Evaluation of the field-in-field technique with lung blocks for breast tangential radiotherapy.

Several studies have reported the advantages of the field-in-field (FIF) technique in breast radiotherapy, including dose reduction in the lungs by using lung field blocks. We evaluated the FIF technique with lung blocks for breast tangential radiotherapy. Sixteen patients underwent free breathing (FB) computed tomography (CT), followed by two CT procedures performed during breath hold after light inhalation (IN) and light exhalation (EX). Three radiotherapy plans were created using the FIF technique based on the FB-CT images: one without lung blocks (LB0) and two with lung blocks whose monitor units (MUs) were 5 (LB5) and 10 (LB10), respectively. These plans were copied to the IN-CT and EX-CT images. V20Gy, V30Gy, and V40Gy of the ipsilateral lung and V100%, V95%, and the mean dose (Dmean) to the planning target volume (PTV) were analyzed. The extent of changes in these parameters on the IN-plan and EX-plan compared with the FB-plan was evaluated. V20Gy, V30Gy, and V40Gy were significantly smaller for FB-LB5 and FB-LB10 than for FB-LB0; similar results were obtained for the IN-plan and EX-plan. V100%, V95%, and Dmean were also significant smaller for FB-LB5 and FB-LB10 than for FB-LB0. The extent of changes in V20Gy, V30Gy, and V40Gy on the IN-plan and EX-plan compared with the FB-plan was not statistically significant. Lung blocks were useful for dose reduction in the lung and a simultaneous PTV decrease. This technique should not be applied in the general population.

Cardiac counterclockwise rotation is a risk factor for high-dose irradiation to the left anterior descending coronary artery in patients with left-sided breast cancer who receiving adjuvant radiotherapy after breast-conserving surgery.

Patients irradiated for left-sided breast cancer have higher incidence of cardiovascular disease than those receiving irradiation for right-sided breast cancer. Most abnormalities were in the left anterior descending (LAD) coronary artery territory. We analyzed the relationships between preoperative examination results and irradiation dose to the LAD artery in patients with left-sided breast cancer. Seventy-one patients receiving breast radiotherapy were analyzed. The heart may rotate around longitudinal axis, showing either clockwise or counterclockwise rotation (CCWR). On electrocardiography, the transition zone (TZ) was judged in precordial leads. CCWR was considered to be present if TZ was at or to the right of V3. The prescribed dose was 50 Gy in 25 fractions. The maximum (Dmax) and mean (Dmean) doses to the LAD artery and the volumes of the LAD artery receiving at least 20 Gy, 30 Gy and 40 Gy (V20Gy, V30Gy and V40Gy, respectively) were significantly higher in CCWR than in the non-CCWR patients. On multivariate analysis, TZ was significantly associated with Dmax, Dmean, V20Gy, V30Gy, and V40Gy. CCWR is a risk factor for high-dose irradiation to the LAD artery. Electrocardiography is useful for evaluating the cardiovascular risk of high-dose irradiation to the LAD artery.

External beam radiotherapy for painful bone metastases from hepatocellular carcinoma: multiple fractions compared with an 8-Gy single fraction.

External beam radiotherapy (EBRT) for hepatocellular carcinoma (HCC) bone metastases has not been popular in palliative therapy, and optimum dose schedules have not been decided because of limited published reports. We here evaluated the palliative effect of EBRT for HCC bone metastases and compared the dose-response relationship between multiple fractions (MFs) and an 8-Gy single fraction (SF). Twenty-eight patients (42 sites) with painful bone metastases who received EBRT and were analyzed retrospectively. Eight patients (12 sites) received SF. Of the remaining 20 patients (30 sites), 10 received MFs at moderate doses (20-30 Gy; 17 sites) and 10 received MFs at high doses (36-52 Gy; 13 sites). Overall response was achieved at 83% (35) of all sites; 75% (9) and 87% (26) for the SF and MF patients (88%, moderate dose; 85%, high dose), respectively. No significant differences in overall response were observed between each fraction schedule. Response duration was significantly longer for the high-dose MF patients than for the SF patients and moderate-dose MF patients (P < 0.05). SF was as effective as MF radiotherapy in terms of pain relief, but high-dose MF delivery relieved pain for a significantly longer duration.

