Biomedical subjects

H Shirato

Publications and source records attributed to H Shirato.

At least 19 recordsLinked to original sources

PubMed2001

Detection of lung tumor movement in real-time tumor-tracking radiotherapy.

PURPOSE: External radiotherapy for lung tumors requires reducing the uncertainty due to setup error and organ motion. We investigated the three-dimensional movement of lung tumors through an inserted internal marker using a real-time tumor-tracking system and evaluated the efficacy of this system at reducing the internal margin. METHODS AND MATERIALS: Four patients with lung cancer were analyzed. A 2.0-mm gold marker was inserted into the tumor. The real-time tumor-tracking system calculates and stores three-dimensional coordinates of the marker 30 times/s. The system can trigger the linear accelerator to irradiate the tumor only when the marker is located within the predetermined "permitted dislocation." The value was set at +/-1 to +/-3 mm according to the patient's characteristics. We analyzed 10,413-14,893 data sets for each of the 4 patients. The range of marker movement during normal breathing (beam-off period) was compared with that during gated irradiation (beam-on period) by Student's t test. RESULTS: The range of marker movement during the beam-off period was 5.5-10.0 mm in the lateral direction (x), 6.8-15.9 mm in the craniocaudal direction (y) and 8.1-14.6 mm in the ventrodorsal direction (z). The range during the beam-on period was reduced to within 5.3 mm in all directions in all 4 patients. A significant difference was found between the mean of the range during the beam-off period and the mean of the range during the beam-on period in the x (p = 0.007), y (p = 0.025), and z (p = 0.002) coordinates, respectively. CONCLUSION: The real-time tumor-tracking radiotherapy system was useful to analyze the movement of an internal marker. Treatment with megavoltage X-rays was properly given when the tumor marker moved into the "permitted dislocation" zone from the planned position.

Aged↗

PubMed2001

Overexpression of homeobox gene HOXD3 induces coordinate expression of metastasis-related genes in human lung cancer cells.

Homeobox-containing genes are expressed in spatiotemporal fashion during embryogenesis and act as master transcription-regulating factors which control the expression of a variety of genes involved in morphogenesis. They are also expressed in a tissue-specific manner in normal adult tissues and appear to give cells spatial information in the maintenance of their architectural integrity. We transfected a HOXD3 class I homeobox-containing gene into human lung cancer A549 cells and investigated alterations in gene expressions and phenotypes related to the maintenance of tissue architecture in HOXD3-overexpressing A549 cells. In the HOXD3-overexpressing cell lines, expression of E-cadherin was lost and plakoglobin was strongly repressed, whereas integrin alpha3 and beta3 were up-regulated and N-cadherin and integrin alpha4 were newly expressed. Compared with parental and control transfectant lines, the HOXD3-overexpressing cell lines showed highly motile and invasive activity. Blocking experiments using anti-integrin beta1 and beta3 suggested that the increased haptotaxis of the HOXD3-overexpressing cells to vitronectin resulted from increased expression and activation of integrin alphavbeta3, and that overexpression of the HOXD3 gene converted the integrin beta1-dependent haptotaxis to fibronectin into both integrin beta1- and beta3-dependent one. HOXD3 overexpression increased production of matrix-degrative enzymes including matrix metalloproteinase-2 and urokinase-plasminogen activator. When the tumor cells were intravenously injected into the tail veins of nude mice, HOXD3 transfectants formed a significantly large number of metastatic foci in lungs compared with the control transfectants. These findings suggest that HOXD3 can act as a metastasis-promoting gene in human lung cancer A549 cells.

Antigens, CD↗

PubMed2001

Medication for hearing loss after fractionated stereotactic radiotherapy (SRT) for vestibular schwannoma.

