Biomedical subjects

L Wang

Publications and source records attributed to L Wang.

At least 145 records · Page 8Linked to original sources

PubMed2005

Estrogen, but not testosterone, down-regulates cytokine production in nicotine-induced murine macrophage.

We have investigated the effects of 17beta-estradiol (E2) and testosterone (Te) on the production of proinflammatory factors by nicotine-induced murine macrophage (Ana-1). Ana-1 pretreated with or without E2/Te was challenged with different doses of nicotine at various time points. TNF-alpha, IL-1beta IFN-gamma, and IL-8 in the supernatant of Ana-1 were detected using radioimmunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA). The presence of estrogen and androgen receptors in Ana-1 was detected by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting. E2 could obviously suppress the expression of TNF-alpha and IL-1beta whereas Te could not. There were no obvious changes in the levels of either IL-8 or IFN-gamma in Ana-1 stimulated with nicotine or sex hormones (p>0.05). The antagonist tamoxifen of E2 abolished the effects of E2 on TNF-alpha and IL-1beta whereas the antagonist cyproterone of Te did not alter the effects of Te on Ana-1. Furthermore, RT-PCR and Western blotting showed that both the estrogen receptors (ER-alpha and ER-beta existed in Ana-1; however, androgen receptor (AR) was not detectable. Our data suggested that E2 could regulate the immunoreaction in the nicotine-induced inflammatory process possibly through classic intercellular ER, whereas Te had no significant effect in this process.

Animals↗

PubMed2005

Testosterone induced Ca2+ influx in bone marrow-derived macrophages via surface binding sites.

The biological activity of testosterone is thought to occur predominantly through binding to the androgen receptor (AR), a member of the nuclear receptor superfamily that functions as a ligand-activated transcription factor. Here, we found that testosterone could induce a rapid rise in the intracellular free Ca2+ concentration ([Ca2+]i) of Fura-2 loaded bone marrow-derived macrophages (BMMs), which was found to be predominantly due to the influx of extracellular Ca2+ through Ni2+-blockable Ca2+ channels in the plasma membrane. However, these effects of testosterone could not be associated with the classical intracellular AR in BMMs, since AR was not detectable using different experimental techniques. Instead, it was found that testosterone could bind to the surface of BMMs by the use of an impermeable testosterone-BSA-FITC, and Ca2+ influx could also be induced by testosterone conjugated to BSA. Our data indicated a novel mode of direct action of testosterone on BMMs, which was not mediated through the classical AR response, but through the binding sites of testosterone on cell surfaces.

Androgen Antagonists↗

PubMed2005

Demonstration of different modes of cell death upon herpes simplex virus 1 infection in different types of oral cells.

The effects of Herpes simplex virus 1 (HSV-1) infection on five different types of oral cancerous cells (neck metastasis of gingival carcinoma (GNM) cells and tongue squamous cells of carcinoma (TSCCa) and non-cancerous cells (buccal mucosal fibroblasts (BF), gingival fibroblasts (GF), oral submucosal fibrosis cells (OSF)) and one type of non-oral cancerous cells (KB cells) were investigated. In HSV-1-infected cells the cell viability, CPE, viral antigens accumulation, caspase-3 activity, annexin V binding and DNA fragmentation were estimated. Three different forms or pathways of cell death were considered: apoptosis (the presence or rise of caspase-3 activity, DNA fragmentation and annexin V binding), slow cell death (the presence or rise of DNA fragmentation, the absence or decline of caspase-3 activity and annexin V binding), and necrosis (the absence of decline of caspase-3 activity, DNA fragmentation and annexin V binding). The viability of all cell types, except for KB cells, was reduced by the infection. CPE and viral antigens data demonstrated that all six types of cells could be infected with HSV-1. Upon HSV-1 infection there occurred (i) a classical apoptosis in GF cells, (ii) apoptosis in the early phase of infection and necrosis in the late phase of infection in GNM and TSCCa cells, (iii) slow cell death followed by necrosis in BF and OSF cells (however, these cells showed a different type of CPE), (iv) a classical slow cell death in KB cells. It is hypothesized that HSV-1 infection has a potential to induce several distinct pathways leading to cell death or several forms of cell death. Moreover, more than one pathway may be involved in the death of particular cell type. As HSV-1 was demonstrated to infect different oral and non-oral cells and cause different pathways or forms of cell death, the safety of using HSV-1 as a vector for gene therapy should be re-considered.

