Carbon ion radiotherapy for elderly patients 80 years and older with stage I non-small cell lung cancer.

Surgical resection is the standard treatment for stage I non-small cell lung cancer (NSCLC). However, elderly patients with NSCLC often suffer from other conditions, such as chronic obstructive pulmonary disease (COPD) or cardiovascular disease, and are not suitable candidates for surgery. Different modalities to treat stage I NSCLC have been developed, such as stereotactic radiotherapy (SRT), proton beam radiotherapy and carbon ion radiotherapy (CIRT). Between April 1999 and November 2003, we treated 129 patients with stage I NSCLC using CIRT. In this study, we focused on 28 patients aged 80 years and older who underwent CIRT, and analyzed the effectiveness of CIRT in treating their lung cancer and the impact on their activity of daily life (ADL). The 5-year local control rate for these patients was 95.8%, and the 5-year overall survival rate was 30.7%, but there were no patients who started home oxygen therapy or had decreased ADL. Our data demonstrate that CIRT was effective in treating elderly patients with stage I NSCLC.

Dosimetric variation due to CT inter-slice spacing in four-dimensional carbon beam lung therapy.

When CT data with thick slice thickness are used in treatment planning, geometrical uncertainty may induce dosimetric errors. We evaluated carbon ion dose variations due to different CT slice thicknesses using a four-dimensional (4D) carbon ion beam dose calculation, and compared results between ungated and gated respiratory strategies. Seven lung patients were scanned in 4D mode with a 0.5 mm slice thickness using a 256-multi-slice CT scanner. CT images were averaged with various numbers of images to simulate reconstructed images with various slice thicknesses (0.5-5.0 mm). Two scenarios were studied (respiratory-ungated and -gated strategies). Range compensators were designed for each of the CT volumes with coarse inter-slice spacing to cover the internal target volume (ITV), as defined from 4DCT. Carbon ion dose distribution was computed for each resulting ITV on the 0.5 mm slice 4DCT data. The accumulated dose distribution was then calculated using deformable registration for 4D dose assessment. The magnitude of over- and under-dosage was found to be larger with the use of range compensators designed with a coarser inter-slice spacing than those obtained with a 0.5 mm slice thickness. Although no under-dosage was observed within the clinical target volume (CTV) region, D95 remained at over 97% of the prescribed dose for the ungated strategy and 95% for the gated strategy for all slice thicknesses. An inter-slice spacing of less than 3 mm may be able to minimize dose variation between the ungated and gated strategies. Although volumes with increased inter-slice spacing may reduce geometrical accuracy at a certain respiratory phase, this does not significantly affect delivery of the accumulated dose to the target during the treatment course.

Changes in tumor volume of sacral chordoma after carbon ion radiotherapy.

OBJECTIVE: We evaluated changes in tumor volume in cases of sacral chordoma after carbon ion radiotherapy. METHODS: Thirty-four patients with sacral chordoma underwent carbon ion radiotherapy between June 1996 and June 2003. We assessed 23 patients without previous surgery using T2-weighted magnetic resonance imaging. The tumor volume was calculated semiautomatically. RESULTS: Two cases showed local recurrence. The median interval of this examination was 46 months. At the end of the treatment, the tumor showed an enlargement larger than 10% of its volume in 13 of the 23 cases, no change in 4 cases, and regression in 6 cases. At the last examination, 20 cases showed a reduction in tumor volume, and the median ratio, determined as the tumor volume at the last examination divided by that before the treatment, was 0.36. CONCLUSIONS: An increase in tumor volume at the end of the treatment does not indicate the ineffectiveness of carbon ion radiotherapy.

Magnitude of residual internal anatomy motion on heavy charged particle dose distribution in respiratory gated lung therapy.

