ABSTRACT
PURPOSE: The outcomes of five fraction stereotactic radiotherapy (hfSRT) following brain metastasectomy were evaluated and compared with published series. METHODS: 30 Gy in 5 fractions HfSRT prescribed to the surgical cavity was reduced to 25 Gy if the volume of 'brain-GTV' receiving 20 Gy exceeded 20 cm3. Endpoints were local recurrence, nodular leptomeningeal recurrence, new brain metastases and radionecrosis. The literature was searched for reports of clinical and dosimetric outcomes following postoperative hfSRT in 3-5 fractions. RESULTS: 39 patients with 40 surgical cavities were analyzed. Cavity local control rate at 1 year was 33/40 (82.5%). 3 local failures followed 30 Gy/5 fractions and 4 with 25 Gy/5 fractions. The incidence of leptomeningeal disease (LMD) was 7/40 (17.5%). No grade 3-4 toxicities, particularly no radionecrosis, were reported. The incidence of distant brain metastases was 15/40 (37.5%). The median overall survival was 15 months. Across 13 published series, the weighted mean local control was 83.1% (adjusted for sample size), the mean incidence of LMD was 14.9% (7-34%) and the mean rate of radionecrosis was 10.3% (0-20.6%). CONCLUSION: Postoperative hfSRT can be delivered with 25-30 Gy in 5 fractions with efficacy in excess of 82% and no significant toxicity when the dose to 'brain-GTV' does not exceed 20 cm3.
Subject(s)
Brain Neoplasms , Metastasectomy , Radiation Injuries , Radiosurgery , Brain , Brain Neoplasms/radiotherapy , Brain Neoplasms/surgery , Humans , Meningeal Neoplasms , Radiation Dose Hypofractionation , Radiosurgery/adverse effects , Retrospective Studies , Treatment OutcomeABSTRACT
The multiple inert gas elimination technique (MIGET) using gas chromatography (GC) is an established but time-consuming method of determining ventilation/perfusion (VA/Q) distributions. MIGET-when performed using Micropore Membrane Inlet Mass Spectrometry (MMIMS)-has been proven to correlate well with GC-MIGET and reduces analysis time substantially. We aimed at comparing shunt fractions and dead space derived from MMIMS-MIGET with Riley shunt and Bohr dead space, respectively. Thirty anesthetized pigs were randomly assigned to lavage or pulmonary embolism groups. Inert gas infusion (saline mixture of SF6, krypton, desflurane, enflurane, diethyl ether, acetone) was maintained, and after induction of lung damage, blood and breath samples were taken at 15-min intervals over 4 h. The samples were injected into the MMIMS, and resultant retention and excretion data were translated to VA/Q distributions. We compared MMIMS-derived shunt (MM-S) to Riley shunt, and MMIMS-derived dead space (MM-VD) to Bohr dead space in 349 data pairs. MM-S was on average lower than Riley shunt (- 0.05 ± 0.10), with lower and upper limits of agreement of - 0.15 and 0.04, respectively. MM-VD was on average lower than Bohr dead space (- 0.09 ± 0.14), with lower and upper limits of agreement of - 0.24 and 0.05. MM-S and MM-VD correlated and agreed well with Riley shunt and with Bohr dead space. MM-S increased significantly after lung injury only in the lavage group, whereas MM-VD increased significantly in both groups. This is the first work evaluating and demonstrating the feasibility of near real-time VA/Q distribution measurements with the MIGET and the MMIMS methods.
Subject(s)
Lung Injury/physiopathology , Lung/surgery , Pulmonary Embolism/physiopathology , Respiratory Dead Space , Anesthesia, General , Animals , Blood Gas Analysis , Chromatography, Gas , Gases , Hemodynamics , Lung Injury/surgery , Mass Spectrometry , Micropore Filters , Propofol/administration & dosage , Pulmonary Embolism/surgery , Swine , Ventilation-Perfusion RatioABSTRACT
Etomidate is an intravenous hypnotic with a favourable clinical profile in haemodynamic high-risk scenarios. Currently, there is an active debate about the clinical significance of the drug's side effects and its overall risk-benefit ratio. Etomidate-induced transient adrenocortical suppression is well documented and has been associated with increased mortality in sepsis. In surgical patients at risk of hypotensive complications, however, a review of current literature provides no robust evidence to contraindicate a single-bolus etomidate induction. Large randomised controlled trials as well as additional observational data are required to compare safety of etomidate and its alternatives.
