Robust and optimal dose distribution for brain metastases with robotic radiosurgery system: recipe for an inflection point.

Purpose.This study aims to establish a robust dose prescription methodology in stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) for brain metastases, considering geometrical uncertainty and minimising dose exposure to the surrounding normal brain tissue.Methods and Materials.Treatment plans employing 40%-90% isodose lines (IDL) at 10% IDL intervals were created for variously sized brain metastases. The plans were constructed to deliver 21 Gy in SRS. Robustness of each plan was analysed using parameters such as the near minimum dose to the tumour, the near maximum dose to the normal brain, and the volume of normal brain irradiated above 14 Gy.Results.Plans prescribed at 60% IDL demonstrated the least variation in the near minimum dose to the tumour and the near maximum dose to the normal brain under conditions of minimal geometrical uncertainty relative to tumour radius. When the IDL-percentage prescription was below 60%, geometrical uncertainties led to increases in these doses. Conversely, they decreased with IDL-percentage prescriptions above 60%. The volume of normal brain irradiated above 14 Gy was lowest at 60% IDL, regardless of geometrical uncertainty.Conclusions.To enhance robustness against geometrical uncertainty and to better spare healthy brain tissue, a 60% IDL prescription is recommended in SRS and SRT for brain metastases using a robotic radiosurgery system.

Suitability of Metastatic Lung Tumors for Stereotactic Body Radiotherapy.

We investigated factors influencing local control of lung metastases treated with stereotactic body radiotherapy (SBRT) and determined the type of lesions for which SBRT is more suitable. Ninety-six patients and 196 tumors were included. Median follow-up duration was 32.0 months (range 4.7-95.8). The two-year local recurrence rate was 15.2% (95% confidence interval: 10.2-21.3). Multivariate analysis revealed biological effective dose, ultracentral tumor location, reirradiation, and prior chemotherapy as significant factors. SBRT is suitable for lung metastases, especially for peripheral tumors and those located in the inner lung parenchyma. For ultracentral lesions and recurrent lesions after SBRT, metastasectomy is recommended.

Repeated Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma.

PURPOSE: In clinical practice, whether cirrhotic livers in patients with hepatocellular carcinoma (HCC) can withstand repeated stereotactic body radiation therapy (SBRT) remains unclear. This study aimed to evaluate the outcomes and toxicities in these patients. METHODS AND MATERIALS: This retrospective study included patients with HCC who were treated with SBRT at least twice between January 2012 and June 2019. Local control and overall survival rates were calculated. Liver function before and after irradiation was evaluated using the Child-Pugh score and modified albumin-bilirubin grade. All toxicities were assessed using the Common Terminology Criteria for Adverse Events (version 4.0). RESULTS: Fifty-two patients underwent 136 courses (148 lesions) of SBRT, which was mostly performed for out-of-field tumors but 3 in-field recurrences. The median follow-up duration from the first SBRT was 52.6 months (range, 15.7-89.3 months). The median gross tumor volume was 4.6 cm3 (range, 0.8-55.2 cm3) at the second SBRT. The 3-year local control rate was 94.5% (95% confidence interval, 88.0%-97.5%). The 3-year overall survival rate after the second course was 62.8% (95% confidence interval, 45.1%-76.2%). Although the Child-Pugh score did not deteriorate after the second course, deterioration of the modified albumin-bilirubin grade at 6, 12, and 24 months was statistically significant compared with that before the second course. One patient (1.9%) experienced grade 3 hypoalbuminemia and 2 patients (3.8%) had grade 3 thrombocytopenia 6 months after the second course. Mild fatigue and nausea were reported in 9 (17.3%) and 6 (11.5%) patients, respectively. One instance of grade 5 toxicity was observed. Two patients (1.5%) had grade 2 gastric ulcers. No other grade ≥3 gastrointestinal toxicities occurred. CONCLUSIONS: Repeated SBRT is feasible and produces minimal toxicity in patients with HCC and Child-Pugh scores of ≤7 and a low normal liver dose.

A Novel Dissection Method Using a Flexible Neuroendoscope for Resection of Tumors Around the Aqueduct of Sylvius.

