Radiation dose reduction in CT with adaptive statistical iterative reconstruction (ASIR) for patients with bronchial carcinoma and intrapulmonary metastases.

AIM: To compare the radiation dose and image quality of 64-row chest computed tomography (CT) in patients with bronchial carcinoma or intrapulmonary metastases using full-dose CT reconstructed with filtered back projection (FBP) at baseline and reduced dose with 40% adaptive statistical iterative reconstruction (ASIR) at follow-up. MATERIALS AND METHODS: The chest CT images of patients who underwent FBP and ASIR studies were reviewed. Dose-length products (DLP), effective dose, and size-specific dose estimates (SSDEs) were obtained. Image quality was analysed quantitatively by signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurement. In addition, image quality was assessed by two blinded radiologists evaluating images for noise, contrast, artefacts, visibility of small structures, and diagnostic acceptability using a five-point scale. RESULTS: The ASIR studies showed 36% reduction in effective dose compared with the FBP studies. The qualitative and quantitative image quality was good to excellent in both protocols, without significant differences. There were also no significant differences for SNR except for the SNR of lung surrounding the tumour (FBP: 35±17, ASIR: 39±22). DISCUSSION: A protocol with 40% ASIR can provide approximately 36% dose reduction in chest CT of patients with bronchial carcinoma or intrapulmonary metastases while maintaining excellent image quality.

Translating research into licensed vaccines and validated and licensed diagnostic tests.

The USDA Center for Veterinary Biologics (CVB) has the regulatory authority to issue licenses and permits that allow the marketing of pure, safe, potent, and effective veterinary biological products. Under the standard licensing or permitting process, a manufacturer develops, characterizes, and evaluates a product prior to licensure. The CVB evaluates the submitted information, inspects the manufacturing facilities and methods of production and testing, and confirms key product test results through independent testing. This complete and comprehensive evaluation may not be possible during the emergence of a new animal disease or in response to an introduction of a significant transboundary animal disease agent. Processes are in place in the US that allow for more rapid availability of veterinary products in an emerging or emergency animal health situation. But, it can be advantageous to attain preapproval of products prior to their anticipated need. In this article, issues associated with obtaining approval for use of a biological product under emerging or emergency conditions are discussed.

Olfactory bulb volume and olfactory function in patients with multiple sclerosis.

BACKGROUND: Some studies reported olfactory dysfunction in patients with multiple sclerosis (MS). There is no agreement about the most suitable testing method for measuring olfactory function (OF) in MS patients. Recent studies showed that olfactory bulb volume changes with the degree of olfactory dysfunction. We assessed olfactory bulb volume of MS patients with magnetic resonance imaging (MRI) and related it to the OF. MATERIAL AND METHODS: Volumetric measurements of the right and left olfactory bulb (OB) were performed by manual segmentation within 36 MS patients. Psychophysical testing of the orthonasal OF was performed using threshold-discrimination-identification (TDI) score in MS patients. RESULTS: Of all MS patients, 44.4% displayed olfactory dysfunction. The TDI score of all 36 MS patients, especially the score of the Identification subtest correlated strongly with neurological scores typical of MS. In patients with a decreased OB volume, there was a positive correlation between volumetry of the OB and OF. CONCLUSION: OB volumes may provide valuable information about MS patients with olfactory dysfunction. The TDI test and Identification subtest were very sensitive in detecting olfactory dysfunction in MS patients.

Combined radiotherapy and concurrent tumor treating fields (TTFields) for glioblastoma: Dosimetric consequences on non-coplanar IMRT as initial results from a phase I trial.

