Transperineal prostate biopsy under magnetic resonance image guidance: a needle placement accuracy study

Purpose

To quantify needle placement accuracy of magnetic resonance image (MRI)‐guided core needle biopsy of the prostate.

Materials and Methods

A total of 10 biopsies were performed with 18‐gauge (G) core biopsy needle via a percutaneous transperineal approach. Needle placement error was assessed by comparing the coordinates of preplanned targets with the needle tip measured from the intraprocedural coherent gradient echo images. The source of these errors was subsequently investigated by measuring displacement caused by needle deflection and needle susceptibility artifact shift in controlled phantom studies. Needle placement error due to misalignment of the needle template guide was also evaluated.

Results

The mean and standard deviation (SD) of errors in targeted biopsies was 6.5 ± 3.5 mm. Phantom experiments showed significant placement error due to needle deflection with a needle with an asymmetrically beveled tip (3.2–8.7 mm depending on tissue type) but significantly smaller error with a symmetrical bevel (0.6–1.1 mm). Needle susceptibility artifacts observed a shift of 1.6 ± 0.4 mm from the true needle axis. Misalignment of the needle template guide contributed an error of 1.5 ± 0.3 mm.

Conclusion

Needle placement error was clinically significant in MRI‐guided biopsy for diagnosis of prostate cancer. Needle placement error due to needle deflection was the most significant cause of error, especially for needles with an asymmetrical bevel. J. Magn. Reson. Imaging 2007;26:688–694. © 2007 Wiley‐Liss, Inc.     

Rapid freehand MR‐guided percutaneous needle interventions: An image‐based approach to improve workflow and feasibility

Purpose:

To develop and evaluate software‐based methods for improving the workflow of magnetic resonance (MR)‐guided percutaneous interventions.

Materials and Methods:

A set of methods was developed that allows the user to: 1) plan an entire procedure, 2) directly apply this plan to skin entry site localization without further imaging, and 3) place a needle under real‐time MR guidance with automatic alignment of three orthogonal slices along a planned trajectory with preference to the principal patient axes. To validate targeting accuracy and time, phantom experiments (96 targets) and in vivo paraspinal and kidney needle punctures in two pigs (55 targets) were performed. The influence of trajectory obliquity, level of experience, and organ motion on targeting accuracy and time was analyzed.

Results:

Mean targeting error was 1.8 ± 0.9 mm (in vitro) and 2.9 ± 1.0 mm (in vivo) in all directions. No statistically significant differences in targeting accuracy between single‐ and double‐oblique trajectories, novice and expert users, or paraspinal and kidney punctures were observed. The average time (in vivo) from trajectory planning to verification of accurate needle placement was 6 minutes.

Conclusion:

The developed methods allow for accurate needle placement along complex trajectories and are anticipated to reduce table time for MR‐guided percutaneous needle interventions. J. Magn. Reson. Imaging 2013;37:1202–1212. © 2013 Wiley Periodicals, Inc.     

Image registration for targeted MRI-guided transperineal prostate biopsy

Purpose:

To develop and evaluate image registration methodology for automated re‐identification of tumor‐suspicious foci from preprocedural MR exams during MR‐guided transperineal prostate core biopsy.

Materials and Methods:

A hierarchical approach for automated registration between planning and intra‐procedural T2‐weighted prostate MRI was developed and evaluated on the images acquired during 10 consecutive MR‐guided biopsies. Registration accuracy was quantified at image‐based landmarks and by evaluating spatial overlap for the manually segmented prostate and sub‐structures. Registration reliability was evaluated by simulating initial mis‐registration and analyzing the convergence behavior. Registration precision was characterized at the planned biopsy targets.

Results:

The total computation time was compatible with a clinical setting, being at most 2 min. Deformable registration led to a significant improvement in spatial overlap of the prostate and peripheral zone contours compared with both rigid and affine registration. Average in‐slice landmark registration error was 1.3 ± 0.5 mm. Experiments simulating initial mis‐registration resulted in an estimated average capture range of 6 mm and an average in‐slice registration precision of ±0.3 mm.

Conclusion:

Our registration approach requires minimum user interaction and is compatible with the time constraints of our interventional clinical workflow. The initial evaluation shows acceptable accuracy, reliability and consistency of the method. J. Magn. Reson. Imaging 2012;36:987–992. © 2012 Wiley Periodicals, Inc.     