PURPOSE: To assess the variation in carbon beam dose distribution due to residual motion in lung cancer patients undergoing respiratory-gated radiotherapy. METHODS AND MATERIALS: A total of 11 lung cancer patients underwent four-dimensional computed tomography with a 256-multislice computed tomography scanner under free-breathing conditions. A compensating bolus was designed to cover the treatment beam for all planning target volumes during a 30% duty cycle centered on exhalation (gating window). This bolus was applied to the four-dimensional computed tomography data for one respiratory cycle, and then the carbon beam dose distribution was calculated. RESULTS: A water equivalent pathlength variation of <5 mm was observed in the gating window, but this increased to 95% volume irradiation is dependent on the respiratory phase but not the gating window. However, the dose for >95% volume irradiation correlated well with the tumor displacement distance. More than 90% of the dose for >95% volume irradiation could be delivered in the gating window with <4-mm tumor displacement resulting from exhalation. CONCLUSION: The results of our study have shown that even when the treatment beam delivery occurs outside the gating window, the prescribed dose to the target is not affected in patients with a tumor displacement of <4 mm. Thus, respiratory gating is not required in radiotherapy for patients with <4-mm tumor displacement in a respiratory cycle.

Curative treatment of Stage I non-small-cell lung cancer with carbon ion beams using a hypofractionated regimen.

PURPOSE: A phase I/II study on carbon ion radiotherapy for Stage I non-small-cell lung cancer (NSCLC) was first conducted between 1994 and 1999 and determined the optimal dose. Second, a Phase II study using the optimal dose was performed. The purpose of the present study was to clarify the local control and 5-year survival rates. METHODS AND MATERIALS: Between April 1999 and December 2000, 50 patients with 51 primary lesions were treated. Using a fixed dose of 72 GyE in nine fractions over 3 weeks, the primary tumors were irradiated with carbon ion beams alone. The average age of the patients was 74.5 years. Thirty-three (66%) of these were medically inoperable. Local control and survival were determined by using the Kaplan-Meier method and the data were statistically processed by using the log-rank test. RESULTS: All patients were observed for a minimum of 5 years or until death with a median follow-up time of 59.2 months (range, 6.0-83.0 months). The local control rate for all patients was 94.7%. The patients' 5-year cause-specific survival rate was 75.7% (IA: 89.4; IB: 55.1), and overall survival 50.0% (IA: 55.2; IB: 42.9). No toxic reactions in the lung greater than Grade 3 were detected. CONCLUSIONS: Carbon ion radiotherapy, a new treatment modality with superior benefits in terms of quality of life and activity of daily living, has been proven as a valid alternative to surgery for Stage I NSCLC and to offer particular benefits, especially for elderly and inoperable patients.

Four-dimensional measurement of lung tumor displacement using 256-multi-slice CT-scanner.

The concept of internal target volume is of marked importance for radiotherapy to lung tumors as respiration-induced motion is important. Individualized assessment of motion is required as tumor site may not predict the extent or pattern of tumor motion. We performed volumetric cine scanning using the 256-multi-slice CT (256MSCT) to study tumor motion during free breathing in 14 inpatients who were treated with carbon-ion radiotherapy. Motion assessment in 16 respiratory phases of the cine CT revealed most tumors to show hysteresis-like behavior. Isocenter displacement between peak exhalation and inhalation for the average of the right and left lungs were 7 mm, 7 mm and 15 mm for the upper, middle and lower lobes, respectively. Cine CT with the 256MSCT improved the evaluation of tumor displacement and overcomes some of the limitations associated with current CT methods. Volumetric cine CT data provides useful data on motion for planning in all radiation approaches for lung tumors.

Preliminary study: color map of hepatocellular carcinoma using dynamic contrast-enhanced 256-detector row CT.

To distinguish hepatocellular carcinoma (HCC) from normal liver tissue, a color map was made by dynamic contrast-enhanced 256-detector row CT developed at our institute. Dynamic enhanced CT of the liver of three patients with HCC was studied. The CT has 912 (transverse) x 256 (cranio-caudal) elements, each measuring approximately 0.5 mm x 0.5mm at the center of rotation. Scanning for 10 s (1.0 s/rotation) was started 30 s after intravenous injection of contrast medium. The reconstruction increment was 0.62 mm with a time interval of 0.1s and a matrix size of 512 x 512 x 256. Color maps were generated to show the gradient of the regression line of the time-density change. Due to volume acquisition, the 3D color map can be created using continuous 10-s scanning. The densities of the HCC and liver were decreased and increased during scanning, respectively. The HCC was detected clearly in the color map as a downward-sloping region. Dynamic enhanced 256-detector row CT could be useful for detecting malignant tumors in the liver with a short scan time.

