normal lung grafts from diseased native lungs in single lung recipients. Graft rejection in double lung recipients could not be discriminated.

Dynamic ventilation (3)He-magnetic resonance imaging with lung motion correction: gas flow distribution analysis.

RATIONALE AND OBJECTIVES: Software was developed to correct for lung motion to improve the description of hyperpolarized (3)He gas distribution in the lung. METHODS: Five volunteers were studied by dynamic ventilation (3)He-MRI using an ultrafast FLASH 2D sequence with a temporal resolution of 128 milliseconds. Signal kinetics were evaluated in the trachea and seven parenchymal Regions of Interest. Reference ranges for healthy subjects were defined for motion-corrected and uncorrected images. RESULTS: Motion correction was successfully performed. Reference ranges were 0.11-1.21 seconds for tracheal transit time, 0-0.02 seconds for trachea-alveolar interval, 0.22-0.62 seconds for alveolar rise time and 0-76.6 arbitrary units for alveolar amplitude for motion corrected images, and 0-1.09 seconds, 0-0.11 seconds, 0.26-0.85 seconds, 46.4-99.8 arbitrary units for uncorrected images. CONCLUSIONS: Evaluation of (3)He-distribution in the lung using motion correction of dynamic (3)He-ventilation imaging is feasible and gives more narrow reference ranges.

Dynamic computed tomography: a novel technique to study lung aeration and atelectasis formation during experimental CPR.

OBJECTIVE: To develop an image based technique to study the effect of different ventilatory strategies on lung ventilation and alveolar recruitment during cardiopulmonary resuscitation (CPR). DESIGN: (1) Technical development of the following components: (a) construction of an external chest compression device, which does not interfere with CT imaging, and (b) development of a software tool to detect lung parenchyma automatically and to calculate radiological density parameters. (2) Feasibility studies: three strategies of CPR ventilation were performed and imaged in one animal each (pigs, 25 kg): volume-constant ventilation (VCV), no ventilation, or continuous airway pressure (CPAP). One minute after induction of circulatory arrest inside the CT scanner, external chest compressions started at a rate of 100 cpm, and one of the ventilation modes was initiated. After 1 min, intravenous epinephrine was added as a bolus (40 microg/kg), followed by a continuous infusion (13 microg/kg per min). Six minutes later, dynamic CT acquisitions (temporal resolution: 100 ms) commenced. Simultaneously, arterial blood gases, acid base status and haemodynamics were sampled. RESULTS: Using a modified chest compression device, dynamic CT acquisitions are feasible during closed-chest CPR. In three pilot experiments with different ventilation strategies, the dedicated software tool allowed to quantify ventilated, atelectatic and over-distended fractions of total lung area. VCV showed a large amount of atelectasis, which was recruited during every respiratory cycle. No ventilation led to atelectasis to govern over 50% of the total lung area. CPAP caused less atelectasis as VCV, and no cyclic recruitment and de-recruitment phenomena were observed. CONCLUSIONS: We demonstrate a novel experimental set up, which allows quantification of different lung compartments during ongoing CPR and may become useful in comparing the direct pulmonary effects of different ventilatory strategies in the settings of Basic and Advanced Cardiac Life Support.

[Possibilities and prospects of noninvasive bypass diagnosis. Comparison of different nuclear magnetic resonance tomography methods with conventional coronary angiography]. / Möglichkeiten und Perspektiven der nichtinvasiven Bypassdiagnostik. Vergleich verschiedener kernspintomographischer Methoden mit der konventionellen Koronarangiographie.

OBJECTIVE: The aim of the study was to evaluate the patency of coronary artery bypass grafts (CABGs) with different MR imaging techniques. PATIENTS: 25 patients with 63 bypass grafts and a total of 78 distal anastomoses were studied at a 1.5-Tesla scanner. A 2-D T2-weighted breath-hold turbo spin echo sequence (Haste), a 3-D breath-hold contrast-enhanced MR angiography sequence (Fisp-3-D), and 3-D angiography sequence in navigator techniques were used. RESULTS: With the Haste and Fisp-3-D sequences, 44 of the 47 patent and 14 of the 16 occluded grafts were recognized, the sensitivity and specificity were 94% and 88%, respectively. With the Haste sequence, 80% (43/54) of the distal anastomoses were seen in good image quality, and with the Fish-3-D sequence 70% (38/54). The navigator sequence showed less sensitivity and specificity (74% and 63%, respectively). CONCLUSION: The patency of CABGs can be evaluated noninvasively with the Haste and the Fisp-3-D angiography sequences. Better results can be expected with the development of a blood-pool contrast medium and an improvement of the spatial resolution.

