MR-guided biopsy of musculoskeletal lesions in a low-field system

Image-Guided Percutaneous Needle Biopsy for Benign and Malignant Bone Tumors: Systematic Review and Meta-Analysis

PURPOSE

To compare the diagnostic yield and accuracy of both image-guided core-needle biopsy (CNB) and fine-needle biopsy and evaluate the benefit of performing fine-needle biopsy in addition to CNB in patients with suspected benign and malignant bone tumors.

MATERIALS AND METHODS

A systematic search was performed on March 10, 2021, to determine whether fine-needle aspiration (FNA) plays any role when performed alone or in combination with CNB. The included studies were aggregated for the pooled estimates of diagnostic yield and histologic accuracy of image-guided percutaneous needle biopsy of bone tumors. Twenty-nine studies published between 1996 and 2021 were included.

RESULTS

When all patients with bone tumors were included, the rates of diagnostic yield and accuracy of FNA and CNB were 88.5% and 82.5% and 91.4% and 92.7%, respectively; the rates of both the methods combined were 96.5% and 94.1%, respectively; and for the lytic subgroup, the rates of diagnostic yield and accuracy of CNB and both the methods combined were 94.3% and 100% and 98.9% and 90.4%, respectively. A P value of <.05 was considered statistically significant.

CONCLUSION

The present meta-analysis showed that core biopsy alone outperformed fine-needle biopsy alone in all categories of benign and malignant tumors. Additionally, the diagnostic yield was improved when FNA was used in addition to CNB for lytic bone lesions.

Magnetic resonance imaging-guided biopsies in children

Background

Magnetic resonance imaging (MRI) is used far less as an imaging-guided method for percutaneous biopsies than computed tomography (CT) and ultrasound (US), despite its imaging benefits, particularly in children.

Purpose

To evaluate the feasibility, accuracy and safety of MRI-guided biopsies in paediatric patient population.

Material and Methods

The retrospective study included 57 consecutive paediatric patients (<18 years old). A percutaneous core needle biopsy (PCNB) or trephine biopsy was performed in 53 cases, and an additional fine-needle aspiration biopsy (FNAB) in 26 cases. In 4 cases, a stand-alone FNAB was taken. Biopsies were performed with 0.23 T open and 1.5 T closed MRI scanners. Statistical methods used for confidence intervals and p-values were Wilson score method and chi-square test.

Results

The overall diagnostic accuracy of histologic biopsy was 0.94, with sensitivity 0.82, specificity 1.00, positive predictive value (PPV) 1.00 and negative predictive value (NPV) 0.92. In histological bone biopsies, diagnostic accuracy was 0.96, with sensitivity 0.86, specificity 1.00, PPV 1.00 and NPV 0.94. The FNAB sample diagnosis was associated with the histological diagnosis in 79% of cases. There were no major primary complications and only a few late complications. After biopsy, 83% of the children were ambulatory in 6 h. Anti-inflammatory drugs and paracetamol provided satisfactory pain relief in 96% of the patients after biopsy. Most outpatients (71%) were discharged from hospital either on the same day or 1 day later.

Conclusion

MRI is a technically feasible, accurate and safe guidance tool for performing percutaneous biopsies in children.

Image-guided Sports Medicine and Musculoskeletal Tumor Interventions: A Patient-Centered Model

The spectrum of effective musculoskeletal (MSK) interventions is broadening and rapidly evolving. Increasing demands incite a perpetual need to optimize services and interventions by maximizing the diagnostic and therapeutic yield, reducing exposure to ionizing radiation, increasing cost efficiency, as well as identifying and promoting effective procedures to excel in patient satisfaction ratings and outcomes. MSK interventions for the treatment of oncological conditions, and conditions related to sports injury can be performed with different imaging modalities; however, there is usually one optimal image guidance modality for each procedure and individual patient. We describe our patient-centered workflow as a model of care that incorporates state-of-the-art imaging techniques, up-to-date evidence, and value-based practices with the intent of optimizing procedural success and outcomes at a patient-specific level. This model contrasts interventionalist- and imaging modality-centered practices, where procedures are performed based on local preference and selective availability of imaging modality or interventionalists. We discuss rationales, benefits, and limitations of fluoroscopy, ultrasound, computed tomography, and magnetic resonance imaging procedure guidance for a broad range of image-guided MSK interventions to diagnose and treat sports and tumor-related conditions.

