An open source software for analysis of dynamic contrast enhanced magnetic resonance images: UMMPerfusion revisited.

BACKGROUND: Perfusion imaging has become an important image based tool to derive the physiological information in various applications, like tumor diagnostics and therapy, stroke, (cardio-) vascular diseases, or functional assessment of organs. However, even after 20 years of intense research in this field, perfusion imaging still remains a research tool without a broad clinical usage. One problem is the lack of standardization in technical aspects which have to be considered for successful quantitative evaluation; the second problem is a lack of tools that allow a direct integration into the diagnostic workflow in radiology. RESULTS: Five compartment models, namely, a one compartment model (1CP), a two compartment exchange (2CXM), a two compartment uptake model (2CUM), a two compartment filtration model (2FM) and eventually the extended Toft's model (ETM) were implemented as plugin for the DICOM workstation OsiriX. Moreover, the plugin has a clean graphical user interface and provides means for quality management during the perfusion data analysis. Based on reference test data, the implementation was validated against a reference implementation. No differences were found in the calculated parameters. CONCLUSION: We developed open source software to analyse DCE-MRI perfusion data. The software is designed as plugin for the DICOM Workstation OsiriX. It features a clean GUI and provides a simple workflow for data analysis while it could also be seen as a toolbox providing an implementation of several recent compartment models to be applied in research tasks. Integration into the infrastructure of a radiology department is given via OsiriX. Results can be saved automatically and reports generated automatically during data analysis ensure certain quality control.

Semi-automatic lung segmentation of DCE-MRI data sets of 2-year old children after congenital diaphragmatic hernia repair: Initial results.

In congenital diaphragmatic hernia (CDH), lung hypoplasia and secondary pulmonary hypertension are the major causes of death and severe disability. Based on new therapeutic strategies survival rates could be improved to up to 80%. However, after surgical repair of CDH, long-term follow-up of these pediatric patients is necessary. In this, dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) provides insights into the pulmonary microcirculation and might become a tool within the routine follow-up program of CDH patients. However, whole lung segmentation from DCE-MRI scans is tedious and automated procedures are warranted. Therefore, in this study, an approach to semi-automated lung segmentation is presented. Segmentation of the lung is obtained by calculating the cross correlation and the area under curve between all voxels in the data set and a reference region-of-interest (ROI), here the arterial input function (AIF). By applying an upper and lower threshold to the obtained maps and intersecting these, a final segmentation is reached. This approach was tested on twelve DCE-MRI data sets of 2-year old children after CDH repair. Segmentation accuracy was evaluated by comparing obtained automatic segmentations to manual delineations using the Dice overlap measure. Optimal thresholds for the cross correlation were 0.5/0.95 and 0.1/0.5 for the area under curve, respectively. The ipsilateral (left) lung showed reduced segmentation accuracy compared to the contralateral (right) lung. Average processing time was about 1.4s per data set. Average Dice score was 0.7±0.1 for the whole lung. In conclusion, initial results are promising. By our approach, whole lung segmentation is possible and a rapid evaluation of whole lung perfusion becomes possible. This might allow for a more detailed analysis of lung hypoplasia of children after CDH.

Treatment concept of chronic subdural haematoma according to an algorithm using evidence-based medicine-derived key factors: A prospective controlled study.

