Biomedical subjects

Yong Du

Publications and source records attributed to Yong Du.

At least 19 recordsLinked to original sources

PubMed2026

Associations between gut microbiota on carcass traits and meat quality in Neijiang pigs, Yorkshire pigs, and their hybrids.

This study was designed as an exploratory analysis to compare carcass performance, meat quality traits, and gut microbiota of Neijiang pigs (NN), Yorkshire pigs (YY), and Yorkshire × Neijiang hybrid pigs (YN), with the goal of generating testable hypotheses regarding potential links between gut microbial composition and production phenotypes. Compared with NN pigs, YN hybrids exhibited improved carcass performance while inheriting the favorable meat quality characteristics of Neijiang pigs. The results of 16S rRNA sequencing analysis showed that the relative abundance of the microbiota was similar to that of NN pigs. LDA effect size (LEfSe) results showed that Streptococcus, Treponema, probable_genus_10 and Fibrobacter were the differentially enriched taxa in YN pigs (p < 0.05). Correlation analysis was performed on carcass, meat quality and intestinal microbiota screened out by LEfSe. The results showed that Akkermansia tended to positively associate with body length and oblique length in YN pigs; Dialister correlated positively with dressing rate and pH45min; Treponema showed positive trends with a*45min and a*24h (p < 0.05). Finally, the correlation network model preliminarily mapped associations among production traits, gut microbiota, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for exploratory screening. Nine core microbial taxa exhibited close correlations with phenotypic indicators, which implied that these microbes might modulate metabolic pathways to shape pig performance. Overall, hybrids inherited superior parental carcass and meat quality but harbored unique gut microbial communities relative to purebreds-these preliminary correlative observations generate new hypotheses that gut microbiota may contribute to heterosis-associated phenotypic advantages, which require further targeted validation.

Animals↗

PubMed2008

High-grade mucoepidermoid carcinoma of the accessory parotid gland with distant metastases identified by 18F-FDG PET-CT.

We report a rare case of a metastatic mucoepidermoid carcinoma (MEC) arising from the accessory parotid gland in a 14-year-old male. In the pre-surgical assessment, the MR and CT showed no other abnormalities apart from the primary lesion. The lesion was excised and confirmed as a high-grade MEC. Four months later, he presented with a recurrence in his right temple. A (18)F-FDG PET-CT showed distal metastases in cervical nodes and lungs. In view of the findings and poor prognosis of the patient, surgical intervention and radiotherapy were not given and palliative measures offered. This case shows the potential of molecular imaging with (18)F-FDG PET-CT in these patients.

Adolescent↗

PubMed2007

Femtosecond transient absorption and nanosecond time-resolved resonance Raman study of the solvent-dependent photo-deprotection reaction of benzoin diethyl phosphate.

A combined femtosecond transient absorption (fs-TA) and nanosecond time-resolved resonance Raman (ns-TR3) study was performed to directly detect the dynamics and elucidate the mechanism of the excited state deactivation and solvent-dependent photo-deprotection pathways for benzoin diethyl phosphate (BDP) in neat acetonitrile (MeCN) and 75 % H2O/25 % MeCN. Comparison of the TA spectral evolution observed in the two solvents provides explicit evidence that the photophysical deactivation of the BDP singlet excited state has little solvent dependence. The TA spectra also indicate the related internal conversion (IC) and intersystem crossing (ISC) processes occur rapidly on hundreds of femtoseconds and approximately 2-3 ps time scales, respectively. From this and in conjunction with a photochemistry study and ground state resonance Raman (RR) measurements, the TA results reveal that the phenacyl localized BDP triplet state (that is mainly npi* nature) is the common and immediate precursor to the photo-deprotection reaction in both solvents. However, the triplet deprotection follows different pathways in neat MeCN versus the largely water containing solvent. The deprotection reaction in MeCN was determined to occur with a approximately 11 ns time constant and the reaction was found to be an unimolecular process leading to elimination of the diethyl phosphoric acid apparently concurrent with cyclization to yield the benzofuran product. In the water mixed solvent, the triplet reaction was observed to proceed with a approximately 15 ns time constant and the reaction leads to not only the deprotection-cyclization but also a heterolytic dissociation to release the diethyl phosphate anion through a branching and competing mechanism. The ns-TR3 spectra combined with relevant DFT calculations have been used to characterize the dynamics, structure and vibrational frequencies to help identify the important intermediates as well as to explore the reaction pathway leading to formation of the solvolysis product in the largely water solvent. A consecutive mechanism has been revealed for the heterolysis-solvolysis reaction in the water mixed solvent. The present work provides direct and irrevocable evidence for the dynamics and mechanistic description of the overall photophysics and deprotection related photochemistry for BDP.