BACKGROUND: Flexible endoscopes have both a wide range of movement and a wide field of view and are therefore widely used for endoscopic third ventriculostomy and biopsy. However, tumor resection around the aqueduct of Sylvius using flexible endoscopes has scarcely been reported. CASE DESCRIPTION: We report 2 cases of tumor resection around the aqueduct of Sylvius. The first case is a 38-year-old man presenting with progressive headache, nausea, and diplopia. Magnetic resonance imaging (MRI) revealed a 1.4 cm nonenhancing mass at the entry of the aqueduct of Sylvius and occlusive hydrocephalus. We performed tumor resection and endoscopic third ventriculostomy (ETV) simultaneously. His symptoms disappeared after the operation. Final pathologic diagnosis was ancient schwannoma. The second case is a 78-year-old woman presenting with progressive disturbance of consciousness (coma). MRI showed 0.7 cm nonenhancing mass at the entry of the aqueduct of Sylvius and occlusive hydrocephalus. We performed tumor resection and ETV similarly. Her consciousness improved after the operation. Final tumor diagnosis was cavernous malformation. In both cases there was no additional neurologic deficit after the surgery. CONCLUSIONS: By using a flexible endoscope for tumor dissection, resection of a tumor without a neck, which cannot be removed through aspiration alone, becomes possible. To our knowledge, the presented cases are the first to describe the effectiveness of complete resection of a tumor in the third ventricle using flexible endoscopy.

Evaluation of contrast-enhanced ultrasonography for hepatocellular carcinoma prior to and following stereotactic body radiation therapy using the CyberKnife® system: A preliminary report.

The CyberKnife® is expected to be a novel local treatment for hepatocellular carcinoma (HCC), however, a long-term follow-up using dynamic computed tomography and magnetic resonance imaging is required to determine the effect of treatment in a number of the affected patients. Therefore, there is a requirement to evaluate procedures for early determination of the effect of CyberKnife treatment. The present study aimed to evaluate the changes in the hemodynamics of the tumors and the hepatic parenchyma surrounding the tumor prior to and following CyberKnife treatment for HCC. A total of 4 HCC patients were enrolled in this study. These patients underwent CyberKnife treatment and were evaluated by image analysis prior to and following treatment using contrast-enhanced ultrasonography (CEUS) with Sonazoid. CEUS was performed prior to treatment, at 2 and 4 weeks post-treatment, and every 4 weeks thereafter for as long as possible. The dynamics of the enhancement of the tumor and the hepatic parenchyma surrounding the tumor in the vascular phase, and the presence or absence of a hypoechoic area in the hepatic parenchyma surrounding the tumor in the post-vascular phase were assessed. Results showed that: i) In the patient with earlier changes, hemodynamic changes were evident in the tumor at 4 weeks and in the hepatic parenchyma surrounding the tumor at 2 weeks post-treatment, respectively; ii) the tumor showed hypoenhancement in all patients; and iii) with regard to findings in the hepatic parenchyma surrounding the tumor, strong hyperenhancement appeared in the vascular phase initially, followed by a hypoechoic area in the post-vascular phase. Evaluation of the hemodynamics of tumors and hepatic parenchyma surrounding the tumor using CEUS with Sonazoid may be therapeutically applicable, as it is less invasive than dynamic computed tomography (CT) and provides an early evaluation of the effectiveness of CyberKnife treatment.

Rectal Toxicity After Extremely Hypofractionated Radiotherapy Using a Non-Isocentric Robotic Radiosurgery System for Early Stage Prostate Cancer.

BACKGROUND: The aim of the study was to evaluate toxicity after extremely hypofractionated radiotherapy (EHF-RT) using a non-isocentric robotic radiosurgery system for early stage prostate cancer. METHODS: Eligibility criteria of this feasibility study were 50 - 84 years old, and low-risk to intermediate-risk disease. The prescribed dose to the iso-dose line of 95% of planning target volume was 35 Gy in five fractions over 2 weeks. The primary endpoint was the incidence of ≥ grade 2 acute toxicity which indicated symptoms requiring medications. RESULTS: We enrolled 20 patients from December 2012 to August 2014, and the median follow-up time was 30 months (range: 18 - 36). Sixteen patients had a short overall treatment time (OTT) of EHF-RT (9 - 10 days), and four patients had a long OTT (11 - 12 days) because of national holidays and patient's preference. The incidences of ≥ grade 2 acute toxicity in all sites, that in the rectum, and that in the genitourinary system, were 30%, 20%, and 10%, respectively. No patient developed severe acute toxicity (≥ grade 3). Among 16 patients with a short OTT of EHF-RT, four patients developed grade 2 acute rectal toxicity. Rectum-V28 Gy (rectal volume receiving ≥ 28 Gy) of 3.8 mL or higher had a tendency to increase grade 2 acute rectal toxicity (P = 0.058). One patient developed grade 3 late rectal toxicity and no patient developed severe late genitourinary toxicity. CONCLUSION: The incidences of ≥ grade 2 acute toxicity in all sites and that in the rectum after EHF-RT of 35 Gy in five fractions were 30% and 20%, respectively. High rectum-V28 Gy was associated with grade 2 acute rectal toxicity after EHF-RT for early prostate cancer.

