Biomedical subjects

Jun Duan

Publications and source records attributed to Jun Duan.

At least 19 recordsLinked to original sources

PubMed2006

[Efficacy and safety of extended-release niacin alone or with atorvastatin for lipid profile modification].

OBJECTIVE: To evaluate the efficacy and safety of extended-release niacin (niacin ER) either alone or in combination with atorvastatin for the lipid profile modification in the patients with coronary heart disease (CHD) and its equivalents. METHODS: One hundred and ten patients with CHD and its equivalents with serum total cholesterol (TC) > or = 3.5 mmol/L were randomly assigned into three treatment groups: (1) atorvastatin group (n = 38), receiving atorvastatin 10 mg/d for 8 weeks; (2) niacin ER group (n = 38), given niacin ER 500 mg/d for 4 weeks and then 1000 mg/d for 4 weeks; (3) combination treatment group (n = 34), treated with atorvastatin (10 mg/d) plus niacin ER, with the dose initiating from 500 mg/d, and increasing to 1000 mg/d after 4 weeks, for 8 weeks. The serums lipid profiles and adverse effects were assessed in all the patients before treatment, and 4 and 8 weeks after treatment. RESULTS: (1) After 8 weeks of treatment, the serum level of triglyceride (TG) and high-density lipoprotein cholesterol (HDL-C) were reduced by 30% and 16% respectively in the niacin ER group compared with the baseline values (both P < 0.05). After 8 weeks, the TC, low-density lipoprotein cholesterol (LDL-C), and TG in the atorvastatin group decreased by 19%, 26%, and 17% respectively compared with the baseline values (all P < 0.05). Combination treatment decreased the TC, LDL-C, and TG levels by 28%, 38%, and 39% respectively, and increased the HDL-C level by 23% (all P < 0.05). The improvement in TC and LDL-C achieved by combination treatment was superior to treatment of atorvastatin alone and treatment of niacin ER alone (all P < 0.05). (2) The rate of achieving the LDL-C goal of The National Cholesterol Education Program (NCEP) in Adult Treatment Panel III (ATP III) in the combination therapy group was 73.5%, significantly higher than those of the atorvastatin and niacin groups (47.7% and 42.1% respectively, both P < 0.05). (3) Adverse effect, such as flushing (15.8%) and gastrointestinal symptoms (23.7%) were found in the niacin ER group, however, no more adverse effects were found in the combination therapy group. There were no serious adverse events in all groups. CONCLUSION: Niacin ER has a favorable effect in modulating the blood lipid profile, especially in reducing TG and elevating HDL-C. Combined statin with niacin may produce a more global and effective improvement in lipid blood levels than monotherapy and is generally safe and well tolerable.

Aged↗

PubMed2006

Identification and characterization of piggyBac-like elements in the genome of domesticated silkworm, Bombyx mori.

piggyBac is a short inverted terminal repeat (ITR) transposable element originally discovered in Trichoplusia ni. It is currently the preferred vector of choice for enhancer trapping, gene discovery and identifying gene function in insects and mammals. Many piggyBac-like sequences have been found in the genomes of phylogenetically species from fungi to mammals. We have identified 98 piggyBac-like sequences (BmPBLE1-98) from the genome data of domesticated silkworm (Bombyx mori) and 17 fragments from expressed sequence tags (ESTs). Most of the BmPBLE1-98 probably exist as fossils. A total of 21 BmPBLEs are flanked by ITRs and TTAA host dinucleotides, of which 5 contain a single ORF, implying that they may still be active. Interestingly, 16 BmPBLEs have CAC/GTG not CCC/GGG as the characteristic residues of ITRs, which is a surprising phenomenon first observed in the piggyBac families. Phylogenetic analysis indicates that many BmPBLEs have a close relation to mammals, especially to Homo sapiens, only a few being grouped with the T. ni piggyBac element. In addition, horizontal transfer was probably involved in the evolution of the piggyBac-like elements between B. mori and Daphnia pulicaria. The analysis of the BmPBLEs will contribute to our understanding of the characteristic of the piggyBac family and application of piggyBac in a wide range of insect species.