Journal Article↗

PubMed2007

Therapeutic potential of 90Y- and 131I-labeled anti-CD20 monoclonal antibody in treating non-Hodgkin's lymphoma with pulmonary involvement: a Monte Carlo-based dosimetric analysis.

UNLABELLED: Pulmonary involvement is common in patients with non-Hodgkin's lymphoma (NHL). (90)Y- and (131)I-anti-CD20 antibodies (ibritumomab tiuxetan and tositumomab, respectively) have been approved for the treatment of refractory low-grade follicular NHL. In this work, we used Monte Carlo-based dosimetry to compare the potential of (90)Y and (131)I, based purely on their emission properties, in targeted therapy for NHL lung metastases of various nodule sizes and tumor burdens. METHODS: Lung metastases were simulated as spheres, with radii ranging from 0.2 to 5.0 cm, which were randomly distributed in a voxelized adult male lung phantom. Total tumor burden was varied from 0.2 to 1,641 g. Tumor uptake and retention kinetics of the 2 radionuclides were assumed equivalent; a uniform distribution of activity within tumors was assumed. Absorbed dose to tumors and lung parenchyma per unit activity in lung tumors was calculated by a Monte Carlo-based system using the MCNP4B package. Therapeutic efficacy was defined as the ratio of mean absorbed dose in the tumor to that in normal lung. Dosimetric analysis was also performed for a lung-surface distribution of tumor nodules mimicking pleural metastatic disease. RESULTS: The therapeutic efficacy of both (90)Y and (131)I declined with increasing tumor burden. In treating tumors with radii less than 2.0 cm, (131)I targeting was more efficacious than (90)Y targeting. (90)Y yielded a broader distribution of tumor absorbed doses, with the minimum 54.1% lower than the average dose; for (131)I, the minimum absorbed dose was 33.3% lower than the average. The absorbed dose to normal lungs was reduced when the tumors were distributed on the lung surface. For surface tumors, the reductions in normal-lung absorbed dose were greater for (90)Y than for (131)I, but (131)I continued to provide a greater therapeutic ratio across different tumor burdens and sizes. CONCLUSION: Monte Carlo-based dosimetry was performed to compare the therapeutic potential of (90)Y and (131)I targeting of lung metastases in NHL patients. (131)I provided a therapeutic advantage over (90)Y, especially in tumors with radii less than 2.0 cm and at lower tumor burdens. For both (90)Y- and (131)I-labeled antibodies, treatment is more efficacious when applied to metastatic NHL cases with lower tumor burdens. (131)I has advantages over (90)Y in treating smaller lung metastases.

Adult↗

PubMed2006

A theoretical investigation of p-hydroxyphenacyl caged phototrigger compounds: an examination of the excited state photochemistry of p-hydroxyphenacyl acetate.