[Endovascular aneurysm therapy--long-term treatment outcomes after 7 years]. / Endovaskuläre Aneurysmatherapie--Langzeitergebnisse nach 7 Jahren.

BACKGROUND: Stentgrafts for endovascular treatment of abdominal aortic aneurysms (AAA) have been commercially available since 1994, with now large numbers of implantations all over the world. PATIENTS AND METHODS: From 1994-2001, 115 patients were treated with Stentor, Vanguard and Talent stentgrafts in our institution. RESULTS: Late complications of the first- and second-generation stentgrafts as radiologic or surgical interventions to maintain complete exclusion of the aneurysm amounted to 30% with an additional 22% for observed endoleaks and configuration changes of the stentgraft. Third-generation stentgrafts had a lower complication rate of 12.2% for interventions and 18.3% for late endoleaks and graft changes. CONCLUSION: High costs of the devices, a pretty high late complication rate, and the uncertain maintenance of stentgraft function to prevent aneurysm rupture currently limit the widespread application of this new technology, leaving conventional aneurysmectomy the standard for aneurysm treatment and reserving the endovascular method for selected patients.

Dynamic MR imaging of breast lesions: correlation with microvessel distribution pattern and histologic characteristics of prognosis.

PURPOSE: To evaluate the association of dynamic enhancement parameters of benign and malignant breast lesions at magnetic resonance (MR) imaging with microvessel distribution and histologic prognostic tumor characteristics. MATERIALS AND METHODS: Regional review board approval and informed consent were obtained. Surgical resection specimens of breast lesions (32 benign, 86 malignant) in 118 patients (age range, 28-86 years; mean, 58 years) who had undergone dynamic T1-weighted MR imaging of both breasts were included in the study. Different MR enhancement parameters and microvessel density (MVD) distribution were determined. In malignant lesions, TNM stage, tumor grade, proliferative activity, and hormone receptor expression were determined. Spearman correlation coefficients; Wilcoxon, Fisher exact, Kruskal Wallis, and chi(2) tests; and logistic regression analysis were used for evaluation. RESULTS: Malignant lesions exhibited a higher ratio of microvessels in tumor periphery versus tumor center than did benign lesions (P < .0005). High vessel ratios (P = .001) and low central vessel numbers (P = .007) were associated with high tumor grade. In malignant lesions, initial enhancement ratios of periphery to center of lesion correlated with the corresponding microvessel ratios (r = 0.61). Yet, a high peripheral MVD was not associated with strong peripheral enhancement (r = -0.09). High enhancement ratios, washout rates, and early enhancement peaks were associated with unfavorable, albeit not significant, prognostic indicators. Visible rim enhancement was the most accurate prognostic enhancement criterion for estrogen receptor status (P = .007), tumor grade (P = .06), and lymph node status (P = .046). Washout was the best discriminating criterion for proliferative activity. CONCLUSION: The different enhancement behaviors of malignant and benign breast lesions cannot be explained by MVD alone; however, a low MVD in the center of carcinoma is reflected quantitatively by a high enhancement ratio and qualitatively by rim enhancement, with an implication of adverse prognosis.

Controlling diffusion of 3He by buffer gases: a structural contrast agent in lung MRI.