Annexin A5↗

PubMed2005

Performance of an intensive pond system treating municipal wastewater in a cold region.

A full-scale intensive pond system (IPS) with shorter HRT was designed, constructed and operated in Jining, Inner-Mongolia for the treatment of municipal wastewater, which is a mixed domestic and industrial wastewater characterized by quite high SS and lower BOD5/COD ratio values or lower biodegradability. Therefore, the pond system was designed as an integrated intensive pond system (IIPS) consisting of settling/anaerobic pond (SAP), intensified anaerobic pond (IAP), facultative pond (FP), and polishing ponds (PPs). In order to improve the performance of the IPS, some intensified measures were made, including inlet and outlet even-distribution systems of each unit pond, package of biofilm carrier in IAP for the increase and even distribution of biomass; overflow waterfalls on the dikes between unit ponds for the increase of DO in pond water, gravel filtration dike (or dam) for removing suspended solids including algae, which have improved the performance of the IPS remarkably in terms of removal of main pollutants, such as SS, COD, BOD5, TN, NH3-N, TP and total bacteria. The final effluent from the IPS in warm seasons from May to October were SS 7.2-10.8 mg/L, BOD5 8.5-19.6 mg/L, COD 44.1 - 76.5 mg/L, and NH3-N 1.5-10.2 mg/L, which well meet Chinese national discharge standard (2nd class) of secondary municipal wastewater treatment plants, i.e. BOD5 and SS 30 mg/L respectively, COD 100 mg/L, and NH3-N 25 mg/L.

Ammonia↗

PubMed2005

Performance of a combined eco-system of ponds and constructed wetlands for wastewater reclamation and reuse.

An on-site study on the operational performance of a combined eco-system of ponds and SF constructed wetland for municipal wastewater treatment and reclamation/reuse in Donging City, Shandong, China was carried out from January 2001 through October 2003. The removal efficiencies for various main parameters were: TSS 84.8 +/- 7.3%, BOD5 87.2 +/- 5.3%, CODCr 70.2 +/- 18.6%, TP 52.3 +/- 23.1%, and NH(3)-N 54.8 +/- 23.9% with effluent concentration of TSS 9.12 +/- 5.12 mg/l, BOD5 6.44 +/- 4.58 mg/l, CODCr, 42.8 +/- 6.7 mg/l, TP 0.94 +/- 0.27 mg/l and NH(3)-N 7.95 +/- 2.36 mg/l. In addition, the removal efficiencies for faecal coliforms and total bacteria were > 99.97% and > 99.998% respectively, which well meet Chinese National standards for effluent quality of municipal wastewater treatment plants. The composition of TSS was closely related to CODCr and BOD5 variations, and nitrification-denitrification is the major mechanism of nitrogen removal both in ponds and in wetlands. In addition, sedimentation also played an important role in the removal of TSS, nitrogen, phosphorus and BOD5. The removal efficiencies of various parameters, the number of species and biomass of biological community in the system increased gradually with the ecological maturation.

Ammonia↗

PubMed2005

Performance improvement of hybrid membrane bioreactor with PAC addition for water reuse.

A study was carried out on a hybrid (AS-SBF) membrane bioreactor (HMBR) for the municipal wastewater reclamation and reuse at Chengfengzhuang WWTP in Daqing City, Heilongjiang Province. It was found that the effects of DO and water temperature on performance of the HMBR was significant. Under the conditions of water temperature in range of 10-14 degrees C, pH of 6.6- 7.0, DO of 4-6 mg/l and HRT of 7 h, the HMBR exhibited removal efficiencies for CODcr, BOD5, NH3-N and TN of 96.7%, 98.9%, 93.7% and 60.5% respectively. The turbidity of effluent from HMBR was below 1 NTU. The effluent of HMBR meets the standard of wastewater reclamation for oil exploitation. PAC was added into the bioreactor at the second operating stage, in order to further research parameters variation. The flux was improved by 53.2%, compared to the membrane without PAC-addition, due to formation of a PAC pre-coat layer on the membrane surface, with lots of advantages such as larger granules, higher porosity, non-compressibility, higher filterability and easy removal, compared with pure biomass layer. In addition, the performance of HMBR was further improved, due to adsorption and degradation of SMPs, the average removal of CODcr and TN was further improved by 5.1% and 13.5% respectively. Biomass in the HMBR was quantitatively measured, of which the biofilm played a major role in pollutants removal.

Ammonia↗

PubMed2005

Simultaneous nitrification and de-nitrification in MBR.

