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Biomedical subjects

Takashi Yamashita

Publications and source records attributed to Takashi Yamashita.

15 recordsLinked to original sources
PubMed2006

Dosimetric consideration of individual 125I source strength measurement and a large-scale comparison of that measured with a nominal value in permanent prostate implant brachytherapy.

PURPOSE: We investigated the difference between measured and manufacturer's nominal source strength in a large sample of a single model of (125)I seeds. Physical characteristics of single seed measurement by the well-type ionization chamber were also investigated to provide dosimetric data. MATERIALS AND METHODS: A well-type ionization chamber with a single seed holder was used to measure source strength of all 1935 (125)I seeds implanted in the initial 28 patients in our hospital. Physical characteristics including linearity of readings for different integral time intervals, reproducibility, isotropy, and axial positional sensitivity were assessed. To calculate the source strength, the integral charge during 30 s was measured and converted to air kerma strength. The nominal activity stated by the manufacturer was compared with the measured value. RESULTS: Linearity, reproducibility, and isotropy of the well-type ionization chamber were within 0.2%. Measured source strength was on average 2.1% (range -7.6% to +7.2%), lower than the nominal value. Standard deviation of all measured seeds was 2.0%. The maximum difference between the measured and the manufacturer's nominal source strength in each patient was -3.7%. The standard deviation averaged 1.6%. CONCLUSION: The nominal source strength of the (125)I seeds agreed well with the measured value. Our study can be helpful as guidance for individual (125)I seed source strength measurement.

Brachytherapy↗
PubMed2006

Preliminary study of correction of original metal artifacts due to 1-125 seeds in postimplant dosimetry for prostate permanent implant brachytherapy.

PURPOSE: We investigated a subtraction-based reprojection approach to reduce CT metal artifacts due to I-125 seeds and evaluated the clinical implications in postimplant dosimetry for prostate permanent implant brachytherapy. MATERIALS AND METHODS: The raw projection data were used to reduce metal artifacts due to I-125 seeds. CT images of the metal parts only were separated from the original CT images by setting the threshold for pixel value to that of the I-125 seeds. Using these images, sinograms of CT images with and without seeds were obtained by inverse Radon transform (iRT), and the sinogram of the metal image was subtracted from that of the original image. Finally, the image was reconstructed using the sinogram by Radon transform (RT). This technique was applied to a prostate phantom and to a patient undergoing prostate permanent implant brachytherapy. RESULTS: Metal artifacts from I-125 seeds were reduced in both the phantom and patient studies. This technique decreased the density of the inner region of seeds but enhanced the density of the seed edge, thereby facilitating the identification of seed number, orientation, and location. CONCLUSION: This method reduces metal artifacts from I-125 seeds, and has potential for decreasing the time required for and improving the accuracy of postimplant dosimetry.

Artifacts↗
PubMed2006

A pilot study of wider use of accelerated partial breast irradiation: intraoperative margin-directed re-excision combined with sole high-dose-rate interstitial brachytherapy.

BACKGROUND: Accelerated partial breast irradiation (APBI) is generally limited to patients at extremely low risk of local recurrence. The significance of the risk factors, however, depends on the extent of surgery, radiation, and systemic therapy. In Japan, wide excision is generally supplemented by intraoperative margin-directed re-excision if the frozen section examination yields positive results. This approach combined with conventional radiotherapy achieved an excellent 10-year local control rate of 93%, and young age and ductal carcinoma in situ were not risk factors for local recurrence. To reduce the treatment duration, high-dose-rate interstitial brachytherapy (HDRIB) was employed. The first APBI phase I / II trial in Japan was conducted to determine if wider indications for early breast cancer patients were appropriate. METHODS: The subjects comprised 20 patients including those with extensive intraductal component (n=7), ductal carcinoma in situ (n=2), positive final margins (n=3), and of younger age (< or = 45 years; n=5). Breast-conserving surgery using an intraoperative re-excision approach was followed by intraoperative implantation of applicators. Sole HDRIB of a 36-42 Gy in 6-7 fractions was delivered postoperatively over 3-4 days. Tumors were staged as follows: cT1 (n=12), cT2 (n=8), cN0 (n=20). Systemic therapy was used in 16 patients (80%). The median follow-up period was 52 months (range, 26-86 months). RESULTS: Te five-year crude local, distant control, and Kaplan-Meier cause-specific survival rates were 95%, 95%, and 89%, respectively. Fat necrosis developed in 1 patient. CONCLUSIONS: Sole HDRIB with intraoperative margin-directed re-excision was feasible under wider indications compared to other contemporary APBI series, and achieved acceptable and similar results to these series in terms of the local control rate and complications.