Amino Acid Sequence↗

PubMed2006

Intensity-modulated radiotherapy (IMRT) for carcinoma of the maxillary sinus: a comparison of IMRT planning systems.

The treatment of maxillary sinus carcinoma with forward planning can be technically difficult when the neck also requires radiotherapy. This difficulty arises because of the need to spare the contralateral face while treating the bilateral neck. There is considerable potential for error in clinical setup and treatment delivery. We evaluated intensity-modulated radiotherapy (IMRT) as an improvement on forward planning, and compared several inverse planning IMRT platforms. A composite dose-volume histogram (DVH) was generated from a complex forward planned case. We compared the results with those generated by sliding window fixed field dynamic multileaf collimator (MLC) IMRT, using sets of coplanar beams. All setups included an anterior posterior (AP) beam, and 3-, 5-, 7-, and 9-field configurations were evaluated. The dose prescription and objective function priorities were invariant. We also evaluated 2 commercial tomotherapy IMRT delivery platforms. DVH results from all of the IMRT approaches compared favorably with the forward plan. Results for the various inverse planning approaches varied considerably across platforms, despite an attempt to prescribe the therapy similarly. The improvement seen with the addition of beams in the fixed beam sliding window case was modest. IMRT is an effective means of delivering radiotherapy reliably in the complex setting of maxillary sinus carcinoma with neck irradiation. Differences in objective function definition and optimization algorithms can lead to unexpected differences in the final dose distribution, and our evaluation suggests that these factors are more significant than the beam arrangement or number of beams.

Female↗

PubMed2006

Dosimetric and radiobiological impact of dose fractionation on respiratory motion induced IMRT delivery errors: a volumetric dose measurement study.

Respiratory motion can introduce substantial dose errors during IMRT delivery. These errors are difficult to predict because of the nonsynchronous interplay between radiation beams and tissues. The present study investigates the impact of dose fractionation on respiratory motion induced dosimetric errors during IMRT delivery and their radiobiological implications by using measured 3D dose. We focused on IMRT delivery with dynamic multileaf collimation (DMLC-IMRT). IMRT plans using several beam arrangements were optimized for and delivered to a polystyrene phantom containing a simulated target and critical organs. The phantom was set in linear sinusoidal motion at a frequency of 15 cycles/min (0.25 Hz). The amplitude of the motion was +/- 0.75 cm in the longitudinal direction and +/- 0.25 cm in the lateral direction. Absolute doses were measured with a 0.125 cc ionization chamber while dose distributions were measured with transverse films spaced 6 mm apart. Measurements were performed for varying number of fractions with motion, with respiratory-gated motion, and without motion. A tumor control probability (TCP) model for an inhomogeneously irradiated tumor was used to calculate and compare TCPs for the measurements and the treatment plans. Equivalent uniform doses (EUD) were also computed. For individual fields, point measurements using an ionization chamber showed substantial dose deviations (-11.7% to 47.8%) for the moving phantom as compared to the stationary phantom. However, much smaller deviations (-1.7% to 3.5%) were observed for the composite dose of all fields. The dose distributions and DVHs of stationary and gated deliveries were in good agreement with those of treatment plans, while those of the nongated moving phantom showed substantial differences. Compared to the stationary phantom, the largest differences observed for the minimum and maximum target doses were -18.8% and +19.7%, respectively. Due to their random nature, these dose errors tended to average out over fractionated treatments. The results of five-fraction measurements showed significantly improved agreement between the moving and stationary phantom. The changes in TCP were less than 4.3% for a single fraction, and less than 2.3% for two or more fractions. Variation of average EUD per fraction was small (< 3.1 cGy for a fraction size of 200 cGy), even when the DVHs were noticeably different from that of the stationary tumor. In conclusion, IMRT treatment of sites affected by respiratory motion can introduce significant dose errors in individual field doses; however, these errors tend to cancel out between fields and average out over dose fractionation. 3D dose distributions, DVHs, TCPs, and EUDs for stationary and moving cases showed good agreement after two or more fractions, suggesting that tumors affected by respiration motion may be treated using IMRT without significant dosimetric and biological consequences.