Magnetic-resonance-guided biopsy of focal liver lesions

Image-guided biopsy techniques are widely used in clinical practice. Commonly used methods employ either ultrasound (US) or computed tomography (CT) for image guidance. In certain patients, US or CT guidance may be suboptimal, or even impossible, because of artifacts, suboptimal lesion visualization, or both. We recently began performing magnetic resonance (MR)-guided biopsy of focal liver lesions in select pediatric patients with lesions that are not well visualized by US or CT. This report describes our experience performing MR-guided biopsy of focal liver lesions, with case examples to illustrate innovative techniques and novel aspects of these procedures.

A Recent Advance in Image-Guided Locoregional Therapy for Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and the third most common cause of cancer-related deaths. Hepatic resection and liver transplantation are considered to be the preferred treatment for HCC. However, as novel therapeutic options such as image-guided locoregional therapies have emerged and been refined, the manner in which HCC is treated has changed dramatically compared with what it was considered just 2 decades earlier.

SUMMARY

This study reviews the current results of various image-guided locoregional therapies for treating HCC, especially focusing on thermal ablative and transarterial techniques.

KEY MESSAGE

Advances in image-guided locoregional therapies, including local ablative therapy and transarterial therapy, have led to a major breakthrough in the management of HCC. Both survival rates and cure rates of patients with HCC have improved markedly since the introduction of these techniques.

PRACTICAL IMPLICATIONS

Radiofrequency ablation is currently considered as an alternative to surgical resection for patients with early-stage HCC. A newer technique of ablation such as microwave ablation is increasingly being used, especially for large HCC. Transarterial chemoembolization has become a standard care for asymptomatic patients with multinodular tumors in intermediate-stage disease, and transarterial radioembolization has become the method of choice in HCC cases with portal vein thrombosis. Moreover, combination treatment modalities, such as thermal-based ablation combined with transarterial chemoembolization or ¹²⁵I seed implant brachytherapy, may further broaden their clinical indications for HCC. Moreover, use of localized radiation in combination with thermal ablation has been reported to improve tumor control and long-term survival.

MR-guided vertebroplasty with augmented reality image overlay navigation

PURPOSE

To evaluate the feasibility of magnetic resonance imaging (MRI)-guided vertebroplasty at 1.5 Tesla using augmented reality image overlay navigation.

MATERIALS AND METHODS

Twenty-five unilateral vertebroplasties [5 of 25 (20%) thoracic, 20 of 25 (80%) lumbar] were prospectively planned in 5 human cadavers. A clinical 1.5-Teslan MRI system was used. An augmented reality image overlay navigation system and 3D Slicer visualization software were used for MRI display, planning, and needle navigation. Intermittent MRI was used to monitor placement of the MRI-compatible vertebroplasty needle. Cement injections (3 ml of polymethylmethacrylate) were performed outside the bore. The cement deposits were assessed on intermediate-weighted MR images. Outcome variables included type of vertebral body access, number of required intermittent MRI control steps, location of final needle tip position, cement deposit location, and vertebroplasty time.

RESULTS

All planned procedures (25 of 25, 100%) were performed. Sixteen of 25 (64%) transpedicular and 9 of 25 (36%) parapedicular access routes were used. Six (range 3-9) MRI control steps were required for needle placement. No inadvertent punctures were visualized. Final needle tip position and cement location were adequate in all cases (25 of 25, 100%) with a target error of the final needle tip position of 6.1 ± 1.9 mm (range 0.3-8.7 mm) and a distance between the planned needle tip position and the center of the cement deposit of 4.3 mm (range 0.8-6.8 mm). Time requirement for one level was 16 (range 11-21) min.

CONCLUSION

MRI-guided vertebroplasty using image overlay navigation is feasible allowing for accurate vertebral body access and cement deposition in cadaveric thoracic and lumbar vertebral bodies.

Performing MR-guided biopsies in clinical routine: factors that influence accuracy and procedure time

OBJECTIVE

To assess the accuracy, the duration and factors that influence the duration of MRI-guided liver or soft-tissue biopsies.