Experiments have been carried out to get an understanding of the effect of DO, C/N ratio and pH on the performance of a bench scale membrane bioreactor (MBR) in simultaneous nitrification and denitrification. It was found that under the conditions of MLSS in the range of 8000-9000 mg/L and temperature of water in the MBR of 24 degrees C, influent COD and NH3-N in the range of 523-700 mg/L and 17.24-24 mg/L respectively, the removals of COD, NH3-N and TN were 98%, 99% and 60%; 96.5%, 0,98% and 75%; 96%, 95% and 92%; 90%,70% and 60% respectively at DO of 6, 3, 1 and 0.5 mg/L. It was also found that the changes in C/N ratio and pH in a certain range have a slight effect on COD removal but have significant influence on the removal of NH3-N and TN. The results showed that only under the conditions that each ecological factor was maintained relatively steadily, simultaneous nitrification and de-nitrification proceeded smoothly. It was found that when C/N ratio was 30, the influent pH 7.2, the temperature of water in MBR 24 degrees C and DO 1 mg/L, as optimum conditions, the removals of COD, NH3-N and TN were 96%, 95% and 92% respectively. In addition, mechanism research on simultaneous nitrification and de-nitrification in MBR has been conducted as well.

Ammonia↗

PubMed2004

Dosimetric evaluation of MRI-based treatment planning for prostate cancer.

The purpose of this study is to evaluate the dosimetric accuracy of MRI-based treatment planning for prostate cancer using a commercial radiotherapy treatment planning system. Three-dimensional conformal plans for 15 prostate patients were generated using the AcQPlan system. For each patient, dose distributions were calculated using patient CT data with and without heterogeneity correction, and using patient MRI data without heterogeneity correction. MR images were post-processed using the gradient distortion correction (GDC) software. The distortion corrected MR images were fused to the corresponding CT for each patient for target and structure delineation. The femoral heads were delineated based on CT. Other anatomic structures relevant to the treatment (i.e., prostate, seminal vesicles, lymph notes, rectum and bladder) were delineated based on MRI. The external contours were drawn separately on CT and MRI. The same internal contours were used in the dose calculation using CT- and MRI-based geometries by directly transferring them between MRI and CT as needed. Treatment plans were evaluated based on maximum dose, isodose distributions and dose-volume histograms. The results confirm previous investigations that there is no clinically significant dose difference between CT-based prostate plans with and without heterogeneity correction. The difference in the target dose between CT- and MRI-based plans using homogeneous geometry was within 2.5%. Our results suggest that MRI-based treatment planning is suitable for radiotherapy of prostate cancer.

Humans↗

PubMed2004

Aspergillus fumigatus CY018, an endophytic fungus in Cynodon dactylon as a versatile producer of new and bioactive metabolites.

Aspergillus fumigatus CY018 was recognized as an endophytic fungus for the first time in the leaf of Cynodon dactylon. By bioassay-guided fractionation, the EtOAc extract of a solid-matrix steady culture of this fungus afforded two new metabolites, named asperfumoid (1) and asperfumin (2), together with six known bioactive compounds including monomethylsulochrin, fumigaclavine C, fumitremorgin C, physcion, helvolic acid and 5alpha,8alpha-epidioxy-ergosta-6,22-diene-3beta-ol as well as other four known compounds ergosta-4,22-diene-3beta-ol, ergosterol, cyclo(Ala-Leu) and cyclo(Ala-Ile). Through detailed spectroscopic analyses including HRESI-MS, homo- and hetero-nuclear correlation NMR experiments (HMQC, COSY, NOESY and HMBC), the structures of asperfumoid and asperfumin were established to be spiro-(3-hydroxyl-2,6-dimethoxyl-2,5-diene-4-cyclohexone-(1,3')-5'-methoxyl-7'-methyl-(1'H, 2'H, 4'H)-quinoline-2',4'-dione) and 5-hydroxyl-2-(6-hydroxyl-2-methoxyl-4-methylbenzoyl)-3,6-dimethoxyl-benzoic methyl ester, respectively. All of the 12 isolates were subjected to in vitro bioactive assays against three human pathogenic fungi Candida albicans, Tricophyton rubrum and Aspergillus niger. As a result, asperfumoid, fumigaclavine C, fumitremorgin C, physcion and helvolic acid were shown to inhibit C. albicans with MICs of 75.0, 31.5, 62.5, 125.0 and 31.5 microg/mL, respectively.