Subject(s)
Anesthetics, Intravenous , Etomidate , Hypnotics and Sedatives , Anesthesia, General , Anesthesia, Intravenous/methods , Anesthetics, Intravenous/adverse effects , Anesthetics, Intravenous/pharmacokinetics , Anesthetics, Intravenous/pharmacology , Cardiovascular Diseases/complications , Conscious Sedation , Etomidate/adverse effects , Etomidate/pharmacokinetics , Etomidate/pharmacology , Humans , Hypnotics and Sedatives/adverse effects , Hypnotics and Sedatives/pharmacokinetics , Hypnotics and Sedatives/pharmacology , Hypotension/complications , Hypotension/physiopathology , Risk Assessment , Sepsis/mortalityABSTRACT
BACKGROUND: The non-operative management (NOM) of blunt splenic injuries has gained widespread acceptance. However, there are still many controversies regarding follow-up of these patients. The purpose of this study was to survey active members of the Swiss Society of General and Trauma Surgery (SGAUC) to determine their practices regarding the NOM of isolated splenic injuries. MATERIALS AND METHODS: A survey of active SGAUC members with a written questionnaire was carried out. The questionnaire was designed to elicit information about personal and facility demographics, diagnostic practices, in-hospital management, preferred follow-up imaging and return to activity. RESULTS: Out of 165 SGAUC members 52 (31.5%) completed the survey and 62.8% of all main trauma facilities in Switzerland were covered by the sample. Of the respondents 14 (26.9%) have a protocol in place for treating patients with splenic injuries. For initial imaging in hemodynamically stable patients 82.7% of respondents preferred ultrasonography (US). In cases of suspected splenic injury 19.2% of respondents would abstain from further imaging. In cases of contrast extravasation from the spleen half of the respondents would take no specific action. For low-grade injuries 86.5% chose to admit patients for an average of 1.6 days (range 0-4 days) with a continuously monitored bed. No differences in post-discharge activity restrictions between moderate and high-grade splenic injuries were found. CONCLUSION: The present survey showed considerable practice variation in several important aspects of the NOM of splenic injuries. Not performing further CT scans in patients with suspected splenic injuries and not intervening in cases of a contrast extravasation were the most important discrepancies to the current literature. Standardization of the NOM of splenic injuries may be of great benefit for both surgeons and patients.
Subject(s)
Practice Patterns, Physicians'/statistics & numerical data , Spleen/injuries , Spleen/surgery , Traumatology/statistics & numerical data , Ultrasonography/statistics & numerical data , Wounds, Nonpenetrating/diagnosis , Wounds, Nonpenetrating/therapy , Adolescent , Data Collection , Female , Humans , Male , Physicians/statistics & numerical data , Prevalence , Switzerland/epidemiology , Wounds, Nonpenetrating/epidemiologyABSTRACT
BACKGROUND: In the acute respiratory distress syndrome potentially recruitable lung volume is currently discussed. (3)He-magnetic resonance imaging ((3)He-MRI) offers the possibility to visualize alveolar recruitment directly. METHODS: With the approval of the state animal care committee, unilateral lung damage was induced in seven anesthetized pigs by saline lavage of the right lungs. The left lung served as an intraindividual control (healthy lung). Unilateral lung damage was confirmed by conventional proton MRI and spiral-CT scanning. The total aerated lung volume was determined both at a positive end-expiratory pressure (PEEP) of 0 and 10 mbar from three-dimensionally reconstructed (3)He images, both for healthy and damaged lungs. The fractional increase of aerated volume in damaged and healthy lungs, followed by a PEEP increase from 0 to 10 mbar, was compared. RESULTS: Aerated gas space was visualized with a high spatial resolution in the three-dimensionally reconstructed (3)He-MR images, and aeration defects in the lavaged lung matched the regional distribution of atelectasis in proton MRI. After recruitment and PEEP increase, the aerated volume increased significantly both in healthy lungs from 415 ml [270-445] (median [min-max]) to 481 ml [347-523] and in lavaged lungs from 264 ml [71-424] to 424 ml [129-520]. The fractional increase in lavaged lungs was significantly larger than that in healthy lungs (healthy: 17% [11-38] vs. lavage: 42% [14-90] (P=0.031). CONCLUSION: The (3)He-MRI signal might offer an experimental approach to discriminate atelectatic vs. poor aerated lung areas in a lung damage animal model. Our results confirm the presence of potential recruitable lung volume by either alveolar collapse or alveolar flooding, in accordance with previous reports by computed tomography.