METHODS

Nineteen liver biopsies and 19 soft-tissue biopsies performed using 1.5T-MRI guidance were retrospectively analysed. Diagnostic performance and complications were assessed. Intervention time was subdivided into preparation period, puncture period and control period. Correlation between procedure time and target size, skin-to-target-distance, used sequences and interventionalists' experience were analysed.

RESULTS

Overall sensitivity, specificity and accuracy were 0.86, 1.0 and 0.92, respectively. Two minor complications occurred. Overall median procedure time was 103.5 min. Liver biopsies lasted longer than soft-tissue biopsies (mean([soft-tissue]): 73.0 min, mean([liver]): 134.1 min, P < 0.001). The most time consuming part was the preparation period in both, soft-tissue and liver biopsies corresponding to 59.6% and 47.4% of the total intervention time, respectively. Total procedure time in liver biopsies (P = 0.027) and puncture period in liver and soft-tissue biopsies (P ([liver]) = 0.048, P ([soft-tissue]) = 0.005) was significantly prolonged for longer skin-to-target-distances. Lower numbers of image acquisitions (P ([liver]) = 0.0007, P ([soft-tissue]) = 0.0012) and interventionalists' experience reduces the procedure duration significantly (P < 0.05), besides all false-negative results appeared during the first five biopsies of each individual radiologist.

CONCLUSION

The interventionalists' experience, skin-to-target-distances and number of image acquisition influence the procedure time significantly.

KEY POINTS

•Appropriate training and supervision is essential for inexperienced interventionalists. •Two perpendicular image orientations should confirm the correct biopsy needle position. •Communication between interventionalist and technician is essential for a fluent biopsy procedure. •To shorten intervention time appropriate previous imaging is essential.

Magnetic resonance imaging-guided biopsy of musculoskeletal lesions using open low-field systems

With the development of open-configuration magnetic resonance imaging (MRI) systems, magnetic resonance-compatible navigational tools, and fast pulse sequences, MRI-guided biopsy of musculoskeletal lesions has evolved into an effective and safe, minimally invasive technique. Magnetic resonance-guided percutaneous biopsy of musculoskeletal lesions is especially suited for lesions that are detectable only with MRI, lesions that require double-angulated needle paths, and for patients in which radiation exposure needs to be avoided. In this article, we review pertinent principles, techniques, and clinical applications of low-field MRI for biopsy procedures in the musculoskeletal system.

Magnetic resonance imaging-guided biopsy in the musculoskeletal system using a cylindrical 1.5-T magnetic resonance imaging unit

OBJECTIVES

The objective of this study was to report a single-center experience with magnetic resonance imaging (MRI)-guided biopsy in the musculoskeletal system using a closed-bore, cylindrical, high-magnetic-field (1.5-T) MRI unit.

METHODS

From May 2010 to July 2011, 100 consecutive MRI-guided biopsy sessions were undertaken for musculoskeletal lesions in 97 patients. Patient demographics, tumor characteristics, and biopsy techniques were recorded. Biopsy results, treatment outcomes, and follow-up imaging studies were reviewed.

RESULTS

Biopsy procedures were technically successful in 99 cases (99%). Despite a mean body mass index of 30 kg/m, all patients fit within the bore of the magnet. There were 69 soft-tissue and 31 bone tumors. Most patients had both tissue core (n = 93) and fine-needle aspiration (n = 84) biopsies. All lesions were adequately imaged, localized, and targeted using rapid balanced steady-state free precession imaging (89%), fast T1 (4%), or combination of the 2 techniques (7%). A prototype real-time imaging sequence was used in 29 cases (29%) to guide biopsy needle insertion. There were no major complications. Sensitivity, specificity, and overall accuracy were 97%, 100%, and 97.6%, respectively.

CONCLUSIONS

Magnetic resonance imaging-guided biopsy in a closed-bore, high-field-strength magnet is a safe, easy, and effective technique for evaluation of musculoskeletal lesions. Ideally, the MRI suite should be equipped with an in-room radiofrequency-shielded monitor and a communication system. However, surface coils with adequate opening to grant access to the biopsy site, MRI-compatible needles, and MRI-compatible patient monitoring devices are absolutely necessary to perform MRI-guided biopsies.

