Metastases in mediastinal and hilar lymph nodes in patients with non-small cell lung cancer: quantitative assessment with diffusion-weighted magnetic resonance imaging and apparent diffusion coefficient.

OBJECTIVE: To evaluate diffusion-weighted magnetic resonance (DW-MR) imaging for detection of metastases in lymph nodes by using quantitative analysis. METHODS: Seventy patients with non-small cell lung cancer were examined with DW and short inversion time inversion recovery (STIR) turbo-spin-echo MR imaging. Apparent diffusion coefficient of each lung cancer and lymph node was calculated from DW-MR images. Difference of the apparent diffusion coefficient in a lung cancer and a lymph node was calculated (D1). From STIR turbo-spin-echo MR images, ratios of signal intensity in a lymph node to that in a 0.9% saline phantom was calculated (lymph node-saline ratio [LSR1]). For quantitative analysis, the threshold value for a positive test was determined on a per node basis and tested for ability to enable a correct diagnosis on a per patient basis. Results of quantitative analyses of DW- and STIR-MR images were compared on a per patient basis with McNemar testing. RESULTS: Mean D1 in the lymph node group with metastases was lower than that in the group without metastases (P < 0.001). When an D1 of 0.24 x 10(-3) mm2/s was used as the positive test threshold, sensitivity, specificity, and accuracy were 69.2%, 100%, and 94.0%, respectively, on a per patient basis. There was no significant difference (P > 0.05) between quantitative analyses of DW-MR images and STIR-MR images. CONCLUSIONS: Quantitative analysis of DW-MR images enables differentiation of lymph nodes with metastasis from those without.

Outcome of MR-guided percutaneous cryoablation for hepatocellular carcinoma.

PURPOSE: To assess the mid-term results of MR-guided percutaneous cryoablation for small hepatocellular carcinoma (HCC). METHODS: Using an argon-based cryoablation system, MR-guided percutaneous cryoablation was performed. The number of tumors was three or fewer. The maximum diameter of tumors was less than 5 cm when solitary and no more than 3 cm when multiple. The Kaplan-Meier method was used to calculate the survival of patients. RESULTS: Among 15 patients, 16 tumors were treated. The maximum tumor diameter ranged from 1.2 to 4.5 cm, with a mean of 2.5 +/- 0.8 cm (mean +/- standard deviation). The volume of iceballs measured on MR-images was greater than that of the tumors in all cases. The follow-up period ranged from 10 to 52 months, with a mean of 36.6 +/- 12.1 months. One-year and 3-year overall survival were 93.8 and 79.3%, respectively. The complete ablation rate was 80.8% at 3 years. Immediate complications were pneumothorax, hemothorax, and pleural effusion. An ablation zone was not absorbed and content exuded from a scar of the probe tract 4 months after cryoablation in one patient. CONCLUSION: MR-guided percutaneous cryoablation appears to be a feasible modality and potentially good option for the treatment of small HCC.

Intercepting radiotherapy using a real-time tumor-tracking radiotherapy system for highly selected patients with hepatocellular carcinoma unresectable with other modalities.

PURPOSE: To assess the clinical outcome of intercepting radiotherapy, in which radiotherapy is delivered only when a tumor in motion enters a target area, using a real-time tumor-tracking radiotherapy (RTRT) system for patients with hepatocellular carcinoma who were untreatable with other modalities because the tumors were adjacent to crucial organs or located too deep beneath the skin surface. METHODS AND MATERIALS: Eighteen tumors, with a mean diameter of 36 mm, were studied in 15 patients. All tumors were treated on a hypofractionated schedule with a tight margin for setup and organ motion using a 2.0-mm fiducial marker in the liver and the RTRT system. The most commonly used dose of radiotherapy was 48 Gy in 8 fractions. Sixteen lesions were treated with a BED(10) of 60 Gy or more (median, 76.8 Gy). RESULTS: With a mean follow-up period of 20 months (range, 3-57 months), the overall survival rate was 39% at 2 years after RTRT. The 2-year local control rate was 83% for initial RTRT but was 92% after allowance for reirradiation using RTRT, with a Grade 3 transient gastric ulcer in 1 patient and Grade 3 transient increases of aspartate amino transaminase in 2 patients. CONCLUSIONS: Intercepting radiotherapy using RTRT provided effective focal high doses to liver tumors. Because the fiducial markers for RTRT need not be implanted into the tumor itself, RTRT can be applied to hepatocellular carcinoma in patients who are not candidates for other surgical or nonsurgical treatments.