PURPOSE: To investigate the effectiveness of corticosteroid treatments for patients showing decreases in hearing levels after stereotactic radiotherapy for vestibular schwannoma. METHODS AND MATERIALS: Twenty-one patients experienced a hearing loss in pure-tone average at greater than 20 dB or less than 10 dB within 1 year after irradiation administration of 44 Gy/22 fractions followed by a 4 Gy boost. Eight received oral prednisone at a daily dose of 30 mg, which was gradually decreased (medicated group), and 13 received none (nonmedicated group). The average observation period was 26.7 +/- 16.6 (range: 6--69) months. RESULTS: Hearing recovery was seen after initial onset of the hearing loss in all 8 patients in the medicated group and in 2 of 13 patients in the nonmedicated group (p = 0.001). The hearing recovery, that is, the change in pure-tone average (dB) at the last follow-up from the onset of hearing loss, was 9.8 +/- 6.9 dB (recovery) in the medicated group and -9.4 +/- 12.8 dB (further loss) in the nonmedicated group (p = 0.0013). The hearing recovery rate, normalizing to the degree of the hearing loss before medication, was also significantly higher in the medicated group than in the nonmedicated group (p = 0.0014). CONCLUSIONS: Corticosteroidal intake is suggested to be effective in improving hearing loss after stereotactic radiotherapy, at least in young patients having a useful pretreatment hearing level, if the treatment for hearing loss is administered immediately after the hearing loss is first detected.

Adult↗

PubMed2001

Magnetic resonance imaging system for three-dimensional conformal radiotherapy and its impact on gross tumor volume delineation of central nervous system tumors.

PURPOSE: We developed an MRI system for three-dimensional planning in radiotherapy. Its contribution on gross tumor volume (GTV) delineation of central nervous system (CNS) diseases was evaluated. METHODS AND MATERIALS: The MRI system, with corrected distortion, was registered on computed tomography (CT) by means of fiducial/anatomic landmarks. In 41 consecutive patients with various CNS diseases, GTVs determined by MRI/CT registration (MR/CT-GTV) and CT alone (CT-GTV) were compared. Hard copies of diagnostic MRI were shown to doctors when CT-GTV was determined to simulate a conventional planning situation. Multi-observer volumetric analysis was conducted, assessing interobserver deviations among four radiation oncologists and intermethodological deviations between MR/CT-GTV and CT-GTV. RESULTS: Overall, the mean of geometric distortion was significantly reduced from 1.08 mm to 0.3 mm by distortion correction (p < 0.0001). The contribution of the correction was apparent at >12.0 cm radius from the center of the magnetic field. Interobserver deviation was significantly reduced by MR/CT registration (p = 0.005). The improvement was significant for acoustic neurinoma (p = 0.038), astrocytomas (p = 0.043), and lesions at the cerebellum/brainstem (p = 0.008). The regression coefficient between MR/CT-GTV and CT-GTV was <0.9 for cerebellum/brainstem lesions, suggesting that MRI/CT-GTV was smaller than CT-GTV. CONCLUSIONS: This system is feasible for three-dimensional planning and was shown to reduce interobserver deviations in GTV delineation for CNS diseases.

Brain Neoplasms↗

PubMed2001

Remote verification in radiotherapy using digitally reconstructed radiography (DRR) and portal images: a pilot study.

PURPOSE: To use digitally reconstructed radiography (DRR) and digitally compressed portal images in distant consultation using a telecommunications network, the verification performance of DRR and digitally compressed portal images on the image console was investigated. METHODS AND MATERIALS: A human thoracic phantom was scanned with computed tomography (CT). Radiotherapy was planned at 5 different anatomic locations. A digitally reconstructed radiograph was made; verification films of the phantom were then taken with 6-MV X-rays. The treatment center was intentionally dislocated. Fifty sets of DRR and portal images were seen by 7 doctors on a conventional view-box (view-box method) to judge whether the treatment center was dislocated. These image sets were digitalized by a film scanner, compressed to 1/10 Joint Photographic Experts Group (JPEG) format, and compared on an image console by the same physicians (image-console method). The verification performance of the image console method was compared with that of the view-box method by means of receiver operating characteristic (ROC) analysis. Clinically, 159 portal-image-sets were verified with the image-console method and the appropriateness of the decision was later assessed by the view-box method. RESULTS: The accuracy of the treatment verification was estimated to be 88.8% by the conventional view-box method and 88.3% by the image-console method. There was no statistically significant difference in the verification performances of the conventional method (Az = 0.86+/-0.02) and the image console method (Az = 0.84+/-0.07). Frequent digital image-processing modification was positively related to the accuracy of verification. Clinically, there were 3 (1.8%) major corrections, 31 (19.5%) minor corrections, and 123 cases with no correction. No further correction was called for by the re-evaluation using the view-box method. CONCLUSION: The verification performance of DRR and digitally compressed portal images on the image console was as accurate as the conventional method. Distant consultation using DRR and portal images through telecommunication is usable in clinical practice.

