Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Keywords: CANCER ; Germany ; LUNG ; THERAPY ; chest ; CT ; IMAGES ; imaging ; SYSTEM ; computed tomography ; NUCLEAR-MEDICINE ; TIME ; QUALITY ; MEMBRANE ; COMPUTED-TOMOGRAPHY ; SERIES ; MOTION ; ARTIFACTS ; nuclear medicine ; dynamic MRI ; HELICAL CT ; radiology ; ONCOLOGY ; RE ; EX-VIVO ; DIAPHRAGM ; methods ; PHASE ; NUCLEAR ; IMAGE QUALITY ; respiration ; lungs ; RESPIRATORY MOTION ; phantom ; tumor motion ; MEDICINE ; NOV ; comparison ; DETECTOR CT ; PORCINE LUNGS ; ex-vivo study ; GUIDED RADIOTHERAPY ; retrospective gating
    Abstract: Purpose: To analyse the image quality of retrospectively gated helical CT using controlled respiratory motion of porcine lung explants. Materials and methods: Five porcine lungs were examined inside a chest phantom. A silicone membrane was rhythmically inflated and deflated to simulate diaphragmatic respiration. Dynamic images (regular respiration at 8/min) and static scans (w/o respiration) at 0/25/50/75 and 100% of maximum inspiration were acquired with a 40-row detector CT scanner (rotation time 1 s, pitch 0.1). Image quality on multi-planar reformations was evaluated by two observers. Partial projection artifacts, step ladder-artifacts and noise were compared for upper, middle and lower parts of the lung and different respiratory phases (scores 0-3 for absent, minimal, moderate and diagnostically relevant artifacts). Results: Partial projection effects were limited to dynamic scans (mean score 1.33). Stepladder artifacts predominated in dynamic series compared to static series (mean score 0.55 versus 0.1; p 〈 0.001). Image noise was not related to lung motion (mean scores 0.68-0.81). All artifacts predominated close to the diaphragm compared to the upper and middle parts of the lung (p 〈 0.001 to p = 0.02, respectively). Partial projection and stepladder artifacts were less in end-inspiration and end-expiration than within the respiration (p 〈 0.001 and p = 0.17, respectively). Diagnostically relevant artifacts were noted 9 times (9/9 close to diaphragm, 7/9 partial-projection). Conclusions: Even in ideal realistic conditions, helical 4D-CT produced tolerable artifacts which could be overcome by radiologists. (c) 2007 Elsevier Ireland Ltd. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 17923161
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    Keywords: Germany ; LUNG ; CT ; imaging ; SYSTEM ; VOLUME ; NEW-YORK ; HEART ; RESOLUTION ; MICE ; NUCLEAR-MEDICINE ; QUALITY ; RAT ; animals ; RATS ; CONTRAST ; SIMULATION ; SIGNAL ; PRESSURE ; MOTION ; nuclear medicine ; DERIVATION ; radiology ; RE ; methods ; NUCLEAR ; IMAGE QUALITY ; flat-panel detector ; rodents ; USA ; SCANS ; animal ; respiratory gating ; MEDICINE ; comparison ; VALUES ; CONE-BEAM-CT ; intrinsic gating ; MICRO-COMPUTED-TOMOGRAPHY ; SCAN ; small-animal imaging
    Abstract: Gating in small-animal CT imaging can compensate artefacts caused by physiological motion during scanning. However, all published gating approaches for small animals rely on additional hardware to derive the gating signals. In contrast, in this study a novel method of intrinsic respiratory gating of rodents was developed and tested for mice (n=5), rats (n=5) and rabbits (n=2) in a flat-panel cone-beam CT system. In a consensus read image quality was compared with that of non-gated and retrospective extrinsically gated scans performed using a pneumatic cushion. In comparison to non-gated images, image quality improved significantly using intrinsic and extrinsic gating. Delineation of diaphragm and lung structure improved in all animals. Image quality of intrinsically gated CT was judged to be equivalent to extrinsically gated ones. Additionally 4D datasets were calculated using both gating methods. Values for expiratory, inspiratory and tidal lung volumes determined with the two gating methods were comparable and correlated well with values known from the literature. We could show that intrinsic respiratory gating in rodents makes additional gating hardware and preparatory efforts superfluous. This method improves image quality and allows derivation of functional data. Therefore it bears the potential to find wide applications in small-animal CT imaging