MRI-guided musculoskeletal soft tissue interventions

This article highlights some of current state-of-the-art applications of interventional magnetic resonance imaging (MRI) technology pertaining to the musculoskeletal soft tissues. The rationale for the use of these techniques is to provide modes of minimally invasive diagnosis and/or therapy for a subset of patients whose lesions are not approachable by the traditional modes of interventional radiology and to introduce methods to mark subtle and infiltrative lesions to improve the outcomes of subsequent surgery or radiation therapy. These techniques build on the inherent attributes of MRI, particularly the high soft tissue contrast that made MRI the current mainstay diagnostic modality to identify and characterize musculoskeletal soft tissue lesions. The application of MRI technology to the musculoskeletal system, particularly for lesions related to the appendicular skeleton, does not typically suffer from the complexity related to involuntary organ motion. In addition, MRI-compatible versions of most of the needed instruments and devices for these interventions are currently available on commercial basis. Although musculoskeletal applications were not adopted early during the development of interventional MRI technology, we are likely to observe an increasing use of this technology for musculoskeletal soft tissue applications in the future.

Passive navigation principle for orthopedic interventions with MR fluoroscopy

INTRODUCTION

Of late, computer-assisted surgery has become a novel challenge for orthopedic surgeons. However, for orthopedic interventions magnetic resonance (MR) fluoroscopy is in its early stages of development. The authors have developed an innovative passive navigation concept, which is potentially applicable for many magnetic resonance image (MRI)-guided musculoskeletal interventions. With this method, no switching between different planes is required, since the cross-sectional modality of the MRI is used as a new navigation approach.

MATERIALS AND METHODS

This method was mainly evaluated in retrograde drilling of artificial osteochondral lesions of the talus as an example of difficult navigation in drill placement due to poor visualization with X-ray and complex anatomy. To accomplish this objective, a passive navigation device was constructed and evaluated in nine cadaveric ankle joint specimens. Feasibility and accuracy of navigated drillings were evaluated.

RESULTS

The interactive high-field MR fluoroscopy and the passive aiming device allow precise drilling of osteochondral lesions of the talus, despite the complex anatomy of the ankle. Drillings could be performed with an accuracy of 1.6 mm. The drilling guide was safe and easy to handle.

CONCLUSION

The MR-assisted retrograde drilling of osteochondral lesions may enable precise and safe treatment without radiation exposure. This passive navigation technique for MR fluoroscopy is potentially applicable for many orthopedic interventions and may present an alternative to other navigation methods. Especially, the treatment of pediatric and adolescent patients may benefit from the typical MRI properties.

MRI-guided interventions of the musculoskeletal system

MRI has become the modality of choice for many diagnostic questions in musculoskeletal radiology. Naturally, with the increasing role of MRI in diagnosis of musculoskeletal conditions, clinicians have been eager to explore the possibility of using MR guidance for musculoskeletal procedures. Researchers are actively investigating the utility and practicality of MRI compared with more established modalities for procedure guidance such as computed tomography, fluoroscopy, and ultrasound. Early studies have demonstrated the safety and feasibility of MR guidance for biopsies, spine procedures, cyst aspirations, therapeutic injections, and tumor ablation. Applications in the musculoskeletal system are likely to expand as technology improves and clinicians gain more experience. Hybrid X-ray fluoroscopy/MR imaging systems hold great promise for the future of musculoskeletal intervention by combining the excellent temporal and spatial resolution of X-ray with the anatomic detail provided by MRI.

MR-guided biopsy: a review of current techniques and applications

Biopsy has become a cornerstone of modern medicine and most modern biopsies are performed percutaneously using image guidance, typically computed tomography or ultrasound. MR-guided biopsy offers many advantages over these more traditional modalities, and the recent development of interventional MR imaging techniques has made MR-guided percutaneous biopsies and aspirations a clinical reality. As the field of MR-guided procedures continues to expand and to attract more attention from radiologists, it is important to understand the concepts, techniques, applications, advantages, and limitations of MR-guided biopsy/percutaneous procedures. Radiologists should also recognize the need for their significant involvement in the technical aspects of MR-guided procedures, since several user-defined parameters can alter device visualization in the MR imaging environment and affect procedure safety. This article reviews the prerequisites, systems, and applications of MR-guided biopsy.