Antifungal Agents↗

PubMed2004

1alpha,25(OH)2D3 regulation of integrin expression is substrate dependent.

Osteoblasts are attachment-dependent cells that interact with their surface through integrin-mediated mechanisms. Their differentiation is regulated by 1,25-dihydroxyvitamin D3 [1alpha,25(OH)(2)D(3)] and is affected by substrate chemistry and microtopography, suggesting that 1alpha,25(OH)(2)D(3) may regulate integrin expression in a surface-specific manner. To test this hypothesis, osteoblast-like human MG63 cells were grown on tissue culture plastic and on grit-blasted and acid-etched titanium disks with a complex microtopography to induce osteoblast differentiation. Expression of alpha(2), alpha(5), alpha(v), beta(1), and beta(3) integrins were quantified by real-time polymerase chain reaction (PCR) as a function of time in culture and treatment with 1alpha,25(OH)(2)D(3). Results were correlated with expression of osteocalcin, a marker of a differentiated osteoblast. Osteocalcin mRNA increased with time and 1alpha,25(OH)(2)D(3) treatment and these changes were greater in cultures on the titanium disks. Integrin expression varied with time in culture and this was also surface dependent. At each time point, beta(1) and alpha(2) mRNAs were greater on titanium than on plastic, whereas alpha(5) expression was reduced and alpha(v),beta(3) expression was unaffected. 1alpha,25(OH)(2)D(3) increased beta(1) mRNA on both surfaces at all time points, but it increased alpha(2) expression only in 8-d cultures. 1alpha,25(OH)(2)D(3) caused reduced alpha(5) expression only in cultures grown on plastic for 8 d, and had no effect on either alpha(v) or beta(3) expression regardless of surface. These results show that integrin expression in human osteoblast-like cells is differentially modulated by 1alpha,25(OH)(2)D(3) in a time-dependent manner that is sensitive to the surface on which the cells are grown.

Cell Culture Techniques↗

PubMed2004

Mechanism of electron multipacting with a long-bunch proton beam.

The energy gain and motion of electrons can quantitatively describe the mechanism of electron multipacting in a long-bunched proton machine. Strong multipacting usually happens around the bunches' tails due to the high energy of electrons when they hit the chamber surface. We investigated several important parameters of electron multipacting, proving that it is sensitive to the beam's intensity, the shape of its longitudinal profile, its transverse size, the secondary emission yield, and the energy at peak secondary emission yield. Our analyses, simulations, and experiments are all in agreement.

Journal Article↗

PubMed2004

Microrough implant surface topographies increase osteogenesis by reducing osteoclast formation and activity.

Titanium implant surfaces with rough microtopographies exhibit increased pullout strength in vivo suggesting increased bone-to-implant contact. This is supported by in vitro studies showing that as surface microroughness increases, osteoblast proliferation decreases whereas differentiation increases. Differentiation is further enhanced on microrough surfaces by factors stimulating osteogenesis including 1alpha,25(OH)2D3. Levels of PGE2 and TGF-beta1 are increased in cultures grown on rough microtopographies; this surface effect is enhanced synergistically by 1alpha,25(OH)2D3-treatment. PGE2 and TGF-beta1 regulate osteoclasts as well as osteoblasts, suggesting that surface microtopography may modulate release of other factors from osteoblasts that regulate osteoclasts. To test this hypothesis, we examined the effects of substrate microarchitecture on production of osteoprotegerin (OPG) and receptor activator of nuclear factor kappa B ligand (RANKL), which have been identified as a key regulatory system of bone remodeling. We also examined the production of 1alpha,25(OH)2D3, which regulates osteoblast differentiation and osteoclastogenesis. MG63 osteoblast-like cells were grown on either tissue culture plastic or titanium disks of different surface microtopographies: PT (Ra < 0.2 microm), SLA (Ra = 4 microm), and TPS (Ra = 5 microm). At confluence, cultures were treated for 24 h with 0, 10(-8) M or 10(-7) M 1alpha,25(OH)2D3. RANKL and OPG were determined at the transcriptional level by RT-PCR and real time PCR and soluble RANKL, OPG and 1alpha,25(OH)2D3 in the conditioned media were measured using immunoassay kits. Cell number was reduced on SLA and TPS surfaces and 1alpha,25(OH)2D3 caused further decreases. OPG mRNA levels increased on rougher surfaces and 1alpha,25(OH)2D3 treatment caused a further synergistic increase. While the cells expressed RANKL mRNA, levels were low and independent of surface microtopography. OPG protein was greater when cells were grown on SLA and TPS. 1alpha,25(OH)2D3 increased OPG by 50% on the smooth Ti surface but on SLA, 10(-8) M 1alpha,25(OH)2D3 caused a 100% increase and 10(-7) M 1alpha,25(OH)2D3 increased OPG by 200%. On TPS 10(-7) M 1alpha,25(OH)2D3 increased OPG 350%. Soluble RANKL was not detected in the conditioned media of any of the cultures. 1alpha,25(OH)2D3 was produced endogenously and levels were positively correlated with surface roughness. Thus, on surfaces with rough microtopographies, osteoblasts secrete factors that enhance osteoblast differentiation while decreasing osteoclast formation and activity.