    Type of Publication: Journal article published
    PubMed ID: 18431578
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    Keywords: PERFUSION ; CT ; COMPUTED-TOMOGRAPHY ; REGIONAL VENTILATION
    Abstract: Purpose: To compare unenhanced lung ventilation-weighted (VW) and perfusion-weighted (QW) imaging based on Fourier decomposition (FD) magnetic resonance (MR) imaging with the clinical reference standard single photon emission computed tomography (SPECT)/computed tomography (CT) in an animal experiment. Materials and Methods: The study was approved by the local animal care committee. Lung ventilation and perfusion was assessed in seven anesthetized pigs by using a 1.5-T MR imager and SPECT/CT. For time-resolved FD MR imaging, sets of lung images were acquired by using an untriggered two-dimensional balanced steady-state free precession sequence (repetition time, 1.9 msec; echo time, 0.8 msec; acquisition time per image, 118 msec; acquisition rate, 3.33 images per second; flip angle, 75 degrees; section thickness, 12 mm; matrix, 128 x 128). Breathing displacement was corrected with nonrigid image registration. Parenchymal signal intensity was analyzed pixelwise with FD to separate periodic changes of proton density induced by respiration and periodic changes of blood flow. Spectral lines representing respiratory and cardiac frequencies were integrated to calculate VW and QW images. Ventilation and perfusion SPECT was performed after inhalation of dispersed technetium 99m ((99m)Tc) and injection of (99m)Tc-labeled macroaggregated albumin. FD MR imaging and SPECT data were independently analyzed by two physicians in consensus. A regional statistical analysis of homogeneity and pathologic signal changes was performed. Results: Images acquired in healthy animals by using FD MR imaging and SPECT showed a homogeneous distribution of VW and QW imaging and pulmonary ventilation and perfusion, respectively. The gravitation-dependent signal distribution of ventilation and perfusion in all animals was similarly observed at FD MR imaging and SPECT. Incidental ventilation and perfusion defects were identically visualized by using both modalities. Conclusion: This animal experiment demonstrated qualitative agreement in the assessment of regional lung ventilation and perfusion between contrast media-free and radiation-free FD MR imaging and conventional SPECT/CT.
    Type of Publication: Journal article published
    PubMed ID: 21586678
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    Keywords: CT ; FLOW ; COMPUTED-TOMOGRAPHY ; PULMONARY-EMBOLISM ; proton MRI ; INITIAL-EXPERIENCE ; DUAL-ENERGY TECHNIQUE
    Abstract: PURPOSE: To assess the reproducibility of Fourier decomposition (FD) based ventilation- and perfusion-weighted lung MRI. METHODS: Sixteen healthy volunteers were examined on a 1.5 T whole-body MR-scanner with 4-6 sets of coronal slices over the chest volume with a non-contrast enhanced steady-state free precession sequence. The identical protocol was repeated after 24h. Reconstructed perfusion- and ventilation-weighted images were obtained through non-rigid registration and FD post-processing of images. Analysis of signal in segmented regions of interest was performed for both native and post-processed data. Two blinded chest radiologists rated image quality of perfusion- and ventilation-weighted images using a 3-point scale. RESULTS: Reproducibility of signal between the two time points was very good with intra-class correlation coefficients of 0.98, 0.94 and 0.86 for native, perfusion- and ventilation-weighted images, respectively. Perfusion- and ventilation-weighted images were of overall good quality with proportions of diagnostic images of 87-95% and 69-75%, respectively. Lung signal decreased from posterior to anterior slices with image quality of ventilation-weighted images in anterior areas rated worse than in posterior or perfusion-weighted images. Inter- and intra-observer agreement of image quality was good for perfusion and ventilation. CONCLUSIONS: The study demonstrates high reproducibility of ventilation- and perfusion-weighted FD lung MRI.