Subject(s)
Acute Lung Injury/pathology , Bronchoalveolar Lavage/methods , Helium , Isotopes , Lung/pathology , Magnetic Resonance Imaging/methods , Acute Lung Injury/physiopathology , Animals , Disease Models, Animal , Hemodynamics , Lung/physiopathology , Models, Animal , Positive-Pressure Respiration , Pulmonary Gas Exchange/physiology , Respiratory Function Tests , Swine , Treatment OutcomeABSTRACT
Laparoscopic surgery was introduced into clinical practice in the early 1950s by gynaecologists. Technical improvements allowed its use for more complex and longer lasting procedures. Reduction of postoperative pain, more favourable cosmetic results, quicker recovery and reduced length of hospital stay proved to be advantageous when compared to open surgery. As a result progressively older patients with corresponding pulmonary and cardiovascular comorbidities and morbidly obese patients are now undergoing advanced laparoscopic surgery. Detailed knowledge of the respiratory and hemodynamic pathophysiology induced by capnoperitoneum is necessary to administer safe anaesthesia to such patients. This review addresses the most important effects of capnoperitoneum and recent research as well as the possible implications for clinical practice.
Subject(s)
Carbon Dioxide , Hemodynamics/physiology , Laparoscopy/adverse effects , Pneumoperitoneum, Artificial/adverse effects , Anesthesia, Inhalation , Humans , Positive-Pressure Respiration , Respiration, ArtificialABSTRACT
By studying the conical emission of a blue femtosecond laser filament in air, it is shown that self-improvement of the beams' spatial mode quality occurs for a self-guided laser pulse.
ABSTRACT
PURPOSE: Visual assessment of the ventilation using HRCT and (3)He-MRI in patients after single lung transplantation (SLTX). Analysis of specific ventilation defects found with (3)He-MRI and morphological changes found with HRCT. MATERIALS AND METHODS: We evaluated 8male patients (54 +/- 6 years) suffering from emphysema and six patients (3males and 3 females, 58 +/- 9.5 years) suffering from idiopathic pulmonary fibrosis (IPF) after SLTX. The morphological changes at HRCT were classified and localized. In (3)He-MRI (2D FLASH), 10 to 14 slices (slice thickness 10 mm, gap 5 mm) were acquired in coronal orientation to cover the whole lung. Ventilation defects were localized and characterized. The visually estimated ventilation was recorded on a 5-point scoring system. A double threshold technique was applied to volumetric quantification in (3)He-MRI to serve as internal reference. RESULTS: We found no correlation between morphological changes in HRCT and ventilation defects in (3)He-MRI. The visual assessment of ventilation in (3)He-MRI was sufficient in patients with emphysema, but this was not confirmed in patients with IPF. The visual assessment in HRCT did not correlate with the volumetric evaluation in both conditions. CONCLUSION: The various ventilation defects were not linked to specific morphological changes. For the visually assessed ventilation in patients with emphysema, (3)He-MRI is superior to HRCT.