Factors related to diagnostic sensitivity using an ultrathin bronchoscope under CT guidance.

BACKGROUND: We investigated factors related to the diagnostic sensitivity of CT-guided transbronchial biopsy (TBB) using an ultrathin bronchoscope and virtual bronchoscopy (VB) navigation for small peripheral pulmonary lesions. METHOD: We have performed this procedure on 83 patients with 85 small peripheral pulmonary lesions (< 20 mm in diameter). We analyzed the relationship between the diagnostic sensitivity and the location of the lesions, the bronchial generation to which an ultrathin bronchoscope was inserted, and the lesion-bronchial and lesion-pulmonary arterial relationships on high-resolution CT. RESULTS: Fifty-six of the 85 lesions (66%) were diagnosed following CT-guided TBB using an ultrathin bronchoscope with VB navigation. The lesions located in the left superior segment of the lower lobe (S6) had a significantly low diagnostic sensitivity compared to other locations (p < 0.01). When an ultrathin bronchoscope could be inserted to the fifth or greater bronchial generation, the yield was above the average diagnostic sensitivity of 66%. Moreover, not only the patients with the presence of a bronchus leading directly to a lesion (CT-bronchus sign), but also the patients with the presence of a pulmonary artery leading to a lesion (CT-artery sign), had high diagnostic sensitivity (p < 0.01). Multivariate analysis revealed that the location of lesion was an independent predictor of diagnostic sensitivity (p < 0.05). CONCLUSIONS: The location of the lesion, the bronchial generation to which an ultrathin bronchoscope was inserted, and the presence of a bronchus as well as a pulmonary artery leading to the lesion were valuable for predicting successful CT-guided TBB using an ultrathin bronchoscope with VB navigation.

Contrast-enhanced FLAIR imaging in combination with pre- and postcontrast magnetization transfer T1-weighted imaging: usefulness in the evaluation of brain metastases.

PURPOSE: To assess whether the use of postcontrast fluid-attenuated inversion recovery (FLAIR) imaging in combination with pre- and postcontrast magnetization transfer (MT) T1-weighted imaging (T1WI) can increase diagnostic confidence in the evaluation of brain metastases. MATERIALS AND METHODS: Brain MR images from 41 patients with suspected brain metastases were reviewed. Two radiologists viewed pre- and postcontrast MT-T1W images for the presence of metastatic tumors and rated the possible enhanced lesions using a five-point confidence scale (session 1). The postcontrast FLAIR images were then viewed together with pre- and postcontrast MT-T1W images, and the presence of metastasis was rated again (session 2). RESULTS: A total of 240 possible enhanced lesions were detected in session 1. Judging by follow-up MR examinations, 196 were considered to be nonmetastatic findings and 44 were determined to be metastasis. In session 2 the confidence rating for nonmetastasis increased significantly in the subset of nonmetastatic findings (P < 0.001), and the confidence rating for metastasis increased significantly in the subset of metastases (P < 0.05). CONCLUSION: The addition of postcontrast FLAIR imaging to pre- and postcontrast MT-T1WI improves diagnostic confidence in evaluation of brain metastases.

Capillary telangiectasia of the brain stem diagnosed by susceptibility-weighted imaging.

A case of brain stem capillary telangiectasia diagnosed by susceptibility-weighted imaging is reported. A small enhancing pontine lesion was found on postcontrast T1-weighted MR images in a 56-year-old woman with human T-cell leukemia virus type 1 infection. Imaging diagnosis was difficult with conventional MR imaging because the lesion did not show characteristic signal loss on conventional gradient-echo images. SWI was useful for imaging diagnosis as it demonstrated marked signal loss of the lesion.

Uncertainty in treatment of head-and-neck tumors by use of intraoral mouthpiece and embedded fiducials.

PURPOSE: To reduce setup error and intrafractional movement in head-and-neck treatment, a real-time tumor tracking radiotherapy (RTRT) system was used with the aid of gold markers implanted in a mouthpiece. METHODS AND MATERIALS: Three 2-mm gold markers were implanted into a mouthpiece that had been custom made for each patient before the treatment planning process. Setup errors in the conventional immobilization system using the shell (manual setup) and in the RTRT system (RTRT setup) were compared. Eight patients with pharyngeal tumors were enrolled. RESULTS: The systematic setup errors were 1.8, 1.6, and 1.1 mm in the manual setup and 0.2, 0.3, and 0.3 mm in the RTRT setup in right-left, craniocaudal, and AP directions, respectively. Statistically significant differences were observed with respect to the variances in setup error (p <0.001). The systematic and random intrafractional errors were maintained within the ranges of 0.2-0.6 mm and 1.0-2.0 mm, respectively. The rotational systematic and random intrafractional errors were estimated to be 2.2-3.2 degrees and 1.5-1.6 degrees , respectively. CONCLUSIONS: The setup error and planning target volume margin can be significantly reduced using an RTRT system with a mouthpiece and three gold markers.