Artifacts↗

PubMed2006

Comprehensive evaluation of a commercial macro Monte Carlo electron dose calculation implementation using a standard verification data set.

A commercial electron dose calculation software implementation based on the macro Monte Carlo algorithm has recently been introduced. We have evaluated the performance of the system using a standard verification data set comprised of two-dimensional (2D) dose distributions in the transverse plane of a 15 X 15 cm2 field. The standard data set was comprised of measurements performed for combinations of 9-MeV and 20-MeV beam energies and five phantom geometries. The phantom geometries included bone and air heterogeneities, and irregular surface contours. The standard verification data included a subset of the data needed to commission the dose calculation. Additional required data were obtained from a dosimetrically equivalent machine. In addition, we performed 2D dose measurements in a water phantom for the standard field sizes, a 4 cm X 4 cm field, a 3 cm diameter circle, and a 5 cm X 13 cm triangle for the 6-, 9-, 12-, 15-, and 18-MeV energies of a Clinac 21EX. Output factors were also measured. Synthetic CT images and structure contours duplicating the measurement configurations were generated and transferred to the treatment planning system. Calculations for the standard verification data set were performed over the range of each of the algorithm parameters: statistical precision, grid-spacing, and smoothing. Dose difference and distance-to-agreement were computed for the calculation points. We found that the best results were obtained for the highest statistical precision, for the smallest grid spacing, and for smoothed dose distributions. Calculations for the 21EX data were performed using parameters that the evaluation of the standard verification data suggested would produce clinically acceptable results. The dose difference and distance-to-agreement were similar to that observed for the standard verification data set except for the portion of the triangle field narrower than 3 cm for the 6- and 9-MeV electron beams. The output agreed with measurements to within 2%, with the exception of the 3-cm diameter circle and the triangle for 6 MeV, which were within 5%. We conclude that clinically acceptable results may be obtained using a grid spacing that is no larger than approximately one-tenth of the distal falloff distance of the electron depth dose curve (depth from 80% to 20% of the maximum dose) and small relative to the size of heterogeneities. For judicious choices of parameters, dose calculations agree with measurements to better than 3% dose difference and 3-mm distance-to-agreement for fields with dimensions no less than about 3 cm.

Journal Article↗

PubMed2006

[Molecular cloning, sequence and function analyses and specific expression of gene BmICAD related to apoptosis in silkworm, Bombyx mori].

The DREP-1 gene plays an important role in the process of apoptosis in Drosophila. The amino acid sequence of Drosophila ICAD was searched against the silkworm EST database. The resulted ESTs were clustered and assembled into a consensus sequence. Primers based on the consensus sequence were designed and the full length cDNA of ICAD gene, designated BmICAD, was cloned firstly from Bombyx mori. This BmICAD cDNA was 844-bp in length, containing a 522-bp open reading frame (ORF), which encoded a protein of 174 amino acids; the molecular weight of this protein was estimated to be 19.6 kDa and the isoelectric point was 4.23. The BmICAD protein shares 36% identity with Drosophila DREP-1. No signal has inspected by Northern blot, but RT-PCR analysis showed that BmICAD was testis-specific expressed at the mRNA level. Structure and clustering analysis indicated that this gene might be involved in the process of apoptosis that regulate the degradation of DNA.

Amino Acid Sequence↗

PubMed2005

HISTONE DEACETYLASE19 is involved in jasmonic acid and ethylene signaling of pathogen response in Arabidopsis.