BACKGROUND: Glioblastoma is a rapidly proliferating tumor. Patients bear an inferior prognosis with a median survival time of 14-16 months. Proliferation and repopulation are a major resistance promoting factor for conventionally fractionated radiotherapy. Tumor-Treating-Fields (TTFields) are an antimitotic modality applying low-intensity (1-3 V/cm), intermediate-frequency (100-300 kHz) alternating electric-fields. More recently interference of TTFields with DNA-damage-repair and synergistic effects with radiotherapy were reported in the preclinical setting. This study aims at examining the dosimetric consequences of TTFields applied during the course of radiochemotherapy. METHODS: Cone-beam-computed-tomography (CBCT)-data from the first seven patients of the PriCoTTF-phase-I-trial were used in a predefined way for dosimetric verification and dose-accumulation of the non-coplanar-intensity-modulated-radiotherapy (IMRT)-treatment-plans as well as geometric analysis of the transducer-arrays by which TTFields are applied throughout the course of treatment. Transducer-array-position and contours were obtained from the low-dose CBCT's routinely made for image-guidance. Material-composition of the electrodes was determined and a respective Hounsfield-unit was assigned to the electrodes. After 6D-fusion with the planning-CT, the dose-distribution was recalculated using a Boltzmann-equation-solver (Acuros XB) and a Monte-Carlo-dose-calculation-engine. RESULTS: Overdosage in the scalp in comparison to the treatment plan without electrodes stayed below 8.5% of the prescribed dose in the first 2 mm below and also in deeper layers outside 1cm2 at highest dose as obtained from dose-volume-histogram comparisons. In the clinical target volume (CTV), underdosage was limited to 2.0% due to dose attenuation by the electrodes in terms of D95 and the effective-uniform-dose. Principal-component-analysis (PCA) showed that the first principal-position-component of the variation of repeated array-placement in the direction of the largest variations and the perpendicular second-component spanning a tangential plane on the skull had a standard deviation of 1.06 cm, 1.23 cm, 0.96 cm, and 1.11 cm for the frontal, occipital, left and right arrays for the first and 0.70 cm, 0.71 cm, 0.79 cm, and 0.68 cm, respectively for the second-principal-component. The variations did not differ from patient-to-patient (p > 0.8, Kruskal-Wallis-tests). This motion led to a diminution of the dosimetric effects of the electrodes. CONCLUSION: From a dosimetric point of view, dose deviations in the CTV due to transducer-arrays were not clinically significant in the first 7 patients and confirmed feasibility of combined adjuvant radiochemotherapy and concurrent TTFields. PriCoTTF Trial: A phase I/II trial of TTFields prior and concomitant to radiotherapy in newly diagnosed glioblastoma. DRKS-ID: DRKS00016667. Date of Registration in DRKS: 2019/02/26. Investigator Sponsored/Initiated Trial (IST/IIT): yes. Ethics Approval/Approval of the Ethics Committee: Approved. (leading) Ethics Committee Nr.: 18-8316-MF, Ethik-Kommission der Medizinischen. Fakultät der Universität Duisburg-Essen. EUDAMED-No. (for studies acc. to Medical Devices act): CIV-18-08-025247.

Use of H(2) (15)O-PET for investigating perfusion changes in pelvic tumors due to regional hyperthermia.

PURPOSE: An increase in tumor oxygenation and perfusion due to hyperthermia has been reported for experimental tumors. The present study was performed to investigate this hypothesis in patients who underwent regional hyperthermia. METHODS: Twenty-seven patients with primary or recurrent pelvic tumors were included in this study. Prior to and up to 1 h after regional hyperthermia, perfusion and partition coefficient were quantitatively determined by utilizing H(2) (15)O-PET. First pass PET images were fused with the segmented common iliac artery from separately acquired CT scan. The arterial input function was extracted from the common iliac arteries using the dynamic PET images and the fused CT. The fused images were also used to extract tumor activity-time curves. Perfusion was calculated from the total tumor curves with correction for arterial spill-over. Changes in perfusion and partition coefficient were analyzed and correlated with various treatment parameters. RESULTS: Heating under hyperthermia conditions significantly increased the partition coefficient for pelvic tumors (P = 0.005). The increase correlated with the duration of hyperthermia and was found in patients treated for more than 1 h and persisted for more than 1 h after the end. Significant changes in perfusion were not observed. Perfusion had recurred to initial values 20 min after heating. CONCLUSIONS: The increase in partition coefficient reflects an increased diffusion distance of radio-labeled water. Therefore water diffusion is increased due to hyperthermia. Analogous to water diffusion, the diffusion of inert gases is also facilitated, improving the oxygenation of hypoxic tumor cells. Our results suggest that tumor oxygenation can probably be enhanced by regional hyperthermia for a period of more than 1 h after heating, provided hyperthermia is applied for at least 60 min. The effect was observed to be reversible within one week.

Corrections of arterial input function for dynamic H215O PET to assess perfusion of pelvic tumours: arterial blood sampling versus image extraction.