Subject(s)
Emphysema/diagnosis , Emphysema/surgery , Image Interpretation, Computer-Assisted/methods , Lung Transplantation/diagnostic imaging , Lung Transplantation/pathology , Pulmonary Fibrosis/diagnosis , Pulmonary Fibrosis/surgery , Female , Helium , Humans , Isotopes , Magnetic Resonance Imaging/methods , Male , Middle Aged , Observer Variation , Radiographic Image Enhancement/methods , Radiopharmaceuticals , Reproducibility of Results , Sensitivity and Specificity , Tomography, X-Ray Computed/methods , Treatment OutcomeABSTRACT
BACKGROUND: This study observed adverse events of rescue treatment with high-frequency oscillatory ventilation (HFOV) in head-injured patients with acute respiratory distress syndrome (ARDS). METHODS: Data of five male patients with ARDS and traumatic brain injury, median age 28 years, who failed to respond to conventional pressure-controlled ventilation (PCV) were analyzed retrospectively during HFOV. Adjusted mean airway pressure at initiation of HFOV was set to 5 cm H2O above the last measured mean airway pressure during PCV. Frequency of pulmonary air leak, mucus obstruction, tracheal injury, and need of HFOV termination due to increased intracranial pressure, decreased cerebral perfusion pressure, or deterioration in P(a)CO2 were analyzed. RESULTS: During HFOV we found no complications. We recorded 390 datasets of intracranial pressure, cerebral perfusion pressure and P(a)CO2 simultaneously. Intracranial pressure increased (>25 mmHg) in 11 of 390 datasets, cerebral perfusion pressure was reduced (<70 mmHg) in 66 of 390 datasets, and P(a)CO2 variations (<4.7 kPa; >6.0 kPa) were observed in eight of 390 datasets after initiation of HFOV. All these alterations were responsive to treatment. P(a)O2/F(I)O2-ratio improved in four patients during HFOV. CONCLUSION: High-frequency oscillatory ventilation appears to be a promising alternative rescue treatment in head-injured patients with ARDS if continuous monitoring of intracranial pressure, cerebral perfusion pressure and P(a)CO2 are provided, in particular during initiation of HFOV.
Subject(s)
Brain Injuries/complications , High-Frequency Ventilation/methods , Respiratory Distress Syndrome/complications , Respiratory Distress Syndrome/therapy , Adolescent , Adult , Blood Gas Analysis/methods , Blood Pressure/physiology , Carbon Dioxide/blood , High-Frequency Ventilation/adverse effects , Humans , Intracranial Pressure/physiology , Male , Middle Aged , Monitoring, Physiologic , Retrospective Studies , Time FactorsABSTRACT
PURPOSE: To develop a software tool for quantitative analysis of alveolar oxygen partial pressure (p(A)O(2)) as well as its time course during apnea. MATERIAL AND METHODS: T (1)-relaxation times of hyperpolarized (3)He are reduced by paramagnetic oxygen rendering (3)He-MRI sensitive to oxygen and thus allowing the assessment of the local oxygen partial pressure in the pulmonary airspaces. Oxygen-related relaxation and loss of polarization by RF-excitation can be discriminated by acquiring two image series with varying interscan delay and/or flip angles. Software was developed to calculate the p(A)O(2) and the decay rate in user-defined regions of interest (ROIs) automatically. Moreover, parameter maps can be calculated. In addition to the analysis of 2-dimensional data sets, the software allows the evaluation of 3-dimensional measurements for the first time. Artifacts due to lung motion were reduced by implementing a motion correction algorithm. RESULTS: The software was successfully applied to data sets from healthy volunteers and from patients with various lung diseases. The parameter maps demonstrated a more homogeneous distribution of p(A)O(2) for the volunteers than for the patients. A regional increase in p(A)O(2) was found in a few patients. CONCLUSION: The described software allows the absolute quantification of p(A)O(2) as well as its variation over time. In the future, therefore, the software may gain importance for detecting mismatches between ventilation and perfusion, e. g., in patients with pulmonary embolism or chronic obstructive lung diseases.
Subject(s)
Lung Diseases/physiopathology , Lung/physiology , Magnetic Resonance Imaging/methods , Oxygen/analysis , Software , Adult , Chronic Disease , Helium , Humans , Isotopes , Lung Diseases/diagnosis , Lung Diseases, Obstructive/diagnosis , Lung Diseases, Obstructive/physiopathology , Middle Aged , Models, Theoretical , Partial Pressure , Pulmonary Alveoli/physiology , Pulmonary Embolism/diagnosis , Pulmonary Embolism/physiopathology , RespirationABSTRACT
A decade after the onset of a discussion whether ventilation could be omitted from bystander basic life support (BLS) algorithms, the state of the evidence is reevaluated. Initial animal studies and a prospective randomized patient trial had suggested that omission of ventilation during the first minutes of lay cardiopulmonary resuscitation (CPR) did not impair patient outcomes. More recent studies demonstrate, however, that this may hold true only in very specific scenarios, and that the chest compression-only technique was never superior to standard BLS. Instead of calling basics of BLS training and practice into question, more and better training of lay persons and professionals appears mandatory, and targeted use of dispatcher-guided telephone CPR should be evaluated and, if it improves outcome, it should be encouraged. Future studies should focus much less on the omission but on the optimization of ventilation under the specific conditions of CPR.