Humans↗

PubMed2001

Radiotherapy with concurrent chemotherapy for vulvar adenocarcinoma associated with extramammary Paget's disease.

BACKGROUND: There have been no reports of the efficacy of primary radiotherapy with concurrent chemotherapy for vulvar adenocarcinoma associated with extramammary Paget's disease. In this report we discuss the differential diagnosis and efficacy of treatment for this rare tumor. CASE: The patient was diagnosed as having vulvar carcinoma stage IVb. A dose of 40 Gy in 20 fractions was administered to the vulva, including the tumor mass, and the inguinal-femoral lymph nodes with concurrent systemic chemotherapy. Outside the radiated field, bone scintigraphy showed an increase in abnormal uptake images. However, in the radiated field, the tumors disappeared macroscopically, and bone scintigraphy also showed a disappearance of the abnormal uptake images. CONCLUSION: Within the radiated field, the efficacy was brought about by either radiotherapy only or by radiotherapy together with the sensitizing effects of chemotherapy. As for the chemotherapy itself, it was not effective in this case.

Adenocarcinoma↗

PubMed2001

Clinical efficacy of telemedicine in emergency radiotherapy for malignant spinal cord compression.

The authors developed a Telecommunication-HElped Radiotherapy Planning and Information SysTem (THERAPIST), then estimated its clinical benefit in radiotherapy in district hospitals where consultation with the university hospital was required. The system consists of a personal computer with an image scanner and a digital camera, set up in district hospitals and directly connected via ISDN to an image server, and a treatment planning device set up in a university hospital. Image data and consultative reports are sent to the server. Radiation oncologists at the university hospital determine a treatment schedule and verify actual treatment fields. From 1998 to 1999, 12 patients with malignant spinal cord compression (MSCC) were treated by emergency radiotherapy with the help of this system. Image quality, transmission time, and cost benefit also were satisfactory for clinical use. The mean time between the onset of symptoms and the start of radiotherapy was reduced significantly from 7.1 days to 0.8 days (P < .05) by the introduction of the system. Five of 6 nonambulant patients became ambulant after the introduction of THERAPIST compared with 2 of 8 before the introduction of THERAPIST. The treatment outcome was significantly better after the introduction of the system (P < .05), and suggested to be beyond the international standard. The telecommunication-helped radiotherapy and information system was useful in emergency radiotherapy in district hospitals for patients with MSCC for whom consultation with experienced radiation oncologists at a university hospital was required.

Cost-Benefit Analysis↗

PubMed2001

Treatment outcome of single or hypofractionated single-isocentric stereotactic irradiation (STI) using a linear accelerator for intracranial arteriovenous malformation.

BACKGROUND AND PURPOSE: We investigated the use of hypofractionated stereotactic radiotherapy (HFSR) to reduce adverse radiation effects in comparison to single-fraction stereotactic radiosurgery (SRS) for intracranial arteriovenous malformations (AVMs). MATERIALS AND METHODS: This study includes 53 intracranial AVMs treated between 1991-1998. HFSR was selected for 26 AVMs with a maximum diameter > or 2.5 cm or at eloquent area. Twenty-seven patients were treated with SRS (18 AVMs < 2.5 cm at non-eloquent area, nine patients who were unfit for prolonged ring-wearing). The most frequent minimum dose (Dmin) was 20 Gy for SRS and 28 Gy for HFSR in four fractions. The mean follow-up duration was 34.6 months for SRS and 35.4 months for HFSR. RESULTS: As a whole, the 3 and 5-year actuarial obliteration rates were 64 and 92%. Age <20 years old (P=0.02) and a maximum diameter <2 cm were favorable factors (P=0.05). A difference in the distribution of patients was observed in size (> or =2.5 cm or not) (P<0.001) and location (eloquent or not) (P<0.001) between SRS and HFSR due to the treatment selection. However, no significant differences were observed in the actuarial rates of obliteration and transient increased signals with T2-weighted MR images between SRS and HFSR. Radiation necrosis occurred in two patients treated with SRS and in none with HFSR. Intracranial hemorrhage after treatment happened in two treated with SRS and three with HFSR. CONCLUSIONS: HFSR appears to be at least as effective as SRS in achieving complete obliteration of intracranial AVM, although its definitive role remains to be investigated.

