Fusion Of MR Images Research Articles

Magnetic Resonance Imaging/Ultrasound Fusion Guided Prostate Biopsy Improves Cancer Detection Following Transrectal Ultrasound Biopsy and Correlates With Multiparametric Magnetic Resonance Imaging

A novel platform was developed that fuses pre-biopsy magnetic resonance imaging with real-time transrectal ultrasound imaging to identify and biopsy lesions suspicious for prostate cancer. The cancer detection rates for the first 101 patients are reported. This prospective, single institution study was approved by the institutional review board. Patients underwent 3.0 T multiparametric magnetic resonance imaging with endorectal coil, which included T2-weighted, spectroscopic, dynamic contrast enhanced and diffusion weighted magnetic resonance imaging sequences. Lesions suspicious for cancer were graded according to the number of sequences suspicious for cancer as low (2 or less), moderate (3) and high (4) suspicion. Patients underwent standard 12-core transrectal ultrasound biopsy and magnetic resonance imaging/ultrasound fusion guided biopsy with electromagnetic tracking of magnetic resonance imaging lesions. Chi-square and within cluster resampling analyses were used to correlate suspicion on magnetic resonance imaging and the incidence of cancer detected on biopsy. Mean patient age was 63 years old. Median prostate specific antigen at biopsy was 5.8 ng/ml and 90.1% of patients had a negative digital rectal examination. Of patients with low, moderate and high suspicion on magnetic resonance imaging 27.9%, 66.7% and 89.5% were diagnosed with cancer, respectively (p <0.0001). Magnetic resonance imaging/ultrasound fusion guided biopsy detected more cancer per core than standard 12-core transrectal ultrasound biopsy for all levels of suspicion on magnetic resonance imaging. Prostate cancer localized on magnetic resonance imaging may be targeted using this novel magnetic resonance imaging/ultrasound fusion guided biopsy platform. Further research is needed to determine the role of this platform in cancer detection, active surveillance and focal therapy, and to determine which patients may benefit.

Augmented Lagrangian based reconstruction of non-uniformly sub-Nyquist sampled MRI data

MRI has recently been identified as a promising application for compressed-sensing-like regularization because of its potential to speed up the acquisition while maintaining the image quality. Thereby non-uniform k-space trajectories, such as random or spiral trajectories, are becoming more and more important, because they are well suited to be used within the compressed-sensing (CS) acquisition framework. In this paper, we propose a new reconstruction technique for non-uniformly sub-Nyquist sampled k-space data. Several parts make up this technique, such as the non-uniform Fourier transform (NUFT), the discrete shearlet transform and a augmented Lagrangian based optimization algorithm. Because MRI images are real-valued, we introduce a new imaginary value suppressing prior, which attenuates imaginary components of MRI images during reconstruction, resulting in a better overall image quality. Further, a preconditioning based on the Voronoi cell size of each NUFT data point speeds up the conjugate gradient optimization used as part of the optimization algorithm. The resulting algorithm converges in a relatively small number of iterations and guarantees solutions that fully comply to the imposed constraints. The results show that the algorithm is applicable not only to sub-Nyquist sampled k-space reconstruction, but also to MR image fusion and/or resolution enhancement.

Insular cortex activation in a patient with "sensed presence"/ecstatic seizures

Objective Seizures with an aura of a "sensed presence," a religious emotion, or feelings of euphoria (ecstatic seizures) are characterized by heightened self-awareness. A previous case report on a patient with epilepsy and "sensed presence" as an aura described hypoperfusion in both temporal lobes and a local ictal increase in the left frontoparietal area. A reexamination of the data was suggested by a recent study of patients with ecstatic seizures, which proposed that hyperactivation of the left anterior insula might be a potential cause. Methods We reanalyzed the laboratory data on the case with "sensed presence" aura using a fusion of SPECT and MR images of the brain, which had not previously been available, and a close examination of the subdural ictal EEG registrations. Results Examination of the ictal EEG recordings from subdural strip electrodes implanted subtemporally and temporally on both sides showed that seizure activity occurred first at the most medial subtemporal electrode on the left side. From an anatomical point of view, this electrode position is close to the ventral aspect of the left anterior insula, and it is possible that the seizure activity was initiated there. Reexamination of the SPECT data after fusion with contemporary MR images clearly indicated that the region of strong hyperactivation overlies the left anterior insula. Hyperactive regions also appear on the midinsula bilaterally. Together with the neurophysiological ictal EEG, this evidence supports a reinterpretation that this aura of "sensed presence" can be attributed to hyperactivation of the left anterior insula. Conclusion The present findings support the proposal that ecstatic seizures or "sensed presence" auras can originate from the left anterior insula, a region that has been suggested to engender self-awareness associated with positive feelings.