Assessment of perfusion with 15O-labelled water (H215O) requires measurement of the arterial input function (AIF). The arterial time activity curve (TAC) measured using the peripheral sampling scheme requires corrections for delay and dispersion. In this study, parametrizations with and without arterial spillover correction for fitting of the tissue curve are evaluated. Additionally, a completely noninvasive method for generation of the AIF from a dynamic positron emission tomography (PET) acquisition is applied to assess perfusion of pelvic tumours. This method uses a volume of interest (VOI) to extract the TAC from the femoral artery. The VOI TAC is corrected for spillover using a separate tissue TAC and for recovery by determining the recovery coefficient on a coregistered CT data set. The techniques were applied in five patients with pelvic tumours who underwent a total of 11 examinations. Delay and dispersion correction of the blood TAC without arterial spillover correction yielded in seven examinations solutions inconsistent with physiology. Correction of arterial spillover increased the fitting accuracy and yielded consistent results in all patients. Generation of an AIF from PET image data was investigated as an alternative to arterial blood sampling and was shown to have an intrinsic potential to determine the AIF noninvasively and reproducibly. The AIF extracted from a VOI in a dynamic PET scan was similar in shape to the blood AIF but yielded significantly higher tissue perfusion values (mean of 104.0 +/- 52.0%) and lower partition coefficients (-31.6 +/- 24.2%). The perfusion values and partition coefficients determined with the VOI technique have to be corrected in order to compare the results with those of studies using a blood AIF.

Differentiation of prostate cancer from normal prostate tissue in an animal model: conventional MRI and dynamic contrast-enhanced MRI.

PURPOSE: To differentiate orthotopically implanted prostate cancer from normal prostate tissue using magnetic resonance imaging (MRI) and Gd-DTPA-BMA-enhanced dynamic MRI in the rat model. MATERIAL AND METHODS: Tumors were induced in 15 rats by orthotopic implantation of G subline Dunning rat prostatic tumor cells. MRI was performed 56 to 60 days after tumor cell implantation using T1-weighted spin-echo, T2-weighted turbo SE sequences, and a 2D FLASH sequence for the contrast medium based dynamic study. The interstitial leakage volume, normalized permeability and the permeability surface area product of tumor and healthy prostate were determined quantitatively using a pharmacokinetic model. The results were confirmed by histologic examination. RESULTS: Axial T2-weighted TSE images depicted low-intensity areas suspicious for tumor in all 15 animals. The mean tumor volume was 46.5 mm(3). In the dynamic study, the suspicious areas in all animals displayed faster and more pronounced signal enhancement than surrounding prostate tissue. The interstitial volume and the permeability surface area product of the tumors increased significantly by 420 % (p < 0.001) and 424 % (p < 0.001), respectively, compared to normal prostate tissue, while no significant difference was seen for normalized permeability alone. CONCLUSION: The results of the present study demonstrate that quantitative analysis of contrast-enhanced dynamic MRI data enables differentiation of small, slowly growing orthotopic prostate cancer from normal prostate tissue in the rat model.

Bedside microdialysis reflects dysfunction of cerebral energy metabolism in patients with aneurysmal subarachnoid hemorrhage as confirmed by 15 O-H2 O-PET and 18 F-FDG-PET.

OBJECTIVE: To compare microdialysis (MD) and positron emission tomography (PET) in the detection of ischemia in aneurysmal subarachnoid hemorrhage (SAH) patients. METHODS: 15 SAH patients (13F/2M, 48+/-13 years, WFNS Grade I-V) were prospectively included in the study. A MD-catheter was inserted into the brain parenchyma most likely to be affected by vasospasm directly after aneurysm clipping. Glucose, pyruvate, lactate, glutamate and glycerol were analyzed hourly (CMA 600). 15O-H2O-PET scans (n=10) and 18F-FDG-PET scans (n=13) were performed between the day 2 and 17 after SAH. 15O-H2O-PET data were merged with CT scans to provide quantification of rCBF within the MD-ROI (rCBFMD; Amira, ZIB Berlin, Germany). 18F-FDG-PET data were evaluated visually by visual analysis. RESULTS: Regions of glucose hypometabolism were observed in 10 patients with symptoms of ischemia. Their rCBF was lower compared to asymptomatic patients (p<0.05). The MD levels of glutamate, lactate, the L/P ratio and glycerol were significantly higher in symptomatic than asymptomatic patients (p<0.05). Out of all measured MD parameters, glutamate showed the closest correlation with rCBF (r=-0.66, p=0.014). Microdialysis parameters were well correlated with glucose hypometabolism (18F-FDG-PET) and symptoms of ischemia. However, the threshold for a metabolic derangement was above the limits of cerebral ischemia defined by PET. CONCLUSION: MD is a useful tool to monitor ischemia, especially in patients with high-grade SAH.