Adult↗
PubMed2005

Rewritable phosphorescent paper by the control of competing kinetic and thermodynamic self-assembling events.

Security inks have become of increasing importance. They are composed of invisible substances that provide printed images that are not able to be photocopied, and are readable only under special environments. Here we report a novel photoluminescent ink for rewritable media that dichroically emits phosphorescence due to a structural bistability of the self-assembled luminophor. Long-lasting images have been developed by using conventional thermal printers, which are readable only on exposure to ultraviolet light, and more importantly, are thermally erasable for rewriting. Although thermally rewritable printing media have already been developed using visible dyes and cholesteric liquid crystals, security inks that allow rewriting of invisible printed images are unprecedented. We realized this unique feature by the control of kinetic and thermodynamic processes that compete with one another in the self-assembly of the luminophor. This strategy can provide an important step towards the next-generation security technology for information handling.

Crystallization↗
PubMed2005

Phosphorescent organogels via "metallophilic" interactions for reversible RGB-color switching.

A trinuclear Au(I) pyrazolate complex bearing long alkyl chains (1) in hexane self-assembles via a Au(I)-Au(I) metallophilic interaction, to form a red-luminescent organogel (lambda(em) = 640 nm, lambda(ext) = 284 nm). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis of an air-dried gel with 1 show the presence of heavily entangled fibers, each consisting of a rectangularly packed columnar assembly of 1. Doping of the organogel with a small amount of Ag(+) results in a blue luminescence (lambda(em) = 458 nm, lambda(ext) = 370 nm) without disruption of the gel, while removal of doped Ag(+) with cetyltrimethylammonium chloride results in complete recovery of the original red-luminescent gel. Upon heating, these organogels undergo gel-to-sol transition due to the destabilization of the metallophilic interactions, where the red luminescence of the nondoped system becomes hardly visible, while the blue luminescence of the Ag(+)-doped system turns green (lambda(em) = 501 nm, lambda(ext) = 370 nm). On cooling, these solutions undergo gelation and synchronously recover the original luminescences. The observed RGB (red-green-blue) luminescences are all long-lived (3-6 micros) and assigned to electronic transitions from triplet-excited states.

Journal Article↗
PubMed2005

Minor but key chlorophylls in photosystem II.

A 'metal-free' chlorophyll (Chl) a, pheophytin (Phe) a, functions as the primary electron acceptor in PS II. On the basis of Phe a/PS II = 2, Phe a content is postulated as an index for estimation of the stoichiometry of pigments and photosystems. We found Phe a in a Chl d-dominant cyanobacterium Acaryochloris marina, whereas Phe d was absent. The minimum Chl a:Phe a ratio was 2:2, indicating that the primary electron donor is Chl a, accessory is Chl d, and the primary electron acceptor is Phe a in PS II of A. marina. Chl d was artificially formed by the treatment of Chl a with papain in aqueous organic solvents. Further, we will raise a key question on the mechanisms of water oxidation in PS II.

Chlorophyll↗
PubMed2005

High-level expression of single-chain Fv-Fc fusion protein in serum and egg white of genetically manipulated chickens by using a retroviral vector.