Animals↗

PubMed2004

Mechanism responsible for initiating carbon nanotube vacuum breakdown.

We report a physical mechanism responsible for initiating a vacuum breakdown process of a single carbon nanotube (CNT) during field emission. A quasidynamic method has been developed to simulate the breakdown process and calculate the critical field, critical emission current density and critical temperature beyond which thermal runaway occurs before the CNT temperature reaches its melting point. This model is in good agreement with experiments carried out with a single CNT on a silicon microtip.

Journal Article↗

PubMed2004

Iron wheels on silicon: wetting behavior and electronic structure of adsorbed organostannoxane clusters.

Atomic force microscopy and synchrotron radiation (SR) spectroscopy have been used to study the wetting behavior and electronic structure of thin films of a novel organometallic cluster--[BuSn(O)OC(O)Fc]6 ("Fc" = ferrocenyl)--on silicon substrates. This cluster comprises six ferrocene units connected to a stannoxane central core--"an iron wheel on a tin drum" (V. Chandrasekhar; et al. Angew. Chem., Int. Ed. 2000, 39, 1833). Thin films spin-cast onto native oxide-terminated silicon readily dewet the substrate. We have utilized advanced image analysis techniques based on Minkowski functionals to provide a detailed quantitative analysis of the morphology of the stannoxane overlayers. This analysis shows that the dewetting patterns are rather far removed from those expected to arise from a simple Poisson distribution of centers, and we discuss the implications of this finding in terms of nucleated and spinodal dewetting. Variations in both the surface roughness and the in-plane correlation length have been followed as a function of annealing time to probe the surface dewetting dynamics. SR valence band photoemission illustrates that the highest occupied molecular orbital (HOMO) of the cluster is found 2 eV below the Fermi level. Fe 2p --> 3d and Sn 3d --> 5p resonant photoemission spectroscopy have been used to enhance the cross sections of the partial density of states associated with the Fe and Sn atoms. Sn atoms make a large contribution to the HOMO of the cluster, whereas the Fe atoms are associated with an electronic environment seemingly very similar to that in the "parent" ferrocene molecule.

Journal Article↗

PubMed2004

Physical mapping of a rice lesion mimic gene, Spl1 , to a 70-kb segment of rice chromosome 12.

The rice lesion mimic mutant spotted leaf 1 ( spl1) was first identified in the rice ( Oryza sativa) cultivar Asahi in 1965. This mutant displayed spontaneous disease-like lesions in the absence of any pathogen, and was found to confer resistance to multiple isolates of rice blast. We employed a map-based cloning strategy to localize the Spl1 gene. A total of ten cleaved amplified polymorphic sequence (CAPS) markers linked to the Spl1 gene were identified and mapped to an 8.5-cM region on chromosome 12. A high-resolution genetic map was developed using these ten CAPS markers and a segregating population consisting of 3202 individuals. A BAC contig containing four BAC clones was constructed, and Spl1 was localized to a 423-kb region. Seven spl1 mutants were obtained from the IR64 deletion mutant collection, and molecular analysis using these mutants delimited the Spl1 gene to a 70-kb interval, covered by two BAC clones. These results provide the basis for cloning this gene, which is involved in cell death and disease resistance in rice.

Genetic Markers↗

PubMed2004

Supernumerary tricentric derivative chromosome 15 in two boys with intractable epilepsy: another mechanism for partial hexasomy.