Impact of respiratory motion on breast tangential radiotherapy using the field-in-field technique compared to irradiation using physical wedges.

BACKGROUND: This study aimed to evaluate whether the field-in-field (FIF) technique was more vulnerable to the impact of respiratory motion than irradiation using physical wedges (PWs). PATIENTS AND METHODS: Ten patients with early stage breast cancer were enrolled. Computed tomography (CT) was performed during free breathing (FB). After the FB-CT data set acquisition, 2 additional CT scans were obtained during a held breath after light inhalation (IN) and light exhalation (EX). Based on the FB-CT images, 2 different treatment plans were created for the entire breast for each patient and copied to the IN-CT and EX-CT images. The amount of change in the volume of the target receiving 107%, 95%, and 90% of the prescription dose (V107%, V95%, and V90%, respectively), on the IN-plan and EX-plan compared with the FB-plan were evaluated. RESULTS: The V107%, V95%, and V90% were significantly larger for the IN-plan than for the FB-plan in both the FIF technique and PW technique. While the amount of change in the V107% was significantly smaller in the FIF than in the PW plan, the amount of change in the V95% and V90% was significantly larger in the FIF plan. Thus, the increase in the V107% was smaller while the increases in the V95% and V90% were larger in the FIF than in the PW plan. CONCLUSIONS: During respiratory motion, the dose parameters stay within acceptable range irrespective of irradiation technique used although the amount of change in dose parameters was smaller with FIF technique.

Significance of target location relative to the depth from the brain surface and high-dose irradiated volume in the development of brain radionecrosis after micromultileaf collimator-based stereotactic radiosurgery for brain metastases.

The objective of this study was to investigate the factors that potentially lead to brain radionecrosis (RN) after micromultileaf collimator-based stereotactic radiosurgery (SRS) for brain metastases. We retrospectively evaluated 131 lesions with a minimum follow-up of 6 months, 43.5% of which received prior whole-brain radiotherapy (WBRT). The three-tiered location grade (LG) was defined, as follows, for each target by considering mainly the depth from the brain surface: grade 1 (superficial), involving the region at a depth of ≤5 mm from the brain surface; grade 2 (deep), located at a depth of >5 mm from the brain surface; and grade 3 (central), located in the brainstem, cerebellar peduncle, diencephalon, or basal ganglion. The predictive factors for RN, including high-dose irradiated isodose volumes (IIDVs) and LG, were evaluated by univariate and multivariate analysis. Symptomatic RN (S-RN) and asymptomatic RN (A-RN) were observed in 8.4% and 6.9% of cases, respectively. Multivariate analysis indicated that the significant factors for both types of RN were LG, V12 Gy, and V22 Gy in all cases; V22 Gy and LG for the non-WBRT cases; and V15 Gy and LG for the WBRT cases. For the non-WBRT cases, the cutoff values of V22 Gy were 2.62 and 2.14 cm(3) for S-RN and both RN, respectively. For the WBRT cases, the cutoff values of V15 Gy were 5.61 and 5.20 cm(3) for S-RN and both RN, respectively. In addition to the IIDV data, LG helps predict the risk of RN. High-dose IIDV, V22 Gy, was also significantly correlated with RN, particularly for patients treated with SRS alone.

Computed tomographic findings of Kawasaki disease with cervical lymphadenopathy.

