Validation of a DNA-based method for identifying Chrysomyinae (Diptera: Calliphoridae) used in a death investigation

Many authors have proposed DNA-based methods for identifying an insect specimen associated with human remains. However, almost no attempt has been made to validate these methods using additional observations. We tested a protocol for identifying insects in the blow fly subfamily Chrysomyinae (Diptera: Calliphoridae) often found to be associated with a human corpse in Canada or the USA. This method uses phylogenetic analysis of DNA sequence from a short segment of the mitochondrial gene for cytochrome oxidase one (COI). Test chrysomyine COI sequences were obtained from 245 newly sequenced specimens and 51 specimens from the published literature. Published sequences from representatives of nonchrysomyine genera were also included to check for the possibility of a false positive identification. All of the chrysomyine test haplotypes were correctly identified with strong statistical support, and there were no false positives. This method appears to be an accurate and robust technique for identifying chrysomyine species from a death investigation in this geographic region. The far northern species Protophormia atriceps was not evaluated; therefore, caution is required in applying this method at very high latitudes in North America.     

Development of a collimator blurring compensation method using fine angular sampling projection data in SPECT

Due to the collimator aperture, spatial resolution of SPECT data varies with source-to-detector distance. Since the radius of detector rotation is bigger when scanning larger patients, spatial resolution is degraded in these cases. Emitted gamma rays travel not only along the central axis of the collimator hole but also off-axis due to the collimator aperture. However, an off-axis ray at one angle would be a central-axis ray at another angle; therefore, raw projection data at one angle can be thought of as an ensemble of central-axis rays collected from a small arc equal to the collimator aperture. Thus, fine angular sampling can compensate for collimator blurring. By using a sampling pitch of less than half the collimator aperture angle, compensation was performed by subtracting the weighted sum of the projection data from the raw projection data. Collimator geometry and detector rotation radius determined the weighting function. Cylindrical phantom with four different-sized rods and torso phantom for Tl-201 cardiac SPECT simulation were used for evaluation. Aperture angle of the collimator was 7 degrees. Projection sampling pitch was 2 degrees. In both phantom studies, the proposed method showed improvement in contrast and reduction of partial volume effect, thereby indicating that the proposed method can compensate adequately for image blurring caused by the collimator aperture.     

Directional correlation characterization and classification of white matter tracts.

To study the architectural characteristics of white matter (WM) tracts, the directional correlation (DC), defined as the inner product of the major eigenvector of adjacent pixels, was used as a quantitative index to investigate directional similarity in WM tracts. A region-growing algorithm was employed to propagate an area from a seed point as a function of the DC threshold (DCt) to critically evaluate the directional properties of WM tracts. As the DCt was increased, more pixels were excluded from the propagated region as their DC fell below the DCt, and neighboring WM tracts could be distinguished as the area decreased. Taking the DC into account, a systematic classification routine for WM tracts was devised and tested on a mouse brain in vivo. The results show that individual WM tracts possess a high degree of directional similarity, and, by careful choice of the DCt value, the proposed classification algorithm can recognize all possible WM tracts in a given data set.     

Quantitative analysis of short echo time (1)H-MRSI of cerebral gray and white matter.

Quantitative analysis of (1)H-magnetic resonance spectroscopic imaging (MRSI) data was developed using the user-independent spectral analysis routine LCModel. Tissue segmentation was performed using statistical parametric mapping software (SPM 96), and the results were used to correct for cerebrospinal fluid contamination. A correction was developed for the imperfections in the spectroscopic excitation profile in order to improve the uniformity of metabolite images. After validation in phantoms, these techniques were applied to study differences in metabolite concentrations between gray and white matter in normal volunteers (n = 13). A positive correlation was found between concentration and gray matter content for most metabolites studied. The estimated ratios of metabolite concentration in gray vs. white matter were: N-acetyl aspartate + N-acetyl aspartyl glutamate (NAc) = 1.16+/- 0.11; creatine = 1.7+/-0.3; glutamate + glutamine = 2.4+/-0.5; myo-inositol = 1.6+/-0.3; choline = 0.9+/-0.2. The ratio of NAc/Cr was negatively correlated with gray matter content: gray/white = 0.69 +/-0.08. These methods will be useful in the evaluation of metabolite concentrations in MRSI voxels with mixed tissue composition in patient groups.     

T(1) and T(2) selective method for improved SNR in CSF-attenuated imaging: T(2)-FLAIR.

We present here a method for improving SNR in CSF-attenuated imaging relative to the standard technique of using an inversion pulse and imaging at the null point of CSF. In this new method the inversion pulse is replaced with a 90(x)-180(y)-90(x) preparation sequence that provides T(1) and T(2) selectivity. This allows the tissue magnetization to recover more rapidly, allows for the use of shorter TR values, and reduces T(1) weighting. Magn Reson Med 45:529-532, 2001.     

Simplification for measuring input function of FDG PET: investigation of 1-point blood sampling method.

The current method for quantitative FDG PET study requires application of multiple arterial blood sampling for measuring the input function, but the procedure is invasive and complicated. The purpose of this study was to establish a 1-point blood sampling technique that gives data comparable with the data of more elaborate serial arterial sampling. METHODS: We established a time point for 1-point arterial sampling that exhibited the highest correlation between plasma radioactivity at the time point and the real integrated value (IV) of the measured input function obtained by multiple arterial sampling in 120 patients and the smallest coefficient of variation of the real IV divided by plasma radioactivity at the time point in 120 patients. Scaling factors for estimation at each sampling point were determined, and a reference table was established to make the supposed input function. RESULTS: The optimal time for 1-point arterial sampling was 12 min after FDG injection. A good correlation was observed between the real IVs and those estimated from 1-point arterial blood sampling at 12 min using the supposed input function (n = 120; P < 0.001). The time point at which the difference between values of arterial and venous blood disappeared was 40 min after FDG injection. The percentage errors of IV estimation by 1-point sampling were 1.70% (n = 120) for arterial blood at 12 min and 3.64% (n = 10) for venous blood at 40 min. CONCLUSION: We conclude that the simplified 1-point sample method works in a manner that is comparable with serial arterial sampling and should be useful for clinical PET.     