We report here the generation of transgenic chickens using a retroviral vector for the production of recombinant proteins. It was found that the transgene expression was suppressed when a Moloney murine leukemia virus-based retroviral vector was injected into chicken embryos at the blastodermal stage. When a concentrated viral solution was injected into the heart of developing embryos after 50 to 60 h of incubation, transgene expression was observed throughout the embryo, including the gonads. For practical production, a retroviral vector encoding an expression cassette of antiprion single-chain Fv fused with the Fc region of human immunoglobulin G1 (scFv-Fc) was injected into chicken embryos. The birds that hatched stably produced scFv-Fc in their serum and eggs at high levels (approximately 5.6 mg/ml). We obtained transgenic progeny from a transgenic chicken generated with this procedure. The transgene was stably integrated into the chromosomes of transgenic progeny. The transgenic progeny also expressed scFv-Fc in the serum and eggs.

Animals↗
PubMed2005

Classification of ipsilateral breast tumor recurrence after breast-conserving therapy: new primary cancer allows a good prognosis.

PURPOSE: To classify and assess ipsilateral breast tumor recurrences (IBTR) after breast-conserving therapy. METHODS: Between 1986 and 2001, 2,137 patients who had breast cancer underwent breast-conserving surgery with or without radiotherapy at the Cancer Institute Hospital of the Japanese Foundation for Cancer Research. Of these patients, 83 (3.9%) had an IBTR. We classified the IBTR as a new primary cancer (NP) if the primary tumor had completely negative margins at first operation by detailed pathological examination and if the IBTR had an intraductal component. All other IBTRs were judged true local recurrence (TR). RESULTS: Of the 83 patients, 42 patients were classified as TR (29 had no radiotherapy) and 41 as NP (40 had no radiotherapy). Mean time to disease recurrence was 37 months for TR (52% were within 2 years) versus 55 months for NP (19% were within 2 years) (p=0.031). Six patients (14%) with TR did not receive re-operation, and 67% received salvage mastectomy and 19% re-lumpectomy. All cases of NP were operable, 78% underwent salvage mastectomy and 22% underwent re-lumpectomy. Distant metastases were observed in 33% of patients with TR and 5% of patients with NP, and cause-specific death occurred in 6 cases with TR and in one with NP. The patients with NP had improved 5-year rates of overall survival (NP 91% vs. TR 76%, P=0.0627) and distant disease-free survival (NP 93% vs. TR 61%, P=0.0028). Patients with NP more often developed contralateral breast cancer (NP 37% vs. TR 12%, P=0.018) CONCLUSIONS: Patients with NP had better survival rates than those with TR. Distinguishing new primary breast carcinomas from local disease recurrences may have importance in therapeutic decisions and chemoprevention strategies.

Breast Neoplasms↗
PubMed2004

Stereotactic hypofractionated high-dose irradiation for stage I nonsmall cell lung carcinoma: clinical outcomes in 245 subjects in a Japanese multiinstitutional study.

BACKGROUND: Stereotactic irradiation (STI) has been actively performed using various methods to achieve better local control of Stage I nonsmall cell lung carcinoma (NSCLC) in Japan. The authors retrospectively evaluated results from a Japanese multiinstitutional study. METHODS: Patients with Stage I NSCLC (n = 245; median age, 76 years; T1N0M0, n = 155; T2N0M0, n = 90) were treated with hypofractionated high-dose STI in 13 institutions. Stereotactic three-dimensional treatment was performed using noncoplanar dynamic arcs or multiple static ports. A total dose of 18-75 gray (Gy) at the isocenter was administered in 1-22 fractions. The median calculated biologic effective dose (BED) was 108 Gy (range, 57-180 Gy). RESULTS: During follow-up (median, 24 months; range, 7-78 months), pulmonary complications of National Cancer Institute-Common Toxicity Criteria Grade > 2 were observed in only 6 patients (2.4%). Local progression occurred in 33 patients (14.5%), and the local recurrence rate was 8.1% for BED > or = 100 Gy compared with 26.4% for < 100 Gy (P < 0.05). The 3-year overall survival rate of medically operable patients was 88.4% for BED > or = 100 Gy compared with 69.4% for < 100 Gy (P < 0.05). CONCLUSIONS: Hypofractionated high-dose STI with BED < 150 Gy was feasible and beneficial for curative treatment of patients with Stage I NSCLC. For all treatment methods and schedules, local control and survival rates were better with BED > or = 100 Gy compared with < 100 Gy. Survival rates in selected patients (medically operable, BED > or = 100 Gy) were excellent, and were potentially comparable to those of surgery.