OBJECTIVE: The purpose of this study was to describe CT findings in patients with Kawasaki disease with cervical lymphadenopathy. MATERIALS AND METHODS: Twelve patients with cervical lymphadenopathy were difficult to diagnose at the initial visit and underwent CT for the assessment of lymphadenopathy. Computed tomographic images were assessed for numbers, sizes, locations of enlarged nodes, and other imaging findings. RESULTS: Seventy-two enlarged nodes were identified. The maximum diameter of enlarged nodes ranged from 1.0 to 2.5 cm (mean, 1.5 cm). Lymphadenopathy was unilateral in 8 patients (67%) and located at level IB in 2 patients, II in 50 patients, III in 10 patients, IV in 1 patient, and V in 9 patients. Perinodal infiltration was found in 10 patients (83%), and 3 patients (25%) had focal low attenuation within nodes. Retropharyngeal hypodense area was present in 4 patients (33%), peritonsilar hypodense area in 3 patients (25%), and enlarged tonsils in 4 patients (33%). CONCLUSIONS: Cervical lymphadenopathy in Kawasaki disease usually showed unilateral distribution predominantly at levels II, III, and V with perinodal infiltration occasionally accompanied by retropharyngeal hypodense area, peritonsilar hypodense area, and enlarged tonsils.

Uneven haustra on CT colonography: a clue for the detection of transperitoneal invasion from gastric cancer.

Two patients with gastric carcinoma underwent CT colonography (CTC) for preoperative work-up. Although no obvious peritoneal nodules were seen on axial CT images, colonic wall deformities were noted on three-dimensional (3D) air images. Multiplanar-reformatted images revealed corresponding colonic wall thickening at the deformities, and in addition, dense cordlike structures connecting the primary gastric cancer and colonic wall thickening were also observed. In one patient, cordlike indurations consistent with peritoneal invasion were found to connect the primary gastric cancer, gastrocolic ligament, and transverse mesocolon during exploratory surgery, and in the other, colonic scars consistent with peritoneal invasion after chemotherapy were observed. These observations suggest that CTC could be of potential use for the differentiation of transperitoneal colonic invasion and gastric cancer.

Computer-aided diagnosis for detection of lacunar infarcts on MR images: ROC analysis of radiologists' performance.

The purpose of this study was to retrospectively evaluate radiologist performance in detection of lacunar infarcts on T1- and T2-weighted images, without and with the use of a computer-aided diagnosis (CAD) scheme. Thirty T1-weighted and 30 T2-weighted MR images obtained from 30 patients were used for assessing observer performance. These images were acquired using the fast spin-echo sequence with a 1.5-T MR imaging scanner. The group included 15 patients (age range, 48-83 years; mean age, 67.2 years; 10 men and five women) with a lacunar infarct and 15 patients (age range, 39-76 years; mean age, 64.0 years; eight men and seven women) without lacunar infarcts. Nine radiologists participated in the study. The radiologists initially interpreted the T1- and T2-weighted images without and then with the use of CAD, which indicated their confidence levels regarding the presence (or absence) of lacunar infarcts and the most likely position of a lesion on each MR scan. The observers' performance without and with the computer output was evaluated by performing receiver operating characteristic analysis. For the nine radiologists, the mean area under the best-fit binormal receiver operating characteristic curve plotted for unit square values of radiologists who interpreted the images without and with the scheme were 0.891 and 0.937, respectively. The performance of the radiologists improved significantly when they used the computer output (p=0.032). The CAD scheme has potential to improve the accuracy of radiologists' performance in detection of lacunar infarcts.

Salivary gland function evaluated by diffusion-weighted MR imaging with gustatory stimulation: preliminary results.

PURPOSE: To evaluate the usefulness of diffusion-weighted MR imaging using a transient gustatory stimulation method in patients with xerostomia. MATERIALS AND METHODS: Ten consecutive patients complaining of xerostomia and 10 healthy volunteers were examined with a 1.5 Tesla (T) MR unit. All study subjects completed a questionnaire, and patients underwent salivary gland scintigraphy and Saxon test. T1-, T2-, and diffusion-weighted MR images were obtained before stimulation. One minute after gustatory stimulation with lemon juice, diffusion-weighted sequence was repeated 9 times. A radiologist evaluated signal intensities and apparent diffusion coefficients (ADCs) in parotid and submandibular glands. ADC increase rate (IR) and times to maximum ADC (Tmax) were assessed. RESULTS: IRs showed a moderate positive correlation with washout rates by scintigraphy for parotid (r = 0.554, P < 0.05) and submandibular (r = 0.617, P < 0.01) glands. Furthermore, Tmax values of parotid and submandibular glands were significantly higher in patients (420 ± 226 and 357 ± 232 s, respectively) than in volunteers (181 ± 68 and 200 ± 75 s, respectively) (P < 0.01). CONCLUSION: Our preliminary results indicate that diffusion-weighted MR imaging using a transient gustatory stimulation method is potentially useful for evaluating patients with xerostomia.