2131 ELASTIC REGISTRATION OF 3D PROSTATE BIOPSY TRAJECTORY BY REAL-TIME 3D TRUS WITH MR/TRUS FUSION: PILOT PHATOM STUDY

You have accessJournal of UrologyProstate Cancer: Detection and Screening1 Apr 20112131 ELASTIC REGISTRATION OF 3D PROSTATE BIOPSY TRAJECTORY BY REAL-TIME 3D TRUS WITH MR/TRUS FUSION: PILOT PHATOM STUDY Osamu Ukimura, Mihir Desai, Monish Aron, Andrew Hung, Andre Berger, Samuel Valencerina, Suzanne Palmer, and Inderbir Gill Osamu UkimuraOsamu Ukimura Los Angeles, CA More articles by this author , Mihir DesaiMihir Desai Los Angeles, CA More articles by this author , Monish AronMonish Aron Los Angeles, CA More articles by this author , Andrew HungAndrew Hung Los Angeles, CA More articles by this author , Andre BergerAndre Berger Los Angeles, CA More articles by this author , Samuel ValencerinaSamuel Valencerina Los Angeles, CA More articles by this author , Suzanne PalmerSuzanne Palmer Los Angeles, CA More articles by this author , and Inderbir GillInderbir Gill Los Angeles, CA More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.2328AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Current, standard TRUS biopsies are insufficiently accurate to localize prostate cancer lesions with sub-millimeter accuracy. For the development of a clinically-relevant prostate focal therapy protocol, precise three-dimensional (3D) localization of the interventional needle (for biopsy or ablation) is critical. Real-time 3D TRUS with computer-guidance of biopsy needle placement could precisely document the actual location of every biopsy-sampled tissue. Such information would be critical for precise focal therapy targeting. In addition, multimodal MR is emerging as a reliable imaging modality for detection of clinically significant prostate cancer. In developing focal therapy, use of MR-image guidance could potentially increase the spatial accuracy of targeted biopsy or focal intervention. The aim of study is to determine the accuracy of a computer-aided 3D TRUS system with MR image fusion for guiding prostate biopsy using phantoms. METHODS We used 3 phantoms (CIRS-053), which contain 3 randomly located hypo-echoic lesions 0.5cc in volume, and 3 other phantoms (CIRS-066), which contain 3 randomly located iso-echoic but MR-visible lesions 0.5cc in volume. We performed 3 targeted biopsies in each lesion, and the biopsy tracts were discriminated by gadolinium-based contrast agent mixed with different colored India inks, to assess the accuracy with 1-mm step-section MRI and step-section analysis of the phantoms. The external software (Koelis, France) is capable of registering 3D trajectory of each biopsy in the 3D TRUS volume data of the prostate. RESULTS A total of 27 US-guided biopsies were targeted into 9 hypo-echoic lesions; each biopsy (27/27; 100%) successfully hit the target, resulting in a procedural error of 1.5±0.8mm. Adding the system registration error of 0.83, the mean total targeting error into US-visible lesions was 2.4mm. Of 27 MR fusion guided biopsies targeted into 9 iso-echoic MR-only-visible lesions, 24 (89%) successfully hit the target, of which 3 missed biopsies occurred during initial targeting due to the learning curve, resulting in a procedural targeting error of 2.1±1.3mm. Adding the system registration error, the mean needle registration error into MR-only-visible lesions was 2.9mm. CONCLUSIONS The computer-guided 3D TRUS guided biopsy localization system with MR/US fusion achieved encouraging accuracy (<3mm error) in the registration of each biopsy trajectory in the 3D prostatic space for use in future interventions. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e853 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Osamu Ukimura Los Angeles, CA More articles by this author Mihir Desai Los Angeles, CA More articles by this author Monish Aron Los Angeles, CA More articles by this author Andrew Hung Los Angeles, CA More articles by this author Andre Berger Los Angeles, CA More articles by this author Samuel Valencerina Los Angeles, CA More articles by this author Suzanne Palmer Los Angeles, CA More articles by this author Inderbir Gill Los Angeles, CA More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...