Ab initio and density functional theory methods were employed to study the excited states and potential energy surfaces of the p-hydoxyphenacyl acetate (HPA) phototrigger compound. Complete active space (CAS) ab initio calculations predicted adiabatic electronic transition energies for the HPA-T(1)((3)npi), HPA-T(2)((3)pipi), HPA-S(1)((1)npi), HPA-T(3)((3)npi), HPA-S(2)((1)npi), HPA-S(3)((1)pipi) <-- HPA-S(0) transitions that were similar to and in agreement with those found experimentally for closely related aromatic ketones such as p-hydroxyacetophenone and results from similar calculations for other related aromatic carbonyl systems. The alpha or beta bond cleavage reactions from the S(1) excited state were both found to have relatively high barriers to reaction, and the S(1), T(1), and T(2) states are close in energy with the three S(1)((1)npi), T(1)((3)npi), and T(2)((3)pipi) surfaces intersecting at the same region. The calculations suggest that intersystem crossing (ISC) can occur very fast from the S(1) state to the nearby triplet states. This is consistent with results from ultrafast spectroscopy experiments that observe the S(1) state ISC occurs within about 1-2 ps to produce a triplet state for HPA and related pHP compounds. The alpha and beta bond cleavage reactions for the T(1) state of HPA are both predicted to have fairly high barriers and compete with one another. However, this is not completely consistent with experiments that observe the photodeprotection reactions (e.g. the beta bond cleavage) of HPA and some other pHP phototriggers in largely water containing solvents are predominant and occur very fast to release the leaving group. Comparison of the computational results with experimental results for HPA and related pHP compounds suggests that water molecules likely play an important part in changing the triplet state beta bond cleavage so that it becomes the predominant pathway and occurs very fast to give an efficient deprotection reaction. The results reported here provide new insight into the photophysics, reaction pathways, and photochemistry of the p-hydoxyphenacyl acetate and related pHP caged phototrigger compounds and also provide a benchmark for further and more sophisticated investigations in the future.

Acetates↗

PubMed2006

Defective expression of Galpha12 in the testes of azoospermia patients and in the spermatozoa with low motility.

Antibody to the Galpha12-subunit of guanine nucleotide regulatory proteins was used to determine whether the Galpha12 is present in adult human spermatogenic cells and to determine its role in dyszoospermia. Immunoblots from testes and spermatozoa demonstrated the presence of Galpha12 in the samples. Immunohistochemical analyses of testes found that Galpha12 was expressed in the cytoplasm of Leydig cells and was expressed in spermatids from the elongating Sb phase to mature sperm. Indirect immunofluorescence of human spermatozoa revealed the presence of Galpha12 in the neck region and the midpiece of the sperm. Galpha12 in spermatids and spermatozoa partially co-localized with F-actin and alpha-tubulin. Immunohistochemical analyses of tissues from three patients with non-obstructive azoospermia showed abnormal expression of Galpha12 in more than 45% of spermatids. Furthermore, Western blots and indirect immunofluorescence found defective expression of Galpha12 in low-motility spermatozoa with midpieces that were bent on themselves. Therefore, it suggests that Galpha12 plays a role in polarity and tail formation as spermatids mature. Furthermore, Galpha12 may be a candidate protein responsible for azoospermia caused by spermatogenic disturbance or midpiece deformities.

Actins↗

PubMed2006

Microvasculature change and placenta growth factor expression in the early stage of a rat remnant kidney model.

BACKGROUND/AIM: There is significant loss of microvasculature and impaired angiogenesis in rat remnant kidney (RK). Placenta growth factor (PlGF) is a potential angiogenic growth factor. In this study, we investigate the changes of microvasculature and expression of PlGF in the first 4 weeks of the early stage of a rat RK model. METHOD: RK was induced by right nephrectomy and ligation of two of the three branches of the left renal arteries (equivalent to 5/6 subtotal nephrectomy). Blood urea nitrogen (BUN), serum creatinine (Scr), and blood pressure (BP) were measured. Proliferation of endothelial cells was identified by double staining of two antibodies, anti-rat endothelial cell (RECA-1) and antiproliferating cell nuclear antigen (PCNA). RT-PCR and Western blot were used for PlGF analysis. RESULTS: BUN, Scr and BP remained stable after rising within the first week. An angiogenic response occurred in RKs, with an increase in the proliferation of peritubular and glomerular endothelial cells. Both PlGF protein and mRNA expression were significantly upregulated 2- to 3-fold in RK at week 1 and week 2, compared to the sham-operated group (p < 0.05). CONCLUSION: The expression of PlGF is upregulated and coincident with an early angiogenic response in rat RK, suggesting that PlGF may be involved in angiogenesis in progressive renal injury.