INTRODUCTION: Surgical treatment for chronic subdural haematoma (CSH) has been analysed by applying evidence-based medicine (EBM) criteria earlier. Whether implementation of EBM-derived key factors into an optimised treatment algorithm would improve outcome, however, needs to be clarified. MATERIAL AND METHODS: Symptomatic patients with CSH who fulfilled the inclusion criteria were either assigned to an optimised treatment algorithm (OA-EBM group) or to a control group treated by the standard departmental surgical technique (SDST group) in a prospective design. For the OA-EBM algorithm only one burr hole, extensive intraoperative irrigation and a closed system drainage with meticulous avoidance of entry of air was mandatory. A two-catheter technique was used to reduce intracavital air. Final endpoints were neurological outcome (Markwalder Score), recurrence and the amount of intracranial air. RESULTS: A total of 93 out of 117 patients were evaluated accounting for 113 cases because 20 patients had bilateral haematomas. Demographic data of 68 cases in the SDST group did not differ from 45 cases in the OA-EBM group. The Markwalder Score showed greater improvement in the OA-EBM group (0.5 ± 0.6 vs. 1.0 ± 1.0, p = 0.003). The recurrence rate was 18% (12 patients) in the SDST group versus 2% (1 patient) in the OA-EBM group (p < 0.05). The amount of intracranial air was significantly lower in the OA-EBM group (3.3 ± 5.0 cm(3) vs. 5.2 ± 7.7 cm(3)) with p = 0.04. In the standard group computerised tomography scanning was performed slightly earlier (3 ± 1.7 days vs. 3.6 ± 1.4 days). When comparing only non-recurrent cases in both groups no significant difference was apparent. CONCLUSIONS: Implementation of EBM key factors into a treatment algorithm for CSH can improve neurological outcome in a typical neurosurgical department, reduce recurrence and minimise the amount of postoperative air within the haematoma cavity.

Dose and image quality of cone-beam computed tomography as compared with conventional multislice computed tomography in abdominal imaging.

OBJECTIVES: Recent technical developments have facilitated the application of cone-beam computed tomography (CBCT) for interventional and intraoperative imaging. The aim of this study was to compare the radiation doses and image quality in CBCT with those of conventional multislice spiral computed tomography (MSCT) for abdominal and genitourinary imaging. METHODS: Different CBCT and MSCT protocols for imaging soft tissues and hard-contrast objects at different dose levels were investigated in this study. Local skin and organ doses were measured with thermoluminescent dosimeters placed in an anthropomorphic phantom. Moreover, the contrast-to-noise ratio, the noise-power spectrum, and the high-contrast resolution derived from the modulation transfer function were determined in a phantom with the same absorption properties as those of anthropomorphic phantom. RESULTS: The effective dose of the examined abdominal/genitourinary CBCT protocols ranged between 0.35 mSv and 18.1 mSv. As compared with MSCT, the local skin dose of CBCT examinations could locally reach much higher doses up to 190 mGy. The effective dose necessary to realize the same contrast-to-noise ratio with CBCT and MSCT depended on the MSCT convolution kernel: the MSCT dose was smaller than the corresponding CBCT dose for a soft kernel but higher than that for a hard kernel. The noise-power spectrum of the CBCT images at tube voltages of 85/90 kV(p) is at least half of that of images measured at 103/115 kV(p) at any arbitrarily chosen spatial frequency. Although the pixel size and slice thickness of CBCT were half of those of the MSCT images, high-contrast resolution was inferior to the MSCT images reconstructed with a hard convolution kernel. CONCLUSIONS: As compared with MSCT using a medium-hard convolution kernel, CBCT produces images at medium noise levels and, simultaneously, medium spatial resolution at approximately the same dose. It is well suited for visualizing hard-contrast objects in the abdomen with relatively low image noise and patient dose. For the detection of low-contrast objects at standard tube voltages of approximately 120 kV(p), however, MSCT should be preferred.

On-call service of neurosurgeons in Germany: organization, use of communication services, and personal acceptance of modern technologies.

