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Results for “protocol optimization”

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PubMed1996

Evaluation of local immune response after intravesical bacille Calmette-Guérin treatment for superficial bladder cancer.

OBJECTIVE: To help define the optimal protocol of Bacille Calmette-Guérin (BCG) treatment for transitional cell carcinoma (TCC) of the bladder by examining cytokine production and antigen presentation to effector cells after instillations of BCG in patients with bladder TCC. PATIENTS AND METHODS: Sixty-four urine samples from 11 patients were tested for the production of interferon gamma (IFN-gamma) using a modified commercial enzyme-linked immunosorbent assay (ELISA) kit. Urine was collected before and at intervals up to 24 h after the intravesical instillation of BCG. Immunohistological studies were also carried out using a two-step alkaline phosphatase technique to explore the expression of tumour-associated antigens (TAAs) (E7, 19A211, T138), major histocompatibility complex (MHC) molecules and lymphocyte subset infiltrates (CD3, CD4, CD8) in bladder biopsies before and 3 weeks after the completion of treatment in seven patients. RESULTS: IFN-gamma was only detected 4, 6 and 8 h after instillation, with a maximum concentration at 6 h (2.9-34.7 IU/mL in 10 patients). During a 6-week course of BCG, IFN-gamma was barely detectable after the first two instillations, but gradually increased from the third instillation onwards. TAA and MHC II antigens, which were absent or faintly expressed on normal urothelial cells before treatment, were expressed strongly in five patients after treatment. The local recruitment of immunocompetent cells was detected in all patients. CONCLUSION: These results suggest that the local immune response after the intravesical instillation of BCG can be quantified using simple ELISA tests and could be useful in defining objective criteria for rationalizing treatment (dose and duration), and in determining the relation between the immune response and anti-tumour activity. There is evidence that antigen presentation is enhanced after BCG instillations, suggesting that a T cell-MHC restricted pathway might be involved in the anti-tumour response. This study supports the search for tumour-rejection antigens in bladder cancer.

Antigens, Neoplasm↗

PubMed2000

A novel flow cytometric steroid hormone receptor assay for paraffin-embedded breast carcinomas: an objective quantification of the steroid hormone receptors and direct correlation to ploidy status and proliferative capacity in a single-tube assay.

Semiquantitative estimation of steroid hormone receptors by immunohistochemistry applied to paraffin sections is common practice in surgical pathology. Flow cytometric (FCM) analysis of estrogen receptor (ER) and progesterone receptor (PR) levels provides a faster and more objective quantitative assay. However, a major problem in such FCM analyses of solid tumor samples is the admixture of tumor cells with normal epithelial, stromal, and inflammatory cells. The aim of the underlying study was to investigate the applicability of a recently developed multiparameter flow cytometric methodology for the accurate estimation of the fraction of steroid hormone receptor-positive tumor cells and to explore whether this multiparameter approach allows the detection of specific, clinically relevant subsets of tumors, based on a combination of ploidy level, steroid hormone receptor status, and cell cycle characteristics. For this purpose, samples of 42 breast cancer patients, from which routine immunohistochemistry for ER and PR also was available, were analyzed. From each case, a cell suspension was prepared from the paraffin block by applying a heating and short pepsin digestion step to 50-microm-thick sections. These cell suspensions were double-immunostained for cytokeratin to identify the epithelial cells, and ER or PR, whereas DNA was quantitatively stained with propidium iodide using an optimized protocol. In the entire group of breast tumors, the percentages of ER- and PR-positive cells were registered in the epithelial subfraction, in combination with DNA ploidy and S phase fraction (SPF). A significant correlation was found between the fraction of hormone receptor-positive cells as found by the immunohistochemical and FCM procedures. For ER, a correlation coefficient of r = .87 was found, and for PR r = .62, both P < .0001. It became clear that all the diploid breast tumors had more than 30% tumor cells positive for ER with a SPF lower than 10%, whereas aneuploid tumors contained on average a smaller percentage of steroid hormone receptor-positive cells, and simultaneously an SPF greater than 10%. Our results show that this multiparameter FCM analysis allows an objective and reproducible quantification of the fraction of steroid hormone receptor-positive cells in the relevant epithelial cell compartment in relation to DNA ploidy status and proliferative capacity in a single-tube assay.