Histone acetylation is modulated through the action of histone acetyltransferases and deacetylases, which play key roles in the regulation of eukaryotic gene expression. Previously, we have identified a yeast histone deacetylase REDUCED POTASSIUM DEPENDENCY3 (RPD3) homolog, HISTONE DEACETYLASE19 (HDA19) (AtRPD3A), in Arabidopsis thaliana. Here, we report further study of the expression and function of HDA19. Analysis of Arabidopsis plants containing the HDA19:beta-glucuronidase fusion gene revealed that HDA19 was expressed throughout the life of the plant and in most plant organs examined. In addition, the expression of HDA19 was induced by wounding, the pathogen Alternaria brassicicola, and the plant hormones jasmonic acid and ethylene. Using green fluorescent protein fusion, we demonstrated that HDA19 accumulated in the nuclei of Arabidopsis cells. Overexpression of HDA19 in 35S:HDA19 plants decreased histone acetylation levels, whereas downregulation of HDA19 in HDA19-RNA interference (RNAi) plants increased histone acetylation levels. In comparison with wild-type plants, 35S:HDA19 transgenic plants had increased expression of ETHYLENE RESPONSE FACTOR1 and were more resistant to the pathogen A. brassicicola. The expression of jasmonic acid and ethylene regulated PATHOGENESIS-RELATED genes, Basic Chitinase and beta-1,3-Glucanase, was upregulated in 35S:HDA19 plants but downregulated in HDA19-RNAi plants. Our studies provide evidence that HDA19 may regulate gene expression involved in jasmonic acid and ethylene signaling of pathogen response in Arabidopsis.

Arabidopsis↗

PubMed2005

Determination of field size-dependent wedge factors from a few selected measurements.

Some modern treatment-planning systems (TPSs) provide for input of wedge factor (WF) tables covering the entire range of square and elongated fields available on the LINAC. Depending on the field size increment chosen and the number of available wedge orientations, one may have to take more than 100 measurements per wedge and photon energy to commission the TPS. To expedite TPS commissioning while maintaining high accuracy, we demonstrate a simple method that requires only a few measurements per wedge, from which the remaining wedge factors can be found through linear interpolation based on field area. For the externally mounted wedges of two common LINACs, we have shown that WFs are proportional to field area and are nearly independent of field elongation and wedge orientation. Wedge factors computed from five to seven measurements comprised of square fields and a single, large rectangular field agreed with direct measurements throughout the entire range of achievable field dimensions within 0.6% at 6 MV and within 1% at 15 MV. Making the same set of measurements and using the equivalent square method to find WFs at other field sizes leads to errors up to 2%. Measuring the WF for a 10 x 10 cm2 field and applying the same value to all field sizes can lead to errors of up to 10% at both 6 MV and 15 MV.

Algorithms↗

PubMed2005

Identification and expression pattern of Bmlark, a homolog of the Drosophila gene lark in Bombyx mori.

Two Bombyx mori isoforms of the gene lark, which is shown to play an important role in Drosophila circadian rhythms, were identified and named Bmlark-PA and Bmlark-PB, respectively. Bmlark-PA consists of 5 exons and encodes a protein of 343 amino acid residues which contains 3 functional domains: two RRM (RNA recognization motif) domains and an RTZF (retroviral-type zinc finger) and shares 72% identity with the Drosophila gene lark at the amino acid level. Bmlark-PB lacks the sequence between 118 and 791 nt of Bmlark-PA and codes for a protein of 68 amino acid residues, which contains no distinct functional domains. Alignments of the cDNAs of Bmlark to the genomic draft sequence of B. mori showed that the gene Bmlark had a single copy in the genome, suggesting that an alternative splicing mechanism occurs in the gene Bmlark. RT-PCR analysis indicated that Bmlark-PA was expressed only in late pupae and adult but Bmlark-PB was broadly expressed in many tissues and throughout the developmental stages from embryo to adult.

Alternative Splicing↗

PubMed2005

Testicular uptake and radiation dose in patients receiving Zevalin and Pretarget CC49Fusion protein.