Animals↗

PubMed2006

Ultrafast time-resolved transient absorption and resonance raman spectroscopy study of the photodeprotection and rearrangement reactions of p-hydroxyphenacyl caged phosphates.

The kinetics and mechanism of the photodeprotection and rearrangement reactions for the pHP phototrigger compounds p-hydroxyphenacyl diethyl phosphate (HPDP) and diphenyl phosphate (HPPP) were studied using transient absorption (TA) and picosecond time-resolved resonance Raman (ps-TR(3)) spectroscopy. TA spectroscopy was employed to detect the dynamics of the triplet precursor decay as well as to investigate the influence of the solvent and leaving group on the triplet quenching process. Ps-TR(3) spectroscopy was used to directly monitor the formation dynamics for the photosolvolytic rearrangement product and its solvent and leaving group dependence. The TA and TR(3) spectroscopy experiments were also used to characterize the structural and electronic properties of the triplet precursor to the HPDP and HPPP deprotection reactions. The solvent effect observed in conjunction with the leaving group dependence of the triplet decay dynamics are consistent with a concerted solvent assisted triplet cleavage through a heterolytic mechanism for the HPDP and HPPP photodeprotection process. Correlation of the dynamics between the deprotection and rearrangement processes reveals there is a consecutive mechanism and the involvement of an intermediate between the two reaction steps. The reaction rate of the deprotection and rearrangement steps and the influence of the solvent and leaving group were determined and evaluated based on kinetic modeling of the dynamical data obtained experimentally for HPDP and HPPP in H(2)O/MeCN mixed solvents with varying water concentration in the solvent system. A solvation complex with a contact ion pair character was proposed to be the intermediate involved in the deprotection and rearrangement pathway. The results here combined with our previous study on the photophysical events occurring on the early picosecond time scale (Ma; et al. J. Am. Chem. Soc. 2005, 127, 1463-1472) provide a real time overall mechanistic description for the photodeprotection and rearrangement reactions of pHP caged phosphate phototrigger compounds.

Acetophenones↗

PubMed2006

Model-based compensation for quantitative 123I brain SPECT imaging.

Previously we have developed a model-based method that can accurately estimate downscatter contamination from high-energy photons in 123I imaging. In this work we combined the model-based method with iterative reconstruction-based compensations for other image-degrading factors such as attenuation, scatter, the collimator-detector response function (CDRF) and partial volume effects to form a comprehensive method for performing quantitative 123I SPECT image reconstruction. In the model-based downscatter estimation method, photon scatter inside the object was modelled using the effective source scatter estimation (ESSE) technique, including contributions from all the photon emissions. The CDRFs, including the penetration and scatter components due to the high-energy 123I photons, were estimated using Monte Carlo (MC) simulations of point sources in air at various distances from the face of the collimator. The downscatter contamination was then compensated for during the iterative reconstruction by adding the estimated results to the projection steps. The model-based downscatter compensation (MBDC) was evaluated using MC simulated and experimentally acquired projection data. From the MC simulation, we found about 39% of the total counts in the energy window of 123I were attributed to the downscatter contamination, which reduced image contrast and caused a 1.5% to 10% overestimation of activities in various brain structures. Model-based estimates of the downscatter contamination were in good agreement with the simulated data. Compensation using MBDC removed the contamination and improved the image contrast and quantitative accuracy to that of the images obtained from 159 keV photons. The errors in absolute quantitation were reduced to within +/-3.5%. The striatal specific binding potential calculated based on the activity ratio to the background was also improved after MBDC. The errors were reduced from -4.5% to -10.93% without compensation to -0.55% to 4.87% after compensation. The model-based method provided accurate downscatter estimation and, when combined with iterative reconstruction-based compensations, accurate quantitation was obtained with minimal loss of precision.