Value of Retrospective Fusion of PET and MR Images in Detection of Hepatic Metastases: Comparison with 18F-FDG PET/CT and Gd-EOB-DTPA–Enhanced MRI

The purpose of this study was to compare the accuracy of lesion detection and diagnostic confidence between (18)F-FDG PET/CT, gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI, and retrospectively fused PET and MRI (PET/MRI). Thirty-seven patients (mean age +/- SD, 60.2 +/- 12 y) with suspected liver metastases underwent PET/CT and Gd-EOB-DTPA-enhanced MRI within 0-30 d (mean, 11.9 +/- 9 d). PET and Gd-EOB-DTPA-enhanced MR image data were retrospectively fused. Images were reviewed independently by 2 readers who identified and characterized liver lesions using PET/CT, Gd-EOB-DTPA-enhanced MRI, and PET/MRI. Each liver lesion was graded on a 5-point confidence scale ranging from definitely benign (grade of 1) to definitely malignant (grade of 5). The accuracy of each technique was determined by receiver-operating-characteristic analysis. Histopathology served as the standard of reference for all patients with malignant lesions. A total of 85 liver lesions (55 liver metastases [65%] and 30 benign lesions [35%]) were present in 29 (78%) of the 37 patients. Twenty-four (65%) of the 37 patients had liver metastases. The detection rate of liver lesions was significantly lower for PET/CT than for Gd-EOB-DTPA-enhanced MRI (64% and 85%; P = 0.002). Sensitivity in the detection and characterization of liver metastases for PET/CT, Gd-EOB-DTPA-enhanced MRI, PET/MRI in reader 1, and PET/MRI in reader 2 was 76%, 91%, 93%, and 93%, respectively; the respective specificity values were 90%, 100%, 87%, and 97%. The difference in sensitivity between PET/CT and PET/MRI was significant (P = 0.023). The level of confidence regarding liver lesions larger than 1 cm in diameter was significantly higher in PET/MRI than in PET/CT (P = 0.046). Accuracy values (area under the receiver-operating-characteristic curve) for PET/CT, Gd-EOB-DTPA-enhanced MRI, PET/MRI in reader 1, and PET/MRI in reader 2 were 0.85, 0.94, 0.92, and 0.96, respectively. The sensitivity of Gd-EOB-DTPA-enhanced MRI and PET/MRI in the detection of liver metastases is higher than that of PET/CT. Diagnostic confidence was significantly better with PET/MRI than with PET/CT regarding lesions larger than 1 cm in diameter. Compared with Gd-EOB-DTPA-enhanced MRI, PET/MRI resulted in a nonsignificant increase in sensitivity and diagnostic confidence.

CT-MR image fusion in the delineation of gross target volume for nasopharyngeal carcinoma