OBJECTIVE: Radiation dose to the testes from radionuclide therapies is of concern. This study evaluated image-quantification methods for testicular uptake in a phantom and in patients. METHODS: A 50-mL vial and a large water tank were used to simulate testes and the body, respectively. Activity concentration in the vial and water tank was prepared to generate testes-to-background concentrations of 1.3 and 1.1. Five male lymphoma patients who received a Zevalin (Biogen Idec, Cambridge, MA) regimen and 6 male colorectal cancer patients who received a Pretarget (Neo Rx, Seattle, WA) CC49Fusion protein were evaluated. Testicular activity was quantified using two methods: (1) geometric-mean, background-corrected testicular region of interest (ROI) counts as a fraction of body counts without explicit attenuation correction (Zevalin Kit); (2) background-corrected anterior testicular ROI counts with attenuation correction using known depth in the phantom and CT depth in patients. RESULTS: In the phantom study, Method 1 underestimated 49% and 39%, at image contrast of 1.3 and 1.1, respectively. Quantification was improved using Method 2 (7% for a 1.3 contrast, -17% for a 1.1 contrast). Method 2 was used in patients because background-corrected posterior ROI counts were statistically unreliable due to poor image contrast. In patients receiving Zevalin, the median peak percent injected dose (%ID)/testis was 0.10 (range, 0.08-0.18) with a median biologic half-time (T(bio1/2)) of 156 (range, 91-4200) hours. The median dose was 2.4 (range, 1.5-3.6) Gy/GBq, compared to the originally reported mean dose of 9.1 (range, 5.4-11.4) Gy/GBq (Zevalin package insert). In patients receiving the Pretarget CC49Fusion protein, the median peak %ID/testis was 0.22 (range, 0.05-0.29) with a median T(bio1/2) of 44 (range, 37-64) hours. The median dose was 0.84 (range, 0.3-1.2) Gy/GBq. CONCLUSION: This study found that testicular doses from Zevalin were much lower than that originally reported in the package insert. The median testicular dose from Pretarget CC49Fusion protein was less than half that of the median testicular dose from Zevalin.

Antibodies, Monoclonal↗

PubMed2005

Monte Carlo techniques for scattering foil design and dosimetry in total skin electron irradiations.

Total skin electron irradiation (TSEI) with single fields requires large electron beams having good dose uniformity, dmax at the skin surface, and low bremsstrahlung contamination. To satisfy these requirements, energy degraders and scattering foils have to be specially designed for the given accelerator and treatment room. We used Monte Carlo (MC) techniques based on EGS4 user codes (BEAM, DOSXYZ, and DOSRZ) as a guide in the beam modifier design of our TSEI system. The dosimetric characteristics at the treatment distance of 382 cm source-to-surface distance (SSD) were verified experimentally using a linear array of 47 ion chambers, a parallel plate chamber, and radiochromic film. By matching MC simulations to standard beam measurements at 100 cm SSD, the parameters of the electron beam incident on the vacuum window were determined. Best match was achieved assuming that electrons were monoenergetic at 6.72 MeV, parallel, and distributed in a circular pattern having a Gaussian radial distribution with full width at half maximum = 0.13 cm. These parameters were then used to simulate our TSEI unit with various scattering foils. Two of the foils were fabricated and experimentally evaluated by measuring off-axis dose uniformity and depth doses. A scattering foil, consisting of a 12 x 12 cm2 aluminum plate of 0.6 cm thickness and placed at isocenter perpendicular to the beam direction, was considered optimal. It produced a beam that was flat within +/-3% up to 60 cm off-axis distance, dropped by not more than 8% at a distance of 90 cm, and had an x-ray contamination of <3%. For stationary beams, MC-computed dmax, Rp, and R50 agreed with measurements within 0.5 mm. The MC-predicted surface dose of the rotating phantom was 41% of the dose rate at dmax of the stationary phantom, whereas our calculations based on a semiempirical formula in the literature yielded a drop to 42%. The MC simulations provided the guideline of beam modifier design for TSEI and estimated the dosimetric performance for stationary and rotational irradiations.

Calibration↗

PubMed2005

Simultaneous optimization of sequential IMRT plans.