Dose escalation study of carbon ion radiotherapy for locally advanced carcinoma of the uterine cervix.

PURPOSE: To evaluate the toxicity and efficacy of carbon ion radiotherapy (CIRT) for locally advanced cervical cancer by two phase I/II clinical trials. METHODS AND MATERIALS: Between June 1995 and January 2000, 44 patients were treated with CIRT. Thirty patients had Stage IIIB disease, and 14 patients had Stage IVA disease. Median tumor size was 6.5 cm (range, 4.2-11.0 cm). The treatment consisted of 16 fractions of whole pelvic irradiation and 8 fractions of local boost. In the first study, the total dose ranged from 52.8 to 72.0 gray equivalents (GyE) (2.2-3.0 GyE per fraction). In the second study, the whole pelvic dose was fixed at 44.8 GyE, and an additional 24.0 or 28.0 GyE was given to the cervical tumor (total dose, 68.8 or 72.8 GyE). RESULTS: No patient developed severe acute toxicity. In contrast, 8 patients developed major late gastrointestinal complications. The doses resulting in major complications were > or =60 GyE. All patients with major complications were surgically salvaged. The 5-year local control rate for patients in the first and second studies was 45% and 79%, respectively. When treated with > or =62.4 GyE, the local control was favorable even for the patients with stage IVA disease (69%) or for those with tumors > or =6.0 cm (64%). CONCLUSIONS: In CIRT for advanced cervical cancer, the dose to the intestines should be limited to <60 GyE to avoid major complications. Although the number of patients in this study was small, the results support continued investigation to confirm therapeutic efficacy.

Respiratory correlated segment reconstruction algorithm towards four-dimensional radiation therapy using carbon ion beams.

PURPOSE: To enhance the precision of treatment planning for tumors which move under respiration, we developed a respiratory-correlated segment reconstruction method (RS) based on the Feldkamp--Davis--Kress algorithm (FDK) which provides high temporal resolution and a high signal-to-noise ratio. We compared full-scan (FS-FDK) and RS-FDK with regard to dose distribution in heavy ion treatment planning. MATERIALS AND METHODS: Data acquisition for RS-FDK is done using a respiratory sensing system in cine scan mode with a 256-multi-detector row CT (256-MDCT). To evaluate the accuracy of irradiation of moving tumors, dose distributions with each algorithm were compared in heavy ion treatment planning using beam parameters obtained with FS-FDK. RESULTS: Images obtained using RS-FDK did not show motion artifacts and visualized the edges of the liver and pulmonary vessels more clearly than those with FS-FDK. The iso-dose distributions for FS-FDK covered the target volume; in contrast, RS-FDK with the beam parameter of FS-FDK image provided an insufficient dose to the target and a considerable dose to normal tissues around it. CONCLUSIONS: The information provided by RS-FDK improves accuracy in the prescription of dose-to-target volume. Further, RS-FDK allows greater precision in the delivery of radiotherapy, including 4D radiation therapy.

A combination-weighted Feldkamp-based reconstruction algorithm for cone-beam CT.

The combination-weighted Feldkamp algorithm (CW-FDK) was developed and tested in a phantom in order to reduce cone-beam artefacts and enhance cranio-caudal reconstruction coverage in an attempt to improve image quality when utilizing cone-beam computed tomography (CBCT). Using a 256-slice cone-beam CT (256CBCT), image quality (CT-number uniformity and geometrical accuracy) was quantitatively evaluated in phantom and clinical studies, and the results were compared to those obtained with the original Feldkamp algorithm. A clinical study was done in lung cancer patients under breath holding and free breathing. Image quality for the original Feldkamp algorithm is degraded at the edge of the scan region due to the missing volume, commensurate with the cranio-caudal distance between the reconstruction and central planes. The CW-FDK extended the reconstruction coverage to equal the scan coverage and improved reconstruction accuracy, unaffected by the cranio-caudal distance. The extended reconstruction coverage with good image quality provided by the CW-FDK will be clinically investigated for improving diagnostic and radiotherapy applications. In addition, this algorithm can also be adapted for use in relatively wide cone-angle CBCT such as with a flat-panel detector CBCT.