Brain↗

PubMed2006

Association of MEGSIN 2093C-2180T haplotype at the 3' untranslated region with disease severity and progression of IgA nephropathy.

BACKGROUND: MEGSIN is a gene predominantly expressed in the renal mesangium, and is upregulated in IgA nephropathy (IgAN). Our previous study has shown that the 2093C and 2180T alleles at the 3' untranslated region (3'UTR) of the gene are associated with susceptibility to IgAN, but the relationships of these genetic variants with the clinical manifestations and renal histological lesions of IgAN have not been examined previously. METHODS: 302 IgAN patients followed up for 52.8+/-22.5 months were investigated. Haplotypes at the 3'UTR were constructed using the 2093C/T and 2180C/T alleles. The genotype-phenotype relationship was studied by correlations of haplotypes and the clinical data and renal histopathological changes. RESULTS: The 2093C-2180T haplotype was present more often in patients with disease that progressed more rapidly (chi2((C-T/others)) = 8.429, P = 0.004), and was also correlated with hypertension (chi2((C-T/others)) = 6.459, P = 0.012), severe proteinuria (>or=2 g/d) (chi2((C-T/others)) = 6.332, P = 0.013), and Lee's class IV and V histological changes (chi2((C-T/others)) = 9.640, P = 0.008). CONCLUSION: In this Chinese population, the 2093C-2180T haplotype at the 3'UTR of MEGSIN gene is associated with more severe forms of IgAN, and more rapid disease progression. This provides further evidence for the involvement of genetic variations of MEGSIN in the pathogenesis of IgAN.

3' Untranslated Regions↗

PubMed2006

Human testis specific protein 1 expression in human spermatogenesis and involvement in the pathogenesis of male infertility.

Human testis specific protein 1 (TPX1) exists in the cytomembrane and cytoplasm of spermatogenic cells from pachytene spermatocytes to elongated spermtids, including pachytene spermatocytes, round spermtids and elongated spermtids. It is localized in the connecting piece, the flagellum, and the acrosome of mature human spermatozoa. The protein level and localization of TPX1 were altered in patients with spermatogenic arrest and in infertile men with oligoasthenoteratospermia syndrome.

Adult↗

PubMed2006

Involvement of ALF in human spermatogenesis and male infertility.

We conducted this study to explore functions of TF II Aalpha/beta-like factor (ALF) during human spermatogenesis, and the relationship of its expression levels with male infertility. The RT-PCR and Western blot analyses illustrated that ALF was highly expressed in adult testis. Immunohistochemistry and immunoflurescence showed that ALF is located in the spermatid nuclei and in the annulus of spermatozoa. Further, to reveal whether ALF is related to male infertility, we performed the same experiments in infertility patients. The changes in the expression levels of ALF in the male infertility samples lead us to believe that ALF may function in spermatogenesis, especially in spermiogenesis. We also detected the ALF DNA methylation level by real-time methylation-specific PCR (MSP) both in testes of adult, fetal and infertile patient. The differential expression level of ALF gene in different types of testes was regulated by DNA methylation. Our research identified ALF as a human spermatogenesis related gene, the abnormal expression of ALF might be the partial cause for human infertility.

Gene Expression Profiling↗

PubMed2006

[Impact of gender and age on in-hospital mortality after coronary artery bypass graft].