Magnetic resonance-guided percutaneous cryoablation of uterine fibroids: early clinical experiences.

PURPOSE: Uterine fibroids (leiomyomas) are the most common tumors of the uterus. The present study evaluated the feasibility and effectiveness of magnetic resonance (MR)-guided percutaneous cryoablation for uterine fibroids as a minimally invasive treatment alternative. METHODS: From August 2001 to June 2002, MR-guided percutaneous cryoablation was performed on seven uterine fibroids in 6 patients who displayed clinical symptoms related to tumors. Using a horizontal-type open MR system, cryoablation probes were percutaneously placed in fibroids. Fibroids were ablated, and the site and size of ice balls were monitored on MR imaging. Postoperatively, patients completed a questionnaire to assess changes in presenting clinical symptoms, and MR images were obtained for all patients at follow-up. Changes in clinical symptoms and tumor volume were evaluated in each patient. RESULTS: All treated patients showed reductions in tumor size. Mean volume reduction rate was 40.3% at 6 weeks postoperatively, and 79.4% at 9-12 months. All patients reported fever after treatment. Surgical drainage was required for abscess in the probe channel in one patient, and transient liver damage occurred in another. Subjective symptoms improved in all patients except one who had multiple tumors, and no patient complained of new symptoms after cryoablation during follow-up. CONCLUSION: MR-guided percutaneous cryoablation represents a feasible and effective treatment for uterine fibroids.

Speed and amplitude of lung tumor motion precisely detected in four-dimensional setup and in real-time tumor-tracking radiotherapy.

BACKGROUND: To reduce the uncertainty of registration for lung tumors, we have developed a four-dimensional (4D) setup system using a real-time tumor-tracking radiotherapy system. METHODS AND MATERIALS: During treatment planning and daily setup in the treatment room, the trajectory of the internal fiducial marker was recorded for 1 to 2 min at the rate of 30 times per second by the real-time tumor-tracking radiotherapy system. To maximize gating efficiency, the patient's position on the treatment couch was adjusted using the 4D setup system with fine on-line remote control of the treatment couch. RESULTS: The trajectory of the marker detected in the 4D setup system was well visualized and used for daily setup. Various degrees of interfractional and intrafractional changes in the absolute amplitude and speed of the internal marker were detected. Readjustments were necessary during each treatment session, prompted by baseline shifting of the tumor position. CONCLUSION: The 4D setup system was shown to be useful for reducing the uncertainty of tumor motion and for increasing the efficiency of gated irradiation. Considering the interfractional and intrafractional changes in speed and amplitude detected in this study, intercepting radiotherapy is the safe and cost-effective method for 4D radiotherapy using real-time tracking technology.

Percutaneous transluminal angioplasty for hepatic artery stenosis after living donor liver transplantation.

The purpose of this study was to evaluate the efficacy of percutaneous transluminal angioplasty (PTA) for treatment of hepatic artery stenosis after living donor liver transplantation. Eighteen patients with hepatic artery stenosis after living donor liver transplantation were included in this study. The success rate and complications of PTA and recurrent stenosis of the hepatic artery were evaluated. Seventeen of 18 patients (94.4%) were successfully treated without complication by a first PTA procedure. Recurrence of hepatic artery stenosis occurred in 6 patients (33.3%). Repeated PTA was performed 12 times for the 6 patients. Two complications occurred as arterial dissection and perforation. As a consequence, the complication rate was 6.7%, involving 2 of 30 procedures in total. In conclusion, PTA is effective for treatment of hepatic artery stenosis after living donor liver transplantation without an increase in the complication rate.

Magnetic resonance imaging findings and histopathological observations after percutaneous renal cryoablation in the rabbit model.