Percutaneous local ablation of unifocal subclinical breast cancer: clinical experience and preliminary results of cryotherapy

Objectives

To assess the ablative effectiveness, the oncological and cosmetic efficacy of image-guided percutaneous cryoablation in the treatment of single breast nodules with subclinical dimensions after identification with ultrasonography (US), mammography, magnetic resonance (MRI) and characterization by vacuum assisted biopsy.

Materials

Fifteen women with a mean age of 73?±?5?years (range 64?C82?years) and lesion diameter of 8?±?4?mm were undergoing cryotherapy technology with a single probe under US-guidance associated with intra-procedural lymph-node mapping and excision of the sentinel node. All the patients underwent surgical resection (lumpectomy) from 30 to 45?days after the percutaneous ablation.

Results

The iceball size generated by the cryoprobe during the procedure at minus 40°C was 16?×?41?mm. In 14 of the 15 patients was observed a complete necrosis of the cryo-ablated lesion both in post-procedural MRI follow-up and anatomo-pathological evaluation after surgical resection. In one case there was a residual disease in post-procedural MRI and postoperative histological examination, probably justified by an incorrect positioning of the probe.

Conclusion

The percutaneous cryoablation as a ??minimally invasive?? technique can provide excellent oncological and cosmetic results on selected cases handled by experienced operators by using the tested devices.     

3.0‐T MR‐guided focused ultrasound for preoperative localization of nonpalpable breast lesions: An initial experimental ex vivo study

Purpose

To compare the accuracy of magnetic resonance‐guided focused ultrasound (MRgFUS) with MR‐guided needle‐wire placement (MRgNW) for the preoperative localization of nonpalpable breast lesions.

Materials and Methods

In this experimental ex vivo study, 15 turkey breasts were used. In each breast phantom an artificial nonpalpable “tumor” was created by injecting an aqueous gel containing gadolinium. MRgFUS (n = 7) was performed with the ExAblate 2000 system (InSightec). With MRgFUS the ablated tissue changes in color and increases in stiffness. A rim of palpable and visible ablations was created around the tumor to localize the tumor and facilitate excision. MRgNW (n = 8) was performed by MR‐guided placement of an MR‐compatible needle‐wire centrally in the tumor. After surgical excision of the tumor, MR images were used to evaluate tumor‐free margins (negative/positive), minimum tumor‐free margin (mm), and excised tissue volume (cm³).

Results

With MRgFUS localization no positive margins were found after excision (0%). With MRgNW two excision specimens (25%) had positive margins (P = 0.48). Mean minimum tumor‐free margin (±SD) with MRgFUS was significantly larger (5.5 ± 2.4 mm) than with MRgNW (0.9 ± 1.4 mm) (P < 0.001). Mean volume ± SD of excised tissue did not differ between MRgFUS and MRgNW localization, ie, 44.0 ± 9.4 cm³ and 39.5 ± 10.7 cm³ (P = 0.3).

Conclusion

The results of this experimental ex vivo study indicate that MRgFUS can potentially be used to localize nonpalpable breast lesions in vivo. J. Magn. Reson. Imaging 2009;30:884–889. © 2009 Wiley‐Liss, Inc.     

MRI‐guided procedures in various regions of the body using a robotic assistance system in a closed‐bore scanner: Preliminary clinical experience and limitations

Purpose:

To present the clinical setup and workflow of a robotic assistance system for image‐guided interventions in a conventional magnetic resonance imaging (MRI) environment and to report our preliminary clinical experience with percutaneous biopsies in various body regions.

Materials and Methods:

The MR‐compatible, servo‐pneumatically driven, robotic device (Innomotion) fits into the 60‐cm bore of a standard MR scanner. The needle placement (n = 25) accuracy was estimated by measuring the 3D deviation between needle tip and prescribed target point in a phantom. Percutaneous biopsies in six patients and different body regions were planned by graphically selecting entry and target points on intraoperatively acquired roadmap MR data.

Results:

For insertion depths between 29 and 95 mm, the average 3D needle deviation was 2.2 ± 0.7 mm (range 0.9–3.8 mm). Patients with a body mass index of up to ≈30 kg/m² fitted into the bore with the device. Clinical work steps and limitations are reported for the various applications. All biopsies were diagnostic and could be completed without any major complications. Median planning and intervention times were 25 (range 20–36) and 44 (36–68) minutes, respectively.