Adolescent↗

PubMed2001

Annual rate of hearing loss falls after fractionated stereotactic irradiation for vestibular schwannoma.

PURPOSE: The rate of hearing loss in a population before and after irradiation was investigated to determine the effect of irradiation on hearing impairment. METHODS AND MATERIALS: In 72 patients with vestibular schwannoma who received fractionated stereotactic irradiation from 1992 to 1999, 21 had had their hearing levels examined 3 months or more before the treatment. The mean time between the initial examination and treatment was 18.6 months (range: 3-89 months), and the mean time between treatment and the last follow-up was 24.2 months (12-69 months). Thirty-six to 50 Gy in 20-25 fractions over 5 to 6 weeks was given using an X-ray beam from a linear accelerator. Pure tone average (PTA) was measured using the mean hearing level at five frequencies, and the annual rate of hearing loss was defined as [(hearing loss in PTA(dB))/(follow-up period (months)x12)]. RESULTS: The actual cumulative curve of decrease in tumor size of 2 mm or more was 38.3% at 2 years and 80.0% at 3 years. The mean of hearing loss in PTA was 11.6+/-10.3 dB (-1 to 35 dB) from the initial examination to the start of irradiation and 11.9+/-14.4 dB (-14 to 37 dB) from the start of irradiation to the last follow-up. The mean annual rates of hearing loss before irradiation and in the 1st,2nd,3rd and 4th years after irradiation were, respectively, 18.6, 11.2, 6.2, 5.1, and 5.0 dB/year. The annual rates of hearing loss in the 2nd year (P=0.025) and 3rd year (P=0.018) were significantly slower than the rate before irradiation. CONCLUSIONS: The mean annual rate of hearing loss was higher before irradiation than after irradiation, and hearing loss slowed rather than accelerated after irradiation. Although hearing loss after the treatment was usually permanent, fractionated stereotactic irradiation was suggested to be effective to lower the rate of hearing loss.

Adult↗

PubMed2001

Pretreatment apoptotic scores do not predict response to radiation therapy in oropharyngeal squamous cell carcinoma.

The prognostic value of tumor apoptosis was studied in patients with oropharyngeal squamous cell carcinoma treated with radical radiotherapy. Forty-eight patients with oropharyngeal squamous cell carcinoma who received radical radiotherapy between 1990 and 1995 were enrolled in the study. The radiation treatment for all patients involved the administration of 65 Gy in 26 fractions over a 6.5-week period. The apoptotic index (AI; the apoptotic cell count per 1000 tumor cells ) was distributed from 0 to 10 with a median at 2 and a mode of 1. There was a significant linear correlation between the AI and mitotic index (MI) (r=0.393, 95% confidence interval: 0.129-0.605). The cause-specific 5-year survival for patients with AI greater than the median was 46% and for the counterpart was 41%. There was no difference in cause-specific survival between AI/MI greater than the median (50%) and AI/MI smaller than the median (36%). The number of patients was too small to draw definite conclusions, but the AI and the AI/MI before treatment were not shown to have a prognostic value for oropharyngeal squamous cell carcinoma in our study. The primary sites and treatment methods may influence the prognostic value of AI even for the same histological types.

Adult↗

PubMed2001

Supratentorial astrocytomas and oligodendrogliomas treated in the MRI era.