[Stereotactic Body Radiotherapy with CyberKnife®for Liver Metastases from Colorectal Cancer].

For treatment of colorectal liver metastases, liver resection is recommended for resectable cases in the clinical guidelines for colorectal cancer. On the other hand, there are currently no data supporting the efficacy of radiation therapy as a topical treatment, and this treatment can therefore not presently be recommended. With CyberKnife®, it is possible to perform stereotactic radiation therapy using a linear accelerator with high accuracy, even for lesions in the trunk area such as liver metastases. Between December 2009 and September 2014 in our hospital, we performed radiation treatment using CyberKnife® for 14 cases with 22 colorectal liver metastases. As a result, we obtained response and local control rates of 76.2%and 81.0%, respectively. Moreover, no advanced adverse events were observed. Thus, we consider that CyberKnife® treatment for colorectal liver metastases is effective as a topical treatment, with low invasiveness and high safety.

Comparison of percutaneous radiofrequency ablation and CyberKnife(®) for initial solitary hepatocellular carcinoma: A pilot study.

AIM: To compare therapeutic outcomes and adverse events in initial solitary hepatocellular carcinoma (HCC) treated with radiofrequency ablation (RFA) and CyberKnife(®). METHODS: Seventy three consecutive patients with initial solitary HCC treated with RFA (38 patients; RFA group) and CyberKnife(®) (35 patients; CK group) were enrolled in this study. Background factors were compared between the two groups. Local and intrahepatic distant recurrence control, and cumulative survival rates were compared between the two groups. These were determined using the Kaplan-Meier method, and the significance of differences was analyzed by log-rank test. The presence of more grade 3 on CTCAE ver. 4.0 early and late adverse events was investigated. RESULTS: In background factors, age was significantly higher (P = 0.005) and the tumor diameter was significantly larger (P = 0.001) in the CK group. The 1-year local recurrence control rates were 97.4% and 97.1% in the RFA and CK groups, respectively (P = 0.71); the 1-year intrahepatic distant recurrence control rates were 85.6% and 86.1%, respectively (P = 0.91); and the 1-year cumulative survival rates were 100% and 95.2%, respectively (P = 0.075), showing no significant difference in any rate between the two groups. There were no late adverse event in the RFA group, but 11.4% in the CK group had late adverse events. In the CK group, the Child-Pugh score at 12 mo after treatment was significantly higher than that in the RFA group (P = 0.003) and significantly higher than the score before treatment (P = 0.034). CONCLUSION: The occurrence of adverse events is a concern, but CyberKnife(®) treatment is likely to become an important option for local treatment of early HCC.

Endovascular intervention for acute cervical carotid artery occlusion.