Subject(s)
Cardiopulmonary Resuscitation , Respiration, Artificial , Cardiopulmonary Resuscitation/education , Emergency Medical Technicians/education , Humans , Quality Assurance, Health Care , Thorax/physiology , Tidal Volume/physiologyABSTRACT
PURPOSE: Dynamic CT (dCT) allows visualization and quantification of ventilated lung and atelectases with high temporal resolution during continuous ventilation. This study compares a quantitative image analysis in a subcarinal single slice dCT series versus a whole lung spiral-CT, in order to analyze, whether the distribution of atelectasis of a single dCT series is representative for the whole lung. MATERIALS AND METHODS: dCT in sliding windows technique (slice thickness 1 mm, temporal increment 100 ms) was performed in 8 healthy pigs 3 cm caudal to the carina during continuous mechanical ventilation. Subsequently, a spiral-CT of the whole lung (slice thickness 2 mm; pitch 1.5; increment 2 mm) was acquired during inspiratory breath hold (airway pressure 20 mbar). Lung segmentation and planimetry of predefined density ranges were achieved using a dedicated software tool in both data-sets. Thus, the fractions of the following functional lung compartments were averaged over time: hyperinflated lung (- 1024 to - 910 HE), normal ventilated lung -900 to -300 HE) and atelectasis (-300 to +200 HE). RESULTS: Quantitative analysis of dCT-series during continuous respiration correlated with the density analysis in spiral-CT as follows: hyperinflated lung r = 0.56; normal ventilated lung r = 0.83 and atelectases r = 0.84. Analysis of spiral-CT showed the following distribution of functional lung compartments: hyperinflated lung 3.1% normal ventilated lung 77.9% and atelectasis 19.0%. In dCT, hyperinflated lung represented 6.4%, normal ventilated lung 65.2% and atelectasis 28.4% of total the lung area. CONCLUSION: The results of our study demonstrate that dCT allows monitoring of atelectasis formation in response to different ventilatory strategies. However, a deviation between dCT and spiral-CT has to be taken into account. In subcarinal dCT series, hyperinflated lung areas and atelectases were overestimated due to a craniocaudal gradient of atelectases, whereas normal ventilated lung was underestimated.
Subject(s)
Lung/diagnostic imaging , Pulmonary Atelectasis/diagnostic imaging , Radiography, Thoracic , Respiration, Artificial , Tomography, Spiral Computed , Tomography, X-Ray Computed , Animals , Lung/physiology , Respiration , Swine , Tomography, X-Ray Computed/methodsABSTRACT
BACKGROUND AND OBJECTIVE: This prospective observational study analyses cardiovascular changes in adult patients with acute respiratory distress syndrome (ARDS) during transition from pressure-controlled ventilation to high-frequency oscillatory ventilation (HFOV), using transoesophageal echocardiography (TOE) and invasive haemodynamic monitoring. METHODS: Nine patients (median age 65 years; range 42-70) with ARDS were studied. HFOV was started and maintained with an adjusted mean airway pressure of 5 cmH2O above the last measured mean airway pressure during pressure-controlled ventilation. Haemodynamic and TOE measurements were performed in end-expiration during baseline pressure-controlled ventilation, and again 5 and 30 min after the start of during uninterrupted HFOV. RESULTS: Right atrial pressure increased immediately (P = 0.004). After 30 min, pulmonary arterial occlusion pressure increased (P = 0.008), cardiac index decreased (P = 0.01), stroke volume index decreased (P = 0.02) and both left ventricular end-diastolic and end-systolic area indices decreased (P = 0.02). Fractional area change, left ventricular end-systolic wall stress, heart rate, mean arterial pressure and mean pulmonary artery pressure remained unchanged. CONCLUSIONS: Transition to HFOV at a mean airway pressure of 5 cmH2O above that during pressure-controlled ventilation induced significant, but clinically minor, haemodynamic effects, which are most probably due to airway pressure-related preload reduction.