BACKGROUND: A significant proportion of acute care neurosurgical patients present to hospital outside regular working hours. The objective of our study was to evaluate the structure of neurosurgical on-call services in Germany, the use of modern communication devices and teleradiology services, and the personal acceptance of modern technologies by neurosurgeons. MATERIALS AND METHODS: A nationwide survey of all 141 neurosurgical departments in Germany was performed. The questionnaire consisted of two parts: one for neurosurgical departments and one for individual neurosurgeons. The questionnaire, available online and mailed in paper form, included 21 questions about on-call service structure; the availability and use of communication devices, teleradiology services, and other information services; and neurosurgeons' personal acceptance of modern technologies. RESULTS: The questionnaire return rate from departments was 63.1% (89/141), whereas 187 individual neurosurgeons responded. For 57.3% of departments, teleradiology services were available and were frequently used by 62.2% of neurosurgeons. A further 23.6% of departments described using smartphone screenshots of computed tomography (CT) images transmitted by multimedia messaging service (MMS), and 8.6% of images were described as sent by unencrypted email. Although 47.0% of neurosurgeons reported owning a smartphone, only 1.1% used their phone for on-call image communication. CONCLUSION: Teleradiology services were observed to be widely used by on-call neurosurgeons in Germany. Nevertheless, a significant number of departments appear to use outdated techniques or techniques that leave patient data unprotected. On-call neurosurgeons in Germany report a willingness to adopt more modern approaches, utilizing readily available smartphones or tablet technology.

Correlation analysis of dual-energy CT iodine maps with quantitative pulmonary perfusion MRI.

AIM: To correlate dual-energy computed tomography (DECT) pulmonary angiography derived iodine maps with parameter maps of quantitative pulmonary perfusion magnetic resonance imaging (MRI). METHODS: Eighteen patients with pulmonary perfusion defects detected on DECT derived iodine maps were included in this prospective study and additionally underwent time-resolved contrast-enhanced pulmonary MRI [dynamic contrast enhanced (DCE)-MRI]. DCE-MRI data were quantitatively analyzed using a pixel-by-pixel deconvolution analysis calculating regional pulmonary blood flow (PBF), pulmonary blood volume (PBV) and mean transit time (MTT) in visually normal lung parenchyma and perfusion defects. Perfusion parameters were correlated to mean attenuation values of normal lung and perfusion defects on DECT iodine maps. Two readers rated the concordance of perfusion defects in a visual analysis using a 5-point Likert-scale (1 = no correlation, 5 = excellent correlation). RESULTS: In visually normal pulmonary tissue mean DECT and MRI values were: 22.6 ± 8.3 Hounsfield units (HU); PBF: 58.8 ± 36.0 mL/100 mL per minute; PBV: 16.6 ± 8.5 mL; MTT: 17.1 ± 10.3 s. In areas with restricted perfusion mean DECT and MRI values were: 4.0 ± 3.9 HU; PBF: 10.3 ± 5.5 mL/100 mL per minute, PBV: 5 ± 4 mL, MTT: 21.6 ± 14.0 s. The differences between visually normal parenchyma and areas of restricted perfusion were statistically significant for PBF, PBV and DECT (P < 0.0001). No linear correlation was found between MRI perfusion parameters and attenuation values of DECT iodine maps (PBF: r = 0.35, P = 0.15; PBV: r = 0.34, P = 0.16; MTT: r = 0.41, P = 0.08). Visual analysis revealed a moderate correlation between perfusion defects on DECT iodine maps and the parameter maps of DCE-MRI (mean score 3.6, κ 0.45). CONCLUSION: There is a moderate visual but not statistically significant correlation between DECT iodine maps and perfusion parameter maps of DCE-MRI.

UMMPerfusion: an open source software tool towards quantitative MRI perfusion analysis in clinical routine.