Rearrangements of chromosome 15q, including isodicentric 15 chromosomes and interstitial duplications and triplications, have been previously reported in association with autism spectrum disorders. We have identified two boys with exceptionally large der(15) chromosomes that are tricentric and contain four copies of the proximal long arm, including the Prader Willi/Angelman critical region, and leading to hexasomy of the involved segment. Biallelic inheritance of maternal alleles and methylation analysis indicate that the markers are maternally derived. Clinical assessment of the boys indicated severe cognitive impairment associated with marked delays in gross and fine motor skills. Social and language deficits were present in both, although the severity of the mental retardation precluded diagnosis of autism (both were considered to have pervasive developmental disorder-not otherwise specified). Neurologic manifestations included infantile spasms evolving into intractable early-onset myoclonic seizures, psychomotor regression, and profound diffuse hypotonia. These patients represent the most severe end of the spectrum of phenotypes associated with segmental aneuploidy for chromosome 15q11-q13.

Abnormalities, Multiple↗

PubMed2004

Monitor unit calculation for Monte Carlo treatment planning.

In this work, we investigate a formalism for monitor unit (MU) calculation in Monte Carlo based treatment planning. By relating MU to dose measured under reference calibration conditions (central axis, depth of dose maximum in water, 10 cm x 10 cm field defined at 100 cm source-to-surface distance) our formalism determines the MU required for a treatment plan based on the prescription dose and Monte Carlo calculated dose distribution. Detailed descriptions and formulae are given for various clinical situations including conventional treatments and advanced techniques such as intensity-modulated radiotherapy (IMRT) and modulated electron radiotherapy (MERT). Analysis is made of the effects of source modelling, beam modifier simulation and patient dose calculation accuracy, all of which are important factors for absolute dose calculations using Monte Carlo simulations. We have tested the formalism through phantom measurements and the predicted MU values were consistent with measured values to within 2%. The formalism has been used for MU calculation and plan comparison for advanced treatment techniques such as MERT, extracranial stereotactic IMRT, MRI-based treatment planning and intensity-modulated laser-proton therapy studies. It is also used for absolute dose calculations using Monte Carlo simulations for treatment verification, which has become part of our comprehensive IMRT quality assurance programme.

Dose-Response Relationship, Radiation↗

PubMed2004

Stereotactic IMRT for prostate cancer: dosimetric impact of multileaf collimator leaf width in the treatment of prostate cancer with IMRT.

The focus of this work is the dosimetric impact of multileaf collimator (MLC) leaf width on the treatment of prostate cancer with intensity-modulated radiation therapy (IMRT). Ten patients with prostate cancer were planned for IMRT delivery using two different MLC leaf widths--4mm and 10mm--representing the Radionics micro-multileaf collimator (mMLC) and Siemens MLC, respectively. Treatment planning was performed on the XKnifeRT2 treatment-planning system (Radionics, Burlington, MA). All beams and optimization parameters were identical for the mMLC and MLC plans. All the plans were normalized to ensure that 95% of the planning target volume (PTV) received 100% of the prescribed dose. The differences in dose distribution between the two different plans were assessed by dose-volume histogram (DVH) analysis of the target and critical organs. We specifically compared the volume of rectum receiving 40 Gy (V40), 50 Gy (V50), 60 Gy (V60), the dose received by 17% and 35% of rectum (D17 and D35), and the maximum dose to 1 cm3 of the rectum for a prescription dose of 74 Gy. For the urinary bladder, the dose received by 25% of bladder (D25), V40, and the maximum dose to 1 cm3 of the organ were recorded. For PTV we compared the maximum dose to the "hottest" 1 cm3 (Dmax1 cm3) and the dose to 99% of the PTV (D99). The dose inhomogeneity in the target, defined as the ratio of the difference in Dmax1 cm3 and D99 to the prescribed dose, was also compared between the two plans. In all cases studied, significant reductions in the volume of rectum receiving doses less than 65 Gy were seen using the mMLC. The average decrease in the volume of the rectum receiving 40 Gy, 50 Gy, and 60 Gy using the mMLC plans was 40.2%, 33.4%, and 17.7%, respectively, with p < 0.0001 for V40 and V50 and p < 0.012 for V60. The mean dose reductions for D17 and D35 for the rectum using the mMLC were 20.4% (p < 0.0001) and 18.3% (p < 0.0002), respectively. There were consistent reductions in all dose indices studied for the bladder. The target dose inhomogeneity was improved in the mMLC plans by an average of 29%. In the high-dose range, there was no significant difference in the dose deposited in the "hottest" 1 cm3 of the rectum between the two plans for all cases (p > 0.78). In conclusion, the use of the mMLC for IMRT of the prostate resulted in significant improvement in the DVH parameters of the prostate and critical organs, which may improve the therapeutic ratio.

Equipment Design↗