Analysis of bone mineral density distribution at trabecular bones in thoracic and lumbar vertebrae using X-ray CT images.

The number of participants in thoracic or abdominal examinations using multi-detector-row CT (MDCT) has been increasing recently. If the degree of progress of osteoporosis can be estimated using these images, it may be useful as it will allow predictions of vertebral fractures without an additional radiation exposure. The aims of this study were to investigate segmental variations in bone mineral density (BMD) distributions of thoracic and lumbar vertebral bodies and to show specific differences according to age and gender. A large database including 1,031 Japanese subjects for whom MDCT was used to examine various organs and tissues was utilized in this study for trabecular BMD at thoracic and lumbar vertebrae. In relationship to vertebral level, L3 had the lowest trabecular BMD. BMD tended to gradually increase from L3 to T1 in all age categories. Also, there was a moderate correlation between vertebrae whose distance from each other was great whereas there was a high correlation between adjacent vertebrae. It may be appropriate to use an arbitrary vertebra as a first approximation for assessing vertebrae that are in the area of predilection for the fracture; however, to better understand their behavior, it may be necessary to measure BMD directly in this region. This study showed trabecular BMD distribution at healthy thoracic and lumbar vertebrae in Japanese subjects and specific differences in age and gender. Improved knowledge about vertebral BMD may help with the diagnosis of primary osteoporosis using MDCT.

Preoperative detection of prostate cancer: a comparison with 11C-choline PET, 18F-fluorodeoxyglucose PET and MR imaging.

PURPOSE: To compare (11)C-choline positron emission tomography (C-PET), (18)F-fluorodeoxyglucose PET (FDG-PET), and MR imaging in the preoperative detection of prostate cancer. MATERIALS AND METHODS: C-PET, FDG-PET, and MR images were obtained in 43 consecutive patients with suspected prostate cancer, and prostate cancers were histopathologically confirmed in 26 patients. Unenhanced T1-weighted, T2-weighted, and gadolinium-enhanced MR images were obtained. C-PET and FDG-PET were conducted 1.5 and 60 minutes after injection of 5.5 and 5.0 MBq/kg tracers, respectively. A nuclear and a genitourinary radiologist retrospectively reviewed PET and MR images at random, respectively, and assigned a confidence level for the presence of prostate cancer using a four-point scale. Diagnostic performance was tested using the McNemar test and receiver operating characteristic curve analysis. RESULTS: The sensitivity was greater (P < 0.05) with MR (88%) and C-PET (73%) images than with FDG-PET images (31%). The accuracy was greater (P < 0.05) with MR images (88%) than with C-PET (67%) and FDG-PET (53%) images. The area-under-curve value with MR (0.90) was greater than those with C-PET (0.53) and FDG-PET (0.54) images (P < 0.01). CONCLUSION: MR imaging should be primarily performed in the preoperative detection of prostate cancer. C-PET and FDG-PET did not improve the detection.

Head and neck squamous cell carcinoma: usefulness of diffusion-weighted MR imaging in the prediction of a neoadjuvant therapeutic effect.