To develop a generic Open Source MRI perfusion analysis tool for quantitative parameter mapping to be used in a clinical workflow and methods for quality management of perfusion data. We implemented a classic, pixel-by-pixel deconvolution approach to quantify T1-weighted contrast-enhanced dynamic MR imaging (DCE-MRI) perfusion data as an OsiriX plug-in. It features parallel computing capabilities and an automated reporting scheme for quality management. Furthermore, by our implementation design, it could be easily extendable to other perfusion algorithms. Obtained results are saved as DICOM objects and directly added to the patient study. The plug-in was evaluated on ten MR perfusion data sets of the prostate and a calibration data set by comparing obtained parametric maps (plasma flow, volume of distribution, and mean transit time) to a widely used reference implementation in IDL. For all data, parametric maps could be calculated and the plug-in worked correctly and stable. On average, a deviation of 0.032 ± 0.02 ml/100 ml/min for the plasma flow, 0.004 ± 0.0007 ml/100 ml for the volume of distribution, and 0.037 ± 0.03 s for the mean transit time between our implementation and a reference implementation was observed. By using computer hardware with eight CPU cores, calculation time could be reduced by a factor of 2.5. We developed successfully an Open Source OsiriX plug-in for T1-DCE-MRI perfusion analysis in a routine quality managed clinical environment. Using model-free deconvolution, it allows for perfusion analysis in various clinical applications. By our plug-in, information about measured physiological processes can be obtained and transferred into clinical practice.

Establishing end-to-end security in a nationwide network for telecooperation.

Telecooperation is used to support care for trauma patients by facilitating a mutual exchange of treatment and image data in use-cases such as emergency consultation, second-opinion, transfer, rehabilitation and out-patient aftertreatment. To comply with data protection legislation a two-factor authentication using ownership and knowledge has been implemented to assure personalized access rights. End-to-end security is achieved by symmetric encryption in combination with external trusted services which provide the symmetric key solely at runtime. Telecooperation partners may be chosen at departmental level but only individuals of that department, as a result of checking the organizational assignments maintained by LDAP services, are granted access. Data protection officers of a federal state have accepted the data protection means. The telecooperation platform is in routine operation and designed to serve for up to 800 trauma centers in Germany, organized in more than 50 trauma networks.

First description of MR mammographic findings in the tumor bed after intraoperative radiotherapy (IORT) of breast cancer.

The aim was to investigate changes in the tumor bed on magnetic resonance mammography (MRM) after intraoperative radiotherapy (IORT) and whether they would limit the diagnostic value of posttherapeutic MRM. We retrospectively investigated 36 patients undergoing MRM after IORT (median interval 2.8 years, range 0.4-7.1). Wound cavities with fat necrosis were common after IORT (81%). They were associated with persisting contrast enhancement, i.e., enhancement was mostly seen irrespective of the posttherapeutic interval. It normally presented as rim enhancement and did not cause any diagnostic uncertainty if viewed together with other tissue characteristics. We do not expect a limited diagnostic value of MRM after IORT.

Computed tomographies and cancer risk in children: a literature overview of CT practices, risk estimations and an epidemiologic cohort study proposal.

Radiation protection is a topic of great public concern and of many scientific investigations, because ionizing radiation is an established risk factor for leukaemia and many solid tumours. Exposure of the public to ionizing radiation includes exposure to background radiation, as well as medical and occupational exposures. A large fraction of the exposure from diagnostic procedures comes from medical imaging. Computed tomography (CT) is the major single contributor of diagnostic radiation exposure. An increase in the use of CTs has been reported over the last decades in many countries. Children have smaller bodies and lower shielding capacities, factors that affect the individual organ doses due to medical imaging. Several risk models have been applied to estimate the cancer burden caused by ionizing radiation from CT. All models predict higher risks for cancer among children exposed to CT as compared to adults. However, the cancer risk associated with CT has not been assessed directly in epidemiological studies. Here, plans are described to conduct an historical cohort study to investigate the cancer incidence in paediatric patients exposed to CT before the age of 15 in Germany. Patients will be recruited from radiology departments of several hospitals. Their individual exposure will be recorded, and time-dependent cumulative organ doses will be calculated. Follow-up for cancer incidence via the German Childhood Cancer Registry will allow computation of standardized incidence ratios using population-based incidence rates for childhood cancer. Dose-response modelling and analyses for subgroups of children based on the indication for and the result of the CT will be performed.

8-bit or 11-bit monochrome displays--which image is preferred by the radiologist?