OBJECTIVE: The purpose of this study was to explore the association of gender and age on in-hospital mortality after coronary artery bypass graft (CABG) among the Chinese population. METHODS: A total of 2682 patients (male: 2316, female: 366) who underwent CABG surgery were retrospectively investigated between January 1st, 1997 and December 31st, 2001 for perioperative risk factors and in-hospital mortality rate after CABG. RESULTS: Preoperative comorbidity rate and postoperative complication rate were higher in women than that in men, although left ventricular ejection fraction was higher and the number of diseased vessels fewer in women than in men. The in-hospital mortality rate was three times higher in women than that in men (3.01% vs. 1.12%, P = 0.001), especially in the younger age group (2.6% vs. 0.5%, P = 0.001, risk-adjusted odds ratio 4.844, 95% CI: 1.549 - 15.142). In older patients, there was no notable difference in in-hospital mortality between the genders (3.7% for women vs. 2.4% for men, P = 0.383). CONCLUSIONS: Chinese woman, especially in younger age, had a higher in-hospital mortality rate post CABG than that in men, suggesting that younger female gender is an independent risk factor for in-hospital mortality after CABG. Future studies are warranted to clarify the underlying mechanisms.

Age Factors↗

PubMed2006

Characterization of uptake of the new PET imaging compound 18F-fluorobenzyl triphenyl phosphonium in dog myocardium.

UNLABELLED: 18F-Labeled p-fluorobenzyl triphenyl phosphonium cation (18F-FBnTP) is a member of a new class of positron-emitting lipophilic cations that may act as myocardial perfusion PET tracers. Here, we characterize the 18F-FBnTP uptake and retention kinetics, in vitro and in vivo, as well as the myocardial and whole-body biodistribution in healthy dogs, using PET. METHODS: Time-dependent accumulation and retention of 18F-FBnTP in myocytes in vitro was studied. Seven anesthetized, mongrel dogs underwent dynamic PET scans of the heart after intravenous administration of 126-240 MBq 18F-FBnTP. In 4 of the 7 dogs, at the completion of a 60-min dynamic scan, whole-body scans (4 bed positions, 5-min emission and 3-min transmission per bed) were acquired. Arterial blood samples were collected at 0, 5, 10, 20, 30, and 60 min after administration, plasma activity was counted, and high-performance liquid chromatographic analyses for metabolites were performed. The extent of defluorination was assessed by measuring 18F-FBnTP bone uptake in mice, compared with 18F-fluoride. RESULTS: The metabolite fraction comprised <5% of total activity in blood at 5 min and gradually increased to 25% at 30 min after injection. In vivo, 18F-FBnTP myocardial concentration reached a plateau level within a few minutes, which was retained throughout the scanning time. In contrast, activity in the blood pool and lungs cleared rapidly (half-life = 19.5 +/- 4.4 and 30.7 +/- 11.6 s, respectively). Liver uptake did not exceed the activity measured in the myocardium. At 60 min, the uptake ratios of left ventricular wall to blood, lung, and liver (mean of 7 dogs) were 16.6, 12.2, and 1.2, respectively. Summation of activity from 5 to 15 min and from 30 to 60 min after injection produced high-quality cardiac images of similar contrast. Circumferential sampling and a polar plot revealed a uniform distribution, near unitary value, throughout the entire myocardium. The mean coefficient of variance, on 30- to 60-min images along the septum-to-anterior wall and the apex-to-base axes was 7.58% +/- 1.04% and 6.11% +/- 0.89% (mean +/- SD; n = 7), respectively, and on 5- to 15-min images was 7.25% +/- 1.43% and 6.12% +/- 1.88%, respectively. 18F-FBnTP whole-body distribution was highly organ specific with the kidney cortex being the major target organ, followed by the heart and the liver. CONCLUSION: 18F-FBnTP is a promising new radionuclide for cardiac imaging using PET with rapid kinetics, uniform myocardial distribution, and favorable organ biodistribution.

Animals↗

PubMed2006

Lung dosimetry for radioiodine treatment planning in the case of diffuse lung metastases.