Imaging-Based Liver Function Tests--Past, Present and Future.

UNLABELLED: Preoperative assessment of liver function and prediction of postoperative functional reserve are important in patients scheduled for liver resection. While determination of absolute liver function currently mostly relies on laboratory tests and clinical scores, postoperative remnant liver function is estimated volumetrically using imaging data obtained with computed tomography (CT) or magnetic resonance imaging (MRI). Accurate estimation of hepatic function is also relevant for intensive care patients, oncologic patients, and patients with diffuse liver disease. The indocyanine green (ICG) test is still the only established test for estimating true global liver function. However, more recent tools such as the LiMAx test also allow global assessment of hepatic function. These tests are limited when liver function is inhomogeneously distributed, which is the case in such conditions as unilateral cholestasis or after portal vein embolization. Imaging-based liver function tests were first developed in nuclear medicine and, compared with laboratory tests, have the advantage of displaying the spatial distribution of liver function. Nuclear medicine scans are obtained using tracers such as 99mTc galactosyl and 99mTc mebrofenin. Liver function is typically assessed using planar scintigraphy. However, three-dimensional volumetry is possible with single-photon emission computed tomography (SPECT-CT). Another technique for image-based liver function estimation is Gd-EOB-enhanced MRI. While metabolization of Gd-EOB in the body is similar to that of ICG and mebrofenin, its distribution in the liver can be displayed by MRI with higher temporal and spatial resolution. Moreover, MRI-based determination of liver function can be integrated into routine preoperative imaging. This makes MRI an ideal candidate for preoperative determination of liver function, though the best pulse sequence and the parameter to be derived from the image information remain to be identified. Another question to be answered is how the results may be affected by renal function and the presence of hyperbilirubinemia. As more results from clinical evaluation including comparison with postoperative liver function data become available, image-based liver function tests, especially with use of Gd-EOB as the contrast medium, have the potential to add another dimension to preoperative imaging. KEY POINTS: Liver function consists of a multitude of subfunctions such as biotransformation, excretion and storage. Global liver function tests are score-based tests such as Child-Pugh or MELD as well as the ICG- and LiMAx-test. Imaging-based liver function tests add spatial information. Current clinical standard is the 99mTc-Mebrofenin-scintigraphy. MRI-based function tests with Gd-EOB-DTPA have the potential to integrate seamlessly into clinical workup, feature a higher temporal and spatial resolution and do not rely on ionizing radiation.

Polymerase chain reaction (PCR) amplification for the detection of porcine parvovirus.

A polymerase chain reaction (PCR) amplification method was developed and evaluated to detect porcine parvovirus (PPV). A pair of 20-base primers and an oligonucleotide probe were derived from the DNA sequences common to two isolates of PPV, NADL-8 and NADL-2. The primers flanked 118-bp nucleotides within the region coding for the major structural protein VP2. After DNA amplification of PPV replicative form (RF), a 158-bp fragment was detected in agarose gels. This amplified fragment was shown to be specific for PPV DNA after Southern transfer and hybridization to a 20-base internal probe. The amplified fragment also contained a single EcoRI cleavage site. Various conditions, such as number of cycles and annealing temperature, were examined to optimize the conditions for detecting viral DNAs from infected cell cultures and swine fetal tissues. Four different isolates of PPV, NADL-8, NADL-2, KBSH and Kresse, and two other viruses, canine parvovirus (CPV) and pseudorabies virus (PRV), were included to determine specificity of amplification. Slot blot hybridization with a radiolabeled probe was used to evaluate the sensitivity of PCR amplification. The optimized protocol was specific for PPV detecting equally all four strains of PPV, but failing to amplify CPV or PRV sequences. The PCR method could detect at least 100 fg of viral replicative form (RF) DNA or the equivalent of 1 PFU of infectious virus. The applications of this method include routine detection of PPV in clinical samples and as a contaminant in mammalian cell lines.

Determination of the thermal neutron flux in a fast neutron beam by use of a boron-coated ionization chamber.