La résonance magnétique interventionnelle en pathologie ostéoarticulaire

Magnetic resonance (MR) imaging is well established for the diagnosis of musculoskeletal diseases. The excellent tissue contrast and the multiplanar imaging capability have both contributed to the improvement of this technique. The development of fast acquisition techniques, sufficient patient access obtained with open magnet configurations and advances in the technology of MR compatible instruments allow a new approach to interventional radiology. These recently commercially available open-bored high-field magnets allow standard interventions such as biopsies or intra-articular infiltrations. Moreover, new interventions e.g. preoperative marking of soft tissue or bone marrow tumors are now possible with the better tissue contrast of MR imaging.

Method for automatic localization of MR-visible markers using morphological image processing and conventional pulse sequences: Feasibility for image-guided procedures

PURPOSE

To evaluate the feasibility and accuracy of an automated method to determine the 3D position of MR-visible markers.

MATERIALS AND METHODS

Inductively coupled RF coils were imaged in a whole-body 1.5T scanner using the body coil and two conventional gradient echo sequences (FLASH and TrueFISP) and large imaging volumes up to (300 mm(3)). To minimize background signals, a flip angle of approximately 1 degrees was used. Morphological 2D image processing in orthogonal scan planes was used to determine the 3D positions of a configuration of three fiducial markers (FMC). The accuracies of the marker positions and of the orientation of the plane defined by the FMC were evaluated at various distances r(M) from the isocenter.

RESULTS

Fiducial marker detection with conventional equipment (pulse sequences, imaging coils) was very reliable and highly reproducible over a wide range of experimental conditions. For r(M) </= 100 mm, the estimated maximum errors in 3D position and angular orientation were 1.7 mm and 0.33 degrees , respectively. For r(M) </= 175 mm, the respective values were 2.9 mm and 0.44 degrees .

CONCLUSIONS

Detection and localization of MR-visible markers by morphological image processing is feasible, simple, and very accurate. In combination with safe wireless markers, the method is found to be useful for image-guided procedures.

CT-guided percutaneous biopsy of spinal lesions

Accurate diagnosis of spine lesions is important for its successful management. Imaging–guided percutaneous biopsy is gaining increasing acceptance as a means for obtaining tissue for diagnosis. Most biopsies can be rapidly performed under local anaesthesia, with little patient discomfort and improved safety. Spinal anatomy is, however, complex with many adjacent vital structures. Good knowledge of anatomy and precise needling technique is, therefore, important. Today, biopsy of spinal lesions is best performed under computed tomography (CT) fluoroscopic guidance. Indications for imaging-guided biopsy include confirming metastasis in a patient with a known primary tumour, determining the nature of a solitary bone lesion, excluding malignancy in vertebral body compression, and investigating for infection. Among the various issues to be considered are site of lesion, location of adjacent vital structures, approach, and type and size of needle. Complications are rare, particularly when a meticulous technique is applied. In summary, CT-guided percutaneous biopsy is a safe and an effective technique for the evaluation of spinal lesions and useful in planning therapy.

Interventional and intraoperative MRI at low field scanner--a review

Magnetic resonance imaging (MRI) is a cutting edge imaging modality in detecting diseases and pathologic tissue. The superior soft tissue contrast in MRI allows better definition of the pathology. MRI is increasingly used for guiding, monitoring and controlling percutaneous procedures and surgery. The rapid development of interventional techniques in radiology has led to integration of imaging with computers, new therapy devices and operating room like conditions. This has projected as faster and more accurate imaging and hence more demanding procedures have been applied to the repertoire of the interventional radiologist. In combining features of various other imaging modalities and adding some more into them, interventional MRI (IMRI) has potential to take further the interventional radiology techniques, minimally invasive therapies and surgery. The term "Interventional MRI" consists in short all those procedures, which are performed under MRI guidance. These procedures can be either percutaneous or open surgical of nature. One of the limiting factors in implementing MRI as guidance modality for interventional procedures has been the fact, that most widely used magnet design, a cylindrical magnet, is not ideal for guiding procedures as it does not allow direct access to the patient. Open, low field scanners usually operating around 0.2 T, offer this feature. Clumsy hardware, bad patient access, slow image update frequency and strong magnetic fields have been other limiting factors for interventional MRI. However, the advantages of MRI as an imaging modality have been so obvious that considerable development has taken place in the 20-year history of MRI. The image quality has become better, ever faster software, new innovative sequences, better MRI hardware and increased computing power have accelerated imaging speed and image quality to a totally new level. Perhaps the most important feature in the recent development has been the introduction of open configuration low field MRI devices in the early 1990s; this enabled direct patient access and utilization of the MRI as an interventional device. This article reviews the current status of interventional and intraoperative MRI with special emphasis in low field surrounding.