Radiotherapy often comprises two phases, in which irradiation of a volume at risk for microscopic disease is followed by a sequential dose escalation to a smaller volume either at a higher risk for microscopic disease or containing only gross disease. This technique is difficult to implement with intensity modulated radiotherapy, as the tolerance doses of critical structures must be respected over the sum of the two plans. Techniques that include an integrated boost have been proposed to address this problem. However, clinical experience with such techniques is limited, and many clinicians are uncomfortable prescribing nonconventional fractionation schemes. To solve this problem, we developed an optimization technique that simultaneously generates sequential initial and boost IMRT plans. We have developed an optimization tool that uses a commercial treatment planning system (TPS) and a high level programming language for technical computing. The tool uses the TPS to calculate the dose deposition coefficients (DDCs) for optimization. The DDCs were imported into external software and the treatment ports duplicated to create the boost plan. The initial, boost, and tolerance doses were specified and used to construct cost functions. The initial and boost plans were optimized simultaneously using a gradient search technique. Following optimization, the fluence maps were exported to the TPS for dose calculation. Seven patients treated using sequential techniques were selected from our clinical database. The initial and boost plans used to treat these patients were developed independently of each other by dividing the tolerance doses proportionally between the initial and boost plans and then iteratively optimizing the plans until a summation that met the treatment goals was obtained. We used the simultaneous optimization technique to generate plans that met the original planning goals. The coverage of the initial and boost target volumes in the simultaneously optimized plans was equivalent to the independently optimized plans actually used for treatment. Tolerance doses of the critical structures were respected for the plan sum; however, the dose to critical structures for the individual initial and boost plans was different between the simultaneously optimized and the independently optimized plans. In conclusion, we have demonstrated a method for optimization of initial and boost plans that treat volume reductions using the same dose per fraction. The method is efficient, as it avoids the iterative approach necessitated by currently available TPSs, and is generalizable to more than two treatment phases. Comparison with clinical plans developed independently suggests that current manual techniques for planning sequential treatments may be suboptimal.

Algorithms↗

PubMed2005

[Rapid propagation of Smilax glabra in vitro].

In vitro propagation of Smilax glabra Roxb. was studied. The results indicated that sterilized explants cultured on MS + 6-BA 1.0 mg/L + NAA 0.1 mg/L could lead to budding fastly, the medium MS + 6-BA 1.0 mg/L + NAA 0.1 mg/L + 15% CM suitable for the proliferation, 3/2MS + 6-BA 0.05 mg/L + 4% Sugar suitable for buds strong. Treatment on the medium H (modified) + NAA 0.5 mg/L was best for rooting. The survival rate of the test-tube plantlets was 95% in transplanting on media contained turf-sand (1:1).

Culture Media↗

PubMed2004

A dynamic supraclavicular field-matching technique for head-and-neck cancer patients treated with IMRT.