Noise properties for three weighted Feldkamp algorithms using a 256-detecotor row CT-scanner: case study for hepatic volumetric cine imaging.

In cone-beam geometry, image quality may be degraded or artifacts may occur if the cone angle is substantially wide. This is because a cone-beam scan along a circular orbit does not collect the complete set of data required to make an exact reconstruction of all volumetric data. To increase temporal resolution and thus image quality in cone-beam geometry, Silver proposed the new half-scan algorithm (NHS-FDK), which extends Parker's weighting function (HS-FDK) by utilizing a larger range up to 2pi. Here, we evaluated these algorithms for hepatic contrast-enhanced CT in cine scan mode using a 256-detector row CT. The full-scan (FS-FDK) images show uniform distribution of the image noise and CT-number uniformity. Image noise and CT-number uniformity with HS-FDK and NHS-FDK images follow the initial projection angle. HS-FDK images therefore have more changeable higher intensity (brighter) and a lower intensity (darker) areas than respective FS-FDK and NHS-FDK images. We concluded that, considering the trade-off between image quality and temporal resolution, the NHS-FDK algorithm is useful in volumetric cine imaging for the abdomen.

Efficacy and safety of carbon ion radiotherapy in bone and soft tissue sarcomas.

PURPOSE: To evaluate the tolerance for and effectiveness of carbon ion radiotherapy in patients with unresectable bone and soft tissue sarcomas. PATIENTS AND METHODS: We conducted a phase I/II dose escalation study of carbon ion radiotherapy. Fifty-seven patients with 64 sites of bone and soft tissue sarcomas not suited for resection received carbon ion radiotherapy. Tumors involved the spine or paraspinous soft tissues in 19 patients, pelvis in 32 patients, and extremities in six patients. The total dose ranged from 52.8 to 73.6 gray equivalent (GyE) and was administered in 16 fixed fractions over 4 weeks (3.3 to 4.6 GyE/fraction). The median tumor size was 559 cm(3) (range, 20 to 2,290 cm(3)). The minimum follow-up was 18 months. RESULTS: Seven of 17 patients treated with the highest total dose of 73.6 GyE experienced Radiation Therapy Oncology Group grade 3 acute skin reactions. Dose escalation was then halted at this level. No other severe acute reactions (grade > 3) were observed in this series. The overall local control rates were 88% and 73% at 1 year and 3 years of follow-up, respectively. The median survival time was 31 months (range, 2 to 60 months), and the 1- and 3-year overall survival rates were 82% and 46%, respectively. CONCLUSION: Carbon ion radiotherapy seems to be a safe and effective modality in the management of bone and soft tissue sarcomas not eligible for surgical resection, providing good local control and offering a survival advantage without unacceptable morbidity.

Informatics in Radiology (infoRAD): mobile wireless DICOM server system and PDA with high-resolution display: feasibility of group work for radiologists.

A novel mobile system has been developed for use by radiologists in managing Digital Imaging and Communications in Medicine (DICOM) image data. The system consists of a mobile DICOM server (MDS) and personal digital assistants (PDAs), including a Linux PDA with a video graphics array (VGA) display (307,200 pixels, 3.7 inches). The MDS weighs 410 g, has a 60-GB hard disk drive and a built-in wireless local area network (LAN) access point, and supports a DICOM server (Central Test Node). The Linux-based MDS can be accessed with personal computers (PCs) and PDAs by means of a wireless or wired LAN, and client-server communications can be established at any time. DICOM images can be displayed by using any PDA or PC by means of a Web browser. Simultaneous access to the MDS is possible for multiple authenticated users. With most PDAs, image compression is necessary for complete display of DICOM images; however, the VGA screen can display a 512 x 512-pixel DICOM image almost in its entirety. This wireless system allows efficient management of heavy loads of lossless DICOM image data and will be useful for collaborative work by radiologists in education, conferences, and research.

[(11)C]methionine positron emission tomography and survival in patients with bone and soft tissue sarcomas treated by carbon ion radiotherapy.