Subject(s)
Heart Function Tests/statistics & numerical data , Heart/physiopathology , Hemodynamics/physiology , High-Frequency Ventilation/methods , Respiratory Distress Syndrome/therapy , Adult , Aged , Blood Pressure/physiology , Catheterization, Swan-Ganz/methods , Echocardiography, Transesophageal/methods , Female , Heart Function Tests/methods , Heart Rate/physiology , Humans , Male , Middle Aged , Monitoring, Physiologic/methods , Prospective Studies , Stroke Volume/physiology , Time FactorsABSTRACT
BACKGROUND: Fast dynamic computed tomography (dCT) has been used to assess regional dynamics of lung inflation and deflation processes. The aim of this study was to relate ventilation-induced changes in lung density distribution, as measured over several respiratory cycles by dCT, to oxygenation and shunt fraction in a lavage acute respiratory distress syndrome model. METHODS: Six anaesthetized pigs underwent pressure-constant ventilation (FIO2=1.0, inspiratory:expiratory ratio=1:1) before and after induction of lung damage by saline lavage. Mean airway pressure (Paw) was varied (8, 13, 18, 23, 28, 33, and 38 cm H2O) in random order. At each Paw level, dCT acquisitions were performed over several respiratory cycles (Somatom Plus4, Siemens; supradiaphragmatic transverse slice; thickness=1 mm; temporal resolution=100 ms). During scanning at each Paw, arterial and mixed venous blood were obtained for blood gas analysis and shunt calculation. In each CT image, fractional areas (FA) of defined density ranges representing ventilated lung and atelectasis were determined by planimetry using dedicated software. The FA data of individual 100 ms scans were averaged over several respiratory cycles, and expressed as mean FA in percentage of total lung area at each Paw. For atelectatic lung parenchyma a quantitative relationship of the respective mean FA to shunt fraction was studied using regression analysis. RESULTS: Under steady-state conditions, mean FA of atelectasis correlated linearly with the calculated shunt fraction (healthy lungs, r=+0.76; lavaged lungs, r=+0.89). There is a non-linear relationship between mean FA of ventilated lung parenchyma and mean FA of atelectasis with PaO2. CONCLUSIONS: We conclude that dCT allows assessment of the effects of ventilator adjustments and resultant Paw; changes upon lung aeration and oxygenation rapidly, and with good spatial and temporal resolution. This may benefit patients with acute lung injury, whose ventilatory pattern may be optimized as early as during their first diagnostic workup.
Subject(s)
Lung/diagnostic imaging , Oxygen Consumption , Respiratory Distress Syndrome/diagnostic imaging , Tomography, X-Ray Computed , Animals , Carbon Dioxide/blood , Hemodynamics , Image Processing, Computer-Assisted , Oxygen/blood , Partial Pressure , Respiratory Distress Syndrome/physiopathology , SwineABSTRACT
PURPOSE: 3He-MRI of the lung has been shown to be a sensitive method for functional imaging of the lung. A previous study compared 3He-MRI (coronal planes) with CT (transverse planes) by looking for ventilation defects and their pathomorphologic correlation. Anatomic structures, such as lobar fissures and hilar vessels, were used for orientation, but the reliable assignment of ventilation defects to lung segments is problematic. The present work compares multiplanar reformations of 3He-MRI and HR-CT, which were generated from planes determined by the respective method, and investigates their suitability as a solution of this problem. MATERIALS AND METHODS: A total of 16 data sets taken from 15 patients with unilateral lung transplantation and one patient with lung emphysema were retrospectively evaluated. Transverse planes of 3He-MRI and coronal planes of HR-CT were reformatted on an external workstation and images evaluated by two readers in consensus. The evaluation searched for ventilation defects on 3He-MRI and their corresponding defects on HR-CT. The defects were related to anatomic structures, with hilar vessels and tracheobronchial tree selected for 3He-MRI reformations and lobar fissures for HR-CT reformations. RESULTS: All cases were successfully reformatted and all ventilation defects were correctly assigned to anatomic structures. On HR-CT reformations, the lobar fissures were partially visible in 12 of 16 cases and completely visible in the remaining 4 cases. Since reformation compromises the spatial resolution, the reformatted images should be evaluated together with the source images. CONCLUSION: Looking at HR-CT and 3He-MRI images and their reformations enables the detection of ventilation defects and their assignment to lung segments, facilitating the correlation of ventilation defects with a pathomorphologic pattern on HR-CT.