PURPOSE: The conventional single-isocenter and half-beam (SIHB) technique for matching supraclavicular fields with head-and-neck (HN) intensity-modulated radiotherapy (IMRT) fields is subject to substantial dose inhomogeneities from imperfect accelerator jaw/MLC calibration. It also limits the isocenter location and restricts the useful field size for IMRT. We propose a dynamic field-matching technique to overcome these limitations. METHODS AND MATERIALS: The proposed dynamic field-matching technique makes use of wedge junctions for the abutment of supraclavicular and HN IMRT fields. The supraclavicular field was shaped with a multileaf collimator (MLC), which was orientated such that the leaves traveled along the superoinferior direction. The leaves that defined the superior field border moved continuously during treatment from 1.5 cm below to 1.5 cm above the conventional match line to generate a 3-cm-wide wedge-shaped junction. The HN IMRT fields were optimized by taking into account the dose contribution from the supraclavicular field to the junction area, which generates a complementary wedge to produce a smooth junction in the abutment region. This technique was evaluated on a polystyrene phantom and 10 HN cancer patients. Treatment plans were generated for the phantom and the 10 patients. Dose profiles across the abutment region were measured in the phantom on films. For patient plans, dose profiles that passed through the center of the neck lymph nodes were calculated using the proposed technique and the SIHB technique, and dose uniformity in the abutment region was compared. Field mismatches of +/- 1 mm and +/- 2 mm because of imperfect jaw/MLC calibration were simulated, and the resulting dose inhomogeneities were studied for the two techniques with film measurements and patient plans. Three-dimensional volumetric doses were analyzed, and equivalent uniform doses (EUD) were computed. The effect of field mismatches on EUD was compared for the two match techniques. RESULTS: For a perfect jaw/MLC calibration, dose profiles for the 10 patients in the 3-cm match zone had an average inhomogeneity range of -1.6% to +1.6% using the dynamic-matching technique and -3.7% to +3.8% according to the SIHB technique. Measurements showed that dose inhomogeneities that resulted from 1-mm and 2-mm jaw/MLC calibration errors were reduced from as large as 27% and 45% with the SIHB technique to less than 2% and 5.7% with the dynamic technique, respectively. For -1-mm, -2-mm, +1-mm, and +2-mm jaw/MLC calibration errors, respectively, treatment plans for the 10 patients yielded average dose inhomogeneities of -5.9%, -3.0%, +2.7%, and +5.8% with the dynamic technique as compared to -22.8%, -11.1%, +9.8%, and +22.1% with the SIHB technique. Calculation based on a dose-volume histogram (DVH) showed that the SIHB technique resulted in larger changes in EUD of the PTV in the junction area than did the dynamic technique. CONCLUSION: Compared with the conventional SIHB technique, the dynamic field-matching technique provides superior dose homogeneity in the abutment region between the supraclavicular and HN IMRT fields. The dynamic feathering mechanism substantially reduces dose inhomogeneities that result from imperfect jaw/MLC calibration. In addition, isocenter location in the dynamic field-matching technique can be chosen for reproducible patient setup and for adequate IMRT field size rather than being dictated by the match position. It also allows angling of the supraclavicular field to reduce the volume of healthy lung irradiated, which is impractical with the SIHB technique. In principle, this technique should be applicable to any treatment site that requires the abutment of static and intensity-modulated fields.

Calibration↗

PubMed2004

IMRT dose escalation for positive para-aortic lymph nodes in patients with locally advanced cervical cancer while reducing dose to bone marrow and other organs at risk.

PURPOSE: To evaluate the feasibility of dose-escalated para-aortic lymph node (PALN) intensity modulated radiation therapy (IMRT) in reducing the dose to bone marrow, bowel, spinal cord, and kidneys, compared with conventional radiation techniques of PALNs in patients with locally advanced cervical cancer and PALN metastases. METHODS AND MATERIALS: Computed tomography scans and MRI studies of 5 cervical cancer patients with PALN involvement were transferred to an IMRT treatment planning workstation (Eclipse/Helios) for image fusion and definition of target volumes and critical structures. The positive PALNs identified on fused computed tomography-magnetic resonance images were defined as the gross target volume (GTV), and the PALN region was defined as the planning target volume. There were 2 distinct treatment regions: the PALN region superior to the isocenter and the whole-pelvis region inferior to the isocenter. Three treatment planning techniques were compared: AP/PA (both regions), 4-field box (both regions), and PALN-IMRT with 4-field box to the whole-pelvis field. With IMRT, the radiation dose to the GTV was escalated from the conventional 45 Gy to 60 Gy (2.4 Gy/fraction), whereas the planning target volume and whole-pelvis region received 45 Gy. The treatment planning isocenter was placed at the L4-L5 vertebral body interspace, and this allowed the two treatment regions to be abutted using independent jaws. RESULTS: This study has demonstrated the feasibility of escalating the dose delivered to grossly positive PALNs to 60 Gy (2.4 Gy/fraction) with a 95.6% median GTV coverage, concomitantly with conventional treatment of the whole-pelvis region. PALN-IMRT significantly reduced V(40) bone marrow compared to the AP/PA and 4-field box techniques with a median of 21.3%, 98%, and 49.7%, respectively. The PALN-IMRT and 4-field box techniques showed a reduction in V(45) bowel over the AP/PA technique, but a level of statistical significance was not reached. The spinal cord received a significantly higher maximum dose when PALNs were treated with AP/PA fields. Alternatively, the use of the 4-field box technique yielded a significant increase in V(22) kidney on both sides. The placement of the treatment planning isocenter at the L4-L5 interspace allowed the PALN-IMRT and whole-pelvis regions to be treated with a relatively uniform dose at the abutment region. CONCLUSION: In this dosimetric analysis, we demonstrated that dose-escalated PALN-IMRT with conventional whole-pelvis radiotherapy is feasible with significant sparing of critical normal structures compared to PALN conventional radiation techniques.