Conclusion:

Preliminary clinical results in a standard MRI environment suggest that the presented robotic device provides accurate guidance for percutaneous procedures in various body regions. Shorter procedure times may be achievable by optimizing technical and workflow aspects. J. Magn. Reson. Imaging 2010;31:964–974. ©2010 Wiley‐Liss, Inc.     

Coronary anomalies assessed by whole‐heart isotropic 3D magnetic resonance imaging for cardiac morphology in congenital heart disease

Purpose

To determine the value of whole‐heart three‐dimensional magnetic resonance imaging (MRI) for coronary artery imaging in children/adolescents with congenital heart disease (CHD).

Materials and Methods

Forty children/adolescents (median age: 14 years, range 2.6–25.8) with CHD underwent free‐breathing navigator‐gated isotropic three‐dimensional steady‐state free‐precession (3D‐SSFP) MRI for cardiac morphology. Two observers independently evaluated visibility of origin, course, vessel lengths, image quality (IQ), and contrast between coronary lumen and myocardium. A subgroup was compared with cardiac catheter.

Results

The total scan time was 6.3 ± 3.2 minutes (mean ± SD, at mean heart rate 76 ± 15/min). The mean vessel length for right coronary artery (RCA) by observer 1 was 97 ± 43 mm (observer 2: 94 ± 37 mm), for left main and anterior descending artery (LM/LAD) 91 ± 40 mm (observer 2: 90 ± 40 mm), and for left circumflex artery (LCX) 64 ± 28mm (observer 2: 66 ± 28 mm). The mean vessel contrast was 0.34 ± 0.05 (range: 0.23–0.45; maximum = 1, minimum = 0). On a 4‐level score (1 = nondiagnostic, 4 = excellent), mean IQ scores ranged between 2.3–2.9 (±0.8–1.0). Both observers agreed on the presence/proximal course of RCA in 40/40, LM/LAD in 38/40, and LCX in 36/40 patients. There was complete agreement with invasive coronary angiography available in 12/40 patients (six anomalies).

Conclusion

Isotropic whole‐heart 3D‐MRI for cardiac morphology allows reliable discrimination between normal and abnormal coronary anatomy in children/adolescents with CHD. J. Magn. Reson. Imaging 2009;29:320–327. © 2009 Wiley‐Liss, Inc.     

Fluoroscopy-Guided Percutaneous Vertebral Body Biopsy Using a Novel Drill-Powered Device: Technical Case Series

Background

A novel coaxial biopsy system powered by a handheld drill has recently been introduced for percutaneous bone biopsy. This technical note describes our initial experience performing fluoroscopy-guided vertebral body biopsies with this system, compares the yield of drill-assisted biopsy specimens with those obtained using a manual technique, and assesses the histologic adequacy of specimens obtained with drill assistance.

Methods

Medical records of all single-level, fluoroscopy-guided vertebral body biopsies were reviewed. Procedural complications were documented according to the Society of Interventional Radiology classification. The total length of bone core obtained from drill-assisted biopsies was compared with that of matched manual biopsies. Pathology reports were reviewed to determine the histologic adequacy of specimens obtained with drill assistance.

Results

Twenty eight drill-assisted percutaneous vertebral body biopsies met study inclusion criteria. No acute complications were reported. Of the 86 % (24/28) of patients with clinical follow-up, no delayed complications were reported (median follow-up, 28 weeks; range 5–115 weeks). The median total length of bone core obtained from drill-assisted biopsies was 28 mm (range 8–120 mm). This was longer than that obtained from manual biopsies (median, 20 mm; range 5–45 mm; P = 0.03). Crush artifact was present in 11 % (3/28) of drill-assisted biopsy specimens, which in one case (3.6 %; 1/28) precluded definitive diagnosis.

Conclusions

A drill-assisted, coaxial biopsy system can be used to safely obtain vertebral body core specimens under fluoroscopic guidance. The higher bone core yield obtained with drill assistance may be offset by the presence of crush artifact.