Adult↗
PubMed2004

Improved detection of axillary hot nodes in lymphoscintigraphy in breast cancer located in the upper lateral quadrant with additional projection imaging.

BACKGROUND: Sentinel node (SN) biopsy has been becoming a standard method for early stage breast cancer. Scintigraphic image of SN helps the biopsy procedure. It is reported that the scintigraphic detection rate is not 100%. The value of taking additional projection view in SN detection was assessed in breast cancer patients. PATIENTS AND METHODS: Consecutive 114 breast cancer patients with upper lateral quadrant tumor were included in this study. After injection of 99mTc-phytate, scintigram was taken at the projection of anterior oblique (AO) 30 degrees view and an additional AO 60 degrees view. Images were evaluated visually. RESULTS: In 7 of 114 patients, an axillary hot node was hidden on the activity at the injected site on AO 30 degrees view, and was visualized on AO 60 degrees view. In 17 of 114 patients, the axillary hot node was seen as a hump from the injected activity, and was separate on AO 60 degrees view. In 90 of 114 patients, the axillary hot node was separately seen on AO 30 degrees view. CONCLUSION: Multi-directional views are helpful to depict the axillary sentinel nodes that are concealed behind the injected radioactivity.

Axilla↗
PubMed2004

Improvement in the prognosis of Japanese breast cancer patients from 1946 to 2001--an institutional review.

BACKGROUND: Breast cancer has emerged as one of the most frequent malignancies among Japanese women; however, the long-term survival of Japanese breast cancer patients is uncertain. METHODS: We analyzed the chronological changes in the clinical and pathological characteristics, treatment procedures and the long-term prognosis of 15 416 Japanese women with 16 217 primary breast cancers treated in the Cancer Institute Hospital in Tokyo between 1946 and 2001. RESULTS: Our analysis revealed a chronological increase in the mean patient age, postmenopausal patients and non-invasive carcinomas. Operative procedures became less extensive, with approximately 45% of breast cancer patients in 2000-2001 receiving breast-conserving treatment. Radiotherapy to the regional lymph nodes decreased, while postoperative chemotherapy and hormonal treatments have become more frequent. The survival rate has improved steadily during the past 5 decades. The 10-year crude overall survival rate improved from 61% before 1960 to 83% in the 1990s. CONCLUSIONS: The survival rate of Japanese women with breast cancer has dramatically improved during the past 5 decades.

Adult↗
PubMed2003

Process and preliminary outcome of a patterns-of-care study of esophageal cancer in Japan: patients treated with surgery and radiotherapy.