Aorta↗

PubMed2004

Serum hepatic enzyme manifestations in patients with severe acute respiratory syndrome: retrospective analysis.

AIM: To evaluate the hepatic function in patients with severe acute respiratory syndrome (SARS) and possible causes of hepatic disorder in these patients. METHODS: One hundred and eighty-two patients with SARS were employed in a retrospective study that investigated hepatic dysfunction. Liver alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactic dehydrogenase (LDH) were analyzed in these patients. Patients with different hospital treatments were further investigated. RESULTS: Of the 182 patients, 128(70.3%) had abnormal ALT activity, 57(31.3%) had abnormal AST activity and 87(47.8%) had abnormal LDH activity. The peak of elevated hepatic enzyme activities occurred between the sixth day and the tenth day after the first day of reported fever. Of the 182 patients, 160(87.9%) had been treated with antibiotics, 137(75.2%) with Ribavirin, and 115(63.2%) with methylpredisolone. There was no statistically significant correlation between the duration of Ribavirin treatment and hepatic dysfunction. CONCLUSION: Abnormal liver functions were common in patients with SARS and could be associated with virus replication in the liver.

Adolescent↗

PubMed2004

Attenuation of intracavitary applicators in 192Ir-HDR brachytherapy.

Unlike the penetrating monoenergetic 662 keV gamma rays emitted by 137Cs LDR sources, the spectrum of 192Ir used in HDR brachytherapy contains low-energy components. Since these are selectively absorbed by the high-atomic number materials of which intracavitary applicators are made, the traditional neglect of applicator attenuation can lead to appreciable dose errors. We investigated the attenuation effects of a uterine applicator, and of a set of commonly used vaginal cylinders. The uterine applicator consists of a stainless steel source guide tube with a wall thickness of 0.5 mm and a density of 8.02 g/cm3, whereas the vaginal cylinders consist of the same stainless steel tube plus concentric polysulfone cylinders with a radius of 1 or 2 cm and a density of 1.40 g/cm3. Monte Carlo simulations were performed to compute dose distributions for a bare 192Ir-HDR source, and for the same source located within the applicators. Relative measurements of applicator attenuation using ion-chambers (0.125 cm3) confirmed the Monte Carlo results within 0.5%. We found that the neglect of the applicator attenuation overestimates the dose along the transverse plane by up to 3.5%. At oblique angles, the longer photon path within applicators worsens the error. We defined attenuation-corrected radial dose and anisotropy functions, and applied them to a treatment having multiple dwell positions inside a vaginal cylinder.

Algorithms↗

PubMed2004

TCM treatment of infectious atypical pneumonia--a report of 16 cases.

OBJECTIVE: To probe into the mechanism on TCM treatment of infectious atypical pneumonia (severe acute respiratory syndrome, SARS) and evaluate its feasibility and effectiveness. METHOD: Twelve TCM prescriptions of herbal drugs (orally or i.v.) were used to treat 16 cases of SARS without using glucocorticoids, anti-viral agents, immune-regulators or antibiotics (in case there was no definite bacterial infections). The symptoms, signs, chest roentgenograms and lab examinations were carefully monitored and recorded for evaluation of the effectiveness. RESULTS: The average fever abatement time was 4.44 +/- 1.46 days and the mean absorption time of gross pulmonary infiltration was 10.87 +/- 2.92 days. No exacerbation occurred during the treatment. CONCLUSION: TCM intervention could effectively control and alleviate the symptoms and prevent the disease from exacerbation.

Adult↗