BACKGROUND: Acute cervical carotid artery occlusion presents with a severe neurological deficit and is associated with unfavorable outcomes. In this study, the authors report their experience with patients having had acute ischemic stroke due to cervical carotid occlusion, who underwent endovascular intervention. METHOD: Sixteen acute cervical carotid occlusion patients (15 males and 1 female; mean age 67.7 years) were treated by endovascularly between January 2009 and November 2012. Clinical, procedural, and angiographic data were retrospectively evaluated. Successful intracranial recanalization was based on thrombolysis in cerebral infarction score of 2B-3. A favorable outcome was defined as a modified Rankin Scale score of 0-2 at 90 days. FINDINGS: The average score of National Institutes of Health Stroke Scale before treatment was 15.9. Ten of 16 patients (63 %) were associated with intracranial tandem occlusion. Ten (63 %) cases were caused by atherosclerotic, 4 (25 %) by atrial fibrillation (AF), and 2 (13 %) by dissection. Thirteen of 16 (81 %) achieved successful cervical recanalization and 7 of 16 (44 %) patients obtained sufficient cervical and intracranial perfusion. As a result, 5 of 16 (31 %) patients demonstrated favorable outcomes. Five of seven patients (71 %) with successful cervical and intracranial recanalization presented favorable outcomes. In contrast, none of the patients without cervical or intracranial recanalization presented favorable outcomes. Three of 6 (50 %) patients initially without intracranial occlusion showed favorable outcomes, but only 2 of 10 (20 %) patients associated with intracranial occlusion had favorable outcomes. On the aspect of etiology, in atherosclerotic cases, 4 of 10 (40 %) showed favorable outcomes. However, all four AF cases deteriorated into poor outcomes. CONCLUSIONS: This study demonstrated the feasibility of endovascular intervention for acute cervical carotid artery occlusion. Although treatment for tandem occlusion and AF cases is an issue that should be resolved, intervention must be encouraged. Successful cervical and intracranial revascularization will be essential for favorable outcomes.

Japanese structure survey of radiation oncology in 2009 with special reference to designated cancer care hospitals.

BACKGROUND: The structure of radiation oncology in designated cancer care hospitals in Japan was surveyed in terms of equipment, personnel, patient load, and geographic distribution, and compared with the structure in other radiotherapy facilities and the previous survey. METHODS: The Japanese Society for Therapeutic Radiology and Oncology surveyed the national structure of radiation oncology in 2009. The structures of 365 designated cancer care hospitals and 335 other radiotherapy facilities were compared. RESULTS: Designated cancer care hospitals accounted for 50.0% of all the radiotherapy facilities in Japan. The patterns of equipment and personnel in designated cancer care hospitals and the other radiotherapy facilities were, respectively, as follows: linear accelerators per facility: 1.4 and 1.0; dual-energy function: 78.6 and 61.3%; three-dimensional conformal radiotherapy function: 88.5 and 70.0%; intensity-modulated radiotherapy function: 51.6 and 25.3%; annual number of patients per linear accelerator: 301.3 and 185.2; Ir-192 remote-controlled after-loading systems: 31.8 and 4.2%; and average number of full-time equivalent radiation oncologists per facility: 1.8 and 0.8. Compared with the previous survey, the ownership ratio of equipment and personnel improved in both designated cancer care hospitals and the other radiotherapy facilities. Annual patient loads per full-time equivalent radiation oncologist in the designated cancer care hospitals and the other radiotherapy facilities were 225.5 and 247.6, respectively. These values exceeded the standard guidelines level of 200. CONCLUSIONS: The structure of radiation oncology in designated Japanese cancer care hospitals was more mature than that in the other radiotherapy facilities. There is still a shortage of personnel. The serious understaffing problem in radiation oncology should be corrected in the future.

Validation of nomogram-based prediction of survival probability after salvage re-irradiation of head and neck cancer.

OBJECTIVE: Treatment outcomes after salvage re-irradiation in patients with recurrent head and neck cancer vary widely due to heterogeneous patient characteristics, and it is difficult to evaluate optimal re-irradiation schedules. This study aimed to validate a nomogram, originally developed by Tanvetyanon et al., used to predict the survival probability of patients with recurrent head and neck cancer after re-irradiation. METHODS: Twenty-eight patients with recurrent head and neck cancer who underwent salvage re-irradiation between June 2007 and November 2011 were evaluated. The median total dose used for initial radiotherapy was 60 Gy (range, 22-72). Re-irradiation sites included the nasopharynx or Rouviere's node (n = 14), external ear (n = 4), neck lymph node (n = 3) and other sites (n = 7). Overall survival after re-irradiation was calculated using the Kaplan-Meier method, and the 2-year survival probability was estimated using Tanvetyanon's nomogram. RESULTS: Twenty-two patients were treated with stereotactic body radiotherapy using a median total dose of 30 Gy (range, 15-40) in 1-7 fractions and six patients were treated with conventional external beam radiotherapy using 45 Gy (range, 23.4-60) in 10-30 fractions. The 2-year overall survival was 21.7% (95% confidence interval: 9.3-41.3), and the 2-year survival probability was 16.8% (95% confidence interval: 9.9-23.6). The 2-year overall survival in 20 patients with unfavorable prognosis (median 2-year survival probability, 5.5%) and in 8 patients with favorable prognosis (median 2-year survival probability, 45%) were 11.0 and 45.7%, respectively (P = 0.05). CONCLUSIONS: Our findings show that Tanvetyanon's nomogram accurately estimates the survival probability in patients with recurrent head and neck cancer after re-irradiation.