Objective To compare the accuracy and feasibility among CT, MR, and CT-MR image fusion technology in the delineation of gross target volume (GTV) for nasopharyngeal carcinoma (NPC). Methods Thirty-six consecutive patients with newly diagnosed or recurrent NPC were enrolled. Each pa-tient underwent both CT and MR scanning in the same treatment position. Several lead marks were made at the exactly same locations of the body surface before CT and MR scanning. The two sets of images were then transferred to the Tomcon workstation for image fusion. CT-MR image registration was performed using Land-Mark methods. GTV of each patient was contoured on CT (GTV_(CT)), MR (GTV_(MR)) and CT-MR (GTV_(CT-MR)) images. Results The mean GTV_(CT), GTV_(MR) and GTV_(CT-MR) were 27.60 cm~3, 30.99 cm~3 and 31.71 cm~3, respectively (F = 7.48, P = 0.001). Significant difference was found between GTV_(CT) and GTV_(MR) (q =2.54,P=0.016), GTV_(CT) and GTV_(CT-MR) (q =3.10,P =0.004), but not GTV_(MR) and GTV_(CT-MR) (q = 1.31 ,P = 0. 199). Significant difference among GTV_(CT), GTV_(MR) and GTV_(CT-MR) was found in patients with skull base invasion (35.65, 42.70 and 44.22 cm~3 ; F = 14. 13, P = 0. 000), but not in those without skull base invasion (20.79 cm~3, 20.46 cm~3 and 21.18 cm~3 ; F = 0.18, P = 0.832). Significant difference between GTV_(CT) and GTV_(CT-MR) was found in patients with T_3 and T_4 tumor (t = -2.17,P =0. 036), but not in those with T_1 and T_2 (t = -0.66 ,P = 0.514). Conclusions CT-MR image fusion is helpful in GTV de-lineation for NPC, particularly for patients with skull base invasion. Key words: Nasopharyngeal neoplasms/radiotherapy; Target delineation; Image fusion

Reperfusion Phenomenon Masking Acute and Subacute Infarcts at Dynamic Perfusion CT: Confirmation by Fusion of CT and Diffusion-Weighted MR Images

The purpose of this study was to evaluate cerebral blood flow, cerebral blood volume, mean transit time, time to peak, and delay in a selected sample of patients with visually normal or increased cerebral blood volume to facilitate detection of a postischemic CT perfusion hyperperfusion-reperfusion phenomenon that may mask subacute and acute infarcts. Ten patients were included who had visually normal or elevated cerebral blood volume in infarcts larger than 1.5 cm confirmed on diffusion-weighted MR images within 48 hours of perfusion CT. The cases were selected from 371 perfusion CT studies of stroke patients (99 associated with positive diffusion-weighted imaging findings) reviewed over 2.5 years on a 64-MDCT scanner. The perfusion CT images were fused to the diffusion-weighted images for measurement of cerebral blood volume, cerebral blood flow, mean transit time, time to peak, and delay in each infarct versus the contralateral hemisphere. Two neuroradiologists reviewed the images in consensus. The mean time between symptom onset and perfusion CT was 3.9 days. Infarcts were in the middle cerebral artery (n = 7) and posterior cerebral artery (n = 3) distributions. Significant differences versus the contralateral finding were found in cerebral blood volume (p = 0.016; mean increase, 30.0%), mean transit time (p = 0.007; mean increase, 38.1%), time to peak (p = 0.005; mean increase, 17.7%), and delay (p = 0.030; mean increase, 124.9%). The difference in cerebral blood flow (p = 0.785; mean increase, 1.8%) was not statistically significant. Infarcts became enhanced on the dynamic perfusion CT images of eight of 10 patients and on the contrast-enhanced T1-weighted MR images of six of nine patients. Visual inspection of cerebral blood volume and cerebral blood flow maps alone is insufficient in the evaluation of infarcts. Mean transit time, time to peak, and delay maps also should be reviewed with dynamic source images to prevent misinterpretation of findings as false-negative. This phenomenon is unlikely to occur hyperacutely (< 8 hours after onset).

On the accuracy of a mutual information algorithm for PET-MR image registration

Image registration has been increasingly used in radiation diagnosis and treatment planning as a means of information integration from different imaging modalities (e.g. MRI, PET, CT). Especially for brain lesions, accurate 3D registration and fusion of MR and PET images can provide comprehensive information about the patient under study by relating functional information from PET images to the detailed anatomical information available in MR images. However, direct PET-MR image fusion in soft tissue is complicated mainly due to the lack of conspicuous anatomical features in PET images. This study describes the implementation and validation of a mutual information registration algorithm for this purpose. Ten patients with brain lesions underwent MR and PET/CT scanning. MR-PET registration was performed a) based on the well validated MR-CT registration technique and copying the transformation to the PET images derived from the PET/CT scan (MR/PET/CT registration method) and b) directly from the MR and PET images without taking into account the CT images (MR/PET registration method). In order to check the registration accuracy of the MR/PET method, the lesion (target) was contoured in the PET images and it was transferred to the MR images using both the above methods. The MR/PET/CT method served as the gold standard for target contouring. Target contours derived by the MR/PET method were compared with the gold standard target contours for each patient and the deviation between the two contours was used to estimate the accuracy of the PET-MR registration method. This deviation was less than 3 mm (i.e. comparable to the imaging voxel of the PET/CT scanning) for 9/10 of the cases studied. Results show that the mutual information algorithm used is able to perform the PET-MR registration reliably and accurately.

