Martin Fiebich

Automatic bone segmentation technique for CT angiographic studies

PURPOSE The purpose of this work was to develop and evaluate an automatic bone segmentation technique for CT angiographic studies. METHOD An automatic bone segmentation scheme was developed and applied to 40 CT examinations. The results of the segmentation were evaluated subjectively by two radiologists. RESULTS The bone segmentation was, on average, rated between excellent and good. Automatic segmentation required approximately 25 s/case. CONCLUSION With this high quality technique, bone can be segmented easily and accurately and subsequently can be removed from CT data sets for further 3D visualization and analysis of various organs.

Protection of Eye Lens in Computed Tomography - Dose Evaluation on an Anthropomorphic Phantom using Thermo-Luminescent Dosimeters and Monte-Carlo Simulations

PURPOSE The lens of an eye is a particularly radiosensitive organ. This study investigates two different materials for eye shielding during CT scanning, i. e. a commercially available bismuth protector and a newly developed material for eye shielding, comprised of an alloy of Bi/Sb/Gd/W. MATERIALS AND METHODS The radiation dose during head CT scanning was measured using thermoluminescence dosimeters and an anthropomorphic Alderson-RANDO phantom. A radiation dose reduction was compared to two shielding materials and to the condition without any eye shielding. The effect of gantry angulation that excludes the eyes from beam path was also investigated. Radiation dose measurements were validated using a Monte-Carlo simulation. For this simulation we used the EGSsnr code system, and a new application CTDOSPP was developed for simulation of the computed tomography examination. Eight radiologists evaluated the diagnostic quality of the images. RESULTS Dose measurements and Monte-Carlo simulations are in good agreement. If the eye shields are placed in the primary beam path, bismuth eye shielding and the new material reduce the dose by up to 38 % and 48 %, respectively. Angling the gantry causes an 88 % reduction in radiation dose. All shielding materials generate beam hardening artifacts located close to the protector, but the artifacts do not spread into the brain. CONCLUSION The application of eye shields during CT examination of a head causes a significant reduction in radiation dose. The new protector material shows a significantly higher dose reduction in contrast to the commercially available bismuth shield. The best protection from radiation dose can be attained using gantry angulation.

Reduction Of Uterus Dose In Clinical Thoracic Computed Tomography

PURPOSE The aim of this study was to investigate the potential dose reduction in the uterus as a result of lead apron protection during thoracic CT scans. Moreover, the distribution of the radiation dose in the uterus was determined in order to obtain information about the ratio of internally and externally scattered radiation. MATERIALS AND METHODS The uterus doses during thoracic CT were determined by measuring organ doses using an Alderson-RANDO®-Phantom and thermoluminescent dosimeters. A 0.25 mm lead equivalent protective apron was used to shield the abdominal area. Three measurement conditions were evaluated: without lead apron, covered with lead apron and wrapped with lead apron. The uterus dose with and without shielding describes the mean value and standard deviation of all examinations and all measurement points in the organ. RESULTS The uterus dose by thoracic CT was measured to be approximately 66.5 ± 3.1 µGy. If the abdomen is covered with a 0.25 mm Pb equivalent lead apron in the front area and on both sides, the uterus dose is reduced to 49.4 ± 2.8 µGy (26% reduction, p < 0.001). If a lead apron is wrapped around the abdomen, providing 0.50 mm Pb shielding in the anterior section due to overlap, and 0.25 mm Pb in the posterior section and on both sides, the uterus dose is reduced even more to 43.8 ± 2.5 µGy (34% reduction, p < 0.001). The dose distribution when the lead apron covers the abdomen shows that the shielding is effective for the scatter radiation that comes from the anterior part. Moreover, the wrapped apron protects the uterus from all directions and is even more effective for dose reduction than the covering apron. CONCLUSION Our findings demonstrate that protective aprons are an effective dose reduction technique without additional costs and little effect on patient examination time.

Evaluation and quantification of spectral information in tissue by confocal microscopy

Abstract. A confocal imaging and image processing scheme is introduced to visualize and evaluate the spatial distribution of spectral information in tissue. The image data are recorded using a confocal laser-scanning microscope equipped with a detection unit that provides high spectral resolution. The processing scheme is based on spectral data, is less error-prone than intensity-based visualization and evaluation methods, and provides quantitative information on the composition of the sample. The method is tested and validated in the context of the development of dermal drug delivery systems, introducing a quantitative uptake indicator to compare the performances of different delivery systems is introduced. A drug penetration study was performed in vitro. The results show that the method is able to detect, visualize and measure spectral information in tissue. In the penetration study, uptake efficiencies of different experiment setups could be discriminated and quantitatively described. The developed uptake indicator is a step towards a quantitative assessment and, in a more general view apart from pharmaceutical research, provides valuable information on tissue composition. It can potentially be used for clinical in vitro and in vivo applications.

Dose management for X-ray and CT: systematic comparison of exposition values from two institutes to diagnostic reference levels and use of results for optimisation of exposition.