BACKGROUND: There is at present no consensus on the policy for the treatment of patients with low-grade gliomas (LGGs). METHODS: This report is a retrospective multi-institutional study of 100 patients (ages 16-65 years) with astrocytoma (grade II), oligodendroglioma, anaplastic oligodendroglioma and anaplastic oligoastrocytoma of the supratentorial areas which were treated with surgery and postoperative radiotherapy at five university hospitals in northern Japan between 1990 and 1997 when MRI was routinely used to determine the target volume. Most patients were irradiated with 50-60 Gy. The target volume usually covered the areas with T2 prolongation of MRI with a margin of 2 cm. RESULTS: The disease-specific 5-year survival rate was 87.4% for patients with oligodendroglioma and 75.3% for patients with astrocytoma. Survival for patients with astrocytoma in the MRI era appears to be improved compared with historical controls in the literature. Patients with astrocytoma aged 40 years and under had a significantly better disease-specific survival rate than those over 40 years (P < 0.05) and patients with oligodendroglioma and oligoastrocytoma showed a similar tendency. Patients with astrocytoma who had over 50% of their tumor removed had a significantly better survival rate than those who had less than 50% removed (P < 0.05). Chemotherapy appeared to improve the disease-specific survival rate of patients with oligodendroglioma but not that of patients with astrocytoma. CONCLUSION: Oligodendroglioma has a more protracted course of disease progression than astrocytoma. This particular feature and the sensitivity of LGGs to chemotherapy as well as their relevant prognostic factors, such as age, histopathology and amount of tumor removal, should be taken into account before any decision on treatment methods for LGGs is made.

Adult↗

PubMed2000

Fractionated stereotactic radiotherapy for vestibular schwannoma (VS): comparison between cystic-type and solid-type VS.

PURPOSE: To compare the effectiveness and complications of fractionated stereotactic radiotherapy (SRT) for cystic-type vestibular schwannoma (VS) with those of solid-type VS. METHODS AND MATERIALS: In 65 patients treated with fractionated SRT between 1991 and 1999, 20 were diagnosed with cystic VS, in which at least one-third of the tumor volume was a cystic component on magnetic resonance imaging (MRI), and 45 were diagnosed with solid VS. Thirty-six Gy to 50 Gy in 20-25 fractions was administered to the isocenter and approximately 80% of the periphery of the tumor. All cystic and solid components were included in the gross tumor volume. The mean follow-up period was 37 months, ranging from 6 to 97 months. RESULTS: The actuarial 3-year rate of no episode of enlargement greater than 2.0 mm was 55% for cystic-type and 75% for solid-type VS; the difference was statistically significant (p = 0.023). The actuarial 3-year tumor-reduction (reduction in tumor size greater than 2.0 mm) rates were 93% and 31%, respectively (p = 0.0006). The overall actuarial tumor control rate (no tumor growth greater than 2. 0 mm after 2 years or no requirement of salvage surgery) was 92% at 5 years in 44 patients with a follow-up period of 2 or more years. There was no difference in the class hearing preservation rate between cystic VS and solid VS. No permanent trigeminal or facial nerve palsy was observed in either group. CONCLUSION: Transient tumor enlargement occurs in cystic VS more frequently than in solid-type VS, but the subsequent tumor-reduction rate in cystic VS is better.

Actuarial Analysis↗

PubMed2000

Use of an implanted marker and real-time tracking of the marker for the positioning of prostate and bladder cancers.

PURPOSE: A real-time tracking radiotherapy was investigated to assess its usefulness in precise localization and verification of prostate and bladder cancers. METHODS AND MATERIALS: The real-time tracking radiation therapy (RTRT) system consists of implantation of a 2.0-mm gold marker into a clinical target volume (CTV), three-dimensional radiation treatment planning (3DRTP) system, and the use of two sets of diagnostic x-ray television systems in the linear accelerator room, image processing units, and an image display unit. The position of the patient can be corrected by adjusting the actual marker position to the planned marker position, which has been transferred from the 3DRTP and superimposed on the fluoroscopic image on the display unit of the RTRT system. The position of the markers can be visualized during irradiation and after treatment delivery to verify the accuracy of the localization. Ten patients with prostate cancer and 5 patients with bladder cancer were examined using this system for the treatment setup on 91 occasions. RESULTS: After manual setup using skin markers, the median of absolute value of discrepancies between the actual position of the marker and the planned position of the marker for prostate cancer was 3.4 (0.1-8.9) mm, 4.1 (0.2-18.1) mm, and 2.3 (0.0-10.6) mm for the lateral, anteroposterior, and craniocaudal directions, respectively. The 3D median distance between the actual and planned positions of the marker was 6.9 (1.1-18.2) mm for prostate cancer and 6.9 (1.7-18.6) mm for bladder cancer. After relocation using RTRT, the 3D distance between the actual and planned position of the marker was 0.9 +/- 0.9 mm. Median 3D distances between actual positions after treatment delivery and planned positions were 1.6 (0.0-6.3) mm and 2.0 (0.5-8.0) mm during daily radiotherapy for the marker in patients with prostate cancer and bladder cancer, respectively. CONCLUSION: We believe the new positioning system can reduce uncertainty due to setup error and internal organ motion, although further improvement is needed for the system to account for the rotational and elastic changes of the affected tissues.