Breast Neoplasms↗

PubMed2004

Progress in CT imaging for the cardiac surgeon.

The aim of this article is to critically assess the role of multidetector-row CT (MDCT) in the field of cardiothoracic surgery. In the beginning, a short overview is given about technical aspects such as scan protocols, optimal image reconstruction, image reformation techniques, data evaluation, and data presentation. This is followed by sections about possible indications for cardiothoracic surgery and future prospects for this technology. For the cardiac surgeon, the main benefit of MDCT lies in the combination of large scan-volume coverage, high spatial resolution, proper identification of calcifications, and the simultaneous registration of other thoracic structures. Preoperative applications may include the assessment of cardiac valves, noninvasive evaluation of large thoracic vessels, staging of cardiac tumors, and planning of minimally invasive surgical procedures. After surgery, MDCT examinations particularly facilitate an early identification of severe postoperative complications. MDCT may also be used to assess coronary artery bypass graft patency and to identify transplant-related complications in heart transplant recipients at an early stage. New technological developments such as 64-row MDCT or flat panel computed tomography will further increase the field of possible indications.

Coronary Artery Bypass↗

PubMed2002

[Multislice helical CT (MSCT) for mid-facial trauma: Optimization of parameters for scanning and reconstruction].

PURPOSE: To determine the optimal scan parameters in multislice helical CT (MSCT) of the facial bone complex for both axial scanning and multiplanar reconstructions. MATERIAL AND METHODS: An anthropomorphic skull phantom was examined with a MSCT. Axial scans were performed with continuously increasing collimations (4 x 1.25 - 4 x 2.5 mm), tube current (20 - 200 mA) and table speeds (3.75 mm/rot. and 7.5 mm/rot.). Multiplanar reconstructions in coronal and parasagittal planes with different reconstruction increment and slice thickness were evaluated in terms of image noise, contour artifacts and visualisation of anatomical structures. RESULTS: The best image quality was obtained with a collimation of 4 x 1.25 mm and a table speed of 3.75 mm/rot. A reconstruction increment of 0.6 mm achieved the best time to image quality relation. With these parameters the bone structures were depicted in an optimal way without artifacts. The tube current could be reduced to 50 mA without significant loss of image quality. The optimized protocol was used for regular routine examinations in patients with facial trauma (n = 66). CONCLUSIONS: Low-dose MSCT using thin collimation, low table speed and small reconstruction increments provides excellent data for both axial images and multiplanar reconstructions in patients with facial trauma. An additional examination in coronal orientation is therefore no longer necessary.

Adult↗

PubMed1997

The duration of administration of monoclonal antibody OKT3 for induction immunosuppression after heart transplantation.

The effective treatment of refractory allograft rejection with murine antihuman monoclonal antibody muromonab-CD3 (OKT3) and of patients with renal dysfunction has led to its use as induction therapy. The optimal protocol for OKT3 prophylaxis remains to be established. We compared 59 patients consecutively transplanted with the total orthotopic technique between 1/92 and 5/94. The first 21 patients were treated with OKT3 for 14 days, the next 19 for 10 days, and the last 19 for 7 days. Patients operated with different surgical techniques or other induction treatment were excluded. We compared length of stay (total and ICU), time to first rejection, rejection incidence and infection incidence (cytomegalovirus separately), and survival. Preoperative characteristics were similar except for significantly younger age in the 10-day group (p = 0.04). Preoperative hemodynamic parameters were similar except for a significantly higher left-ventricular ejection fraction (21%) in the 7-day group. Length of stays in the ICU and hospital were similar for the three groups (p = NS). Freedom from cellular rejection was lower with the 7 days course (p = 0.02), but freedom from humoral rejection was slightly higher (p = 0.11). However, patients in the 7-day group required treatment for rejection less frequently than patients in the other two groups (95% untreated at 2 months vs. 43% in the 14-day and 53% in the 10-day group; p = 0.002). There were no differences in incidence of infections, including cytomegalovirus. Survival was similar between the groups. There was one death in the 14-day and 1 in the 10-day group, both due to rejection. In conclusion, OKT3 therapy can be reduced safely to 7 days with a higher overall incidence of rejection but no increased necessity to treat for rejection, and no difference in infection incidence.