Core-needle biopsy performed by the cytopathologist: a technique to complement fine-needle aspiration of soft tissue and bone lesions

BACKGROUND

Fine-needle aspiration cytology (FNAC) is gaining increased popularity in the diagnosis of musculoskeletal lesions; and, in many patients, a definitive diagnosis can be rendered from aspiration smears alone. The main limitation of FNAC of soft tissue and bone neoplasms is in the evaluation of tissue architecture. In addition cytologic specimens are not always adequate for ancillary studies.

METHODS

A consecutive series of 130 patients with soft tissue and bone lesions was examined by core-needle biopsy (CNB) performed by a cytopathologist in conjunction with FNAC. The findings of this combined diagnostic approach were compared with histologic diagnoses made on surgical biopsies and resected specimens from 86 patients. Adequate follow-up was available in all patients.

RESULTS

FNAC combined with CNB correctly could identify 77 of 78 malignant lesions and 50 of 52 benign lesions. Only seven patients underwent incisional biopsy. The tumor subtype was determined correctly in 30 of 39 patients (77%) and the malignancy grade was determined in 35 of 39 patients (90%) with primary soft tissue and bone sarcomas compared with the biopsy or operative specimens.

CONCLUSIONS

FNAC of musculoskeletal tumors/lesions complemented with CNB combined cytomorphology with tissue architecture and ancillary procedures. In the current study, obtaining FNAC as well as CNB at the same clinic visit and by the cytopathologist made preliminary diagnosis on the day of referral possible. This speeded diagnosis increased the number of correct diagnoses and usually enabled correct subtyping and malignancy grading of sarcomas.

Percutaneous Biopsy from Blinded to MR Guided: An Update on Current Techniques and Applications

The advent of interventional MR imaging techniques as well as their adoption to guide percutaneous biopsies and aspirations has served as a further step along a series of technical refinements that commenced with the implementation of image-guided approaches for tissue sampling. Nowadays, the practice of and the expectations from these procedures are quite different from those of the blind percutaneous thrusts performed in the late nineteenth and early twentieth centuries. As the field of interventional MR imaging continues to flourish and to attract more radiologists who realize the many opportunities that this technology can offer to their patients, there is a need for a full comprehension of the concepts, techniques, limitations, and cost-effectiveness of MR imaging guidance to present this service to clinical partners in the appropriate setting. Radiologists should also recognize the need for their significant involvement in the technical aspects of MR-guided procedures, because several user-defined parameters and trajectory decisions can alter device visualization in the MR imaging environment and hence affect procedure safety.

High- Versus Low-Field MR Imaging

The role of MR imaging as a noninvasive technique in the detection and evaluation of musculoskeletal diseases is unquestionable. Most of the studies reported in the literature are based on high-field MR imaging. Initial studies performed with low-field-strength have reported unsatisfactory results in the assessment of the musculoskeletal system. Recent improvements, however, have generated a renewed interest in low-field-strength MR imaging. This article presents the principal applications and results published in the literature.

Pediatric MR-guided interventions

MRI guided interventions are a relatively new but steadily growing field within surgery in pediatric age. Besides the advantages of MRI, such as multiplanar capability and excellent soft tissue contrast and spatial resolution, particularly relevant for the pediatric population is the lack of ionizing radiation. There is meanwhile a group of well defined diagnostic or therapeutic indications for applying MR imaging during pediatric interventions. Aim of this review is to give an overview about indications of MR-guided procedures in children as well as the advantages and disadvantages of MR-guided interventions. We also briefly discuss interventional MR-systems and MR-compatible devices. It is our opinion that MR-guidance for pediatric interventions is a promising technique at the beginning of its development.