The thermal neutron distribution in slow and fast neutron beams is usually determined using the foil activation method. In this work a small magnesium walled ionization chamber, in which the inner surface of the wall has been coated with 10B to increase the sensitivity for thermal neutrons, is used to estimate the thermal neutron component of the beam. After calibration and determination of the directional response in a thermal neutron beam a comparison with foil activation at different depths in water was performed to investigate the reliability of the ionization measurements. The chamber was used in a computer controlled water phantom to measure the depth and lateral distribution of the thermal neutron dose. With this arrangement two-dimensional scans of the thermal neutrons could be performed quickly and with high accuracy.

Use of BANG polymer gel for dose measurements in a 68 MeV proton beam.

BANG polymer gel dosimetry using magnetic resonance imaging (MRI) was applied to an ophthalmologic 68 MeV proton beam. The object was to examine the use of BANG gel for the verification of proton fields in eye tumor therapy and to explore the applicability of polymer gel dosimetry in proton therapy under practical aspects. The gel phantoms were irradiated with monoenergetic and modulated proton beams. MRI analysis was carried out at clinical 1.5 and 3 T MR scanners. At constant LET, results show a linear relationship between spin-spin relaxation rates and dose. However, depth dose curves in BANG gel reveal a quenching of the Bragg maximum due to LET effects. The dose response of the gel for monoenergetic protons and spread-out depth dose distributions can be calculated based on ionization chamber measurements. Experiment and calculations show good agreement and indicate that BANG polymer gels might become a valuable tool in proton therapy quality assurance.

Detection of bovine virus diarrhea virus in cell culture using an immunoperoxidase technique.

An indirect immunoperoxidase staining technique was developed for identifying cell cultures infected with bovine virus diarrhea virus. Infected cell monolayers stained intensely while uninfected monolayers remained colorless. Immunoperoxidase staining was as sensitive as direct immunofluorescence in detecting endpoint dilutions of virus suspensions. Using the immunoperoxidase technique, infected monolayers were detectable by macroscopic, as well as microscopic, observation.

Pharmacokinetic analysis of glioma compartments with dynamic Gd-DTPA-enhanced magnetic resonance imaging.

Dynamic contrast-enhanced magnetic resonance imaging (MRI) is widely used for measuring perfusion and blood volume, especially cerebral blood volume (CBV). In case of blood-brain barrier (BBB) disruption, the conventional techniques only partially determine the pharmacokinetic parameters of contrast medium (CM) exchange between different compartments. Here a modified pharmacokinetic model is applied, which is based on the bidirectional CM exchange between blood and two interstitial compartments in terms of the fractional volumes of the compartments and the vessel permeabilities between them. The evaluation technique using this model allows one to quantify the fractional volumes of the different compartments (blood, cells, slowly and fast enhancing interstitium) as well as the vessel permeabilities and cerebral blood flow (CBF) with a single T1-weighted dynamic MRI measurement. The method has been successfully applied in 25 glioma patients for generating maps of all of these parameters. The fractional volume maps allow for the differentiation of glioma vascularization types. The maps show a good correlation with the histological grading of these tumors. Furthermore, regions with enhanced interstitial volumes are found in high-grade gliomas. Differences in permeability maps of Gd-DTPA apart from BBB disruption do not exist between different tissue types. CBF measured in high-grade glioma is less pronounced than it would be expected from their blood volume. Therefore pharmacokinetic imaging provides an additional tool for glioma characterization.

Use of statistical parametric mapping of (18) F-FDG-PET in frontal lobe epilepsy.

AIM: Evaluation of the use of statistical parametrical mapping (SPM) of FDG-PET for seizure lateralization in frontal lobe epilepsy. PATIENTS: 38 patients with suspected frontal lobe epilepsy supported by clinical findings and video-EEG monitoring. METHOD: Statistical parametrical maps were generated by subtraction of individual scans from a control group, formed by 16 patients with negative neurological/psychiatric history and no abnormalities in the MR scan. The scans were also analyzed visually as well as semiquantitatively by manually drawn ROIs. RESULTS: SPM showed a better accordance to the results of surface EEG monitoring compared with visual scan analysis and ROI quantification. In comparison with intracranial EEG recordings, the best performance was achieved by combining the ROI based quantification with SPM analysis. CONCLUSION: These findings suggest that SPM analysis of FDG-PET data could be a useful as complementary tool in the evaluation of seizure focus lateralization in patients with supposed frontal lobe epilepsy.

Regulatory considerations for emergency use of non-USDA licensed vaccines in the United States.