OBJECTIVES: Vendors of medical displays promise a better diagnostic performance using 10- or 11-bit instead of 8-bit monochrome displays. We measured the gain of "Just Noticeable Difference" (JND) steps using high grayscale resolutions and evaluated the preference of radiologists regarding different aspects of image quality. METHODS: The amount of JND steps was measured on a display using 8-, 10- and 11-bit Look Up Tables (LUT). Radiological images were presented simultaneously using an 8-bit and an 11-bit LUT, radiologists where asked to determine the better image presentation regarding quality parameters like sharpness, contrast and detectability of details. RESULTS: The 10-bit technology realized more than twice the number of JND steps compared to an 8-bit LUT, an 11-bit LUT presented only few additional JND steps. The radiologists did not attest the higher grayscale resolution a better image quality, they regarded the 8-bit technology to show a better sharpness and contrast, although this had no impact on the detectability of details. CONCLUSIONS: Our measurements confirmed that the higher grayscale resolution results in a more complete visualization of image information. But radiologists partially judged this as a lack of sharpness and contrast and generally preferred the 8-bit display.

[Patient-centered image and data management in radiation oncology]. / Patientenbezogenes Bild- und Datenmanagement in der Radioonkologie.

BACKGROUND: : Recent changes in the radiotherapy (RT) workflow through the introduction of complex treatment paradigms such as intensity-modulated radiotherapy (IMRT) and, recently, image-guided radiotherapy (IGRT) with their increase in data traffic for different data classes have mandated efforts to further integrate electronic data management for RT departments in a patient- and treatment-course-centered fashion. METHODS: : Workflow in an RT department is multidimensional and multidirectional and consists of at least five different data classes (RT/machine data, patient-related documents such as reports and letters, progress notes, DICOM [Digital Imaging and Communications in Medicine] image data, and non-DICOM image data). Data has to be handled in the framework of adaptive feedback loops with increasing frequency. This is in contrast to a radiology department where mainly DICOM image data and reports have to be widely accessible but are dealt with in a mainly unidirectional manner. When compared to a diagnostic Radiology Information System (RIS)/Picture Archiving and Communication System (PACS), additional legal requirements have to be conformed to when an integrated electronic RT data management system is installed. Among these are extended storage periods, documentation of treatment plan approval by physicians and physicist, documentation of informed consent, etc. CONCLUSION: : Since the transition to a paper- and filmless environment in medicine and especially in radiation oncology is unavoidable, this review discusses these issues and suggests a possible hardware and organizational architecture of an RT department information system under control of a Hospital Information System (HIS), based on combined features of genuine RT Record and Verify (R&V) Systems, PACS, and Electronic Medical Records (EMR).

Prediction of anastomotic leakage after pancreatic head resections by dynamic magnetic resonance imaging (dMRI).

PURPOSE: The texture of the pancreatic tissue is a main risk factor for leakage after pancreaticojejunostomy and can be differentiated using dynamic contrast enhanced magnetic resonance imaging (dMRI). In order to identify risk factors and to assess the role of pancreatic dMRI, a cohort of patients was retrospectively reviewed. PATIENTS AND METHODS: One hundred seven consecutive patients were identified in the departmental database and examined by means of a standardized dMRI protocol using a 1.5-T MRI system. Signal intensity (SI) measurements (aorta, body of the pancreas, muscle tissue) were performed in the axial T1-weighted sequences before and after 25 and 60 s after i.v. application of gadolinium-diethylenetriaminepentaacetic acid. For all patients with a standardized contrast medium curve in the aorta (n = 72), a muscle-normalized signal intensity curve (SIC) with SI(ratio) was calculated. SI(ratio)s were classified in two groups: rapid increase (SI(ratio) >or= 1.1, early arterial value > portal-venous value, "soft" pancreas) and delayed increase (SI(ratio) <1.1, "firm" or "hard" pancreas). All patients received pancreatic head resection with a duct-to-mucosa pancreaticojejunostomy. The dMRI data was correlated with prospectively acquired clinical data. RESULTS: Leakage of the pancreaticojejunostomy occurred more frequently (12/37 vs. two of 35, 32% vs. 6%, p = 0.006) in patients with a rapid increase and an SI(ratio) >or= 1.1 ("soft" pancreas, n = 37) compared to those with delayed perfusion (SI(ratio) <1.1, "hard" pancreas, n = 35). The more severe type B and C anastomotic leakages occurred only in the group of patients with SI(ratio) >or= 1.1. Patients with a rapid increase had significantly better preoperative American Society of Anesthesiologists staging, lower carbohydrate antigen 19-9 values, and smaller tumor sizes. Most of them had not only benign tumors but also longer postoperative hospital stay, in comparison to patients with delayed perfusion (SI(ratio) <1.1). Multivariate analysis revealed SI(ratio) of >or=1.1 to be the only preoperative parameter predicting leakage significantly with an odds ratio of 7.9. CONCLUSION: dMRI with SI(ratio) calculation provided reliable information for the prediction of pancreatic texture. Patients with a SI(ratio) >or= 1.1 had a 7.9-fold increased risk of anastomotic leakage and a prolonged hospital stay. SIC with measurements of SI(ratio) in dMRI could therefore define patients at risk for anastomotic leakage.