UNLABELLED: The lungs are the most frequent sites of distant metastasis in differentiated thyroid carcinoma. Radioiodine treatment planning for these patients is usually performed following the Benua-Leeper method, which constrains the administered activity to 2.96 GBq (80 mCi) whole-body retention at 48 h after administration to prevent lung toxicity in the presence of iodine-avid lung metastases. This limit was derived from clinical experience, and a dosimetric analysis of lung and tumor absorbed dose would be useful to understand the implications of this limit on toxicity and tumor control. Because of highly nonuniform lung density and composition as well as the nonuniform activity distribution when the lungs contain tumor nodules, Monte Carlo dosimetry is required to estimate tumor and normal lung absorbed dose. Reassessment of this toxicity limit is also appropriate in light of the contemporary use of recombinant thyrotropin (thyroid-stimulating hormone) (rTSH) to prepare patients for radioiodine therapy. In this work we demonstrated the use of MCNP, a Monte Carlo electron and photon transport code, in a 3-dimensional (3D) imaging-based absorbed dose calculation for tumor and normal lungs. METHODS: A pediatric thyroid cancer patient with diffuse lung metastases was administered 37 MBq of (131)I after preparation with rTSH. SPECT/CT scans were performed over the chest at 27, 74, and 147 h after tracer administration. The time-activity curve for (131)I in the lungs was derived from the whole-body planar imaging and compared with that obtained from the quantitative SPECT methods. Reconstructed and coregistered SPECT/CT images were converted into 3D density and activity probability maps suitable for MCNP4b input. Absorbed dose maps were calculated using electron and photon transport in MCNP4b. Administered activity was estimated on the basis of the maximum tolerated dose (MTD) of 27.25 Gy to the normal lungs. Computational efficiency of the MCNP4b code was studied with a simple segmentation approach. In addition, the Benua-Leeper method was used to estimate the recommended administered activity. The standard dosing plan was modified to account for the weight of this pediatric patient, where the 2.96-GBq (80 mCi) whole-body retention was scaled to 2.44 GBq (66 mCi) to give the same dose rate of 43.6 rad/h in the lungs at 48 h. RESULTS: Using the MCNP4b code, both the spatial dose distribution and a dose-volume histogram were obtained for the lungs. An administered activity of 1.72 GBq (46.4 mCi) delivered the putative MTD of 27.25 Gy to the lungs with a tumor absorbed dose of 63.7 Gy. Directly applying the Benua-Leeper method, an administered activity of 3.89 GBq (105.0 mCi) was obtained, resulting in tumor and lung absorbed doses of 144.2 and 61.6 Gy, respectively, when the MCNP-based dosimetry was applied. The voxel-by-voxel calculation time of 4,642.3 h for photon transport was reduced to 16.8 h when the activity maps were segmented into 20 regions. CONCLUSION: MCNP4b-based, patient-specific 3D dosimetry is feasible and important in the dosimetry of thyroid cancer patients with avid lung metastases that exhibit prolonged retention in the lungs.

Algorithms↗

PubMed2005

A Monte Carlo and physical phantom evaluation of quantitative In-111 SPECT.

Accurate estimation of the 3D in vivo activity distribution is important for dose estimation in targeted radionuclide therapy (TRT). Although SPECT can potentially provide such estimates, SPECT without compensation for image degrading factors is not quantitatively accurate. In this work, we evaluated quantitative SPECT (QSPECT) reconstruction methods that include compensation for various physical effects. Experimental projection data were obtained using a GE VH/Hawkeye system and an RSD torso phantom. Known activities of In-111 chloride were placed in the lungs, liver, heart, background and two spherical compartments with inner diameters of 22 mm and 34 mm. The 3D NCAT phantom with organ activities based on clinically derived In-111 ibritumomab tiuxetan data was used for the Monte Carlo (MC) simulation studies. Low-noise projection data were simulated using previously validated MC simulation methods. Fifty sets of noisy projections with realistic count levels were generated. Reconstructions were performed using the OS-EM algorithm with various combinations of attenuation (A), scatter (S), geometric response (G), collimator-detector response (D) and partial volume compensation (PVC). The QSPECT images from the various combinations of compensations were evaluated in terms of the accuracy and precision of the estimates of the total activity in each organ. For experimental data, the errors in organ activities for ADS and PVC compensation were less than 6.5% except the smaller sphere (-11.9%). For the noisy simulated data, the errors in organ activity for ADS compensation were less than 5.5% except the lungs (20.9%) and blood vessels (15.2%). Errors for other combinations of compensations were significantly (A, AS) or somewhat (AGS) larger. With added PVC, the error in the organ activities improved slightly except for the lungs (11.5%) and blood vessels (3.6%) where the improvement was more substantial. The standard deviation/mean ratios were all less than 1.5%. We conclude that QSPECT methods with appropriate compensations provided accurate In-111 organ activity estimates. For the collimator used, AGS was almost as good as ADS and may be preferable due to the reduced reconstruction time. PVC was important for small structures such as tumours or for organs in close proximity to regions with high activity. The improved quantitative accuracy from QSPECT methods has the potential for improving organ dose estimations in TRT.