PURPOSE: To study the influence of admixing inert buffer gases to laser-polarized (3)He in terms of resulting diffusion coefficients and the consequences for image contrast and resolution. MATERIALS AND METHODS: The diffusion coefficient of (3)He was altered by admixing buffer gases of various molecular weights ((4)He, N(2), and SF(6)). The influence of the pulse sequence and the diffusion coefficient on the appearance of MRI of (laser-polarized) gases was analyzed by comparison of basic theoretical concepts with demonstrative experiments. RESULTS: Excellent agreement between theoretical description and observed signal in simple gradient echoes was observed. A maximum signal gain can be predicted and was experimentally validated. Images acquired under such conditions revealed improved resolution. The nature and concentration of the admixed gas defines a structural threshold for the observed apparent diffusion coefficient (ADC) as demonstrated with diffusion-weighted MRI on a pig's lung flooded with suitable gas mixtures. CONCLUSION: A novel procedure is proposed to control the diffusion coefficient of gases in MRI by admixture of inert buffer gases. Their molecular mass and concentration enter as additional parameters into the equations that describe structural contrast. This allows for setting a structural threshold up to which structures contribute to the image. For MRI of the lung this enables images of very small structural elements (alveoli) only, or in the other extreme, all airways can be displayed with minimal signal loss due to diffusion.

Local staging of rectal carcinoma and assessment of the circumferential resection margin with high-resolution MRI using an integrated parallel acquisition technique.

PURPOSE: To assess the diagnostic accuracy of integrated parallel acquisition technique (iPAT) in local staging of rectal carcinoma in comparison to conventional high-resolution MRI. MATERIALS AND METHODS: A total of 28 patients with a neoplasm of the rectum and 15 control patients underwent MRI of the pelvis. High-resolution images were acquired conventionally and with iPAT using a modified sensitivity encoding (mSENSE). Image quality, signal-to-noise and contrast-to-noise ratios (SNR, CNR), tumor extent, nodal status, and delineation of the circumferential resection margin (CRM) were compared. In 19 patients with a carcinoma, MR findings were correlated with the histopathological diagnosis. Tumor distance to the CRM was matched with resection specimen in 12 cases. RESULTS: The comparison of both MR techniques revealed no clinically relevant differences in tumor staging and delineation of the CRM, though SNR and CNR were significantly lower in mSENSE images. Tumor stage was concordant in 17 of 19 cases compared to histopathology. In four of nine patients with T3 and T4 carcinomas, the histopathological resection margin was < or =2 mm, in five cases MRI predicted a margin of < or =2 mm. CONCLUSION: The application of iPAT in local staging of rectal carcinoma is time-saving and does not degrade diagnostic accuracy. Tumor stage, nodal status, and the CRM can be assessed equally compared to conventional acquisition techniques.

MRI versus helical CT for endoleak detection after endovascular aneurysm repair.

OBJECTIVE: The objective of our study was to investigate the diagnostic accuracy of MRI and helical CT for endoleak detection. SUBJECTS AND METHODS: Fifty-two patients underwent endovascular aneurysm repair with nitinol stent-grafts. Follow-up data sets included contrast-enhanced biphasic CT and MRI within 48 hr after the intervention; at 3, 6, and 12 months; and yearly thereafter. The endoleak size was categorized as < or = 3%, > 3% < or = 10%, > 10% < or = 30%, or > 30% of the maximum cross-sectional aneurysm area. A consensus interpretation of CT and MRI was defined as the standard of reference. RESULTS: Of 252 data sets, 141 showed evidence for endoleaks. The incidence of types I, II, and III endoleaks and complex endoleaks was 3.2%, 40.1%, 8.7%, and 4.0%, respectively. The sensitivity for endoleak detection was 92.9%, 44.0%, 34.8%, and 38.3% for MRI, biphasic CT, uniphasic arterial CT, and uniphasic late CT, respectively. The corresponding negative predictive values were 91.7%, 58.4%, 54.7%, and 56.1%, respectively. The overall accuracy of endoleak detection and correct sizing was 95.2%, 58.3%, 55.6%, and 57.1% for MRI, biphasic CT, uniphasic arterial CT, and uniphasic late CT, respectively. CONCLUSION: MRI is significantly superior to biphasic CT for endoleak detection and rating of endoleak size, followed by uniphasic late and uniphasic arterial CT scans. MRI shows a significant number of endoleaks in cases with negative CT findings and may help illuminate the phenomenon of endotension. Endoleak rates reported after endovascular aneurysm repair substantially depend on the imaging techniques used.

Assessment of left ventricular function by breath-hold cine MR imaging: Comparison of different steady-state free precession sequences.