    Type of Publication: Journal article published
    PubMed ID: 23295084
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    Keywords: CANCER ; IRRADIATION ; radiotherapy ; tumor ; Germany ; LUNG ; MODEL ; VIVO ; chest ; CT ; imaging ; INFORMATION ; SYSTEM ; VOLUME ; NEW-YORK ; computed tomography ; NUCLEAR-MEDICINE ; TIME ; PATIENT ; treatment ; NO ; LESIONS ; DIFFERENCE ; REPRODUCIBILITY ; REQUIRES ; VARIABILITY ; tomography ; STRATEGIES ; COMPUTED-TOMOGRAPHY ; SELECTION ; TRACKING ; ARTIFACTS ; nuclear medicine ; RECONSTRUCTION ; dynamic MRI ; HELICAL CT ; ORGAN MOTION ; VOLUMES ; radiology ; ONCOLOGY ; EX-VIVO ; DIAPHRAGM ; methods ; NUCLEAR ; technique ; USA ; EVALUATE ; lungs ; MULTISLICE CT ; phantom ; SMALL PULMONARY NODULES ; respiratory gating ; tumor motion ; MEDICINE ; 4-DIMENSIONAL RADIOTHERAPY ; computer-assisted volumetry ; DETECTOR CT ; lung nodules ; nodule volumetry ; PORCINE LUNGS
    Abstract: Purpose: Motion-adapted radiotherapy with gated irradiation or tracking of tumor positions requires dedicated imaging techniques such as four-dimensional (4D) helical computed tomography (CT) for patient selection and treatment planning. The objective was to evaluate the reproducibility of spatial information for small objects on respiratory-gated 4D helical CT using computer-assisted volumetry of lung nodules in a ventilated ex vivo system. Methods and Materials: Five porcine lungs were inflated inside a chest phantom and prepared with 55 artificial nodules (mean diameter, 8.4 mm +/- 1.8). The lungs were respirated by a flexible diaphragm and scanned with 40-row detector CT (collimation, 24 x 1.2 mm; pitch, 0.1; rotation time, 1 s; slice thickness, 1.5 mm; increment, 0.8 mm). The 4D-CT scans acquired during respiration (eight per minute) and reconstructed at 0-100% inspiration and equivalent static scans were scored for motion-related artifacts (0 or absent to 3 or relevant). The reproducibility of nodule volumetry (three readers) was assessed using the variation coefficient (VC). Results: The mean volumes from the static and dynamic inspiratory scans were equal (364.9 and 360.8 mm(3), respectively,p = 0.24). The static and dynamic end-expiratory volumes were slightly greater (371.9 and 369.7 mm(3), respectively, p = 0.019). The VC for volumetry (static) was 3.1%, with no significant difference between 20 apical and 20 caudal nodules (2.6% and 3.5%,p = 0.25). In dynamic scans, the VC was greater (3.9%,p = 0.004; apical and caudal, 2.6% and 4.9%; p = 0.004), with a significant difference between static and dynamic in the 20 caudal nodules (3.5% and 4.9%,p = 0.015). This was consistent with greater motion-related artifacts and image noise at the diaphragm (p 〈 0.05). The VC for interobserver variability was 0.6%. Conclusion: Residual motion-related artifacts had only minimal influence on volumetry of small solid lesions. This indicates a high reproducibility of spatial information for small objects in low pitch helical 4D-CT reconstructions. (c) 2007 Elsevier Inc
    Type of Publication: Journal article published
    PubMed ID: 18035217
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    Keywords: Germany ; ALGORITHM ; CT ; segmentation ; SYSTEM ; HEART ; MICE ; QUALITY ; RAT ; REGION ; MOTION ; ORGAN MOTION ; motion gating ; gating ; MICRO-COMPUTED-TOMOGRAPHY ; SCAN ; 4D ; Extrinsic ; Intrinsic ; Small-animal ; cardiac ; FREE-BREATHING RODENTS
    Abstract: A fully automated, intrinsic gating algorithm for small animal cone-beam CT is described and evaluated. A parameter representing the organ motion, derived from the raw projection images, is used for both cardiac and respiratory gating. The proposed algorithm makes it possible to reconstruct motion-corrected still images as well as to generate four-dimensional (4D) datasets representing the cardiac and pulmonary anatomy of free-breathing animals without the use of electrocardiogram ( ECG) or respiratory sensors. Variation analysis of projections from several rotations is used to place a region of interest (ROI) on the diaphragm. The ROI is cranially extended to include the heart. The centre of mass (COM) variation within this ROI, the filtered frequency response and the local maxima are used to derive a binary motion-gating parameter for phase-sensitive gated reconstruction. This algorithm was implemented on a flat-panel-based cone-beam CT scanner and evaluated using amoving phantom and animal scans ( seven rats and eight mice). Volumes were determined using a semiautomatic segmentation. In all cases robust gating signals could be obtained. The maximum volume error in phantom studies was less than 6%. By utilizing extrinsic gating via externally placed cardiac and respiratory sensors, the functional parameters ( e. g. cardiac ejection fraction) and image quality were equivalent to this current gold standard. This algorithm obviates the necessity of both gating hardware and user interaction. The simplicity of the proposed algorithm enables adoption in a wide range of small animal cone-beam CT scanners
    Type of Publication: Journal article published
    PubMed ID: 20299735
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    Keywords: EX-VIVO ; SIZE ; ENGLAND ; tumour ; SYSTEM ; LUNG ; CT ; BEAM ; REPRODUCIBILITY ; ONCOLOGY
    Type of Publication: Meeting abstract published
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...