A novel imaging technique for fusion of high-quality immobilised MR images of the head and neck with CT scans for radiotherapy target delineation

Uncertainty and inconsistency are observed in target volume delineation in the head and neck for radiotherapy treatment planning based only on CT imaging. Alternative modalities such as MRI have previously been incorporated into the delineation process to provide additional anatomical information. This work aims to improve on previous studies by combining good image quality with precise patient immobilisation in order to maintain patient position between scans. MR images were acquired using quadrature coils placed over the head and neck while the patient was immobilised in the treatment position using a five-point thermoplastic shell. The MR image and CT images were automatically fused in the Pinnacle treatment planning system using Syntegra software. Image quality, distortion and accuracy of the image registration using patient anatomy were evaluated. Image quality was found to be superior to that acquired using the body coil, while distortion was < 1.0 mm to a radius of 8.7 cm from the scan centre. Image registration accuracy was found to be 2.2 mm (+/- 0.9 mm) and < 3.0 degrees (n = 6). A novel MRI technique that combines good image quality with patient immobilization has been developed and is now in clinical use. The scan duration of approximately 15 min has been well tolerated by all patients.

Image fusion of MR and SPECT images for localization of epileptogenic focus

Image fusion of MR and SPECT images for localization of epileptogenic focus

Initial clinical experience with real‐time transrectal ultrasonography‐magnetic resonance imaging fusion‐guided prostate biopsy

To evaluate the feasibility and utility of registration and fusion of real-time transrectal ultrasonography (TRUS) and previously acquired magnetic resonance imaging (MRI) to guide prostate biopsies. Two National Cancer Institute trials allowed MRI-guided (with or with no US fusion) prostate biopsies during placement of fiducial markers. Fiducial markers were used to guide patient set-up for daily external beam radiation therapy. The eligible patients had biopsy-confirmed prostate cancer that was visible on MRI. A high-field (3T) MRI was performed with an endorectal coil in place. After moving to an US suite, the patient then underwent TRUS to visualize the prostate. The US transducer was equipped with a commercial needle guide and custom modified with two embedded miniature orthogonal five-degrees of freedom sensors to enable spatial tracking and registration with MR images in six degrees of freedom. The MRI sequence of choice was registered manually to the US using custom software for real-time navigation and feedback. The interface displayed the actual and projected needle pathways superimposed upon the real-time US blended with the prior MR images, with position data updating in real time at 10 frames per second. The registered MRI information blended to the real-time US was available to the physician who performed targeted biopsies of highly suspicious areas. Five patients underwent limited focal biopsy and fiducial marker placement with real-time TRUS-MRI fusion. The Gleason scores at the time of enrollment on study were 8, 7, 9, 9, and 6. Of the 11 targeted biopsies, eight showed prostate cancer. Positive biopsies were found in all patients. The entire TRUS procedure, with fusion, took approximately 10 min. The fusion of real-time TRUS and prior MR images of the prostate is feasible and enables MRI-guided interventions (like prostate biopsy) outside of the MRI suite. The technique allows for navigation within dynamic contrast-enhanced maps, or T2-weighted or MR spectroscopy images. This technique is a rapid way to facilitate MRI-guided prostate therapies such as external beam radiation therapy, brachytherapy, cryoablation, high-intensity focused ultrasound ablation, or direct injection of agents, without the cost, throughput, or equipment compatibility issues that might arise with MRI-guided interventions inside the MRI suite.