PURPOSE: To compare steady-state free precession (SSFP) sequence protocols with different acquisition times (TA) and temporal resolutions (tRes) due to the implementation of a view sharing technique called shared phases for the assessment of left ventricular (LV) function by breath-hold cine magnetic resonance (MR) imaging. MATERIALS AND METHODS: End-diastolic and end-systolic volumes (EDV, ESV) were measured in contiguous short-axis slices with a thickness of 8 mm acquired in 10 healthy male volunteers. The following true fast imaging with steady-state precession (TrueFISP) sequence protocols were compared: protocol A) internal standard of reference, segmented: tRes 34.5 msec, TA 18 beats per slice; protocol B) segmented, shared phases: tRes 34.1 msec, TA 10 beats per slice; and protocol C) real-time, shared phases, parallel acquisition technique: tRes 47.3 msec, TA 24 beats for 12 slices covering the entire left ventricle. RESULTS: Phase sharing leads to a significant decrease in EDV, stroke volume (SV), and ejection fraction (EF) (median difference -7.0 mL [*], -9.6 mL, and -3.4%, respectively, for protocol B; -15.3 mL, -13.3 mL, and -2.4% for protocol C; P = 0.002, *P = 0.021). The observed median difference of real-time EDV and SV estimates is of clinical relevance. Real-time cine MR imaging shows a greater variability of EDV and SV. No relevant differences in ESV were observed. CONCLUSION: The true cine frame duration of both shared phases sequence protocols exceeds the period of isovolumetric contraction (IVCT) of the left ventricle resulting in a systematic and significant underestimation of EDV and consequently SV and EF. SSFP sequence protocol parameters, particularly tRes and use of view sharing techniques, should therefore be known at follow-up examinations in order to be able to assess LV remodeling in patients with heart failure.

Preoperative assessment of breast cancer: sonography versus MR imaging.

OBJECTIVE: The purposes of our study were to compare the diagnostic value of whole-breast sonography and MR imaging as adjunctive techniques to mammography and to determine whether MR imaging should be used routinely in the preoperative assessment of patients with suspected breast cancer. SUBJECTS AND METHODS: . One hundred four women (age range, 34-84 years; mean age, 60 years) with findings highly suggestive of malignancy in the breast were examined with mammography, sonography, and dynamic MR imaging before undergoing surgery. All visualized suspicious lesions were correlated histologically. The diagnostic relevance of sonographic and MR imaging findings was compared with the diagnostic value of the findings of clinical examination and mammography alone. RESULTS: . Twenty-seven tumors showed multifocal or multicentric invasive growth at pathology. Of these 27, 48% were correctly diagnosed via mammography alone; 63%, via the combination of mammography and sonography; and 81%, via MR imaging. Nine of the index tumors were invisible on mammography but were detected on sonography. Use of sonography benefited 13 patients and produced two studies with false-positive findings. Use of MR imaging benefited seven patients and produced eight studies with false-positive findings. In summary, 93% of all patients gained no advantage from MR imaging. Relevant additional findings were significantly more frequent in patients with dense breasts. CONCLUSION: Although MR imaging is most sensitive for the detection of small tumors, routine preoperative MR imaging appears to be unnecessary for most patients if a combination of mammography and whole-breast sonography is used. Additional MR imaging can be restricted to problematic cases in women with dense breast parenchyma.

Quantification of myocardial blood flow and blood flow reserve in the presence of arterial dispersion: a simulation study.

Myocardial blood flow (MBF) can be quantified using dynamic T1-weighted MRI of diffusible tracers and a mathematical model of underlying vasculature. Quantification of MBF by means of T1- weighted MRI requires knowledge of the arterial input function (AIF). The AIF can be estimated from the left ventricular (LV) cavity. However, dispersion may occur between the LV and the tissue of interest because of the laminar blood flow profiles, branching of venules, and because of stenosis. To evaluate the influence of dispersion on the results of MBF quantification, a simulation study was performed. The dispersion was described as a convolution of the AIF with an exponential residue function. Synthetic tissue and AIF curves were analyzed and the derived parameters fit to the simulated parameters. The results show that an unaccounted dispersion may result in a systematic underestimation of MBF up to approximately 50%. Underestimation increases with increasing dispersion and with increasing MBF. Assuming equal dispersion at rest and during hyperemia, myocardial perfusion reserve (MPR) estimates are also susceptible to underestimation of approximately 20%. An unaccounted dispersion therefore can lead to systematic underestimation of both blood flow and perfusion reserve.