[Considerations about the realization of DICOM-E-mail in China].

Considering the real conditions in China, the strategy and scheme of DICOM-E-Mail's clinical applications in China are discussed in this paper.

Online availability check of teleradiology components.

For a region-wide teleradiology network in Germany a vendor-independent Uptime-server concept was defined. The Uptime-server was realized for the availability check and prospective error-detection of the emergency teleradiology servers and clients based on encrypted digital imaging and communication in medicine (DICOM)-e-mail transfers. The concept and the experiences of 2 years of use with more than 30 clients and servers in 15 hospitals and in nine other regional partners are shown. The Uptime-server does provide automated availability checks for all servers and clients, automated checks of the download speed of the Internet lines, and a graphical user interface for the clinical user and the system administrator. A clinical user can display the availability information from all clients and servers in the network (see http://www.teleradiologie-rnd.de). In case of malfunctions during an emergency transfer, immediate reactions are possible, often without the need for help of a hotline or a system administrator. The chosen Uptime-server concept proofed to be reliable; it worked with products from nine different manufacturers without problems. Its statistical output can be used to fulfill the legal requirements of regular availability checks for teleradiology lines.

Urothelial carcinoma of the ureter, giant rectal stone and sigmoid carcinoma 55 years after ureterosigmoidostomy.

We present the case of a unique accumulation of complications 55 years after ureterosigmoidostomy for bladder exstrophy and discuss possible implications for follow-up strategies.

Assessment of cardiac preload and left ventricular function under increasing levels of positive end-expiratory pressure.

OBJECTIVE: (1) To assess the impact of high intrathoracic pressure on left ventricular volume and function. (2) To test the hypothesis that right ventricular end-diastolic volume (RVEDV) and intrathoracic blood volume (ITBV) represent cardiac preload and are superior to central venous pressure (CVP) or pulmonary capillary wedge pressure (PCWP). The validity of these parameters was tested by means of correlation with left ventricular end-diastolic volume (LVEDV), the true cardiac preload. DESIGN: Prospective animal study. SUBJECTS: Fifteen adult sheep. INTERVENTIONS: All animals were studied before and after saline washout-induced lung injury, undergoing volume-controlled ventilation with increasing levels of PEEP (0, 7, 14 and 21 cmH2O, respectively). MEASUREMENTS AND MAIN RESULTS: Left ventricular ejection fraction (LVEF), stroke volume (LVSV) and LVEDV were measured using computed tomography. ITBV and RVEDV were obtained by the thermal dye dilution technique. At PEEP 21 cmH2O, LVSV significantly decreased compared to baseline, PEEP 0 and PEEP 7 cmH2O. LVEDV was maintained except for the highest level of PEEP, while LVEF remained unchanged. RVEDV and RVEF also remained unchanged. The overall correlation of RVEDV and ITBV with LVEDV was satisfactory ( r=0.56 and r=0.62, respectively) and clearly superior to cardiac filling pressures. CONCLUSION: In the present study, (1) ventilation with increasing levels of PEEP did not alter RV function, while LV function was impaired at the highest level of PEEP; (2) unlike cardiac filling pressures, ITBV and RVEDV both provide valid estimates of cardiac preload even at high intrathoracic pressures.