Subject(s)
Image Enhancement/methods , Lung Transplantation , Magnetic Resonance Imaging/methods , Postoperative Complications/diagnosis , Pulmonary Emphysema/diagnosis , Pulmonary Fibrosis/diagnosis , Tomography, Spiral Computed/methods , Adult , Female , Humans , Lung/pathology , Male , Middle Aged , Postoperative Complications/pathology , Pulmonary Atelectasis/diagnosis , Pulmonary Atelectasis/pathology , Pulmonary Emphysema/pathology , Pulmonary Emphysema/surgery , Pulmonary Fibrosis/pathology , Pulmonary Fibrosis/surgery , Sensitivity and Specificity , Ventilation-Perfusion Ratio/physiologyABSTRACT
BACKGROUND: To use 3Helium (3He)-MRI in patients with unilateral lung grafts to assess the contributions of graft and native lung to total ventilated lung volume, and second to compare conventional measurements of intrapulmonary gas volume (spirometry, body plethysmography) with image-based volumetry of ventilated lung parenchyma visualized by hyperpolarized 3He-MRI. METHODS: With Ethics Committee approval, five patients with single lung transplantation (SLTX) for idiopathic pulmonary fibrosis (IPF) underwent both conventional pulmonary function testing (PFT) and 3He-MRI of the lung. Intrapulmonary gas volume (GV) during the inspiratory breathhold for 3He-MRI was calculated from measured functional residual capacity (corrected for supine position) and inspired tidal volume. Image-based global and regional lung volumetries (LV) were performed in three-dimensionally reconstructed 3He-MR images (corrected for the fraction of tissue and blood). RESULTS: Transplanted lungs were characterized by a homogeneous distribution of signal intensity, whereas the native lungs of the patients suffering from IPF displayed an inhomogeneous signal distribution pattern with numerous round or wedge-shaped ventilation defects. Total ventilated lung volume determined by 3He-MRI correlated well with PFT-based measurements, but with a systematic overestimation of the 3He-based lung volumetry of approximately 20%. Functioning lung grafts contributed 66+/-6% and their corresponding native IPF lungs 34+/-6% to total ventilated volume (P<0.05; mean+/-SD). CONCLUSION: 3Helium-MRI of the lung offers a novel approach to regional determination of ventilated lung volume, including its blood and tissue compartments. The advantage of this technique over computed tomography or ventilation scintigraphy is the lack of radiation exposure, and hence its repeatability. Follow up of SLTX patients with this new technique may allow the monitoring of functional and structural developments of grafted lungs with better sensitivity and specificity than PFT.
Subject(s)
Helium , Lung Transplantation , Lung Volume Measurements , Magnetic Resonance Imaging , Female , Humans , Imaging, Three-Dimensional , Isotopes , Lung/pathology , Male , Middle Aged , Plethysmography, Whole Body , Pulmonary Fibrosis/surgery , Respiratory Function Tests , Spirometry , Vital CapacityABSTRACT
MRI of the lungs using hyperpolarized helium-3 ((3)He) allows the determination of intrapulmonary oxygen partial pressures (p(O2)). The need to separate competing processes of signal loss has hitherto required two different imaging series during two different breathing maneuvers. In this work, a new imaging strategy to measure p(O2) by a single series of consecutive scans is presented. The feasibility of the method is demonstrated in three healthy human volunteers. Maps and histograms of intrapulmonary p(O2) are calculated. Changes in the oxygen concentration of the inhaled gas mixture are well reproduced in the histograms. Monte Carlo (MC) simulations of the temporal evolution of (3)He hyperpolarization within the lungs were performed to evaluate the accuracy of this measurement technique, and its limitations.