Humans↗

PubMed2000

Identification and characterization of a novel protein inhibitor of type 1 protein phosphatase.

We have isolated human cDNA for a novel type 1 protein phosphatase (PP1) inhibitory protein, named inhibitor-4 (I-4), from a cDNA library of germ cell tumors. I-4, composed of 202 amino acids, is 44% identical to a PP1 inhibitor, inhibitor-2 (I-2). I-4 conserves functionally important structure of I-2 and exhibited similar biochemical properties. I-4 inhibited activity of the catalytic subunit of PP1 (PP1C), specifically with an IC(50) of 0.2 nM, more potently than I-2 with an IC(50) of 2 nM. I-4 weakly inhibited the activity of myosin-associated phosphates (PP1M). However, the level of inhibition of PP1M was increased during preincubation of PP1M with I-4, suggesting that the inhibition is caused by interaction of I-4 with PP1C in such a manner that it competes with the M subunit of PP1M. Gel overlay experiments showed that I-4 binds PP1C directly. Three I-4 peptides containing the N-terminal residues 1-123, 1-131, and 1-142 all showed strong binding ability to PP1C but did not show PP1 inhibitory activity, whereas an I-2 peptide (residues 1-134), lacking the corresponding C-terminal residues, potently inhibited PP1C activity as previously reported. Removal of the 18 N-terminal amino acid residues from I-4 dramatically reduced the PP1 binding activity with a correlated loss of inhibitory activity, whereas removal of the 10 N-terminal residues had only a little effect. The two peptides GST-I-4(19-131) and GST-I-4(132-202) showed ability to bind to PP1C, albeit very weakly. These results strongly suggest a multiple-point interaction between I-4 and PP1C, which is thought to cause the inhibition of I-4 which is stronger than the inhibition of I-2.

Amino Acid Sequence↗

PubMed2000

Physical aspects of a real-time tumor-tracking system for gated radiotherapy.

PURPOSE: To reduce uncertainty due to setup error and organ motion during radiotherapy of tumors in or near the lung, by means of real-time tumor tracking and gating of a linear accelerator. METHODS AND MATERIALS: The real-time tumor-tracking system consists of four sets of diagnostic X-ray television systems (two of which offer an unobstructed view of the patient at any time), an image processor unit, a gating control unit, and an image display unit. The system recognizes the position of a 2.0-mm gold marker in the human body 30 times per second using two X-ray television systems. The marker is inserted in or near the tumor using image guided implantation. The linear accelerator is gated to irradiate the tumor only when the marker is within a given tolerance from its planned coordinates relative to the isocenter. The accuracy of the system and the additional dose due to the diagnostic X-ray were examined in a phantom, and the geometric performance of the system was evaluated in 4 patients. RESULTS: The phantom experiment demonstrated that the geometric accuracy of the tumor-tracking system is better than 1.5 mm for moving targets up to a speed of 40 mm/s. The dose due to the diagnostic X-ray monitoring ranged from 0.01% to 1% of the target dose for a 2.0-Gy irradiation of a chest phantom. In 4 patients with lung cancer, the range of the coordinates of the tumor marker during irradiation was 2.5-5.3 mm, which would have been 9.6-38.4 mm without tracking. CONCLUSION: We successfully implemented and applied a tumor-tracking and gating system. The system significantly improves the accuracy of irradiation of targets in motion at the expense of an acceptable amount of diagnostic X-ray exposure.

Algorithms↗

PubMed2000

Three-dimensional small-volume irradiation for residual or recurrent nasopharyngeal carcinoma.