     

Magnetic resonance imaging and three‐dimensional ultrasound of carotid atherosclerosis: Mapping regional differences

Purpose

To evaluate differences in carotid atherosclerosis measured using magnetic resonance imaging (MRI) and three‐dimensional ultrasound (3DUS).

Materials and Methods

Ten subject volunteers underwent carotid 3DUS and MRI (multislice black blood fast spin echo, T1‐weighted contrast, double inversion recovery, 0.5 mm in‐plane resolution, 2 mm slice, 3.0 T) within 1 hour. 3DUS and MR images were manually segmented by two observers providing vessel wall and lumen contours for quantification of vessel wall volume (VWV) and generation of carotid thickness maps.

Results

MRI VWV (1040 ± 210 mm³) and 3DUS VWV (540 ± 110 mm³) were significantly different (P < 0.0001). When normalized for the estimated adventitia volume, mean MRI VWV decreased 240 ± 50 mm³ and was significantly different from 3DUS VWV (P < 0.001). Two‐dimensional carotid maps showed qualitative evidence of regional differences in the plaque and vessel wall thickness between MR and 3DUS in all subjects. Power Doppler US confirmed that heterogeneity in the common carotid artery in all patients resulted from apparent flow disturbances, not atherosclerotic plaque.

Conclusion

MRI and 3DUS VWV were significantly different and carotid maps showed homogeneous thickness differences and heterogeneity in specific regions of interest identified as MR flow artifacts in the common carotid artery. J. Magn. Reson. Imaging 2009;29:901–908. © 2009 Wiley‐Liss, Inc.     

Evaluation of lactate and alanine as metabolic biomarkers of prostate cancer using 1H HR‐MAS spectroscopy of biopsy tissues

The goal of this study was to investigate the use of lactate and alanine as metabolic biomarkers of prostate cancer using ¹H high‐resolution magic angle spinning (HR‐MAS) spectroscopy of snap‐frozen transrectal ultrasound (TRUS)‐guided prostate biopsy tissues. A long‐echo‐time rotor‐synchronized Carr‐Purcell‐Meiboom‐Gill (CPMG) sequence including an electronic reference to access in vivo concentrations (ERETIC) standard was used to determine the concentrations of lactate and alanine in 82 benign and 16 malignant biopsies (mean 26.5% ± 17.2% of core). Low concentrations of lactate (0.61 ± 0.28 mmol/kg) and alanine (0.14 ± 0.06 mmol/kg) were observed in benign prostate biopsies, and there was no significant difference between benign predominantly glandular (N = 54) and stromal (N = 28) biopsies between patients with (N = 38) and without (N = 44) a positive clinical biopsy. In biopsies containing prostate cancer there was a highly significant (P < 0.0001) increase in lactate (1.59 ± 0.61 mmol/kg) and alanine (0.26 ± 0.07 mmol/kg), and minimal overlap with lactate concentrations in benign biopsies. This study demonstrates for the first time very low concentrations of lactate and alanine in benign prostate biopsy tissues. The significant increase in the concentration of both lactate and alanine in biopsy tissue containing as little as 5% cancer could be exploited in hyperpolarized ¹³C spectroscopic imaging (SI) studies of prostate cancer patients. Magn Reson Med 60:510–516, 2008. © 2008 Wiley‐Liss, Inc.     

Three‐dimensional analysis of segmental wall shear stress in the aorta by flow‐sensitive four‐dimensional‐MRI

Purpose

To assess the distribution and regional differences of flow and vessel wall parameters such as wall shear stress (WSS) and oscillatory shear index (OSI) in the entire thoracic aorta.

Materials and Methods

Thirty‐one healthy volunteers (mean age = 23.7 ± 3.3 years) were examined by flow‐sensitive four‐dimensional (4D)‐MRI at 3T. For eight retrospectively positioned 2D analysis planes distributed along the thoracic aorta, flow parameters and vectorial WSS and OSI were assessed in 12 segments along the vascular circumference.

Results

Mean absolute time‐averaged WSS ranged between 0.25 ± 0.04 N/m² and 0.33 ± 0.07 N/m² and incorporated a substantial circumferential component (–0.05 ± 0.04 to 0.07 ± 0.02 N/m²). For each analysis plane, a segment with lowest absolute WSS and highest OSI was identified which differed significantly from mean values within the plane (P < 0.05). The distribution of atherogenic low WSS and high OSI closely resembled typical locations of atherosclerotic lesions at the inner aortic curvature and supraaortic branches.