Multicenter clinical experience with large core soft tissue biopsy without vacuum assistance

The increasing interest in accurate pretreatment diagnosis of solid tumours by morphology, immunohistochemistry, genetics and molecular biology requires clinicians to obtain undamaged large core biopsies. Simultaneously, medical imaging and surgery give priority to minimal tissue injury, affordable technology and optimal patient compliance. A new large core soft tissue biopsy device has been developed to meet the above criteria. After intensive preclinical testing, 30 patients gave informed consent and 26 underwent the new diagnostic biopsy procedure. The sample was studied by morphology, immunohistochemistry and, where indicated, by molecular biology. Successful diagnosis was considered when in line with clinical follow-up and, as for all malignant lesions, when confirmed by open biopsy or surgery. No difficulties in the technique were encountered in 25 patients. In one patient the procedure was prematurely stopped because of anxiety. In all other 25 procedures a complete diagnosis was reached with regard to morphology, immunohistochemistry and molecular biology. A number of radiologists suggested some automation of the technique. This new large core soft tissue biopsy system performs well in the clinical context without injury to the breast parenchyma or artefacts in the harvested tissue specimen. The system meets almost all of the proposed technical and financial requirements. Automation is underway.

Interventional and intraoperative MR: review and update of techniques and clinical experience

The concept of interventional magnetic resonance imaging (MRI) is based on the integration of diagnostic and therapeutic procedures, favored by the combination of the excellent morphological and functional imaging characteristics of MRI. The spectrum of MRI-assisted interventions ranges from biopsies and intraoperative guidance to thermal ablation modalities and vascular interventions. The most relevant recently published experimental and clinical results are discussed. In the future, interventional MRI is expected to play an important role in interventional radiology, minimal invasive therapy and guidance of surgical procedures. However, the associated high costs require a careful evaluation of its potentials in order to ensure cost-effective medical care.

Preoperative marking of musculoskeletal tumors guided by magnetic resonance imaging

BACKGROUND

The purpose of this study was to evaluate a new stereotactic method for preoperative coil-marking of musculoskeletal tumors with use of interventional magnetic resonance imaging.

METHODS

Nine patients with a soft-tissue or bone-marrow tumor were referred to our department for preoperative marking of the extent of the lesion. In one patient, two lesions were marked. Guidance for the punctures and the delivery of the coils was provided by an open low-field magnetic resonance imaging system with horizontal access. After imaging of the extent of the lesion, magnetic resonance imaging-compatible titanium coils were placed with use of nearly real-time or step-by-step magnetic resonance imaging control. The coils were placed up to seventy-two hours before the surgery. The inclusion of the tumor borders within the area of the excision was examined with cross-sectional histological analysis of surgical specimens.

RESULTS

The tumor-marking intervention was successfully performed with the guidance of magnetic resonance imaging only in all patients. Preoperatively, nineteen coils were used to mark the ten lesions in the nine patients. All of the coils were easily located with intraoperative fluoroscopy. No coil migrated between the time of the percutaneous marking and the surgery. Histological examination of the resection borders revealed no residual tumor cells. No complications were observed, and, after a mean of twenty-three months of follow-up, no tumor had recurred.

CONCLUSIONS

Preoperative coil-marking guided by magnetic resonance imaging for exact delineation of a musculoskeletal tumor is technically feasible and can readily demonstrate the full extent of the tumor. Use of magnetic resonance fluoroscopy reduces the time needed for the intervention. We recommend the coil-marking technique.

MR imaging-guided laser ablation of osteoid osteomas with use of optical instrument guidance at 0.23 T

The purpose of this study was to determine the feasibility and features of low-field MR imaging in performing interstitial laser ablation of osteoid osteomas. Between September 2001 and April 2002, five consecutive patients with clinical and imaging findings suggesting osteoid osteoma and referred for removal of osteoid osteoma were treated with interstitial laser treatment. A low-field open-configuration MRI scanner (0.23 T, Outlook Proview, Philips Medical Systems, Finland) with optical instrument guidance hardware and software was used. Laser device used was of ND-Yag type (Fibertom medilas, Dornier Medizin Technik, Germany). A bare laser fiber (Dornier Medizin Technik, Germany) with a diameter of 400 microm was used. Completely balanced steady-state (CBASS; true fast imaging with steady precession) imaging was used for lesion localization, instrument guidance, and thermal monitoring. A 14-G (Cook Medical, USA) bone biopsy drill was used for initial approach. Laser treatment was conducted through the biopsy canal. All the lesions were successfully localized, targeted, and treated under MRI guidance. All the patients were symptom free 3 weeks and 3 months after the treatment. There was one recurrence reported during follow-up (6 months). The MRI-guided percutaneous interstitial laser ablation of osteoid osteomas seems to be a feasible treatment mode.