PURPOSE In 2 institutions exposure values were evaluated and compared with the 2010 updated diagnostic reference levels (DRL) and possibilities for decreasing the dose assessed. MATERIALS AND METHODS Mean exposure values obtained during a 3-month period were calculated for all modalities (X-ray: imaging plate system and digital detector; dual-source 64- and 16- slice spiral CT) as well as examination types were compared to old diagnostic reference levels in addition to DRLs introduced in 2010. Then 10 examinations of all modalities and types were accompanied by a medical physicist and optimized stepwise if necessary. RESULTS The mean values of X-ray examinations were above DRL. All accompanied examinations were beyond DRL except lateral lumbar spine (LSP) and lateral thoracic X-ray, which were elevated due to statistical outliers from morbidly obese patients or patients with metallic implants. For a-p LSP tube voltage was increased. While image quality was maintained, dose area product (DAP) was reduced by 50% to 123 ± 61 cGy · cm² for LSP a-p and 30% for lateral LSP to 229 ± 116 cGy · cm². For CT examinations, dose was below DRL. Accompanied examinations of the lumbar spine performed on a 16-slice spiral CT demonstrated a result 68% above DRL with dose length product (DLP) of 840 ± 252 cGy · cm. For optimization, pitch and tube voltage were stepwise increased and DLP reduced below DRL. CONCLUSION Systematic analysis of our internal exposure values on the occasion of adaptation of DRL is crucial for prompt detection of exceeded values independently from assessment by the responsible authority and initiation of proper measures for decreasing exposure dose. Hereby active dose management is attained. KEY POINTS ► Analysis of exposure values for high data volumes obtained from the Radiology Information System (RIS) is possible independent of weight. ► Summation of small groups of patients with different weights might result in high exposure values (DRL 70  kg). ► If high exposure values are observed in small groups of patients, individual analysis of examinations is mandatory. ► Active dose management can be obtained by an analysis of average exposure of all examinations obtained during a specific observation period. ► Potential for optimization of exposure values might be possible even they fall below DRL.

Preliminary clinical results: an analyzing tool for 2D optical imaging in detection of active inflammation in rheumatoid arthritis

Optical imaging (OI) is a relatively new method in detecting active inflammation of hand joints of patients suffering from rheumatoid arthritis (RA). With the high number of people affected by this disease especially in western countries, the availability of OI as an early diagnostic imaging method is clinically highly relevant. In this paper, we present a newly in-house developed OI analyzing tool and a clinical evaluation study. Our analyzing tool extends the capability of existing OI tools. We include many features in the tool, such as region-based image analysis, hyper perfusion curve analysis, and multi-modality image fusion to aid clinicians in localizing and determining the intensity of inflammation in joints. Additionally, image data management options, such as the full integration of PACS/RIS, are included. In our clinical study we demonstrate how OI facilitates the detection of active inflammation in rheumatoid arthritis. The preliminary clinical results indicate a sensitivity of 43.5%, a specificity of 80.3%, an accuracy of 65.7%, a positive predictive value of 76.6%, and a negative predictive value of 64.9% in relation to clinical results from MRI. The accuracy of inflammation detection serves as evidence to the potential of OI as a useful imaging modality for early detection of active inflammation in patients with rheumatoid arthritis. With our in-house developed tool we extend the usefulness of OI imaging in the clinical arena. Overall, we show that OI is a fast, inexpensive, non-invasive and nonionizing yet highly sensitive and accurate imaging modality.-

IT-Based Dose Management in Diagnostic Radiology

Documentation of patient exposure is mandatory in most countries. However the documented data are rarely used for statistical review of patient doses or assessment of the requirement to optimize dose. In this study the documented dose values stored in the PACS are extracted and used for further statistical analysis. In a first attempt this was performed and data were analyzed and as an example dose optimization was performed. It was shown that with the available tools the documented data can be used for statistical analyses, dose alerts and dose optimization. This should be an extension to all PACS systems.

Quantifying fluorescence signals in confocal image stacks deep in turbid media

When confocal depth stacks are taken, the collected signal (normally the fluorescence signal), decays dependent of the depth of the confocal slice in the turbid medium. This decay is caused by scattering and absorption of the exciting light and of the fluorescence light. As the attenuation parameters, i.e. scattering and absorption coefficients, are normally unknown when observing a new sample, a method is proposed to compensate for the attenuation of the involved light by correcting the fluorescence signal using the attenuation behavior of the sample measured directly on the spot where the fluorescence stack is taken. The method works without any a priori knowledge about the optical properties of the sample. Using this self-reference technique, a confocal fluorescence depth stack can be created where the signal intensity is not dependent on the scattering and absorption caused intensity decay. The proposed method is tested on fluorescent beads embedded in scattering and absorbing hydrogel phantoms.

Spectrally resolved visualization of fluorescent dyes permeating into skin

We present a spectrally resolved confocal imaging approach to qualitatively asses the overall uptake and the penetration depth of fluorescent dyes into biological tissue. We use a confocal microscope with a spectral resolution of 5 nm to measure porcine skin tissue after performing a Franz-Diffusion experiment with a submicron emulsion enriched with the fluorescent dye Nile Red. The evaluation uses linear unmixing of the dye and the tissue autofluorescence spectra. The results are combined with a manual segmentation of the skins epidermis and dermis layers to assess the penetration behavior additionally to the overall uptake. The diffusion experiments, performed for 3h and 24h, show a 3-fold increased dye uptake in the epidermis and dermis for the 24h samples. As the method is based on spectral information it does not face the problem of superimposed dye and tissue spectra and therefore is more precise compared to intensity based evaluation methods.

Fluorescent nanodiamonds as highly stable biomarker for endotoxin verification

Fluorescent nanodiamonds (ND) provide advantageous properties as a fluorescent biomarker for in vitro and in vivo studies. The maximum fluorescence occurs around 700 nm, they do not show photobleaching or blinking and seem to be nontoxic. After a pretreatment with strong acid fluorescent ND can be functionalized and coupled to endotoxin. Endotoxin is a decay product of bacteria and causes strong immune reactions. Therefore endotoxin has to be removed for most applications. An effective removal procedure is membrane filtration. The endotoxin, coupled to fluorescent ND can be visualized by using confocal microscopy which allows the investigation of the separation mechanisms of the filtration process within the membranes.