Conclusion

The normal distribution of vectorial WSS and OSI in the entire thoracic aorta derived from flow‐sensitive 4D‐MRI data provides a reference constituting an important perquisite for the examination of patients with aortic disease. Marked regional differences in absolute WSS and OSI may help explaining why atherosclerotic lesions predominantly develop and progress at specific locations in the aorta. J. Magn. Reson. Imaging 2009;30:77–84. © 2009 Wiley‐Liss, Inc.     

B1 transmission‐field inhomogeneity and enhancement ratio errors in dynamic contrast‐enhanced MRI (DCE‐MRI) of the breast at 3T

Purpose:

To quantify B₁ transmission‐field inhomogeneity in breast imaging of normal volunteers at 3T using 3D T₁‐weighted spoiled gradient echo and to assess the resulting errors in enhancement ratio (ER) measured in dynamic contrast‐enhanced MRI (DCE‐MRI) studies of the breast.

Materials and Methods:

A total of 25 volunteers underwent breast imaging at 3T and the B₁ transmission‐fields were mapped. Gel phantoms that simulate pre‐ and postcontrast breast tissue T₁ were developed. The effects of B₁‐field inhomogeneity on ER, as measured using a 3D spoiled gradient echo sequence, were investigated by computer simulation and experiments on gel phantoms.

Results:

It was observed that by using the patient orientation and MR scanner employed in this study, the B₁ transmission‐field field is always reduced toward the volunteer's right side. The median B₁‐field in the right breast is reduced around 40% of the expected B₁‐field. For some volunteers the amplitude was reduced by more than 50%. Computer simulation and experiment showed that a reduction in B₁‐field decreases ER. This reduction increases with both B₁‐field error and contrast agent uptake.

Conclusion:

B₁ transmission‐field inhomogeneity is a critical issue in breast imaging at 3T and causes errors in quantifying ER. These errors would be sufficient to reduce the conspicuity of a malignant lesion and could result in reduced sensitivity for cancer detection. J. Magn. Reson. Imaging 2010;31:234–239. © 2009 Wiley‐Liss, Inc.     

MRI signal intensity based B‐Spline nonrigid registration for pre‐ and intraoperative imaging during prostate brachytherapy

Purpose:

To apply an intensity‐based nonrigid registration algorithm to MRI‐guided prostate brachytherapy clinical data and to assess its accuracy.

Materials and Methods:

A nonrigid registration of preoperative MRI to intraoperative MRI images was carried out in 16 cases using a Basis‐Spline algorithm in a retrospective manner. The registration was assessed qualitatively by experts' visual inspection and quantitatively by measuring the Dice similarity coefficient (DSC) for total gland (TG), central gland (CG), and peripheral zone (PZ), the mutual information (MI) metric, and the fiducial registration error (FRE) between corresponding anatomical landmarks for both the nonrigid and a rigid registration method.

Results:

All 16 cases were successfully registered in less than 5 min. After the nonrigid registration, DSC values for TG, CG, PZ were 0.91, 0.89, 0.79, respectively, the MI metric was ?0.19 ± 0.07 and FRE presented a value of 2.3 ± 1.8 mm. All the metrics were significantly better than in the case of rigid registration, as determined by one‐sided t‐tests.

Conclusion:

The intensity‐based nonrigid registration method using clinical data was demonstrated to be feasible and showed statistically improved metrics when compare to only rigid registration. The method is a valuable tool to integrate pre‐ and intraoperative images for brachytherapy. J. Magn. Reson. Imaging 2009;30:1052–1058. © 2009 Wiley‐Liss, Inc.

     

Dynamic contrast‐enhanced magnetic resonance imaging of abdominal solid organ and major vessel: Comparison of enhancement effect between Gd‐EOB‐DTPA and Gd‐DTPA

Purpose

To evaluate the differences in enhancement of the abdominal solid organ and the major vessel on dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) obtained with gadolinium ethoxybenzyldiethylenetriamine pentaacetic acid (Gd‐EOB‐DTPA: EOB) and gadolinium diethylenetriamine pentaacetic acid (Gd‐DTPA) in the same patients.