PURPOSE: We investigated sequential changes in MRI and relevant histopathological findings after PRC. MATERIALS AND METHODS: A total of 15 rabbits were examined with MRI and sacrificed immediately (3), and 7 (4), 45 (4) and 90 (4) days after PRC. MRI studies were reviewed for the signal intensity of cryolesions and correlated with pathological findings. MRI and pathological measurements of cryolesion sizes were compared using the paired t test. RESULTS: CCN was produced in central areas of cryolesions and associated with hemorrhage, hemolysis, fibrous granulation and fibrosis that was orderly through days 1 to 90. Signal intensity was slightly hyperintense on T1-weighted spin-echo images immediately after PRC, and hyperintense on T1 and T2-weighted fast spin-echo images at 7 days. On T2-weighted fast spin-echo images there was a hypointense zone in peripheral areas between the central area and renal parenchyma at the prior 2 stages, which was consistent with PCN histologically. It was enhanced at 7 days. At 45 and 90 days the signal intensity of cryolesions was isointense or hypointense on the 2 sequences. Parenchymal injury adjacent to cryolesions was histologically recognized and visible as a hyperintense zone in 2 lesions at 45 days. This zone was enhanced in 2 lesions at 45 and 90 days. No statistical significance was apparent between the 2 measurements of cryolesions and CCN sizes (p <0.05). CONCLUSIONS: The MRI appearance of cryolesions reflects orderly histopathological findings. MRI distinguishes CCN from PCN, reveals injury to the renal parenchyma outside of cryolesions and accurately estimates the size of cryolesions and CCN.

Hypofractionated radiotherapy boost for dose escalation as a treatment option for high-grade spinal cord astrocytic tumor.

PURPOSE: To retrospectively analyze the outcome of post-operative radiotherapy for spinal cord glioma with the emphasis on the hypofractionated radiotherapy boost for dose escalation as a treatment option for high-grade spinal cord astrocytic tumors. MATERIALS AND METHODS: Forty-one patients with spinal cord glioma received post-operative radiotherapy between 1979 and 2003. The median age was 34 years (range, 10-66 years). Median follow-up was 49 months (range, 5-291 months). There were 12 low-grade astrocytic tumors, 11 high-grade astrocytic tumors, 16 low-grade ependymal tumors and 2 high-grade ependymal tumors. Among 11 patients with high-grade astrocytic tumors, 5 with anaplastic astrocytoma and 1 with glioblastoma received hypofractionated radiotherapy boost for dose escalation. The median total dose of the conventional radiotherapy was 45.5 Gy in 19 fractions (range, 30.0-60.0 Gy). The median normalized total dose (using daily dose of 2.0 Gy and an alpha/ per thousandbeta ratio of 2.0) of the hypofractionated radiotherapy boost was 131 Gy2 (range, 85-249). RESULTS: The Kaplan-Meier survival rates at 10 years from the date of the first surgery were 64% for the entire group, 47% for the astrocytic tumors and 84% for the ependymal tumors, respectively (P=0.009). Among 11 patients with high-grade astrocytic tumors, the actuarial survival rate at 10 years was 35%. The actuarial survival rates at 10 years were 67% for those who received hypofractionated radiotherapy boost for dose escalation, and 20% for those who did not (P=0.47). DISCUSSION: The results for ependymal tumors and low-grade astrocytic tumors were comparable to those reported in the literature. Hypofractionated radiotherapy boost for dose escalation may help to prolong the survival of patients with high-grade astrocytic tumors.

Early detection of subacute sclerosing panencephalitis by high b-value diffusion-weighted imaging: a case report.

The authors report a case of subacute sclerosing panencephalitis in which the diagnosis was suggested by high b-value diffusion-weighted imaging (DWI) findings. The signal abnormalities were located asymmetrically at bilateral cerebral corticosubcortical regions. High b-value DWI showed these signal abnormalities as marked hyperintensity with decreased apparent diffusion coefficient values. The signal abnormalities were difficult to identify on other magnetic resonance imaging sequences, including routine DWI. High b-value DWI could be valuable for earlier detection of subacute sclerosing panencephalitis.

The effect of tumor location and respiratory function on tumor movement estimated by real-time tracking radiotherapy (RTRT) system.