PURPOSE: To minimize side effects and to achieve a high local control rate, three-dimensional (3D) small-volume irradiation was used for locally residual or recurrent nasopharyngeal carcinoma. METHODS AND MATERIALS: Between July 1992 and March 1998, 18 tumors (12 residual and 6 local recurrent cases) were treated with 3D planned small-volume irradiation. The total dose (i.e., the dose of conventional radiotherapy plus that of the 3D irradiation) was 78.4 Gy (74.8-91.0 Gy) in its mean value for residual disease and 105.0 Gy (94.8-125 Gy) for recurrence. The mean value of the 90% isodose volume was 40.3 cc (8.0-94.0 cc). The mean follow-up period from the start of the boost or re-irradiation was 39 months. RESULTS: The 3-year local control rate of the 12 residual tumors was 70%. Of 9 T4 residual tumors, 7 were controlled at a follow-up period between 17 and 70 months (median of 42 months). Of 6 recurrent tumors treated with re-irradiation, 3 were controlled at a follow-up period between 7 and 28 months. In the case of booster therapy, trismus occurred in 1 patient with a total dose of 91 Gy. Among the patients receiving re-irradiation, a temporary ulceration of the nasopharyngeal mucosa developed in 1 patient with a total dose of 111 Gy. CONCLUSION: 3D small-volume irradiation was effective and safe in treating residual or recurrent nasopharyngeal carcinoma.

Follow-Up Studies↗

PubMed2000

High-speed magnetic resonance imaging for four-dimensional treatment planning of conformal radiotherapy of moving body tumors.

PURPOSE: High-speed magnetic resonance imaging (MRI) was applied to the determination of the planning target volume (PTV) of moving hepatobiliary tumors. METHODS AND MATERIALS: Three moving tumors, including two metastatic hepatic tumors and one bile duct tumor, were examined using high-speed MRI and reference fiducial markers before external radiotherapy. Patients were examined for 30 seconds under conditions of normal breathing during the examination. The coordinates of the center of the tumor contours were shown on sagittal and coronal images displayed on the monitor. RESULTS: The maximum length of movement was 10.6 +/- 7.0 mm in a craniocaudal direction; 5.2 +/- 1.8 mm in a lateral direction; and 4.6 +/- 1.6 mm in a ventrodorsal direction. When the PTV was determined using MRI at exhalation phase with a 10-mm safety margin, clinical target volume (CTV) was not covered in 19% of all images in the 3 patients. With MRI at inhalation phase with a 10-mm safety margin, CTV was not covered in 36% of all images. CONCLUSION: Four-dimensional treatment planning using high speed MRI, and integrating time and spatial information, has the potential to determine the planning target volume of moving body tumors more precisely than does conventional CT planning.

Bile Duct Neoplasms↗

PubMed2000

Four-dimensional treatment planning and fluoroscopic real-time tumor tracking radiotherapy for moving tumor.

PURPOSE: To achieve precise three-dimensional (3D) conformal radiotherapy for mobile tumors, a new radiotherapy system and its treatment planning system were developed and used for clinical practice. METHODS AND MATERIALS: We developed a linear accelerator synchronized with a fluoroscopic real-time tumor tracking system by which 3D coordinates of a 2.0-mm gold marker in the tumor can be determined every 0.03 second. The 3D relationships between the marker and the tumor at different respiratory phases are evaluated using CT image at each respiratory phase, whereby the optimum phase can be selected to synchronize with irradiation (4D treatment planning). The linac is triggered to irradiate the tumor only when the marker is located within the region of the planned coordinates relative to the isocenter. RESULTS: The coordinates of the marker were detected with an accuracy of +/- 1 mm during radiotherapy in the phantom experiment. The time delay between recognition of the marker position and the start or stop of megavoltage X-ray irradiation was 0.03 second. Fourteen patients with various tumors were treated by conformal radiotherapy with a "tight" planning target volume (PTV) margin. They were surviving without relapse or complications with a median follow-up of 6 months. CONCLUSION: Fluoroscopic real-time tumor tracking radiotherapy following 4D treatment planning was developed and shown to be feasible to improve the accuracy of the radiotherapy for mobile tumors.

Computer Systems↗