PURPOSE: The development of the novel carbon ion radiotherapy (CIRT) in the treatment of refractory cancers has resulted in the need for a way to accurately evaluate patient prognosis. We evaluated whether L-[methyl-(11)C]-methionine (MET) uptake and its change after CIRT were the early survival predictors in patients with unresectable bone and soft tissue sarcomas. EXPERIMENTAL DESIGN: MET positron emission tomography was prospectively performed in 62 patients with unresectable bone and soft tissue sarcomas before and within 1 month after CIRT. Tumor MET uptake was measured with the semiquantitative tumor:nontumor ratio (T/N ratio). The MET uptake in the tumor and relevant clinical parameters were entered into univariate and multivariate survival analysis. RESULTS: The overall median survival time was 20 months. Patients with a baseline T/N ratio of 6 (2-year survival rate: 69.4% versus 32.3%; P = 0.01). Patients with a post-CIRT ratio of 4.4 (2-year survival rate: 63.7% versus 41.3%; P = 0.01). A significant higher survival rate was observed in patients with post-therapeutic MET uptake change of >30% than patients in lower change group (2-year survival rate: 74.6% versus 41.6%; P = 0.049). The multivariate analysis showed that both baseline and post-CIRT T/N ratio were statistically significant independent predictors of patient survival. Tumors with larger T/N ratio had a significantly poorer prognosis. CONCLUSIONS: MET uptake as measured by either baseline or post-CIRT T/N ratio was an independent predictor of survival in patients with bone and soft tissue sarcomas treated by carbon ion radiotherapy, whereas post-therapeutic MET uptake change might have potential value for the same purpose.

Carbon ion radiotherapy for unresectable sacral chordomas.

PURPOSE: The purpose is to evaluate the efficacy and toxicity of carbon ion radiotherapy for unresectable sacral chordomas. EXPERIMENTAL DESIGN: We performed a retrospective analysis of 30 patients with unresectable sacral chordomas treated with carbon ion radiotherapy at the Heavy Ion Medical Accelerator in Chiba, Japan. Twenty-three patients presented with no prior treatment, and the remaining 7 patients had locally recurrent disease following previous surgical resection. The median clinical target volume was 546 cm(3). The applied carbon ion dose ranged from 52.8 to 73.6 GyE (gray equivalent, median 70.4) in 16 fixed fractions over 4 weeks. RESULTS: At median follow-up of 30 months (range, 9 to 87 months), 26 patients were still alive and 24 patients remained continuously disease-free. Overall and cause-specific survival rates at 5 years were 52 and 94%, respectively. The overall local control rate at 5 years was 96%. Two patients experienced severe skin/soft tissue complications requiring skin grafts. No other treatment-related surgical interventions, including colostomy or urinary diversion, were carried out. All patients have remained ambulatory and able to stay at home after carbon ion radiotherapy. CONCLUSIONS: Carbon ion radiotherapy is effective and safe in the management of patients with unresectable sacral chordomas and offers a promising alternative to surgery.

MR imaging of brain injury induced by carbon ion radiotherapy for head and neck tumors.

To clarify the characteristics of magnetic resonance (MR) imaging of radiation-induced brain injury following carbon ion radiotherapy and to observe the changes in lesions over time, we evaluated 40 patients with radiation-induced brain injury from carbon ion radiotherapy for head and neck tumors. Their primary lesions received a radiation dose of 48 to 70.4 Gray equivalent (GyE) in 16 to 18 fractions. MR imaging of radiation-induced brain injury was graded as follows: Grade 1: change in focal white matter; focal contrast enhancement and surrounding edema; Grade 2: nonenhanced area or cystic lesion in enhanced lesion; Grade 3: focal necrosis with mass effect; and Grade 4: mass effect requiring surgical intervention. Radiation-induced brain injury appeared as early as 2 months and as late as 57 months after carbon ion therapy (mean interval, 22.2 months). MR findings of initial lesion were Grade 1 in 26 cases (65.0%), Grade 2 in 13 (32.5%), and Grade 3 in 1 (2.5%). Brain injury was always found in the radiation field initially, but cystic lesion and edema later extended outside the field in 10 cases (25.0%). In follow-up MR studies, size of edema or enhanced lesion was reduced in 17 patients (42.5%) without treatment. Two cases with large cystic lesions required surgery. Improvement of radiation-induced brain injury was observed more often than had been previously described. Because edema and cystic lesion can occasionally extend outside the radiation field, such findings do not exclude the possibility of radiation-induced brain injury. Careful observation is recommended because cystic lesions can enlarge enough to require surgical treatment in some cases.