PURPOSE: The effects of tumor location and pulmonary function on the motion of fiducial markers near lung tumors were evaluated to deduce simple guidelines for determining the internal margin in radiotherapy without fiducial markers. METHODS AND MATERIALS: Pooled data collected by a real-time tumor-tracking radiotherapy system on 42 markers in 39 patients were analyzed. The pulmonary functions of all patients were assessed before radiotherapy. Using chest X-ray film, the position of the marker was expressed relative to the geometry of the unilateral lung. Posterior location meant the area of the posterior half of the lung in a lateral chest X-ray film, and caudal location meant the caudal half of the chest X-ray film; these categories were determined by measuring the distance between the marker and anatomic landmarks, including the apex, costophrenic angle, midline of spinal canal, lateral, anterior, and posterior boundary of the lung. RESULTS: Before the radiotherapy, 18 patients had obstructive respiratory dysfunction (ratio of forced expiratory volume in 1 s to forced vital capacity [FEV1.0/FVC] <70), 5 patients had constrictive dysfunction (percent vital capacity [%VC] <80), and 3 had mixed dysfunction. Means of FEV1.0/FVC and %VC were 97.0% and 66.5%, respectively. Median tumor movements in the x (left-right), y (anteroposterior), and z (craniocaudal) directions were 1.1 mm, 2.3 mm, and 5.4 mm, respectively. There was no significant correlation between respiratory function and magnitude of marker movement in any direction. Median marker movement in the z direction was 2.6 mm for the cranial location and 11.8 mm for the caudal location, respectively (p < 0.001). Median movement in the z direction was 11.8 mm for posterior location and 3.4 mm for anterior location, respectively (p < 0.01). CONCLUSIONS: Simple measurement of the relative location on plain chest X-ray film was related, but respiratory function test was not related, to the craniocaudal amplitude of the motion of the fiducial marker near lung tumors.

Insertion and fixation of fiducial markers for setup and tracking of lung tumors in radiotherapy.

PURPOSE: Internal 1.5-mm fiducial markers were used in real-time tumor-tracking radiotherapy (RT) for lung cancer. The fixation rate of the markers using the bronchial insertion technique, reliability of the setup using markers around the target volume, dislocation of the markers after real-time tumor-tracking RT, and long-term toxicity of marker insertion were investigated. METHODS AND MATERIALS: Between July 2000 and April 2004, 154 gold markers were inserted into 57 patients with peripheral lung cancer. The distances between the implanted markers in 198 measurements in 71 set-ups in 11 patients were measured using two sets of orthogonal diagnostic X-ray images of the real-time tumor-tracking RT system. The distance between the markers and the chest wall was also measured in a transaxial CT image on 186 occasions in 48 patients during treatment planning and during follow-up. The median treatment time was 6 days (range, 4-14 days). RESULTS: In 115 (75%) of the 154 inserted markers, the gold marker was detected throughout the treatment period. In 122 markers detected at CT planning, 115 (94%) were detected until the end of treatment. The variation in the distances between the implanted markers was within +/-2 mm in 95% and +/-1 mm in 80% during treatment. The variation in the distances between the implanted markers was >2 mm in at least one direction in 9% of the setups for which reexamination with a CT scan was indicated. The fixation rate in the left upper lobe was lower than in the other lobes. A statistically significant relationship was found between a shorter distance between the markers and the chest wall and the fixation rate, suggesting that the markers in the smaller bronchial lumens fixed better than those in the larger lumens. A learning curve among the endoscopists was suggested in the fixation rate. The distance between the markers and the chest wall changed significantly within a median of 44 days (range, 16-181 days) after treatment. CONCLUSION: The fixation of markers into the bronchial tree was useful for the setup for peripheral lung cancer and had an accuracy of +/-2 mm during the 1-2-week treatment period. The relationship between the markers and tumor can change significantly after 2 weeks, suggesting that adaptive four-dimensional RT is required.

MR-guided percutaneous cryoablation for bilateral multiple renal cell carcinomas.

A 35-year-old woman with five renal cell carcinomas (RCCs) was treated by percutaneous cryoablation. She had two RCCs in the left kidney and three in the right. Cryoablation was performed using a high-pressure argon-based system with 2- or 3-mm cryoprobes under magnetic resonance (MR) guidance. Three tumors were completely ablated. Two tumors were residual, as they were so close to nearby organs that we were forced to stop the freezing to avoid complications. No complications were encountered, and renal function was preserved. In conclusion, MR-guided cryoablation is a safe procedure even when RCCs are bilateral and multiple.

Early detection of global cerebral anoxia: improved accuracy by high-b-value diffusion-weighted imaging with long echo time.

