Kalman filter-based EM-optical sensor fusion for needle deflection estimation

PURPOSE

In many clinical procedures such as cryoablation that involves needle insertion, accurate placement of the needle's tip at the desired target is the major issue for optimizing the treatment and minimizing damage to the neighboring anatomy. However, due to the interaction force between the needle and tissue, considerable error in intraoperative tracking of the needle tip can be observed as needle deflects.

METHODS

In this paper, measurements data from an optical sensor at the needle base and a magnetic resonance (MR) gradient field-driven electromagnetic (EM) sensor placed 10 cm from the needle tip are used within a model-integrated Kalman filter-based sensor fusion scheme. Bending model-based estimations and EM-based direct estimation are used as the measurement vectors in the Kalman filter, thus establishing an online estimation approach.

RESULTS

Static tip bending experiments show that the fusion method can reduce the mean error of the tip position estimation from 29.23 mm of the optical sensor-based approach to 3.15 mm of the fusion-based approach and from 39.96 to 6.90 mm, at the MRI isocenter and the MRI entrance, respectively.

CONCLUSION

This work established a novel sensor fusion scheme that incorporates model information, which enables real-time tracking of needle deflection with MRI compatibility, in a free-hand operating setup.

MRI findings in injured articular cartilage of the knee correlated with surgical findings

BACKGROUND

There is a strong need for quick noninvasive diagnostic technique that can give a valid estimate of the status of the cartilage reliably, discriminating intact cartilage from various grades of impaired cartilage. The goal of this study was to assess the incidence of knee cartilage injuries and compare the accuracy of two-dimension spin echo (2D SE) and fast spin echo (FSE) (conventional MRI), three-dimensional spoiled gradient echo (3D SPGR), three-dimensional fast imaging employing steady state acquisition (3D FIESTA) MR imaging sequences with surgical examination of the articular cartilage.

METHODS

One hundred and thirty-eight knees with history of knee trauma received conventional MRI, 3D SPGR and 3D FIESTA MRI examination before surgery, and surgical examination of articular cartilage was used as reference standard. A modified version of the Noyes classification system was applied for the evaluation of the lateral femoral condyle (LFC), medial femoral condyle (MFC), lateral tibial plateau (LTP), medial tibial plateau (MTP), trochlea and patella. The incidence and distributions of different injured grades at different articular surfaces of knee were assessed. A series of assessment indeces of 3D SPGR, 3D FIESTA, and the combination of the conventional MRI and 3D SPGR imaging were calculated.

RESULTS

The incidence of cartilage defects (grade 2 to 4) was 22% (183/828), according to surgical examination. Grade 3 and 4 lesions were absent at the medial tibial plateau. The rates of exact match between the grading results of different MRI procedures and surgical examination were 49% of 3D SPGR, 61% of 3D FIESTA, and 82% of the combination of 3D SPGR and conventional MRI. Also, the combination of 3D SPGR and conventional MR imaging provided the highest sensitivity, specificity, accuracy, positive and negative predictive values, at 71%, 97%, 90%, 90% and 90%, respectively.

CONCLUSIONS

For all the articular surfaces of the traumatic knees, about one fifth (22%) were cartilage defects. Both 3D SPGR and 3D FIESTA imaging performed similarly in detecting cartilage lesions of the knee. The increased accuracy in chondral assessment can be achieved by combining 3D SPGR and conventional MRI within a reasonable time.

Late genitourinary and gastrointestinal toxicity after magnetic resonance image-guided prostate brachytherapy with or without neoadjuvant external beam radiation therapy

BACKGROUND

This study was designed to estimate the rates of late genitourinary (GU) and rectal toxicity after magnetic resonance image (MRI)-guided prostate brachytherapy exclusively or in conjunction with external beam radiation therapy (EBRT).

METHODS

Between November 1997 and April 2002, 201 patients with category T1C prostate carcinoma (according to the 2002 American Joint Committee on Cancer staging criteria), prostate specific antigen levels < 10 ng/mL, and biopsy Gleason score 3 + 4 disease were treated with MRI-guided brachytherapy exclusively or in conjunction with EBRT. The MRI-guided technique was designed to spare the urethra based on delivery of the prescription dose to the peripheral zone exclusively. The Kaplan-Meier method was used to estimate rates of freedom from late GU and rectal toxicity. Comparisons were made using a log-rank test.

RESULTS

At a median follow-up of 2.8 years (range, 0.5-5.0 years), the 4-year estimates of rectal bleeding requiring coagulation for patients who underwent implantation therapy, compared with patients who received combined-modality therapy, were 8% versus 30%, respectively (log-rank P value = 0.0001). Although erectile dysfunction was common (range, 82-93%), with the use of sildenafil citrate (Viagra), it was estimated that at least two-thirds of patients had erectile function comparable to or superior to baseline function, independent of whether they received monotherapy or combined-modality therapy (P = 0.46). The 4-year estimate of freedom from radiation cystitis was 100% versus 95% (P = 0.01) for patients who received monotherapy and patients who received combined-modality therapy, respectively. No urethral strictures were observed, and no patients underwent postimplantation transurethral resection of the prostate.

CONCLUSIONS

In the current study, rectal bleeding after MRI-guided prostate brachymonotherapy was infrequent, and urethral and bladder toxicity is reported to be rare and may be attributed to the urethral-sparing technique of the MRI-guided approach.

MR imaging-guided prostate biopsy with surgical navigation software: device validation and feasibility

Magnetic resonance (MR) imaging--guided prostate biopsy in a 0.5-T open imager is described, validated in phantom studies, and performed in two patients. The needles are guided by using fast gradient-recalled echo and T2-weighted fast spin-echo images. Surgical navigation software provided T2-weighted images critical to targeting the peripheral zone and the tumor. MR imaging can be used to guide prostate biopsy.

Computer-based imaging and interventional MRI: applications for neurosurgery

Advances in computer technology and the development of open MRI systems definitely enhanced intraoperative image-guidance in neurosurgery. Based upon the integration of previously acquired and processed 3D information and the corresponding anatomy of the patient, this requires computerized image-processing methods (segmentation, registration, and display) and fast image integration techniques. Open MR systems equipped with instrument tracking systems, provide an interactive environment in which biopsies and minimally invasive interventions or open surgeries can be performed. Enhanced by the integration of multimodal imaging these techniques significantly improve the available treatment options and can change the prognosis for patients with surgically treatable diseases.

Nitric oxide synthesis inhibition attenuates behavioral actions of neuropeptide FF

Neuropeptide FF (NPFF) has certain antiopiate actions and may play a role in opiate tolerance and dependence. Third ventricle injection of 10 micrograms NPFF induces a quasimorphine abstinence syndrome in opiate-naive rats. Nitric oxide synthesis may also contribute to opiate tolerance and dependence. The present study tests the hypothesis that NPFF acts through stimulation of nitric oxide synthase (NOS). Third ventricular injection of 10 micrograms NPFF precipitated an average of 46 abstinence-like signs during a 20-min observation. Pretreatment (30 min earlier) with 7.5 or 15 mg/kg s.c. of the NOS inhibitor nitro-L-arginine (L-NNA) resulted in a significant and dose-dependent alleviation of NPFF-induced abstinence-like signs. The anti-NPFF activity of 15 mg/kg L-NNA was blocked by 750 mg/kg L-arginine, but not by the same amount of D-arginine, indicating that L-NNA attenuates NPFF activity through a stereospecific inhibition of NOS.