Naturally occurring radioactive materials (NORM): a matter of wide societal implication.

Naturally occurring radioactive materials are ubiquitous on Earth and their radioactivity may become concentrated as a result of human activities. Numerous industries produce concentrated radioactivity in their by-products: the coal industry, petroleum extraction and processing, water treatment, etc. The present reference system of radiation protection does not provide a complete framework for the coherent management of all types of radioactively contaminated materials. Inconsistencies in waste management policy and practice can be noted across the board, and especially vis-à-vis the management of radioactive waste from the nuclear industry. This article reviews the present societal approach to manage materials that are radioactive but are often not recognised as being such, and place the management of radioactive materials from the nuclear industry in perspective.     

Human brain glucose metabolism mapping using multislice 2D (1)H-(13)C correlation HSQC spectroscopy.

A method for multivolume 2D (1)H-(13)C correlation spectroscopy, multislice heteronuclear single quantum coherence (HSQC), is proposed. This permits human brain metabolism from glucose to amino acids to be followed using a 2-T whole-body scanner. The modifications from the conventional HSQC are that the 180 degrees ((13)C) and 180 degrees ((1)H) pulses are separated in time in the preparation period and that the 180 degrees ((13)C) pulse is applied at 1/(4J(CH)) before the 90 degrees ((1)H) polarization transfer (PT) pulse. The preparation (echo) time can be set longer than 1/(2J(CH)) so that, even in a whole-body system, slice-selective pulses and gradients can be applied. Another modification is that the 90 degrees ((1)H) reverse PT pulses after the creation of 2I(z)S(z) are used as multislice pulses. The time-course of glutamate C4 could be followed with 15-min temporal resolution from the HSQC spectra obtained from the brains of volunteers after the oral administration of glucose C1, and the maximum S/N was 3.     

The potential of perturbed angular correlation of gamma rays as a tool for dynamic studies of peptides/proteins

Four peptides and serum albumin have been derivatized with the bicyclic anydride of diethylenetriaminepentaacetic acid. Procedures were developed to isolate the labelled species and determine the degree of derivatization. By using perturbed angular correlation of gamma-ray spectroscopy it is possible, through the determination of rotational correlation times, to decide whether labelled peptides interact with other molecules (receptors). In the case of the peptide cholecystokinin it is shown that the interaction between the peptide and its corresponding polyclonal antibody can be determined down to 1 pmol hormone. Experiments on ¹¹¹In- and ^111mCd-labelled Gly-Trp showed that, where the ¹¹¹Cd PAC spectrum directly reflected the rotational motion of the molecule, the ¹¹¹In PAC spectrum was affected by the nuclear transitions to ^111mCd.     

Spin-lattice relaxation (T1) times of cerebral white matter in multiple sclerosis

Magnetic resonance imaging was used to evaluate the cerebral white matter of three subject groups: (1) 22 patients with known multiple sclerosis (MS) (11 with disease of shorter duration (0-5 years) and 11 with disease of longer duration (greater than 5 years]; (2) 9 patients with suspected MS; and (3) 12 normal volunteers. Transverse spin-echo (SE) 30/500 and 120/1000 radiofrequency pulse sequences were used for anatomic localization and plaque identification, respectively, while combined spin echo-inversion recovery was used for T1 determination. T1 values were calculated for grossly normal cerebral white matter in the frontal, parietal, and occipital lobes of normal volunteers and MS patients, and for plaques in MS patients. When compared with normals, the T1 values of plaque-free areas from definite MS patients (shorter and longer duration disease groups combined) were significantly longer in the frontal lobe (MS = 374 +/- 34 ms, Normal = 352 +/- 39 ms, P less than 0.05) and in the occipital lobe (MS = 414 +/- 37, Normal = 378 +/- 40, P less than 0.02). Although the T1 values of the shorter duration MS group were longer than those of normals, the difference was not statistically significant. Thus, the significant difference between the definite MS group (both shorter and longer duration) is more heavily weighted by the longer duration MS group. T1 values in patients with suspected MS without plaques were not significantly different from those of normals. In diagnosed MS patients, T1 values of plaques were significantly longer than T1 values of corresponding normal areas (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Fast multislice T(1) and t(1sat) imaging using a phase acquisition of composite echoes (PACE) technique.

An optimized multislice data acquisition scheme for phase acquisition of composite echoes (PACE) imaging is presented. This new scheme uses a repetition time equal to the mixing time and an appropriate phase cycling scheme, which allows for more efficient exploitation of all composite echoes. These modifications provide true multislice capability in parallel to a reduction of the acquisition time by a factor >2 compared with the original PACE method. Moreover, T(1) values can be obtained directly from phase images without the use of a lookup table. Because of the symmetrical application of the radio frequency pulses, this method is also well suited for T(1sat) imaging. Phantom studies showed a significantly better accuracy of the multislice fast PACE technique compared with a conventional two-point method in multislice acquisition mode, although precision was limited at high T(1) values. T(1) and T(1sat) measurements in brain tissue of eight healthy volunteers confirmed the stability of the fast PACE technique in a clinical setting. Magn Reson Med 42:1089-1097, 1999.