Adult↗

PubMed2003

A systematic review of pneumatic compression for treatment of chronic venous insufficiency and venous ulcers.

INTRODUCTION: As part of a reconsideration of coverage policy, the Centers for Medicare and Medicaid Services requested a systematic review of the evidence on the use of pneumatic compression devices in the home environment for treatment of chronic venous insufficiency (CVI) and venous ulcers. METHODS: Articles were found with a systematic literature search of MEDLINE, EMBASE, and AMED (Allied and Complementary Medicine) databases, hand searches of reference lists, and suggestions of experts. RESULTS: Eight trials that met the inclusion criteria, including several randomized control trials, were found. Most studies were small and may have been underpowered. However, several were well-designed randomized controlled trials. Three studies showed that the devices could alleviate symptoms of CVI. No studies directly measured whether the devices could prevent the occurrence of venous ulcers. Some studies on the treatment of venous ulcers did not show a benefit for pneumatic compression, but other studies showed a benefit for the devices in healing long-standing chronic ulcers that had not healed with other methods. No studies directly compared single-chamber and multiple-chamber devices or studied whether the effectiveness of the pump was dependent on types of treatment used concurrently with the pump. Few adverse events were reported in the trials. Patients generally expressed satisfaction with the pneumatic compression devices, and several studies reported higher compliance than with other compression methods. CONCLUSION: The available data cannot be relied on to inform the optimal choice of compression therapy or optimal protocol for patients with CVI or venous ulcers. Methodologically rigorous research designed to answer these questions would be useful for treatment decisions. The Centers for Medicare and Medicaid Services considered the results of this study and issued a decision that pneumatic compression will only be covered for patients with refractory edema with significant ulceration of the lower extremities after a 6-month trial of standard therapies, such as compression stockings, has failed.

Chronic Disease↗

PubMed2003

Mass spectrometric analysis of protein mixtures at low levels using cleavable 13C-isotope-coded affinity tag and multidimensional chromatography.

In order to identify and compare the protein content of very low quantity samples of high complexity, a protocol has been established that combines the differential profiling strength of a new cleavable 13C isotope-coded affinity tag (cICAT) reagent with the high sequence coverage provided by multidimensional liquid chromatography and two modes of tandem mass spectrometry. Major objectives during protocol optimization were to minimize sample losses and establish a robust procedure that employs volatile buffer systems that are highly compatible with mass spectrometry. Cleavable ICAT-labeled tryptic peptides were separated from nonlabeled peptides by avidin affinity chromatography. Subsequently, peptide samples were analyzed by nanoflow liquid chromatography electrospray ionization tandem mass spectrometry and liquid chromatography matrix-assisted laser desorption/ionization tandem mass spectrometry. The use of two ionization/instrumental configurations led to complementary peptide identifications that increased the confidence of protein assignments. Examples that illustrate the power of this strategy are taken from two different projects: i) immunoaffinity purified complexes containing the prion protein from the murine brain, and ii) human tracheal epithelium gland secretions. In these studies, a large number of novel proteins were identified using stringent match criteria, in addition to many that had been identified in previous experiments. In the latter case, the ICAT method produced significant new information on changes that occur in protein expression levels in a patient suffering from cystic fibrosis.

Amino Acid Sequence↗

PubMed2004

A prototype antibody microarray platform to monitor changes in protein tyrosine phosphorylation.