Materials and Methods

A total of 13 healthy volunteers underwent repeat assessments of abdominal MR examinations with DCE‐MRI using either Gd‐DTPA at a dose of 0.1 mmol/kg body weight or EOB at a dose of 0.025 mmol/kg body weight. DCE images were obtained at precontrast injection and in the arterial phase (AP: 25 seconds), portal phase (PP: 70 seconds), and equilibrium phase (EP: 3 minutes). The signal intensities (SIs) of liver at AP, PP, and EP; the SIs of spleen, renal cortex, renal medulla, pancreas, adrenal gland, aorta at AP; and the SIs of portal vein and inferior vena cava (IVC) at PP were defined using region‐of‐interest measurements, and were used for calculation of signal intensity ratio (SIR).

Results

The mean SIRs of liver (0.195 ± 0.140), spleen (1.35 ± 0.353), renal cortex (1.58 ± 0.517), renal medulla (0.548 ± 0.259), pancreas (0.540 ± 0.183), adrenal gland (1.04 ± 0.405), and aorta (2.44 ± 0.648) at AP as well as the mean SIRs of portal vein (1.85 ± 0.477) and IVC (1.16 ± 0.187) at PP in the EOB images were significantly lower than those (0.337 ± 0.200, 1.99 ± 0.443, 2.01 ± 0.474, 0.742 ± 0.336, 0.771 ± 0.227, 1.26 ± 0.442, 3.22 ± 1.20, 2.73 ± 0.429, and 1.68 ± 0.366, respectively) in the Gd‐DTPA images (P < 0.05 each). There was no significant difference in mean SIR of liver at PP between EOB (0.529 ± 0.124) and Gd‐DTPA (0.564 ± 0.139). Conversely, the mean SIR of liver at EP was significantly higher with EOB (0.576 ± 0.167) than with Gd‐DTPA (0.396 ± 0.093) (P < 0.001).

Conclusion

Lower arterial vascular and parenchymal enhancement with Gd‐EOB, as compared with Gd‐DTPA, may require reassessment of its dose, despite the higher late venous phase liver parenchymal enhancement. J. Magn. Reson. Imaging 2009;29:636–640. © 2009 Wiley‐Liss, Inc.     

Proton,diffusion‐weighted imaging,and sodium (23Na) MRI of uterine leiomyomata after MR‐guided high‐intensity focused ultrasound: A preliminary study

Purpose

To determine the feasibility of using combined proton (¹H), diffusion‐weighted imaging (DWI), and sodium (²³Na) magnetic resonance imaging (MRI) to monitor the treatment of uterine leiomyomata (fibroids).

Materials and Methods

Eight patients with uterine leiomyomata were enrolled and treated using MRI‐guided high‐intensity frequency ultrasound surgery (MRg‐HIFUS). MRI scans collected at baseline and posttreatment consisted of T2‐, T1‐, and ¹H DWI, as well as posttreatment ²³Na MRI. The ²³Na and ¹H MRi were coregistered using a replacement phantom method. Regions of interest in treated and untreated uterine leiomyoma tissue were drawn on ¹H MRI and DWI, wherein the tissue apparent diffusion coefficient of water (ADC) and absolute sodium concentrations were measured.

Results

Regions of treated uterine tissue were clearly identified on both DWI and ²³Na images. The sodium concentrations in normal myometrium tissue were 35.8 ± 2.1 mmol (mM), in the fundus; 43.4 ± 3.8 mM, and in the bladder; 65.3 ± 0.8 mM with ADC in normal myometrium of 2.2 ± 0.3 × 10^?3mm²/sec. Sodium concentration in untreated leiomyomata were 28 ± 5 mM, and were significantly elevated (41.6 ± 7.6 mM, P < 0.05) after treatment. Apparent diffusion coefficient values in the treated leiomyomata (1.30 ± 0.38 × 10^?3 mm²/sec) were decreased compared to areas of untreated leiomyomata (1.75 ± ‐4048μ‐4050μ36 × 10?³ mm²/sec; P = 0.04).

Conclusion

Multiparametric imaging permits identification of uterine leiomyomata, revealing altered ²³Na MRI and DWI levels following noninvasive treatment that provides a mechanism to explore the molecular and metabolic pathways after treatment. J. Magn. Reson. Imaging 2009;29:649–656. © 2009 Wiley‐Liss, Inc.