[Intracardiac migration of a ventriculoatrial shunt catheter treated by endovascular transvenous retrieval].

The authors report a case of intracardiac migration of a ventriculoatrial (VA) shunt catheter and transvenous retrieval of the migrated shunt catheter. A 67-year-old male, who had previously undergone a VA shunt for hydrocephalus after subarachnoid hemorrhage, presented disorientation, memory disturbance and gait disturbance without any cardiopulmonary symptom. Head CT scan revealed ventriculomegaly that indicated hydrocephalus due to shunt malfunction. Radiogram revealed that the caudal segment of the broken atrial catheter had migrated into the heart (right ventricle). The migrated shunt catheter was retrieved by a transfemoral approach with a pigtail catheter and a snare retriever catheter, although the rostral catheter segment partially remained because of tight adhesion. The VA shunt was then reconstructed. Postoperatively, symptoms due to recurrent hydrocephalus were markedly improved and the VA shunt functioned well. Transvenous catheter retrieval was a less invasive and effective method for VA shunt catheter migration.

National medical care system may impede fostering of true specialization of radiation oncologists: study based on structure survey in Japan.

PURPOSE: To evaluate the actual work environment of radiation oncologists (ROs) in Japan in terms of working pattern, patient load, and quality of cancer care based on the relative time spent on patient care. METHODS AND MATERIALS: In 2008, the Japanese Society of Therapeutic Radiology and Oncology produced a questionnaire for a national structure survey of radiation oncology in 2007. Data for full-time ROs were crosschecked with data for part-time ROs by using their identification data. Data of 954 ROs were analyzed. The relative practice index for patients was calculated as the relative value of care time per patient on the basis of Japanese Blue Book guidelines (200 patients per RO). RESULTS: The working patterns of RO varied widely among facility categories. ROs working mainly at university hospitals treated 189.2 patients per year on average, with those working in university hospitals and their affiliated facilities treating 249.1 and those working in university hospitals only treating 144.0 patients per year on average. The corresponding data were 256.6 for cancer centers and 176.6 for other facilities. Geographically, the mean annual number of patients per RO per quarter was significantly associated with population size, varying from 143.1 to 203.4 (p < 0.0001). There were also significant differences in the average practice index for patients by ROs working mainly in university hospitals between those in main and affiliated facilities (1.07 vs 0.71: p < 0.0001). CONCLUSIONS: ROs working in university hospitals and their affiliated facilities treated more patients than the other ROs. In terms of patient care time only, the quality of cancer care in affiliated facilities might be worse than that in university hospitals. Under the current national medical system, working patterns of ROs of academic facilities in Japan appear to be problematic for fostering true specialization of radiation oncologists.

Japanese structure survey of radiation oncology in 2007 with special reference to designated cancer care hospitals.

BACKGROUND AND PURPOSE: The structure of radiation oncology in designated cancer care hospitals in Japan was investigated in terms of equipment, personnel, patient load, and geographic distribution. The effect of changes in the health care policy in Japan on radiotherapy structure was also examined. MATERIAL AND METHODS: The Japanese Society of Therapeutic Radiology and Oncology surveyed the national structure of radiation oncology in 2007. The structures of 349 designated cancer care hospitals and 372 other radiotherapy facilities were compared. RESULTS: Respective findings for equipment and personnel at designated cancer care hospitals and other facilities included the following: linear accelerators/facility: 1.3 and 1.0; annual patients/linear accelerator: 296.5 and 175.0; and annual patient load/full-time equivalent radiation oncologist was 237.0 and 273.3, respectively. Geographically, the number of designated cancer care hospitals was associated with population size. CONCLUSION: The structure of radiation oncology in Japan in terms of equipment, especially for designated cancer care hospitals, was as mature as that in European countries and the United States, even though the medical costs in relation to GDP in Japan are lower. There is still a shortage of manpower. The survey data proved to be important to fully understand the radiation oncology medical care system in Japan.