The Virus-Serum-Toxin Act of 1913 (21 US Code 151-159) provides the legal basis for the regulation of veterinary biologicals in the United States; the United States Department of Agriculture's Center for Veterinary Biologicals (CVB) has the regulatory authority for the issue of licences and permits for such products. The law was intended to establish standards and control the importation of products into the United States and the distribution of products interstate assuring the purity, safety, potency, and efficacy of veterinary biological products. Administrative regulations and standards appear in the Title 9, Code of Federal Regulations, Parts 101-118, with additional programme guidance found in CVB Notices, Veterinary Services Memoranda, General Licensing Considerations, and other guidance documents. Pre-licensing data evaluation procedures are designed to assess the purity, safety, potency, and effectiveness of each product and support all product label claims. To fulfil these criteria, data from all phases of product development are evaluated against these key elements. Under the standard licensing process, this spectrum of evaluation includes complete characterization and identification of seed material and ingredients, laboratory and host animal safety and efficacy studies, stability studies, and post-licensing monitoring of field performance. This comprehensive evaluation may not be possible during the emergence of a new animal disease. While there are no specific regulations addressing the licensing standards of products for an emerging animal disease, there are mechanisms that allow for the availability of products in an emergency animal health situation. These mechanisms include autogenous biologicals, conditional licences, experimental and emergency use authorizations, and the importation of products in use elsewhere in the world. Pre-approved vaccine banks provide an additional mechanism.

Technical note: Influence of the phantom material on the absorbed-dose energy dependence of the EBT3 radiochromic film for photons in the energy range 3 keV-18 MeV.

PURPOSE: Water is the reference medium for radiation therapy dosimetry, but for film dosimetry it is more practical to use a solid phantom. As the composition of solid phantoms differs from that of water, the energy dependence of film exposed within solid phantoms may also differ. The energy dependence of a radiochromic film for a given beam quality Q (energy for monoenergetic beams) has two components: the intrinsic energy dependence and the absorbed-dose energy dependence f(Q), the latter of which can be calculated through a Monte Carlo simulation of radiation transport. The authors used Monte Carlo simulations to study the influence of the phantom material on the f(Q) of the EBT3 radiochromic film (Ashland Specialty Ingredients, Wayne, NJ) for photon beams with energies between 3 keV and 18 MeV. METHODS: All simulations were carried out with the general-purpose Monte Carlo code penelope 2011. The geometrical model consisted of a cylindrical phantom, with the film positioned at different depths depending on the initial photon energy. The authors simulated monoenergetic parallel photon beams and x-ray beams from a superficial therapy system. To validate their choice of simulation parameters, they also calculated f(Q) for older film models, EBT and EBT2, comparing with published results. In addition to water, they calculated f(Q) of the EBT3 film for solid phantom materials commonly used for film dosimetry: RW1 and RW3 (PTW-Freiburg, Freiburg, Germany), Solid Water (Gammex-RMI, Madison, WI), and PMMA. Finally, they combined their calculated f(Q) with published overall energy response data to obtain the intrinsic energy dependence of the EBT3 film in water. RESULTS: The calculated f(Q) for EBT and EBT2 films was statistically compatible with previously published data. Between 10 keV and 18 MeV, the variation found in f(Q) of the EBT3 film for water was within 2.3%, with a standard statistical uncertainty less than 1%. If the quantity dose-to-water in the phantom is considered, which is the common practice in radiation dosimetry, the maximum difference of energy dependence for the solid phantoms with respect to water is about 6%, at an energy of 50 keV. CONCLUSIONS: The EBT3 film shows a reasonably constant absorbed-dose energy dependence when irradiated in water. If the dose-to-water in the phantom is considered, the maximum difference of EBT3 film energy dependence with the solid phantoms studied with respect to water is about 6% (at an energy of 50 keV). The reported overall energy dependence of the EBT3 film in water at energies below 100 keV is mainly due to the intrinsic energy dependence.

Volumetric assessment of optic nerve sheath and hypophysis in idiopathic intracranial hypertension.