CT–MR image data fusion for computer assisted navigated neurosurgery of temporal bone tumors

Purpose To demonstrate the value of multi detector computed tomography (MDCT) and magnetic resonance imaging (MRI) in the preoperative work up of temporal bone tumors and to present, especially, CT and MR image fusion for surgical planning and performance in computer assisted navigated neurosurgery of temporal bone tumors. Materials and methods Fifteen patients with temporal bone tumors underwent MDCT and MRI. MDCT was performed in high-resolution bone window level setting in axial plane. The reconstructed MDCT slice thickness was 0.8 mm. MRI was performed in axial and coronal plane with T2-weighted fast spin-echo (FSE) sequences, un-enhanced and contrast-enhanced T1-weighted spin-echo (SE) sequences, and coronal T1-weighted SE sequences with fat suppression and with 3D T1-weighted gradient-echo (GE) contrast-enhanced sequences in axial plane. The 3D T1-weighted GE sequence had a slice thickness of 1 mm. Image data sets of CT and 3D T1-weighted GE sequences were merged utilizing a workstation to create CT–MR fusion images. MDCT and MR images were separately used to depict and characterize lesions. The fusion images were utilized for interventional planning and intraoperative image guidance. The intraoperative accuracy of the navigation unit was measured, defined as the deviation between the same landmark in the navigation image and the patient. Results Tumorous lesions of bone and soft tissue were well delineated and characterized by CT and MR images. The images played a crucial role in the differentiation of benign and malignant pathologies, which consisted of 13 benign and 2 malignant tumors. The CT–MR fusion images supported the surgeon in preoperative planning and improved surgical performance. The mean intraoperative accuracy of the navigation system was 1.25 mm. Conclusion CT and MRI are essential in the preoperative work up of temporal bone tumors. CT–MR image data fusion presents an accurate tool for planning the correct surgical procedure and is a benefit for the operational results in computer assisted navigated neurosurgery of temporal bone tumors.

Fusion of the MR image to SPECT with possible correction for partial volume effects

Low spatial resolution and the related partial volume effects limit the diagnostic potential of brain single photon emission computed tomography (SPECT) imaging. As a possible remedy for this problem we propose a technique for the fusion of SPECT and MR images, which requires for a given patient the SPECT data and the T1-weighted MR image. Basically, after the reconstruction and coregistration steps, the high-frequency part of the MR, which would be unrecoverable by the set SPECT acquisition system + reconstruction algorithm, is extracted and added to the SPECT image. The tuning of the weight of the MR on the resulting fused image can be performed very quickly, any iterative reconstruction algorithm can be used and, in the case that the SPECT projections are not available, the proposed technique can also be applied directly to the SPECT image, provided that the performance of the scanner is known. The procedure has the potential of increasing the diagnostic value of a SPECT image. Even in the locations of SPECT-MR mismatch it does not significantly affect quantitation over regions of interest (ROIs) whose dimensions are decidedly larger than the SPECT resolution distance. On the other hand, appreciable corrections for partial volume effects are expected in the locations where the contrast in the structural MR matches the corresponding contrast in functional activity.

Po‐Poster ‐ 26: Investigation of normalized mutual information for co‐registration of CT — MR images of permanent prostate implants

Post‐implant dosimetric evaluation is the standard contemporary method for assessing permanent prostate implant quality and determining the dose received by the prostate and organs at risk over the course of treatment. In current practice evaluation is performed using a CT image set typically acquired one month after the implant. However, due to poor visualization of prostate contours on the CT images, the evaluation can be difficult and is only approximate. MRI allows a better appreciation of prostate contours, but the visibility of the ensemble of the seeds is insufficient to allow its use as the only means of evaluating the treatment. Image registration of CT and MR image sets can combine the benefits of both imaging modalities and provide the means for sufficiently accurate dosimetric analysis. Mutual information is an efficient registration technique that can be used to fuse selected volumes of interest such as the prostate and neighbouring tissues. In our study we investigate optimization of registration search parameters, such as threshold level, translation and rotation angle ranges, and volume boundaries for fusing CT — MR images of a tissue equivalent prostate phantom implanted with inactive seeds, simulated image data, and clinical data sets. The results obtained so far are encouraging and suggest that mutual information‐based registration may eventually enable automatic fusion of clinical CT and MR images for prostate implant post‐dosimetry.