Setting mean airway pressure during high-frequency oscillatory ventilation according to the static pressure--volume curve in surfactant-deficient lung injury: a computed tomography study.

BACKGROUND: Numerous studies suggest setting positive end-expiratory pressure during conventional ventilation according to the static pressure-volume (P-V) curve, whereas data on how to adjust mean airway pressure (P(aw)) during high-frequency oscillatory ventilation (HFOV) are still scarce. The aims of the current study were to (1) examine the respiratory and hemodynamic effects of setting P(aw) during HFOV according to the static P-V curve, (2) assess the effect of increasing and decreasing P(aw) on slice volumes and aeration patterns at the lung apex and base using computed tomography, and (3) study the suitability of the P-V curve to set P(aw) by comparing computed tomography findings during HFOV with those obtained during recording of the static P-V curve at comparable pressures. METHODS: Saline lung lavage was performed in seven adult pigs. P-V curves were obtained with computed tomography scanning at each volume step at the lung apex and base. The lower inflection point (Pflex) was determined, and HFOV was started with P(aw) set at Pflex. The pigs were provided five 1-h cycles of HFOV. P(aw), first set at Pflex, was increased to 1.5 times Pflex (termed 1.5 Pflex(inc)) and 2 Pflex and decreased thereafter to 1.5 times Pflex and Pflex (termed 1.5 Pflex(dec) and Pflex(dec)). Hourly measurements of respiratory and hemodynamic variables as well as computed tomography scans at the apex and base were made. RESULTS: High-frequency oscillatory ventilation at a P(aw) of 1.5 Pflex(inc) reestablished preinjury arterial oxygen tension values. Further increase in P(aw) did not change oxygenation, but it decreased oxygen delivery as a result of decreased cardiac output. No differences in respiratory or hemodynamic variables were observed when comparing HFOV at corresponding P(aw) during increasing and decreasing P(aw). Variation in total slice lung volume (TLVs) was far less than expected from the static P-V curve. Overdistended lung volume was constant and less than 3% of TLVs. TLVs values during HFOV at Pflex, 1.5 Pflex(inc), and 2 Pflex were significantly greater than TLVs values at corresponding tracheal pressures on the inflation limb of the static P-V curve and located near the deflation limb. In contrast, TLVs values during HFOV at decreasing P(aw) (i.e., 1.5 Pflex(dec) and Pflex(dec)) were not significantly greater than corresponding TLV on the deflation limb of the static P-V curves. The marked hysteresis observed during static P-V curve recordings was absent during HFOV. CONCLUSIONS: High-frequency oscillatory ventilation using P(aw) set according to a static P-V curve results in effective lung recruitment, and slice lung volumes during HFOV are equal to those from the deflation limb of the static P-V curve at equivalent pressures.

End-expiratory lung volumes and density distribution patterns during partial liquid ventilation in healthy and oleic acid-injured sheep: a computed tomography study.