Subject(s)
Lung/anatomy & histology , Magnetic Resonance Imaging , Computer Simulation , Helium , Humans , Image Processing, Computer-Assisted , Isotopes , Monte Carlo Method , Oxygen , Partial Pressure , Pulmonary Ventilation/physiologyABSTRACT
PURPOSE: Reduced or blocked ventilation of the paranasal sinuses is probably the most important factor in the development of sinusitis. Recently, the use of optically polarized noble gas isotopes has attracted increasing interest for use in a variety of promising MR applications. The aim of this study was to test the feasibility of imaging and visualization ventilation of the nasal cavity and paranasal sinus in MR by inhalation of hyperpolarized (3)helium. The goal was to evaluate ventilation defects of the paranasal sinuses. VOLUNTEERS AND METHODS: Three volunteers were enrolled in the study. (3)Helium was polarized to 40 - 50 % by direct optical pumping. 300 ml of 100 % (3)helium were administered in the left nasal vestibule through a glass tube. With a closed contralateral nasal vestibule, the Valsalva maneuver was performed twice. Using a dedicated application unit, which is also used in MR imaging of the lung, an exact amount of (3)helium gas was administered at the beginning of inspiration. Measurements were carried out on a clinical 1.5 T scanner. Coronal images of the nasal cavity and paranasal sinuses were acquired using ultrafast gradient-echo pulse sequence (TR = 2 ms, TE = 0.7 ms, FA < 2 degrees, 75 x 128, FOV = 500) with an image aquisition time of 130 ms. RESULTS: The oral cavity and nasal cavities display a very high signal intensity after inhalation of polarized (3)helium gas. The signal intensity in the left maxillary sinus was higher compared to the right one. The mean signal intensity on the left side was 526 +/- 86 and on the right side 336 +/- 102. The left and right frontal sinus and ethmoid sinus only show signal of hyperpolarized (3)helium after two Valsalva maneuvers. Because of the low signal intensity of the frontal and ethmoid cells their visualization was incomplete. The signal to noise ratio was 14.1 for the left maxillary sinus, 8.9 for the right side, 6.3 for the left ethmoid sinus, 5.8 for the right side and 6.6 for the left frontal sinus and 7.8 for the right side. CONCLUSION: (3)Helium MR allows imaging of the nasal cavity and the paranasal sinuses. Perhaps this method could be a new tool to visualize the ventilation of the maxillary sinus without ionizing radiation. Interpretations about the ventilation of the frontal and ethmoid cells remain speculative.
Subject(s)
Image Enhancement , Magnetic Resonance Imaging , Nasal Cavity/pathology , Nasal Obstruction/diagnosis , Sinusitis/diagnosis , Administration, Inhalation , Adult , Contrast Media , Female , Helium , Humans , Isotopes , Male , Paranasal Sinuses/pathology , Pulmonary Ventilation/physiology , Sensitivity and Specificity , Valsalva Maneuver/physiologyABSTRACT
In magnetic resonance imaging (MRI), nuclear spins are the source of the image signal. In the lung, low-proton spin density in alveolar gas and abundant gas-tissue interfaces substantially impair conventional native 1H-MRI. Spin polarisation can be increased in two non-radioactive noble gas isotopes, 3He and 129Xe, by exposure to polarised laser light. When inhaled, such "magnetized" gases provide high-intensity MR images of the pulmonary airspaces. Thus, hyperpolarised gas (HPG) MRI opens up new routes to a) morphologic imaging of airways and alveolar spaces, and b) analysis of the intrapulmonary distribution of inhaled aliquots of these tracer gases; c) diffusion-sensitive MRI-techniques allow mapping of the "apparent diffusion coefficient" (ADC) of 3He within lung airspaces, where ADC is physically related to local bronchoalveolar dimensions; d) also, 3He magnetisation decays in an oxygen-containing atmosphere at a rate proportional to ambient PO2. This property allows image-based determination of regional broncho-alveolar PO2 and its decrease during a breathhold. Currently, these modalities of functional lung imaging are being assessed by several European and American research groups in animal models, human volunteers and patients. First results show good imaging quality with excellent spatial and unprecedented temporal resolution, and attest to the reproducibility, feasibility and safety of the technique. Regionally impaired ventilation of both structural and functional origin is detected with high sensitivity, e.g. in smokers, asthmatics, patients with COPD or after lung transplantation. Studies into regional ADC and PO2 measurement demonstrate good agreement with reference methods and physiological predictions. The present limitations of HPG-MRI include the HPG production rate and the US and EU health authorities' still pending final approval for clinical use.