Reversible protein phosphorylation is a key regulatory process in all living cells. Deregulation of modification control mechanisms, especially in the case of tyrosine, may lead to malignant transformation and disease. Phosphotyrosine (p-Tyr) accounts for only 0.05% of the total cellular phospho-amino acid content, yet plays an unusually prominent role in eukaryotic signaling, development, and growth. Tracking temporal and positional p-Tyr changes across the cellular proteome, i.e. tyrosine phosphoproteomics, is therefore tremendously valuable. Here, we describe and evaluate a prototype antibody (Ab) microarray platform to monitor changes in protein Tyr phosphorylation. Availability permitting, a virtually unlimited number of Abs, each recognizing a specific cellular protein, may be arrayed on a chip, incubated with total cell or tissue extracts or with biological fluids, and then probed with a fluorescently labeled p-Tyr-specific monoclonal Ab, PY-KD1, specifically generated for this assay as part of the current study. The optimized protocol allowed detection of changes in the Tyr phosphorylation state of selected proteins using submicrogram to low nanogram of total protein extract, amounts that may conceivably be obtained from a thousand to a hundred thousand cells, or less, depending on the cell or tissue type. The assay platform was evaluated by assessing changes in a rationally selected subset of the Tyr phosphoproteome of Bcr-Abl-expressing cells treated with a specific inhibitor, Gleevec, and of epidermal growth factor (EGF)-treated HeLa cells. The results, ratiometric rather than strictly quantitative in nature, conformed with previous identifications of several Bcr-Abl and EGF receptor targets, and associated proteins, as detected by exhaustive mass spectrometric analyses. The Ab microarray method described here offers advantages of low sample and reagent consumption, scalability, detection multiplexing, and potential compatibility with microfluidic devices and automation. The system may hold particular promise for dissecting signaling pathways, molecular classification of tumors, and profiling of novel target-cancer drugs.

Animals↗

PubMed2005

Use of reverse phase protein microarrays and reference standard development for molecular network analysis of metastatic ovarian carcinoma.

Cancer can be defined as a deregulation or hyperactivity in the ongoing network of intracellular and extracellular signaling events. Reverse phase protein microarray technology may offer a new opportunity to measure and profile these signaling pathways, providing data on post-translational phosphorylation events not obtainable by gene microarray analysis. Treatment of ovarian epithelial carcinoma almost always takes place in a metastatic setting since unfortunately the disease is often not detected until later stages. Thus, in addition to elucidation of the molecular network within a tumor specimen, critical questions are to what extent do signaling changes occur upon metastasis and are there common pathway elements that arise in the metastatic microenvironment. For individualized combinatorial therapy, ideal therapeutic selection based on proteomic mapping of phosphorylation end points may require evaluation of the patient's metastatic tissue. Extending these findings to the bedside will require the development of optimized protocols and reference standards. We have developed a reference standard based on a mixture of phosphorylated peptides to begin to address this challenge.

Carcinoma↗

PubMed2002

Assessment of transcriptional gene activity in situ by application of HOPE-fixed, paraffin-embedded tissues.

We report the use of HOPE-fixation (HOPE = Hepes-Glutamic acid buffer mediated Organic solvent Protection Effect) for specimens utilized for in situ hybridization targeting mRNA. For this purpose, an optimized protocol was developed and repeatedly tested on HOPE-fixed lung specimens. We observed that neither pretreatment, permeabilizing the cells, nor prehybridization is necessary to generate signals. After deparaffinizing, the random primed digoxigenin-labeled probes are directly hybridized together with yeast tRNA for blocking unspecific signals. Detection was performed using anti digoxigenin antibodies conjugated with alkaline phosphatase and new-fuchsine or NBT/BCIP as substrates. The results were verified by RT-PCR and adequate negative controls. Signals for human surfactant protein-A and interferon-gamma-inducible protein-10 developed rapidly within 10 min, accompanied by high signal intensities comparable to those observed in immunohistochemistry. Signal enhancement by biotinyl-tyramide, although giving suitable results as well, did not lead to higher signal intensities, and thus was not necessary in conjunction with the probes tested so far. These experiments were performed with material stored under appropriate conditions (at +4 degrees C) up to five years. To sum up, these initial results, obtained with the novel HOPE-fixative, are promising as regards the enhancement of the capabilities of in situ hybridization in the future.