Algorithms↗

PubMed2005

Comparison of the dehalogenation of dihalomethanes (CH2XI, where X = Cl, Br, I) following ultraviolet photolysis in aqueous and NaCl saltwater environments.

The ultraviolet photolysis of low concentrations of CH(2)XI (X = Cl, Br, I) were investigated in water and saltwater solutions by photochemistry and picosecond time-resolved resonance Raman spectroscopy. Photolysis in both kinds of solutions formed mostly CH(2)(OH)(2) and HI and HX products. However, photolysis of the CH(2)XI molecules in saltwater resulted in production of some CH(2)XCl products not observed in aqueous solutions without salt present. The appearance of these new products in saltwater solutions is accompanied by a decrease in the amount of CH(2)(OH)(2), HI, and HX products compared to photolysis in aqueous solutions without salt present. The possible implications for photolysis of CH(2)XI and other polyhalomethanes in seawater and other salt aqueous environments compared to nonsaltwater solvated environments is briefly discussed.

Journal Article↗

PubMed2005

Water-catalyzed O-H insertion/HI elimination reactions of isodihalomethanes (CH2X-I, where X = Cl, Br, I) with water and the dehalogenation of dihalomethanes in water-solvated environments.

A combined experimental and theoretical investigation of the ultraviolet photolysis of CH2XI (where X = Cl, Br, I) dihalomethanes in water is presented. Ultraviolet photolysis of low concentrations of CH2XI (where X = Cl, Br, I) in water appears to lead to almost complete conversion into CH2(OH)2 and HX and HI products. Picosecond time-resolved resonance Raman (ps-TR3) spectroscopy experiments revealed that noticeable amounts of CH2X-I isodihalomethane intermediates were formed within several picoseconds after photolysis of the CH2XI parent compound in mixed aqueous solutions. The ps-TR3 experiments in mixed aqueous solutions revealed that the decay of the CH2X-I isodihalomethane intermediates become significantly shorter as the water concentration increases, indicating that the CH2X-I intermediates may be reacting with water. Ab initio calculations found that the CH2X-I intermediates are able to react relatively easily with water via a water-catalyzed O-H insertion/HI elimination reaction to produce CH2X(OH) and HI products, with the barrier for these reactions increasing as X changes from Cl to Br to I. The ab initio calculations also found that the CH2X(OH) product can undergo a water-catalyzed HX elimination reaction to make H2C=O and HX products, with the barrier to reaction decreasing as X changes from Cl to Br to I. The preceding two water-catalyzed reactions produce the HI and HX leaving groups observed experimentally, and the H2C=O product further reacts with water to make the other CH2(OH)2 product observed in the photochemistry experiments. This suggests that that the CH2X-I intermediates react with water to form the CH2(OH)2 and HI and HX products observed in the photochemistry experiments. Ultraviolet photolysis of CH2XI (where X = Cl, Br, I) at low concentrations in water-solvated environments appears to lead to efficient dehalogenation and release of two strong acid leaving groups. We very briefly discuss the potential influence of this photochemistry in water on the decomposition of polyhalomethanes and halomethanols in aqueous environments.

Journal Article↗