BACKGROUND AND PURPOSE: Idiopathic intracranial hypertension is a headache syndrome characterized by increased CSF pressure. Compression of the hypophysis and distension of the optic nerve sheath are reliable imaging signs. The purpose of the study was to validate, in patients with idiopathic intracranial hypertension, MR imaging-based volumetric measurements of the optic nerve sheath and hypophysis as an objective observation method for more accurate diagnosis and posttreatment follow-up. MATERIALS AND METHODS: Twenty-three patients with idiopathic intracranial hypertension as well as age-, sex-, and body mass index-matched controls underwent volumetric measurements of the optic nerve, optic nerve sheath, and hypophysis on high-resolution T2-weighted MR images by using a 7-cm surface coil, followed by correlation with CSF opening pressures and clinical symptom scores of visual disturbances and headache. RESULTS: Mean values of optic nerve sheath (341.86 ± 163.69 mm(3) versus 127.56 ± 53.17 mm(3), P < .001) and hypophysis volumes (554.59 ± 142.82 mm(3) versus 686.60 ± 137.84 mm(3), P < .05) differed significantly between healthy and diseased subjects. No significant differences between mean optic nerve volumes were observed. Receiver operating characteristic analysis showed optic nerve sheath volumes of >201.30 mm(3) (sensitivity, 86.96%; specificity, 91.30%) and hypophysis volumes of <611.21 mm(3) (sensitivity, 78.26%; specificity, 69.57%) to be indicative of idiopathic intracranial hypertension diagnosis. In patients with idiopathic intracranial hypertension, no correlations were found between optic nerve sheath and hypophysis volumes and CSF opening pressures or clinical scores of visual disturbances and headache. CONCLUSIONS: Semiautomated volumetric measurement of optic nerve sheath and hypophysis has the potential to more accurately diagnose and follow patients with idiopathic intracranial hypertension.

[Dynamic contrast-enhanced MRI of the prostate: comparison of two different post-processing algorithms]. / Dynamische kontrastmittelunterstützte MRT der Prostata: Vergleich von zwei Auswerteverfahren.

PURPOSE: To evaluate the usefulness of a commercially available post-processing software tool for detecting prostate cancer on dynamic contrast-enhanced magnetic resonance imaging (MRI) and to compare the results to those obtained with a custom-made post-processing algorithm already tested under clinical conditions. MATERIALS AND METHODS: Forty-eight patients with proven prostate cancer were examined by standard MRI supplemented by dynamic contrast-enhanced dual susceptibility contrast (DCE-DSC) MRI prior to prostatectomy. A custom-made post-processing algorithm was used to analyze the MRI data sets and the results were compared to those obtained using a post-processing algorithm from In vivo Corporation (Dyna CAD for Prostate) applied to dynamic T 1-weighted images. Histology was used as the gold standard. RESULTS: The sensitivity for prostate cancer detection was 78 % for the custom-made algorithm and 60 % for the commercial algorithm and the specificity was 79 % and 82 %, respectively. The accuracy was 79 % for our algorithm and 77.5 % for the commercial software tool. The chi-square test (McNemar-Bowker test) yielded no significant differences between the two tools (p = 0.06). CONCLUSION: The two investigated post-processing algorithms did not differ in terms of prostate cancer detection. The commercially available software tool allows reliable and fast analysis of dynamic contrast-enhanced MRI for the detection of prostate cancer.

Dependence of renal blood flow on renal artery stenosis measured using CT angiography.

PURPOSE: The present study investigates the suitability of computed tomography angiography (CTA) depicting the degree of renal artery stenosis for estimating renal blood flow (RBF) in a kidney. MATERIALS AND METHODS: We investigated renal artery stenosis assessment by CTA in eight adult female hybrid pigs with an ultrasound probe implanted at the renal vein for RBF measurement. An inflatable metal-free cuff was placed around the renal artery to control the RBF. The RBF was then reduced in four steps. For each reduced RBF value and baseline RBF, CTA with a reconstructed slice thickness of 0.625 mm was performed in the arterial phase following injection of 80 ml of nonionic intravenous contrast medium. The radius of the stenotic and non-stenotic renal artery segment was measured in the reconstructed images. RESULTS: A significant linear correlation (p < 0.0001) was found between the relative apparent stenosis (calculated as the ratio of the radii of the actual stenotic segment and a non-stenotic renal artery segment) and RBF. The linear regression yielded a slope of 0.57 and a y-axis of 24.1 %. A significant linear correlation (p < 0.0001) was also found between the relative true stenosis (the ratio of the radii of the actual stenotic segment and a non-stenotic renal artery segment at baseline) and the RBF. The linear regression yielded a slope of 0.67 and a y-axis of 13.8 %. CONCLUSION: The results show that the relative stenosis apparent on CTA differs from the true degree of renal artery stenosis. Nevertheless, the degree of renal artery stenosis determined by CTA provides a reliable estimate of the resulting RBF reduction.