The purpose of our study was to evaluate the usefulness of diffusion-weighted imaging in predicting the responses to neoadjuvant therapy for head and neck squamous cell carcinomas. Diffusion-weighted, T2-weighted, and gadolinium-enhanced T1-weighted images were obtained from 28 patients with untreated head and neck squamous cell carcinomas with histological proof. A blinded radiologist evaluated the quantitative and qualitative signal intensities and apparent diffusion coefficients (ADCs) in the lesions on each sequence. All patients were treated by neoadjuvant therapies, and the post-therapeutic tumor regression rate was determined. Both the quantitative and qualitative signal intensities on diffusion-weighted images showed positive correlations (r = 0.367 and 0.412, p < .05), and the ADCs showed a weak, inversed correlation (r = -0.384, p < .05) with the tumor regression rates. Diffusion-weighted imaging including an assessment by ADCs may be able to predict tumor response to neoadjuvant therapy for head and neck squamous cell carcinomas.

Optimal scan delays for multiphasic renal multidetector row computed tomography performed with fixed injection duration of contrast medium.

OBJECTIVE: The purpose of our study was to prospectively determine optimal scan delays for multiphasic imaging of the kidney performed with multidetector row computed tomography (CT) and fixed injection duration of intravenous contrast medium. MATERIALS AND METHODS: One hundred ninety-eight patients underwent 3-phase CT of the kidney with 8-slice CT after receiving 2 mL/kg of an intravenous contrast medium of 300 mg I/mL for a fixed duration of 30 seconds. The patients were prospectively randomized into 4 groups according to different scan delays from the start of injection: group 1 (25, 45, 65 seconds), group 2 (30, 50, 70 seconds), group 3 (35, 55, 75 seconds), and group 4 (40, 60, 80 sec). Mean CT values (Hounsfield units [HU]) of the abdominal aorta, renal arteries, veins, cortexes, and medulla were measured. Increases in CT values from precontrast to postcontrast CT (deltaHU) and renal artery-to-vein and renal cortex-to-medulla differential contrasts (deltaHU) were assessed. Qualitative analysis was also performed. RESULTS: Abdominal aorta and renal artery enhancements peaked at 35 seconds (305 DeltaHU; 253 DeltaHU) after injection start, and renal veins peaked at 45 seconds (196 DeltaHU). Renal cortexes peaked at 40 seconds (197 DeltaHU), and renal medullae peaked at 75 seconds (152 DeltaHU). Renal artery-to-vein differential contrasts were high (95-137 deltaHU) at 25 to 30 seconds, and cortex-to-medulla contrasts were high (79-130 deltaHU) at 30 to 55 seconds and then decreased to less than 10 deltaHU at 75 seconds. Qualitative results were in good agreement with quantitative results. CONCLUSIONS: With a fixed 30-second injection, estimated optimal scan delays for multiphasic imaging the kidney were, from the start of injection, 25 to 30 seconds for renal arterial CT angiography, 35 to 45 seconds for the corticomedullary, and 75 seconds for the nephrographic phase.

MRI-based preplanning in low-dose-rate prostate brachytherapy.

PURPOSE: To compare the dosimetric results between MRI-based and TRUS-based preplanning in permanent prostate brachytherapy, and to estimate the accuracy of MRI-based preplanning by comparing with CT/MRI fusion-based postimplant dosimetry. METHODS AND MATERIALS: Twenty-one patients were entered in this prospective study with written informed consent. MRI-based and TRUS-based preplanning were performed. The seed and needle locations were identical according to MRI-based and TRUS-based preplanning. MRI-based and TRUS-based preplanning were compared using DVH-related parameters. Following brachytherapy, the accuracy of the MRI-based preplanning was evaluated by comparing it with CT/MRI fusion-based postimplant dosimetry. RESULTS: Mean MRI-based prostate volume was slightly underestimated (0.73 cc in mean volume) in comparison to TRUS-based volume. There were no significant differences in the mean DVH-related parameters except with rectal V(100)(cc) between TRUS-based and MRI-based preplanning. Mean rectal V(100)(cc) was 0.74 cc in TRUS-based and 0.29 cc in MRI-based preplanning, respectively, and the values demonstrated a statistical difference. There was no statistical difference in mean rectal V(150)(cc), and rectal V(100)(cc) between MRI-based preplanning and CT/MRI fusion-based postimplant dosimetry. CONCLUSION: Prostate volume estimation and DVH-related parameters in MRI-based preplanning were almost identical to TRUS-based preplanning. From the results of CT/MRI fusion-based postimplant dosimetry, MRI-based preplanning was therefore found to be a reliable and useful modality, as well as being helpful for TRUS-based preplanning. MRI-based preplanning can more accurately predict postimplant rectal dose than TRUS-based preplanning.