Results of the first prospective study of carbon ion radiotherapy for hepatocellular carcinoma with liver cirrhosis.

PURPOSE: To evaluate the toxicity and antitumor effect of carbon ion radiotherapy for hepatocellular carcinoma within a Phase I-II trial. METHODS AND MATERIALS: Between June 1995 and February 1997, 24 patients with histopathologically proven hepatocellular carcinoma were treated to 15 fractions within 5 weeks in a step-wise dose-escalation study. The disease stage was Stage II in 10, IIIA in 6, and IVA in 8 patients. The Common Toxicity Criteria, Radiation Therapy Oncology Group/European Organization for the Research and Treatment of Cancer criteria, and Child-Pugh score were used to evaluate toxicity. The antitumor effect was evaluated by the tumor response, cumulative local control, and survival rates. RESULTS: During a median follow-up of 71 months (range, 63-83 months), no severe adverse effects and no treatment-related deaths occurred. The Child-Pugh score did not increase by >2 points after the start of therapy. In 78% and 75% of all patients, the score did not increase by >1 point in the early and late phase, respectively. The overall tumor response rate was 71%. The local control and overall survival rate was 92% and 92%, 81% and 50%, and 81% and 25% at 1, 3, and 5 years, respectively. CONCLUSION: Carbon ion radiotherapy appears safe and effective for patients with hepatocellular carcinoma. Additional clinical studies using a larger subject group are required to confirm the therapeutic efficacy.

Carbon ion radiotherapy for stage I non-small cell lung cancer.

BACKGROUND AND PURPOSE: Heavy ion radiotherapy is a promising modality because of its excellent dose localization and high biological effect on tumors. Using carbon beams, a dose escalation study was conducted for the treatment of stage I non-small cell lung cancer (NSCLC) to determine the optimal dose. MATERIALS AND METHODS: The first stage phase I/II trial using 18 fractions over 6 weeks for 47 patients and the second one using nine fractions over 3 weeks for 34 patients were conducted by the dose escalation method from 59.4 to 95.4 Gray equivalents (GyE) in incremental steps of 10% and from 68.4 to 79.2 GyE in 5% increments, respectively. The local control and survival rates were obtained using the Kaplan-Meier method. RESULTS: Radiation pneumonitis at grade III occurred in three of 81 patients, but they fully recovered. This was not a dose-limiting factor. The local control rates in the first and second trials were 64% and 84%, respectively. The total recurrence rate in both trials was 23.2%. The infield local recurrence in the first trial was significantly dependent on carbon dose. The doses greater than 86.4 GyE at 18 fractions and 72 GyE at nine fractions achieved a local control of 90% and 95%, respectively. The 5 year overall and cause-specific survivals in 81 patients were 42% and 60%, respectively. CONCLUSIONS: With our dose escalation study, the optimum safety and efficacy dose of carbon beams was determined. Carbon beam therapy attained almost the same results as surgery for stage I NSCLC although this was a I/II study.

Overview of clinical experiences on carbon ion radiotherapy at NIRS.