Cells, Cultured↗

PubMed2000

A multiplex-PCR method to detect enterohemorrhagic (EHEC) and enteropathogenic (EPEC) Escherichia coli in artificially contaminated foods.

In view of the considerable public health risk of the enteropathogenic (EPEC) and enterohemorrhagic (EHEC) Escherichia coli, a multiplex-PCR based method was used for the amplification of the slt genes and of the eaeA gene. Three pairs of primers, different from the oligonucleotides previously used by other authors, were exploited for the amplification. Different E. coli serotypes were tested with the optimized protocol. Fifty three artificially contaminated samples and sixty naturally contaminated samples were processed with the multiplex-PCR. All the artificially contaminated samples gave positive results independently of the number of cells inoculated. On the contrary, the naturally contaminated samples were all negative. The results obtained from this experiment demonstrated that this protocol could be used for monitoring the spread of these organisms in food.

DNA Primers↗

PubMed2002

Comparison of extraction and clean-up procedures for analysis of zearalenone in corn, rice and wheat grains by high-performance liquid chromatography with photodiode array and fluorescence detection.

The aim of this work was the optimization of some procedures usually used in the analysis of zearalenone (ZEA) in corn and other cereals by high-performance liquid chromatography (HPLC) with photodiode array and/or fluorescence detection. The comparison of five extraction solvents is presented. Three solid-phase extraction cartridges (C-18, silica, Florisil) and immuno-affinity columns were also compared to obtain the best recovery of the mycotoxin with the minimal presence of co-extractives in the chromatograms. Mixtures of methanol-1% aqueous NaCl (80.20 or 60:40 v/v) were the best extraction solvents. Florisil provided higher recovery of ZEA than C-18, and silica proved unsuitable. The immuno-affinity column was very efficient in cleaning the extracts, but its sample capacity was lower than that of SPE columns due to saturation. The mobile phase (methanol-water 80:20 v/v) gave a low retention time for ZEA (approximately 5 min), high sensitivity and acceptable separation between this mycotoxin and alpha-zearalenol. The optimized protocol is straightforward, provides high ZEA recoveries in spiked corn (mean 102.4%), has an acceptable sensitivity and has a lack of interference with fluorescence detection (detection limit 4 ng ZEA g(-1) corn). The photodiode array detector was useful, except at very low ZEA levels, to confirm the identity of the mycotoxin. The method was applied to search for ZEA accumulation in corn, wheat and rice grains inoculated with selected strains of Fusarium graminearum, F. oxysporum and method was applied to search for ZEA accumulation in corn, wheat and rice grains inoculated with selected strains of Fusarium graminearum, F. oxysporum and F. culmorum.

Chromatography, High Pressure Liquid↗

PubMed2005

Vitrification of mouse embryos at various stages by open-pulled straw (OPS) method.