MR and CT image fusion for postimplant analysis in permanent prostate seed implants

To compare the outcome of two different image-based postimplant dosimetry methods in permanent seed implantation. Between October 1999 and October 2002, 150 patients with low-risk prostate carcinoma were treated with (125)I and (103)Pd in our institution. A CT-MRI image fusion protocol was used in 21 consecutive patients treated with exclusive brachytherapy. The accuracy and reproducibility of the method was calculated, and then the CT-based dosimetry was compared with the CT-MRI-based dosimetry using the dose-volume histogram (DVH) related parameters recommended by the American Brachytherapy Society and the American Association of Physicists in Medicine. Our method for CT-MRI image fusion was accurate and reproducible (median shift <1 mm). Differences in prostate volume were found, depending on the image modality used. Quality assurance DVH-related parameters strongly depended on the image modality (CT vs. CT-MRI): V(100) = 82% vs. 88%, p < 0.05. D(90) = 96% vs. 115%, p < 0.05. Those results depend on the institutional implant technique and reflect the importance of lowering inter- and intraobserver discrepancies when outlining prostate and organs at risk for postimplant dosimetry. Computed tomography-MRI fused images allow accurate determination of prostate size, significantly improving the dosimetric evaluation based on DVH analysis. This provides a consistent method to judge a prostate seed implant's quality.

A Simple Method to Assess Accuracy of Deep Brain Stimulation Electrode Placement: Pre-Operative Stereotactic CT + Postoperative MR Image Fusion

Objective: To describe a method for the measurement of the accuracy of deep brain stimulation (DBS) electrode placement with the use of image fusion technologies. Patients and Methods: Ten consecutive patients suffering from movement disorders underwent DBS electrode placement. Postoperative MR images were fused with the pre-operative stereotactic CT. The placement error in the anteroposterior, lateral and vertical planes was calculated. Results: The anteroposterior mean error ± SD was 0.61 ± 0.22 mm (range 0.2–0.9 mm). The lateral mean error ± SD was 0.65 ± 0.27 mm (range 0.2–2.2 mm). The vertical mean error ± SD was 0.82 ± 0.31 mm (range 0.3–1.6 mm). Conclusions: This technique provides a simple and precise method for the evaluation of the accuracy of DBS electrode placement.

28 oral MR and CT image fusion: postimplant analysis in prostate seed implantation

28 oral MR and CT image fusion: postimplant analysis in prostate seed implantation

A New Technique for CT/MR Fusion For Skull Base Imaging

This paper presents our initial experience utilizing a new technique which allows CT and MR image fusion in patients with skull base lesions. Eleven patients with a variety of skull base lesions underwent CT and MR imaging prior to surgery. Both sets of images were coregistered using customized software. The CT and MR data sets were then combined and viewed in a single interactive image formar using a high-speed graphic computing system. Image fusion allowed simultaneous visualization of the bony skull base anatomy (CT) and detailed soft tissue anatomy (MR) using a single image format. Combining both modalities was felt to provide a better assessment of the extent of lesions and improve understanding of their relationship to adjacent bony and neurovascular anatomy. Specifically, image fusion enhanced awareness of location of skill base lesions with respect to the cavernous sinuses. Gasserian ganglia, carotid arteries, and jugular foramina. For tumors arising within the internal auditory canal (IAC), fused images allowed better delineation of the lateral aspect of the lesion with respect to the fundus of the IAC. Thus, fusion of CT and MR studies provides a unique image format which has advantages over single modality display. We believe image fusion is beneficial for surgical planning and for treatment planning of complex skull base malignancies treated with radiotherapy.

Fusion of short-axis and long-axis cardiac MR images

A method for fusion of the short-axis and long-axis cardiac MR images into an isotropic volume image is introduced. A volume image obtained by this method contains the left ventricular (LV) cavity in one piece, facilitating measurement of its shape and volume. The main goal in this image fusion is to reconstruct the LV cavity in volume form and in high resolution. The accuracy of the method is measured using a synthetic image, and examples of image fusion using real images are presented.