Automated estimation of the upper surface of the diaphragm in 3-D CT images.

This communication describes a fully automated method by which the position of the diaphragm surface can be estimated by deforming a thin-plate model to match the bottom surface of the lung in CT images. This method was applied to 338 X-ray CT scans, and its validity was proved by the experimental results.

Effect of edema on postimplant dosimetry in prostate brachytherapy using CT/MRI fusion.

PURPOSE: To investigate the time course of prostatic edema and the effect on the dose-volume histograms of the prostate for patients treated with brachytherapy. METHODS AND MATERIALS: A total of 74 patients with prostate cancer were enrolled in this prospective study. A transrectal ultrasound-based preplan was performed 4 weeks before implantation and computed tomography/magnetic resonance imaging fusion-based postimplant dosimetry was performed on the day after implantation (Day 1) and 30 days after implantation (Day 30). The prostate volume, prostate volume covered by 100% of the prescription dose (V100), and dose covering 90% of the prostate (D90) were evaluated with prostatic edema over time. RESULTS: Prostatic edema was greatest on Day 1, with the mean prostate volume 36% greater than the preplan transrectal ultrasound-based volume; it thereafter decreased over time. It was 9% greater than preplan volume on Day 30. The V(100) increased 5.7% from Day 1 to Day 30, and the D90 increased 13.1% from Day 1 to Day 30. The edema ratio (postplan/preplan) on Day 1 of low-quality implants with a V(100) of <80% was significantly greater than that of intermediate- to high-quality implants (>80% V100; p = 0.0272). The lower V100 on Day 1 showed a greater increase from Day 1 to Day 30. A V100 on Day 1 of >92% is unlikely to increase >0% during the interval studied. CONCLUSION: Low-quality implants on Day 1 were highly associated with edema; however, such a low-quality implant on Day 1, with significant edema, tended to improve by Day 30. If a high-quality implant (V100 >92%) can be obtained on Day 1, a re-examination is no longer necessary.

Computer-aided diagnosis scheme for detection of lacunar infarcts on MR images.

RATIONALE AND OBJECTIVES: The detection and management of asymptomatic lacunar infarcts on magnetic resonance (MR) images are important tasks for radiologists to ensure the prevention of severe cerebral infarctions. However, accurate identification of the lacunar infarcts on MR images is a difficult task for the radiologists. Therefore the purpose of this study was to develop a computer-aided diagnosis scheme for the detection of lacunar infarcts to assist radiologists' interpretation as a "second opinion." MATERIALS AND METHODS: Our database comprised 1,143 T1- and 1,143 T2-weighted images obtained from 132 patients. The locations of the lacunar infarcts were determined by experienced neuroradiologists. We first segmented the cerebral region in a T1-weighted image by using a region growing technique for restricting the search area of lacunar infarcts. For identifying the initial lacunar infarcts candidates, a top-hat transform and multiple-phase binarization were then applied to the T2-weighted image within the segmented cerebral region. For eliminating the false positives (FPs), we determined 12 features--the locations x and y, signal intensity differences in the T1- and T2-weighted images, nodular components from a scale of 1 to 4, and nodular and linear components from a scale of 1 to 4. The nodular components and the linear components were obtained using a filter bank technique. The rule-based schemes and a support vector machine with 12 features were applied to the regions of the initial candidates for distinguishing between lacunar infarcts and FPs. RESULTS: Our computerized scheme was evaluated by using a holdout method. The sensitivity of the detection of lacunar infarcts was 96.8% (90/93) with 0.76 FP per image. CONCLUSIONS: Our computerized scheme would be useful in assisting radiologists for identifying lacunar infarcts in MR images.

Comparison of urethral diameters for calculating the urethral dose after permanent prostate brachytherapy.