This study was performed to pursue the optimal condition for the cryopreservation of mouse morulae by a two-step OPS method and to investigate the feasibility of the optimal condition for vitrification of embryos at other developmental stages. First, the mouse morulae were vitrified in OPS using one-step procedure-that is, embryos were vitrified after direct exposure to EDFS30 (15% ethylene glycol (EG), 15% dimethyl sulfoxide (DMSO), Ficoll and sucrose), or two-step method-that is, embryos were first pretreated in 10%E + 10%D (10% EG and 10% DMSO in mPBS) for 30 sec, then exposed to EDFS30 for 15 to 60 sec, respectively. After vitrification and warming, the embryos were morphologically evaluated and assessed by their development to blastocysts, expanded/hatched blastocysts, or to term after transfer. The result showed that all the vitrified-warmed morulae had similar blastocyst rate compared to that of control (91.7% vs. 100%), and the highest developmental rate to expanded blastocysts (100%) or hatched blastocysts (62.3%) was observed when the morulae were pretreated with 10%E + 10%D for 0.5 min, exposed to EDFS30for 25 sec before vitrification and warming in 0.5 M sucrose for 5 min. After transfer, the survival rate (33.1%) in vivo of the vitrified morulae was higher (P > 0.05) than that of the fresh embryos (24.6%). Secondly, embryos at different stages were cryopreserved and thawed following the above program. Most (93.4 to 100%) of the embryos recovered after vitrification were morphologically normal at all the developmental stages. The blastocyst rates of the vitrified one-cell (52.5 to 66.7%) and the two-cell (63.3 to 68.9%) embryos were lower (P < 0.05) than those of the vitrified four-cell embryos (81.7 to 86.4%), the eight-cell embryos (90.0 to 93.3%), morulae (96.7 to 100%), and the expanded blastocysts rate (98.3 to 100.0%) of the vitrified early blastocysts. The highest survival rate in vivo of vitrified embryos were from the early blastocysts (40.4%), which was similar to that of fresh embryos (48.6%). The data demonstrate that the optimal protocol for the cryopreservation of morulae was suitable for the four-cell embryos to early blastocyst stages and that the early blastocyst stage is the most feasible stage for mouse embryo cryopreservation under our experimental conditions.

Animals↗

PubMed2006

Efficient extraction of high-quality total RNA from various hop tissues (Humulus lupulus L.).

The isolation of high-quality RNA is a prerequisite for gene expression studies. RNA quality is of special relevance if PCR-based strategies such as cDNA-AFLP or RT-PCR are followed. Our molecular investigations of hop (Humulus lupulus L.) focus on genes that determine the biosynthesis of prenylflavonoids with interesting biological activities which accumulate in the lupulin glands. However, optimized protocols for RNA extraction from hop cones are not available. In this study, the RNeasy midi kit protocol was modified to isolate high amounts of total RNA from fresh and freeze-dried hop tissues, specifically leaves, female inflorescences, and lupulin-enriched hop cone fractions. The main difficulties in obtaining high RNA yields were related to specific features of hop, including the abundance of secondary metabolites and their accumulation in the sticky lupulin glands. The introduction of a number of modifications into the RNeasy midi kit protocol resulted in RNA of high quality, as assessed by spectrophotometry and electrophoresis in agarose gels. The protocol developed is currently being used to produce cDNA-AFLP fingerprints of hop cones and leaves for genetic screening. Furthermore, the method could provide RNA for further molecular studies, including Northern blot hybridizations and reverse transcription-polymerase chain reactions.

Blotting, Northern↗

PubMed1998

Improvements in absorbed dose measurements for external radiation therapy using ferrous dosimeter gel and MR imaging (FeMRI).

A ferrous gel, based on ferrous (Fe) sulphate and agarose, was used with a clinical magnetic resonance imaging (MRI) scanner to obtain relative dose distribution data from therapeutic photon and electron beams. The FeMRI gel was scanned using a new MRI acquisition protocol optimized for T1 measurements. Thorough comparisons with silicon semiconductor detector and ionization chamber measurements, as well as with Monte Carlo calculations, were performed in order to quantify the improvements obtained using FeMRI for dose estimations. Most of the relative doses measured with FeMRI were within 2% of the doses measured with other methods. The larger discrepancies (2-4%) found at shallow depths are discussed. The uncertainty in relative dose measurements using FeMRI was significantly improved compared with previously reported results (5-10%, one standard deviation, 1 SD), and is today between 1.6% and 3.3% (depending on dose level, 2 SD). This corresponds to an improvement in the minimum detectable dose (3 SD above background) from approximately 2 Gy to better than 0.6 Gy. The results obtained in this study emphasize the importance of obtaining basic FeMRI dose data before the method is extended to complicated treatment regimes.

Electrons↗

PubMed2003

Monte Carlo simulations of a scintillation camera using GATE: validation and application modelling.