BACKGROUND AND PURPOSE: Early and accurate detection of global cerebral anoxia is important for determination of prognosis and further management. We evaluated whether accuracy in early detection of global cerebral anoxia was improved by high-b-value diffusion-weighted imaging (DWI) with long echo time (TE). METHODS: Routine DWI (b = 1000 s/mm(2); TE = 139 ms), high-b-value DWI (b = 3000 s/mm(2); TE = 190 ms), T2-weighted imaging (T2WI), and fluid-attenuated inversion recovery (FLAIR) imaging were acquired in six patients who experienced cardiopulmonary arrest within 24 hours and six volunteers. Region of interest-based analysis was performed. Regions of interest of patients showing significant decrease in apparent diffusion coefficient (ADC) values than volunteers were considered abnormal. Three neuroradiologists independently assessed images of the patients for conspicuity of hyperintensity within regions of interest. Receiver operating characteristic (ROC) analysis was performed, and the area under the curve (Az) was compared among sequences and observers. Average contrast and contrast-to-noise ratios between abnormal regions of interest and regions of interest of normal surrounding parenchyma were calculated. RESULTS: For all observers, high-b-value DWIs achieved the largest Az, and FLAIR imaging the lowest Az. Az of routine DWI and T2WI were between these values. High-b-value DWI and FLAIR imaging showed no significant interobserver variation in Az, whereas routine DWI and T2WI did. High-b-value DWI also achieved the largest contrast and contrast-to-noise ratios. CONCLUSION: High-b-value DWI with long TE improved accuracy in early detection of global cerebral anoxia. Application of the sequence would facilitate early diagnosis.

Long-term results of ethmoid squamous cell or undifferentiated carcinoma treated with radiotherapy with or without surgery.

PURPOSE: Ethmoidal malignant tumors, for which intensity-modulated radiotherapy is expected to improve outcome, consist of heterogeneous pathological types. Reports about their outcome are influenced by the inclusion of favorable histology, such as adenocarcinoma and adenoid cystic carcinoma. We investigated the long-term treatment outcome of squamous cell carcinoma and undifferentiated carcinoma of the ethmoid sinus. MATERIALS AND METHODS: Between August 1976 and April 2002, 25 patients (20 squamous cell carcinomas and five undifferentiated carcinomas) received radical radiotherapy or preoperative radiotherapy in our institution. One (4%) had stage T2 disease, seven (28%) had stage T3, three (12%) had stage T4a, and 14 (56%) had stage T4b. Surgery was performed in 13 patients. Radiation dose varied from 50.4 Gy in 16 fractions (50.4 Gy/16 Fr) to 65 Gy in 26 fractions with or without stereotactic boost irradiation. Eleven patients received chemotherapy consisting mainly of platinum-based compounds. RESULTS: The 3- and 5-year overall survival rates for all 25 patients were 34% (95% confidence interval [CI]: 14%-54%) and 24% (CI: 6%-42%), respectively. The 3- or 5-year local progression-free rates for all patients were 48.9% and 36.7%, respectively. Visual acuity of a single eye was impaired in three patients and was lost in five patients as a result of tumor progression, but no patient had visual impairment or loss due to radiotherapy. CONCLUSION: Ethmoid squamous cell carcinoma or undifferentiated carcinoma was diagnosed at advanced T stages and was treated with radiotherapy; these patients had a poorer outcome than patients with adenocarcinoma or adenoid cystic carcinoma. Prospective trials using advanced technology should be carefully compared with historical controls because pathological types can considerably influence the treatment results.

Comparison of imaging modalities for the accurate delineation of arteriovenous malformation, with reference to stereotactic radiosurgery.

PURPOSE: To investigate the discrepancy between the arteriovenous malformations seen on magnetic resonance angiography (MRA) and on stereotactic digital subtracted angiography (DSA). METHODS AND MATERIALS: The target volume on stereotactic DSA (V(DSA)) and the target volume on MRA (V(MRA)) were separately delineated in 28 intracranial arteriovenous malformations. The coordinates of the center and the outer edges of V(DSA) and V(MRA) were calculated and used for the analyses. RESULTS: The standard deviations (mean value) of the displacement of centers of V(MRA) from V(DSA) were 2.67 mm (-1.82 mm) in the left-right direction, 3.23 mm (-0.08 mm) in the anterior-posterior direction, and 2.16 mm (0.91 mm) in the craniocaudal direction. V(MRA) covered less than 80% of V(DSA) in any dimensions in 9 cases (32%), although no significant difference was seen in the target volume between each method, with a mean value of 11.9 cc for V(DSA) and 12.3 cc for V(MRA) (p = 0.948). CONCLUSION: The shift of centers between each modality is not negligible. Considering no significant difference between V(DSA) and V(MRA), but inadequate coverage of the V(DSA) by V(MRA), it is reasonable to consider that the target on MRA might include the feeding artery and draining vein and possibly miss a portion of the nidus.