PURPOSE: No studies have yet evaluated the effects of a dosimetric analysis for different urethral volumes. We therefore evaluated the effects of a dosimetric analysis to determine the different urethral volumes. METHODS: This study was based on computed tomography/magnetic resonance imaging (CT/MRI) combined findings in 30 patients who had undergone prostate brachytherapy. Postimplant CT/MRI scans were performed 30 days after the implant. The urethra was contoured based on its diameter (8, 6, 4, 2, and 0 mm). The total urethral volume-in cubic centimeters [UrV150/200(cc)] and percent (UrV150%/200%), of the urethra receiving 150% or 200% of the prescribed dose-and the doses (UrD90/30/5) in Grays to 90%, 30%, and 5% of the urethral volume were measured based on the urethral diameters. RESULTS: The UrV150(cc) and UrD30 were statistically different between the of 8-, 6-, 4-, 2-, and 0-mm diameters, whereas the UrD5 was statistically different only between the 8-, 6-, and 4-mm diameters. Especially for UrD5, there was an approximately 40-Gy difference between the mean values for the 8- and 0-mm diameters. CONCLUSION: We recommend that the urethra should be contoured as a 4- to 6-mm diameter circle or one side of a triangle of 5-7 mm. By standardizing the urethral diameter, the urethral dose will be less affected by the total urethral volume.

CT-based postimplant dosimetry of prostate brachytherapy: comparison of 1-mm and 5-mm section CT.

PURPOSE: The aim of this study was to compare the outcomes between 1-mm and 5-mm section computed tomography (CT)-based postimplant dosimetry. MATERIALS AND METHODS: A series of 21 consecutive patients underwent permanent prostate brachytherapy. The postimplant prostate volume was calculated using 1-mm and 5-mm section CT. One radiation oncologist contoured the prostate on CT images to obtain the reconstructed prostate volume (pVol), prostate V(100) (percent of the prostate volume receiving at least the full prescribed dose), and prostate D(90) (mean dose delivered to 90% of the prostate gland). The same radiation oncologist performed the contouring three times to evaluate intraobserver variation and subjectively scored the quality of the CT images. RESULTS: The mean +/-1 SD postimplant pVol was 20.17 +/- 6.66 cc by 1-mm section CT and 22.24 +/- 8.48 cc by 5-mm section CT; the difference in the mean values was 2.06 cc (P < 0.01). The mean postimplant prostate V(100) was 80.44% +/- 7.06% by 1-mm section CT and 77.33% +/- 10.22% by 5-mm section CT. The mean postimplant prostate D(90) was 83.28% +/- 10.81% by 1-mm section CT and 78.60% +/- 15.75% by 5-mm section CT. In the evaluation of image quality, 5-mm section CT was assigned significantly higher scores than 1-mm section CT. In regard to intraobserver variation, 5-mm section CT revealed less intraobserver variation than 1-mm section CT. CONCLUSION: Our current results suggested that the outcomes of postimplant dosimetry using 1-mm section CT did not improved the results over those obtained using 5-mm section CT in terms of the quality of the CT image or reproducibility.

[Automated middle hepatic vessel extraction method using electronic atlas and line enhancement filter on non-contrast torso X-ray CT images].

Classification of the liver region of the Couinaud segment provides significant information for a computer-aided diagnostic system to localize the position of lesions in the liver region. Hepatic vessels provide essential information to classify the liver region of the Couinaud segment. However, automated segmentation and classification of hepatic vessels are difficult in non-contrast CT images owing to the low contrast between hepatic vessels and liver tissue. In this paper, we propose an automated extraction schema for extracting the middle hepatic vein (MHV), and we employ this schema to classify the liver region into right and left lobes. We applied our method to 22 non-contrast X-ray CT images. All of the cases were normal liver cases. The results for the MHV extraction were evaluated using three parameters for the volume ratio to the correct region of liver. The results show that hepatic vessels extracted using the proposed method were found to be satisfactory in 41% (9/22) of cases.