OBJECTIVE: To determine end-expiratory lung volumes (EELVs) and the distribution of gas and perflubron during low- and high-dose partial liquid ventilation (PLV) in healthy and oleic-acid-injured lungs. DESIGN: A prospective, randomized study. SETTING: A university medical school laboratory approved for animal research. SUBJECTS: Adult sheep. INTERVENTIONS: A total of 18 sheep were randomly divided into two groups (healthy and oleic acid lung injury) and received PLV with perflubron at incremental doses. MEASUREMENTS AND MAIN RESULTS: Animals were ventilated in a volume-control mode with a positive end-expiratory pressure of 5 cm H2O. Baseline computed tomographic scans of the entire lung were obtained during end-expiratory hold. Thereafter, the animals were randomized to undergo either PLV alone (healthy group) or after oleic acid lung injury was introduced (injury group). In both groups, PLV was induced by instilling 10 mL/kg perflubron into the endotracheal tube over 5 mins (low-dose PLV). At 60 mins after dosing, another set of computed tomographic scans during end-expiratory hold was obtained. Thereafter, another 20 mL/kg perflubron was instilled in both groups (cumulative dose, 30 mL/kg perflubron, high-dose PLV), and computed tomographic scanning was repeated 60 mins later. EELVs were calculated. To study density distribution patterns, the lungs were divided into nine segments, and the mean Hounsfield attenuation number was calculated for each segment. In healthy animals, low-dose PLV did not change EELV (47.5 +/- 8.1 mL/kg vs. 44.5 +/- 6.1 mL/kg at 10 mL/kg perflubron), whereas high-dose PLV significantly increased EELV (58.1 +/- 3.3 mL/kg, p <.01). Oleic acid lung injury significantly reduced EELV (53.9 +/- 7.5 mL/kg vs. 43.9 +/- 8.7 mL/kg, p <.01). Low-dose PLV reestablished baseline EELV (59.8 +/- 10.5 mL/kg), and high-dose PLV resulted in a significant increase in EELV (89.2 +/- 12 mL/kg, p =.003). PLV increased the mean Hounsfield attenuation number along the ventrodorsal axis in the three coronal blocks in a dose-dependent manner. In the oleic acid lung injury group, PLV produced a more homogeneous pattern of density distribution, with the highest Hounsfield attenuation numbers observed in the medial segments. CONCLUSION: High-dose PLV significantly increased EELV in both states, indicating lung distention. Healthy lungs were filled in a dose-dependent, gravity-governed fashion, showing steep craniocaudal and ventrodorsal gradients. In the oleic acid lung injury model studied, perflubron tended to accumulate on top of the most severely injured dorsal and diaphragmatic parts, rendering effective recruitment by liquid positive end-expiratory pressure in these regions questionable.

PEEP decreases atelectasis and extravascular lung water but not lung tissue volume in surfactant-washout lung injury.

OBJECTIVE: To examine the effects of positive end-expiratory pressure (PEEP) on extravascular lung water (EVLW), lung tissue, and lung volume. DESIGN AND SETTING: Experimental animal study at a university research facility. SUBJECTS: Fifteen adult sheep. INTERVENTIONS: All animals were studied before and after saline washout-induced lung injury while ventilated with sequentially increasing PEEP (0, 7, 14, or 21 cmH(2)O). MEASUREMENTS AND RESULTS: Lung volume was determined by computed tomography and EVLW by the thermal dye dilution technique. Saline washout significantly increased lung tissue volume (21+/-3 to 37+/-5 ml/kg) and EVLW (9+/-2 to 36+/-9 ml/kg). While increasing levels of PEEP reduced EVLW (30+/-7, 24+/-8, and 18+/-4 ml/kg), lung tissue volume remained constant. Total lung volume significantly increased (50+/-8 ml/kg at PEEP 0 to 77+/-12 ml/kg at PEEP 21). Nonaerated lung volume significantly decreased and was closely correlated with the changes in EVLW ( r=0.67). In addition, a highly significant correlation was found between PEEP-induced decrease in nonaerated lung volume and decrease in transpulmonary shunt ( r=0.83). CONCLUSIONS: The main findings are as follows: (a) PEEP effectively decreases EVLW. (b) The decrease in EVLW is closely correlated with the PEEP-induced decrease in nonaerated lung volume, making EVLW a valuable bedside parameter indicating alveolar recruitment, similar to measurements of transpulmonary shunt. (c) As excess tissue volume remained constant, however, EVLW may not be suitable to reflect overall severity of lung disease