Geant4 application for tomographic emission (GATE) is a recently developed simulation platform based on Geant4, specifically designed for PET and SPECT studies. In this paper we present validation results of GATE based on the comparison of simulations against experimental data, acquired with a standard SPECT camera. The most important components of the scintillation camera were modelled. The photoelectric effect. Compton and Rayleigh scatter are included in the gamma transport process. Special attention was paid to the processes involved in the collimator: scatter, penetration and lead fluorescence. A LEHR and a MEGP collimator were modelled as closely as possible to their shape and dimensions. In the validation study, we compared the simulated and measured energy spectra of different isotopes: 99mTc, 22Na, 57Co and 67Ga. The sensitivity was evaluated by using sources at varying distances from the detector surface. Scatter component analysis was performed in different energy windows at different distances from the detector and for different attenuation geometries. Spatial resolution was evaluated using a 99mTc source at various distances. Overall results showed very good agreement between the acquisitions and the simulations. The clinical usefulness of GATE depends on its ability to use voxelized datasets. Therefore, a clinical extension was written so that digital patient data can be read in by the simulator as a source distribution or as an attenuating geometry. Following this validation we modelled two additional camera designs: the Beacon transmission device for attenuation correction and the Solstice scanner prototype with a rotating collimator. For the first setup a scatter analysis was performed and for the latter design. the simulated sensitivity results were compared against theoretical predictions. Both case studies demonstrated the flexibility and accuracy of GATE and exemplified its potential benefits in protocol optimization and in system design.

Algorithms↗

PubMed2005

A dual modality approach to quantitative quality control in emission tomography.

Routine quality control (QC) and optimization of image quality of reconstructed images in single photon emission computed tomography (SPECT) and positron emission tomography (PET) remains a relatively qualitative exercise. With the advent of combined SPECT/CT and PET/CT devices, and accurate post hoc co-registration algorithms, the potential exists to utilize high resolution structural information for QC evaluation in addition to their use for anatomical correlation in clinical studies. The aim of this work was to explore, in principle, the uses of x-ray CT data of QC phantoms used in SPECT and PET to develop more objective assessments of performance of the emission tomographic (ET) devices and reconstructed data. A CT reconstruction of a novel ET QC phantom was segmented into the various compartments it contained. Using software, the voxel values in the different compartments were then altered to correspond to the concentration of the radioactivity in the actual scan of the same phantom on the SPECT system. This produces a high resolution version of a 'perfect' ET scan. Image co-registration techniques were then used to spatially align the synthetic high resolution SPECT scan to the measured SPECT scan. Various parameters can then be objectively derived from the registered data, for example, image contrast, spatial resolution, spatial non-uniformity, etc. In this study, we have used this approach to estimate spatial resolution (full width at half maximum, FWHM) and recovered contrast in reconstructed images of a SPECT phantom. Two independent methods were used to measure spatial resolution, obtaining excellent agreement. In conclusion, the ability to produce high resolution synthetic phantoms in emission tomography QC affords an objective approach to assessing system performance and optimizing protocols which is readily automated and quantifiable.

Algorithms↗

PubMed2005

MRI of perfluorocarbon emulsion kinetics in rodent mammary tumours.

Perfluorocarbon (PFC) emulsions can be imaged directly by fluorine-19 MRI. We developed an optimized protocol for preparing PFC droplets of uniform size, evaluated use of the resulting droplets as blood pool contrast agents, studied their uptake by tumours and determined the spatial resolution with which they can be imaged at 4.7 T. Perfluorocarbon droplets of three different average sizes (324, 293 and 225 nm) were prepared using a microemulsifier. Images of PFC droplets with good signal-to-noise ratio were acquired with 625 microm in-plane resolution, 3 mm slice thickness and acquisition time of approximately 4.5 min per image. Kinetics of washout were determined using a simple mathematical model. The maximum uptake of the PFC droplets was three times greater at the tumour rim than in muscle, but the washout rate was two to three times slower in the tumour. The results are consistent with leakage of the droplets into the tumour extravascular space due to the hyper-permeability of tumour capillaries. PFC droplets may allow practical and quantitative measurements of blood volume and capillary permeability in tumours with reasonable spatial resolution.

Animals↗