Endovascular coil embolization for saccular-shaped blood blister-like aneurysms of the internal carotid artery.

BACKGROUND: Because of their fragile and thin wall, ruptured blood blister-like aneurysms (BBAs) at the anterior wall of the internal carotid artery (ICA) are difficult to manage, both surgically, as well as endovascularly. BBA is usually a tiny and broad-necked aneurysm, but it occasionally demonstrates a relatively saccular-like shape. In addition, the pseudoaneurysm sac often assumes a saccular shape. In this paper, the authors present their experience in treating these saccular-shaped BBAs endovascularly with coil packing. METHOD: Nine saccular-shaped ruptured BBAs in nine patients (one male and eight females; mean age 51.3 years, range 38-76) were treated with coil packing of the lesion between January 2006 and August 2010 in Nagoya University and its affiliated hospitals. Clinical, procedural, and angiographic data were retrospectively evaluated. FINDINGS: Seven BBAs were treated by balloon-assisted coil embolization. Two remaining BBAs were embolized without balloon inflation, though a balloon catheter was on standby at the ICA. In one case, in which a saccular coil embolization could not be achieved, ICA trapping was performed. Three (33.3%) were treated in acute, two (22.2%) in subacute, and four (44.4%) in chronic period. One (11.1%) intraoperative rupture occurred. Six (66.7%) had excellent clinical outcomes, while two (22.2%) proved fatal outcomes. During the follow-up period (mean 18.9 months, range 4-48), two out of seven (28.6%) aneurysms presented an angiographical recurrence, but both were treated by coil embolization without complications. The remaining five (71.4%) aneurysms were completely resolved. CONCLUSIONS: Endovascular coil embolization can be considered as an alternative treatment option for selective saccular-shaped BBAs.

[Development of the method for the similarity detection of descriptions in radiology reports using structuring technology].

Radiologists often spend much time for re-reading some of the past free-text radiology reports and determining interval changes in the physical findings when creating a report for long term cases. The aim of this study was to propose the method to detect semantic similar descriptions in the free-text reports using the structuring method based on text-mining technology. In a previous study, we had developed the structuring method that can semantically analyze the free-text reports and convert them into the description unit consisting of five items: finding/diagnosis, modifier, region, regional modifier, and confidence. Our developed prototype system extracted similar descriptions from the free-text reports by calculating the similarity index between description units. We confirmed similar descriptions extracted by the system applied to free-text reports of cases which had more than one chest CT examination written in actual clinical situation. As a result, it became available to identify candidates of similar descriptions from free-text reports. In some cases regarding practical use, the similar descriptions could not be identified in the sentences which used paraphrasing or where the findings had status changes. A solution of identifying similarity in these cases was necessary to improve the method. With the presented method here, it is expected that interval changes in the findings can be visualized and applied it to support diagnosis.

A comparison of the respiratory signals acquired by different respiratory monitoring systems used in respiratory gated radiotherapy.

PURPOSE: Respiratory monitoring systems are used to detect the respiratory phase of patients during the planning and administration of respiratory gated radiotherapy by using four-dimensional computed tomography (4DCT) or 4D positron-emission tomography/CT (4DPET/CT) and the linear accelerator (linac), respectively. Generally, identical respiratory monitoring systems are used for 4DCT, 4DPET/CT, and linac. However, different systems are sometimes used in combination because the accessibility of the respiratory monitoring systems may differ by manufacturer. The combined use of different respiratory monitoring systems in phase-based gating is of concern because the differences in the timing of tags (end-respiration signals algorithmically determined by the respiratory monitoring system), defined by the two systems, may result in phase differences, The purpose of this study is to estimate this difference and evaluate its effect on 4DCT data. METHODS: Ten patients (seven men and three women) with a median age of 75 yr (range: 57-84 yr) were treated by gated stereotactic body radiation therapy between April and December 2009. Two types of respiratory monitoring systems--RPM (Varian Medical Systems) and AZ-733V (Anzai MEDICAL)--were placed on the abdominal surface of the patients, and the respiratory signals were acquired by both systems. The relationship between the amplitude peak and the tag obtained by each respiratory system was analyzed for each patient. Further, the 4DCT images were reconstructed by using the signals obtained from both the RPM and the AZ-733V systems, and the tumor volumes and the tumor centroid positions in the craniocaudal plane were analyzed for each patient. RESULTS: The correlation factor between the respiratory signals from the RPM system and AZ-733V system was 0.990 (range: 0.940-0.994). The amplitude peak of the RPM system corresponded well with that of the AZ-733V system. The median +/- standard deviation of the phase difference for all the patients ranged from -4.3 +/- 7.1% to 3.5 +/- 2.2%. In the case of some patients, differences were noted between the two systems in the estimation of the tumor centroid position and tumor shape. CONCLUSIONS: The estimation of the position of the tumor centroid and tumor shape may vary with the use of different respiratory monitoring systems. This implies that it is preferable to use the same respiratory monitoring system with 4DCT, 4DPET-CT, and linac.