Systemic pulsatile pressure in type II endoleaks after stent grafting of experimental abdominal aortic aneurysms.

PURPOSE: To investigate pressure and maximum rate of rise of systolic pressure (peak dP/dt) in completely excluded aneurysms and endoleaks to determine the hemodynamic impact of endoleaks. METHODS: In mongrel dogs (n = 36) experimental aneurysms were created by insertion of a patch (portion of rectus abdominis muscle sheath) into the infrarenal aorta. In group I (n = 18), all aortic branches of the aneurysm were ligated and all aneurysms were completely excluded by stent grafts. Group II (n = 18) consisted of aneurysms with patent aortic side branches that represented sources of endoleaks. One week (n = 12), six weeks (n = 12), and six months (n = 12) after stent grafting, hemodynamic measurements were obtained in thrombosed aneurysms and proved endoleaks. Systemic blood pressure and intraaneurysmal pressure were simultaneously measured and the respective peak dP/dt were computed. RESULTS: At the six-month follow-up, the systolic-pressure ratio (intraaneurysmatic pressure: systemic pressure) was significantly increased in endoleaks compared to non-perfused areas (0.879 +/- 0.042 versus 0.438 +/- 0.176, p < 0.01, group II) or completely excluded aneurysms (0.385 +/- 0.221, group I). Peak dP/dt ratio (intraaneurysmal peak dP/dt: systemic peak dP/dt) was 0.922 +/- 0.154 in endoleaks, compared to 0.084 +/- 0.080 in non-perfused areas (group II, p < 0.01), and was 0.146 +/- 0.121 in completely excluded aneurysms (group I). The diastolic-pressure ratio was also increased in endoleaks compared to non-perfused areas (0.929 +/- 0.088 versus 0.655 +/- 0.231, p < 0.01, group II) or completely excluded aneurysms (0.641 +/- 0.278, group I). In excluded aneurysms, pressure exposure declined as the length of the follow-up period increased. CONCLUSION: Type II endoleaks transmit pulsatile pressure of near systemic level and indicate insufficient treatment result. In contrast, complete endovascular exclusion of aneurysms results in significantly reduced pressure exposure.

CT attenuation of paired HRCT scans obtained at full inspiratory/expiratory position: comparison with pulmonary function tests.

The purpose of this prospective study was to measure lung attenuation at paired HRCT obtained at full inspiratory/expiratory position, to correlate with pulmonary function tests (PFTs) and to characterize different types of ventilatory impairment. One hundred fifty-five patients with and without pulmonary disease underwent paired HRCT obtained at full inspiratory/expiratory position. Three scan pairs were evaluated by densito- and planimetry using dedicated software. The PFTs were available for correlation in all patients (mean interval 5 days). Mean lung density (MLD) at full inspiration was -813 HU, and MLD at full expiration was -736 HU; both, as well as the expiratory attenuation increase, demonstrated significant correlations with static and dynamic lung volumes: up to r=0.68, p<0.05 for residual volume. The MLD and emphysema indices correlated markedly better for scans obtained at full expiration than at full inspiration, e.g. correlation with the residual volume: r=0.68 compared with r=0.55. Even better correlations were obtained for the lung area (229 cm(2) at inspiration, 190 cm(2) at expiration), up to r=0.74 for the lung area in expiration and the intrathoracic gas volume. Inspiratory MLD and the expiratory attenuation increase were able to differentiate obstructive and restrictive ventilatory impairment from normal subjects, the best results were obtained from scans obtained at full expiratory position ( p<0.05). In conclusion, scans obtained at full expiratory position reveal more functional information than scans obtained at full inspiratory position. Quantitative analysis of CT obtained at full expiratory position provides good estimations of static and dynamic lung volumes as well as significant differences between normal subjects and patients with ventilatory impairment.