PURPOSE: To evaluate the quality of radiotherapy (RT) in Japan, we have been carrying out a national survey through patterns-of-care studies (PCSs) since 1996. We present the preliminary results of surgery combined with RT with or without chemotherapy for thoracic esophageal cancer. METHODS AND MATERIALS: A Japanese PCS data format for esophageal cancer was established based on one used in the United States and including information used in the surgical registration system in Japan, so that the results in both countries could be compared. An independent panel of radiation oncologists surveyed randomly selected institutions and patients between September 1998 and March 2001. There were 767 esophageal cancer patients, of whom 220 had undergone preoperative or postoperative RT. RESULTS: The median age of the 220 patients was 62.3 years (range 31-89); of them, 88.1% were men. Pathologically, 218 patients (99.5%) had squamous cell carcinoma, predominantly located in the middle and lower thoracic esophagus, 41.7% of the patients had Stage III disease; they accounted for 52.6% of patients in nonacademic institutions and for 37.7% of those in academic institutions (p = 0.016). Sixty-nine patients received preoperative RT; of them, 60.9% received chemotherapy; 145 patients received postoperative RT with or without chemotherapy. The spinal cord of 23 (11.7%) of 196 patients was irradiated with >/=50 Gy. In academic institutions, extended radical "three-field" lymphatic dissection was performed for 72 (48.7%) of 148 patients; however, this sophisticated surgical procedure was done in only 13 (25.5%) of 51 patients in nonacademic settings (p = 0.004). In all large academic institutions (those treating >/=300 patients annually), >/=6 MV of photon energy was used; 30.5% of nonacademic institutes had linear accelerators of <6 MV photon (p = 0.001). No deviations occurred in the radiation dose (median 46 Gy), fractionations, or fields between the two types of institutions. Univariate analyses showed that the statistically significant prognostic factors affecting overall survival were stage (p = 0.001), extended radical "three-field" lymphatic dissection (p = 0.001), no residual tumor (p = 0.001), supraclavicular RT (p = 0.001), mediastinal RT (p = 0.025), Karnofsky performance status (p = 0.006) photon energy (p = 0.011), and stratification of the institutions (p = 0.001). Multivariate analysis showed that the type of institution (p = 0.045, risk ratio = 0.604), stage (p 0.029, risk ratio = 0.572), no residual tumor (p = 0.006, risk ratio = 0.487), photon energy (p = 0.043, risk ratio = 0.579), and use of chemotherapy (p = 0.012, risk ratio = 1.907) significantly affected overall survival. CONCLUSION: This PCS showed that in Japan important issues are present regarding RT for esophageal cancer that should be solved immediately, namely, treatment strategy, photon energy, and dose applied to the spinal cord. The PCS provided important information on how much improvement in structure and process would be required nationwide for RT of esophageal cancer.

Adult↗
PubMed2003

Logical checking function increases the accuracy of data entry in the patterns of care study.

BACKGROUND: For clinical studies, the use of a databases combined with a computer is becoming popular for data capturing. Commercially available database software has a logical checking function, which can restrict the type of data and their range. The study presented here quantitatively and prospectively evaluated the effectiveness for data management with this function using the database of Patterns of Care Study (PCS) in Japan. PATIENTS AND METHODS: The first external audit was performed from September 1998 to March 1999 using the PCS database without the function, and the second from April to September 1999 with the function. We analyzed the numbers and patterns of erroneous data for these two periods obtained with and without the function. RESULTS: In the database without the function, the number of incorrect data was 2,812 out of 596,186 (0.47%), while the corresponding number with the function was significantly reduced to 161 out of 533,656 (0.03%, p < 0.0001). CONCLUSIONS: The data accuracy was improved by using the computer database more extensively than the conventional case report form. By adding the logical checking function to the PCS database, significant improvement in the accuracy of data entry was accomplished. This indicates the potential for increasing the accuracy of data capturing with the aid of a computer.

Data Collection↗
PubMed2002

Effect of multiple application of a dentin adhesive on contraction gap width of a resin-based composite.

PURPOSE: To test the efficacy of the multiple application of a total-etch dentin adhesive was investigated by measuring (1) the contraction gap width of a light-activated resin-based composite in a cylindrical dentin cavity and (2) the early tensile bond strength to a flat dentin surface with the Single Bond Dental Adhesive System. MATERIALS AND METHODS: Contraction gap width was measured in a cylindrical dentin cavity (3 mm x 1.5 mm) treated with a single coat or double coats of the Single Bond adhesive and restored with Silux Plus or Z-100. As control, the cavity was treated with an experimental dentin bonding system consisting of EDTA, 35% GM and Clearfil Photo Bond. Early tensile bond strengths of Silux Plus or Z-100 were measured on the flat dentin surface treated with the three bonding procedures as in the contraction gap study within 10 min. after final cure. RESULTS: The contraction gap of Silux Plus and Z-100 was prevented with the double coats of the Single Bond adhesive, whereas the contraction gap of Z-100 was not prevented with the single coat of the Single Bond and the experimental system. When the film thickness of the Single Bond system was less than 2 microm, the gap could not be prevented. The tensile bond strengths of Silux Plus and Z-100 to flat dentin mediated with the three bonding procedures were not significantly different (P>0.05).

Acid Etching, Dental↗