MR imaging-guided adrenal biopsy using an open low-field-strength scanner and MR fluoroscopy

OBJECTIVE

The aim of our study was to test the feasibility and specific properties of MR imaging-guided adrenal biopsy using an open 0.2-T scanner and MR fluoroscopic fast imaging with steady-state free precession sequences.

CONCLUSION

MR imaging-guided biopsy of the adrenal gland is feasible and safe. In all patients, appropriate specimens were obtained with full diagnostic yield and accuracy. MR fluoroscopy is particularly useful to establish an oblique paravertebral access without pleural transgression. For final needle placement, supplementary breath-hold multislice sequences are required in most cases.

Magnetic resonance-guided transcortical biopsy of bone marrow lesions using a magnetic resonance imaging-compatible piezoelectric power drill: preliminary experience

RATIONALE AND OBJECTIVES

To test utility and specific properties of a commercially available MRI compatible power drill for MR guided transcortical bone biopsy.

METHODS

In 17 patients MR-guided bone biopsy was performed in an open low-field scanner (0.2 T), using a piezoelectrically powered drilling machine. Target lesions were osteoblastic in four and nonsclerosed intramedullary in 13 cases. Titanium drills sized 3 to 4 mm and an outer cannula were coaxially used for power assisted cortical trephination. For intramedullary lesion sampling, spring loaded biopsy guns and sharpened cannulas were additionally applied in seven and fluid aspiration in two patients, respectively.

RESULTS

The piezoelectric device proved to be fully MR compatible. Trephination and subsequent biopsy was successful in all patients without major complications. The drilling procedure could entirely be performed inside the magnet in case of a lateral approach (n = 11). The net drilling time averaged 7.8 minutes for trephination of nonimpaired diaphyseal bone, but was up to 50 minutes in case of thickened femoral bone. Procedures were complicated by frequent drill loosening, drill obstruction by cortical bone (n = 4) and impaired periosteal grip (n = 5) with damage to the outer cannula (n = 3).

CONCLUSIONS

The piezoelectric power drill can be applied safely in a low-field MRI environment and is a valuable tool to facilitate transcortical bone biopsy.

Percutaneous MR-guided discography in a low-field system using optical instrument tracking: a feasibility study

PURPOSE

To evaluate the feasibility of MRI-guided discography with optical tracking.

MATERIAL AND METHODS

12 consecutive patients who had a clinical suspicion of lumbar discogenic pain and/or suggestive finding of disc degeneration in imaging studies (MRI, CT, plain radiography) underwent MRI-guided discography in order to determine possible pain provocation during puncture and contrast injection. An 0.23 T open configuration MRI device with interventional tools (Outlook Proview, Philips Medical Systems, MR Technologies, Finland) was used in procedural imaging and instrument guidance. An optical guidance tool was attached to the MRI compatible needle (Chiba-type MReye, Cook, Bloomington, IN). After initial disc puncture, 1-2 mL of gadolinium contrast (Magnevist, 469 mg/mL, Schering AG, Germany) saline mixture (1:8) was injected into the disc. Immediately after injection, sagittal FE T1 weighted images were obtained to verify the final position of the needle and formation of the MRI discogram. On nine patients, additional noncontrast sagittal fast spin echo (FSE) T1, FSE T2, and axial 3D T1 gradient echo imaging was performed before and after contrast media injection to obtain MRI discograms.

RESULTS

Overall, 35 disc punctures were initialized and 34 MRI discograms were obtained. In all punctures, a positive or negative pain response was obtained. The average time for performing a procedure for three discs was 1 hour 25 minutes (minimum 45 minutes, maximum 2 hours, 15 minutes), and the average number of imaging sequences used for a puncturing one disc was 12. On one disc, the puncture failed and a discogram was not acquired. There was one complication (disc collapse) reported during follow-up.

CONCLUSION

Our results show that MRI guidance in performing discography is accurate and relatively safe. It is a technically comparable method to CT-guidance or fluoroscopy.