     

Diffusion‐weighted imaging of human carotid artery using 2D single‐shot interleaved multislice inner volume diffusion‐weighted echo planar imaging (2D ss‐IMIV‐DWEPI) at 3T: Diffusion measurement in atherosclerotic plaque

Purpose:

To determine if 2D single‐shot interleaved multislice inner volume diffusion‐weighted echo planar imaging (ss‐IMIV‐DWEPI) can be used to obtain quantitative diffusion measurements that can assist in the identification of plaque components in the cervical carotid artery.

Materials and Methods:

The 2D ss‐DWEPI sequence was combined with interleaved multislice inner volume region localization to obtain diffusion weighted images with 1 mm in‐plane resolution and 2 mm slice thickness. Eleven subjects, six of whom have carotid plaque, were studied with this technique. The apparent diffusion coefficient (ADC) images were calculated using DW images with b = 10 s/mm² and b = 300 s/mm².

Results:

The mean ADC measurement in normal vessel wall of the 11 subjects was 1.28 ± 0.09 × 10^?3 mm²/s. Six of the 11 subjects had carotid plaque and ADC measurements in plaque ranged from 0.29 to 0.87 × 10^?3 mm²/s. Of the 11 common carotid artery walls studied (33 images), at least partial visualization of the wall was obtained in all ADC images, more than 50% visualization in 82% (27/33 images), and full visualization in 18% (6/33 images).

Conclusion:

2D ss‐IMIV‐DWEPI can perform diffusion‐weighted carotid magnetic resonance imaging (MRI) in vivo with reasonably high spatial resolution (1 × 1 × 2 mm³). ADC values of the carotid wall and plaque are consistent with similar values obtained from ex vivo endarterectomy specimens. The spread in ADC values obtained from plaque indicate that this technique could form a basis for plaque component identification in conjunction with other MRI/MRA techniques. J. Magn. Reson. Imaging 2009;30:1068–1077. © 2009 Wiley‐Liss, Inc.

     

Comparing Effective Doses During Image-Guided Core Needle Biopsies with Computed Tomography Versus C-Arm Cone Beam CT Using Adult and Pediatric Phantoms

Purpose

To compare the effective doses of needle biopsies based on dose measurements and simulations using adult and pediatric phantoms, between cone beam c-arm CT (CBCT) and CT.

Method

Effective doses were calculated and compared based on measurements and Monte Carlo simulations of CT- and CBCT-guided biopsy procedures of the lungs, liver, and kidney using pediatric and adult phantoms.

Results

The effective doses for pediatric and adult phantoms, using our standard protocols for upper, middle and lower lungs, liver, and kidney biopsies, were significantly lower under CBCT guidance than CT. The average effective dose for a 5-year old for these five biopsies was 0.36 ± 0.05 mSv with the standard CBCT exposure protocols and 2.13 ± 0.26 mSv with CT. The adult average effective dose for the five biopsies was 1.63 ± 0.22 mSv with the standard CBCT protocols and 8.22 ± 1.02 mSv using CT. The CT effective dose was higher than CBCT protocols for child and adult phantoms by 803 and 590 % for upper lung, 639 and 525 % for mid-lung, and 461 and 251 % for lower lung, respectively. Similarly, the effective dose was higher by 691 and 762 % for liver and 513 and 608 % for kidney biopsies.

Conclusions

Based on measurements and simulations with pediatric and adult phantoms, radiation effective doses during image-guided needle biopsies of the lung, liver, and kidney are significantly lower with CBCT than with CT.

     

Navigated MRI-guided liver biopsies in a closed-bore scanner: experience in 52 patients

Objectives

To evaluate clinical effectiveness and diagnostic efficiency of a navigation device for MR-guided biopsies of focal liver lesions in a closed-bore scanner.

Methods

In 52 patients, 55 biopsies were performed. An add-on MR navigation system with optical instrument tracking was used for image guidance and biopsy device insertion outside the bore. Fast control imaging allowed visualization of the true needle position at any time. The biopsy workflow and procedure duration were recorded. Histological analysis and clinical course/outcome were used to calculate sensitivity, specificity and diagnostic accuracy.