Radiosurgical treatment planning for intracranial AVM based on images generated by principal component analysis--a simulation study.

BACKGROUND: One of the most important factors in stereotactic radiosurgery (SRS) for intracranial arteriovenous malformation (AVM) is to determine accurate target delineation of the nidus. However, since intracranial AVMs are complicated in structure, it is often difficult to clearly determine the target delineation. PURPOSE: To investigate the usefulness of principal component analysis (PCA) on intra-arterial contrast enhanced dynamic CT (IADCT) images as a tool for delineating accurate target volumes for stereotactic radiosurgery of AVMs. MATERIALS AND METHODS: IADCT and intravenous contrast-enhanced CT (IVCT) were used to examine 4 randomly selected cases of AVM. PCA images were generated from the IADCT data. The first component images were considered feeding artery predominant, the second component images were considered draining vein predominant, and the third component images were considered background. Target delineations were first carried out from IVCT, and then again while referring to the first and second components of the PCA images. Dose calculation simulations for radiosurgical treatment plans with IVCT and PCA images were performed. Dose volume histograms of the vein areas as well as the target volumes were compared. RESULTS: In all cases, the calculated target volumes based on IVCT images were larger than those based on PCA images, and the irradiation doses for the vein areas were reduced. CONCLUSION: In this study, we simulated radiosurgical treatment planning for intracranial AVM based on PCA images. By using PCA images, the irradiation doses for the vein areas were substantially reduced.

Structuring of free-text diagnostic report.

PURPOSE: It is useful to convert free-text diagnostic reports into structured diagnostic reports by semantic analysis for the secondary investigation of their contents. In this study, we propose a system in which description units are automatically extracted to create structured text reports and we evaluated its usefulness. METHODS: We defined the rules to create description units and developed the system that can automatically extract these description units from free-text diagnostic reports. We applied this system to reports of cerebral perfusion scintigrams and obtained 5 dictionaries of description units, increasing the number of scintigrams from 100 to 500 in increments of 100. Each dictionary was used to analyze another 100 scintigrams. The results obtained using each dictionary were compared with the results of physicians' interpretation. RESULTS: The recall rate of this system to the physicians' interpretation increased when correlated with the number of scintigrams but with 300 cases was almost saturated at 85%. CONCLUSION: We propose a semantic analysis system and show its usefulness in the semantic evaluation of the reports of cerebral perfusion scintigrams.

[Studies on digital watermark embedding intensity against image processing and image deterioration].

In order to apply digital watermarking to medical imaging, it is required to find a trade-off between strength of watermark embedding and deterioration of image quality. In this study, watermarks were embedded in 4 types of modality images to determine the correlation among the watermarking strength, robustness against image processing, and image deterioration due to embedding. The results demonstrated that watermarks which were embedded by the least significant bit insertion method became unable to be detected and recognized on image processing even if the watermarks were embedded with such strength that could cause image deterioration. On the other hand, watermarks embedded by the Discrete Cosine Transform were clearly detected and recognized even after image processing regardless of the embedding strength. The maximum level of embedding strength that will not affect diagnosis differed depending on the type of modality. It is expected that embedding the patient information together with the facility information as watermarks will help maintain the patient information, prevent mix-ups of the images, and identify the test performing facilities. The concurrent use of watermarking less resistant to image processing makes it possible to detect whether any image processing has been performed or not.