BACKGROUND AND PURPOSE: Carbon ion beams provide physical and biological advantages over photons. This study summarizes the experiences of carbon ion radiotherapy at the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences. MATERIALS AND METHODS: Between June 1994 and August 2003, a total of 1601 patients with various types of malignant tumors were enrolled in phase I/II dose-escalation studies and clinical phase II studies. All but malignant glioma patients received carbon ion radiotherapy alone with a fraction number and overall treatment time being fixed for each tumor site, given to one field per day and 3 or 4 days per week. In dose-escalation studies, the total dose was escalated by 5 or 10% increments to ensure a safe patient treatment and to determine appropriate dose levels. RESULTS: In the initial dose-escalation studies, severe late complications of the recto-sigmoid colon and esophagus were observed in those patients who received high dose levels for prostate, uterine cervix and esophageal cancer. Such adverse effects, however, did shortly disappear as a result of determining safe dose levels and because of improvements in the irradiation method. Carbon ion radiotherapy has shown improvement of outcome for tumor entities: (a) locally advanced head and neck tumors, in particular those with non-squamous cell histology including adenocarcinoma, adenoid cystic carcinoma, and malignant melanoma; (b) early stage NSCLC and locally advanced NSCLC; (c) locally advanced bone and soft tissue sarcomas not suited for surgical resection; (d) locally advanced hepatocellular carcinomas; (e) locally advanced prostate carcinomas, in particular for high-risk patients; (f) chordoma and chondrosarcoma of the skull base and cervical spine, and (g) post-operative pelvic recurrence of rectal cancer. Treatment of malignant gliomas, pancreatic, uterine cervix, and esophageal cancer is being investigated within dose-escalation studies. There is a rationale for the use of short-course RT regimen due to the superior dose localization and the unique biological properties of high-LET beams. This has been proven in treatment of NSCLC and hepatoma, where the fraction number has been successfully reduced to 4-12 fractions delivered within 1-3 weeks. Even for other types of tumors including prostate cancer, bone/soft tissue sarcoma and head/neck tumors, it was equally possible to apply the therapy in much shorter treatment times as compared to conventional RT regimen. CONCLUSION: Carbon ion radiotherapy, due to its physical and biologic advantages over photons, has provided improved outcome in terms of minimized toxicity and high local control rates for locally advanced tumors and pathologically non-squamous cell type of tumors. Using carbon ion radiotherapy, hypofractionated radiotherapy with application of larger doses per fraction and a reduction of overall treatment times as compared to conventional radiotherapy was enabled.

Physical performance evaluation of a 256-slice CT-scanner for four-dimensional imaging.

We have developed a prototype 256-slice CT-scanner for four-dimensional (4D) imaging that employs continuous rotations of a cone-beam. Since a cone-beam scan along a circular orbit does not collect a complete set of data to make an exact reconstruction of a volume [three-dimensional (3D) image], it might cause disadvantages or artifacts. To examine effects of the cone-beam data collection on image quality, we have evaluated physical performance of the prototype 256-slice CT-scanner with 0.5 mm slices and compared it to that of a 16-slice CT-scanner with 0.75 mm slices. As a result, we found that image noise, uniformity, and high contrast detectability were independent of z coordinate. A Feldkamp artifact was observed in distortion measurements. Full width at half maximum (FWHM) of slice sensitivity profiles (SSP) increased with z coordinate though it seemed to be caused by other reasons than incompleteness of data. With regard to low contrast detectability, smaller objects were detected more clearly at the midplane (z = 0 mm) than at z = 40 mm, though circular-band like artifacts affected detection. The comparison between the 16-slice and the 256-slice scanners showed better performance for the 16-slice scanner regarding the SSP, low contrast detectability, and distortion. The inferiorities of the 256-slice scanner in other than distortion measurement (Feldkamp artifact) seemed to be partly caused by the prototype nature of the scanner and should be improved in the future scanner. The image noise, uniformity, and high contrast detectability were almost identical for both CTs. The 256-slice scanner was superior to the 16-slice scanner regarding the PSF, though it was caused by the smaller transverse beam width of the 256-slice scanner. In order to compare both scanners comprehensively in terms of exposure dose, noise, slice thickness, and transverse spatial resolution, K=Dsigma2ha3 was calculated, where D was exposure dose (CT dose index), sigma was magnitude of noise, h was slice thickness (FWHM of SSP), and a was transverse spatial resolution (FWHM of PSF). The results showed that the K value was 25% larger for the 16-slice scanner, and that the 256-slice scanner was 1.25 times more effective than the 16-slice scanner at the midplane. The superiority in K value for the 256-slice scanner might be partly caused by decrease of wasted exposure with a wide-angle cone-beam scan. In spite of the several problems of the 256-slice scanner, it took a volume data approximately 1.0 mm (transverse) x 1.3 mm (longitudinal) resolution for a wide field of view (approximately 100 mm long) along the zeta axis in a 1 s scan if resolution was defined by the FWHM of the PSF or the SSP, which should be very useful to take dynamic 3D (4D) images of moving organs.