Results

Fifty-four of 55 liver biopsies were performed successfully with the system. No major and four minor complications occurred. Mean tumour size was 23?±?14 mm and the skin-to-target length ranged from 22 to 177 mm. In 39 cases, access path was double oblique. Sensitivity, specificity and diagnostic accuracy were 88 %, 100 % and 92 %, respectively. The mean procedure time was 51?±?12 min, whereas the puncture itself lasted 16?±?6 min. On average, four control scans were taken.

Conclusions

Using this navigation device, biopsies of poorly visible and difficult accessible liver lesions could be performed safely and reliably in a closed-bore MRI scanner. The system can be easily implemented in clinical routine workflow.

Key Points

? Targeted liver biopsies could be reliably performed in a closed-bore MRI. ? The navigation system allows for image guidance outside of the scanner bore. ? Assisted MRI-guided biopsies are helpful for focal lesions with a difficult access. ? Successful integration of the method in clinical workflow was shown. ? Subsequent system installation in an existing MRI environment is feasible.

     

Magnetic resonance-guided upper abdominal biopsies in a high-field wide-bore 3-T MRI system: feasibility, handling, and needle artefacts

Objective:

To investigate the feasibility and handling of abdominal MRI-guided biopsies in a 3-T MRI system.

Methods:

Over a 1-year period, 50 biopsies were obtained in 47 patients with tumours of the upper abdominal organs guided by 3-T MRI with a large-bore diameter of 70 cm. Lesions in liver (47), spleen (1) and kidney (2) were biopsied with a coaxial technique using a 16-G biopsy needle guided by a T1-weighted three-dimensional gradient recalled echo volumetric interpolated breath-hold examination (T1w-3D-GRE-VIBE) sequence. Sensitivity, specificity, accuracy, complication rate, interventional complexity, room/intervention time and needle artefacts were determined.

Results:

A sensitivity of 0.93, specificity of 1.0 and accuracy of 0.94 were observed. Three patients required a rebiopsy. There was a minor complications rate of 13.6%, and no major complications were observed. Histopathology revealed 38 malignant lesions, and 3-month follow-up confirmed 9 benign lesions. Mean lesion diameter was 3.4?±?3.1 cm (50% being smaller than 2 cm). Mean needle tract length was 10.8?±?3.3 cm. Median room time was 42.0?±?19.8 min and intervention time 9.3?±?8.1 min. Needle artefact size was about 9-fold greater for perpendicular access versus access parallel to the main magnetic field.

Conclusion:

Biopsies of the upper abdomen can be performed with great technical success and easy handling because of the large-bore diameter. The MRI-guided biopsy needle had an acceptable susceptibility artefact at 3 T. However future research must aim to reduce the susceptibility effects of the biopsy systems.     

MR imaging-guided 10-gauge vacuum-assisted breast biopsy: histological characterisation

Purpose

The aim of this study was to evaluate a handheld vacuum-assisted device for magnetic resonance imaging (MRI)-guided breast biopsy.

Materials and methods

In 47 patients, a total of 47 suspicious breast lesions (mean maximum diameter 9 mm) seen with MRI (no suspicious changes on breast ultrasound or mammography) were sampled using a 10-gauge vacuum-assisted breast biopsy (VAB) device under MRI guidance. Histology of biopsy specimens was compared with final histology after surgery or with follow-up in benign lesions.

Results

Technical success was achieved in all biopsies. Histological results from VAB revealed malignancy in 15 lesions (32%), atypical ductal hyperplasia in four lesions (8%) and benign findings in 28 lesions (60%). One of four lesions with atypical ductal hyperplasia was upgraded to ductal carcinoma in situ after surgery. One of seven lesions showing ductal carcinoma was upgraded to invasive carcinoma after surgery. Two lesions diagnosed as infiltrating carcinoma by VAB were not validated at excisional biopsy due to complete removal of the lesion during the procedure. During the follow-up (mean 18 months) of histologically benign lesions, we observed no cases of breast cancer development. Because of morphological changes on follow-up MRI scans, two lesions underwent surgical excision, which confirmed their benign nature. Besides minor complications (massive bleeding, n=1) requiring no further therapeutic intervention, no complications occurred.

Conclusions

MRI-guided biopsy of breast lesions using a handheld vacuum-assisted device is a safe and effective method for the workup of suspicious lesions seen on breast MRI alone.