Dynamic contrast-enhanced MR imaging and MR-guided bone biopsy on a 0.23T open imager

Objective:To assess the feasibility of MR-guided bone biopsies.Methods::Thirty-six consecutive patients with known or suspected benign or malignant bone lesions underwent comprehensive MR imaging.A dynamic contrast-enhanced sequence followed by stationary Ti-weighted sequences were obtained and MR-guided bone biopsy of the tumor at the site with fastest enhancement was performed using an open 0.23 T MR imager.Results:All MR-guided bone biopsies samples were estimated to be sufficient by the pathologists.The biopsy specimens were diagnostic in 34 of 36 cases.Conclusion:MR-guided bone biopsies combined with dynamic contrast-enhanced imaging are feasible and safe for the diagnostic investigation of equivocal bone lesions.     

MRT-gezielte interventionelle Verfahren zur Abkl?rung des Prostatakarzinoms

In recent years magnetic resonance imaging (MRI) has been increasingly established in the diagnosis of prostate cancer in addition to transrectal ultrasonography (TRUS). The use of T2-weighted imaging allows an exact delineation of the zonal anatomy of the prostate and its surrounding structures. Other MR imaging tools, such as dynamic contrast-enhanced T1-weighted imaging or diffusion-weighted imaging allow an inference of the biochemical characteristics (multiparametric MRI). Prostate cancer, which could only be diagnosed using MR imaging or lesions suspected as being prostate cancer, which are localized in the anterior aspect of the prostate and were missed with repetitive TRUS biopsy, need to undergo MR guided biopsy. Recent studies have shown a good correlation between MR imaging and histopathology of specimens collected by MR-guided biopsy. Improved lesion targeting is therefore possible with MR-guided biopsy. So far data suggest that MR-guided biopsy of the prostate is a promising alternative diagnostic tool to TRUS-guided biopsy.     

MR-guided core biopsies of soft tissue tumours on an open 0.23 T imager

Purpose: To assess the feasibility of MR-guided soft tissue core biopsies on an open 0.23 T magnet.Material and Methods: Twenty-nine consecutive patients with known or suspected benign or malignant soft tissue tumours underwent MR imaging. A one-slice dynamic enhancement sequence was used to obtain an enhancement curve of the tumour. MR-guided core biopsy of the tumour was performed in the same session.Results: All biopsies could be performed on an open 0.23 T magnet. Standard MR images and dynamic enhancement curves were used in deciding biopsy route and target. The MR-guided core biopsy specimens were sufficient for histopathological diagnosis in 27 of 29 cases.Conclusion: Open magnet configuration allows easy access to the patient and near real-time imaging guidance of soft tissue tumours. Minimally invasive MR-guided core biopsies of soft tissue tumours are feasible and help to avoid open surgical biopsies.     

Diagnostic yield of MR-guided liver biopsies compared with CT- and US-guided liver biopsies

PURPOSE: To compare diagnostic yield and complication rates of magnetic resonance (MR)-guided versus computed tomography (CT)- and ultrasound (US)-guided liver biopsies. MATERIALS AND METHODS: MR-, CT-, and US-guided liver biopsies performed between 9/96 and 9/98 were compared. Sixty patients (21 men and 39 women, mean age 60 years) underwent MR-guided biopsy of liver lesions. Thirty patients (16 men and 14 women, mean age 59 years) underwent CT-guided biopsy. Eighteen patients (seven men and 11 women, mean age 50 years) underwent US-guided biopsy. MR procedures were performed in an open-configuration 0.5-T Signa SP MR unit. Lesion localization used standard T1 and T2 sequences, whereas biopsies were performed with multiplanar spoiled gradient recalled echo and fast gradient recalled echo sequences. A coaxial system with an MR-compatible 18-gauge stabilizing needle and a 21-gauge aspiration needle was used to obtain all samples. In CT and US procedures, a 19-gauge stabilizing needle and a 21-gauge aspiration or a 20-gauge core biopsy needle were used. A cytotechnologist was present to determine the adequacy of samples. RESULTS: MR had a diagnostic yield of 61%. CT and US had diagnostic yields of 67% and 61%, respectively. No serious complications were reported for MR and US procedures. Two CT biopsies resulted in postprocedural hemorrhage. One patient required surgical exploration and died. CONCLUSIONS: MR-guided biopsy of liver lesions with use of a 0.5-T open-configuration magnet is safe and accurate when compared with CT and US. No statistical difference was observed between the diagnostic yield of biopsies performed with MR, CT, and US guidance. MR enabled biopsy of a number of lesions in the hepatic dome and lesions with low contrast, which would normally be difficult to sample safely with use of CT or US.     

MR-guided transgluteal biopsies with an open low-field system in patients with clinically suspected prostate cancer: technique and preliminary results

The purpose of this study was to examine the feasibility and safety of MR-guided biopsies with a transgluteal approach in patients with uncertain or suspicious prostate lesions. Twenty-five patients with uncertain or suspicious focal prostate lesions detected by high-field MR imaging of the prostate gland using endorectal coil imaging were biopsied with a transgluteal approach in a low-field MRI system (0.2 T, Concerto, Siemens). The procedures were guided using T1-weighted FLASH sequences. The prostate gland was biopsied repeatedly with a coaxial technique through a 15-gauge pencil tip with a 16-gauge biopsy handy (median 3.8 samples per patient). Complications and biopsy findings were documented retrospectively. Using T1-weighted sequences biopsy procedures were performed successfully with MR guidance in all cases without any side effects or complications. The median intervention time was 11.3 min. Pathological findings revealed ten cases of hyperplasia or atrophy, three cases of prostatitis, ten cases of carcinoma and two cases of normal tissue. The clinical follow-up showed that in two patients prostate cancer was missed at MR-guided biopsy. Transgluteal MR-guided biopsy of the prostate gland is a safe and promising approach for histological clarification of uncertain or suspicious lesions.     

Evaluation of angiogenesis and perfusion of bone marrow lesions: role of semiquantitative and quantitative dynamic MRI.

Magnetic resonance imaging (MRI) is a noninvasive technique that complements computed tomography (CT), conventional X-ray, and bone marrow biopsies by sampling a large volume of musculoskeletal bone and providing information that aids the diagnosis, staging, and follow-up of various lesions. Although less sensitive to the mineral components of bones, the MRI appearance of physiologic bone marrow is mainly a reflection of the relative amounts of red marrow, yellow marrow, and trabecular bone. Therefore, use of T1-and T2-weighted MR sequences with or without fat suppression currently remains the most common approach to musculoskeletal bone lesion imaging. An additional imaging strategy to characterize various bone lesions is the application of contrast-enhanced dynamic MRI. This article examines semiquantitative and quantitative dynamic imaging, evaluation, and postprocessing techniques in various benign and malignant musculoskeletal lesions. Practical guidelines for performing a dynamic contrast-enhanced MR examination are proposed.     

介入性MR引导骨骼肌肉病变活检的应用价值

目的 介绍介入性MR引导下骨骼肌肉系统活检的技术操作方法，并评价其应用价值。方法 26例骨骼肌肉系统病变患者，均在介入性MR引导下进行经皮活检，所用设备为开放式0．23T常导MR检查仪，并配有iPath200光学引导系统(Proview，Philips)。其中10例病人术后行外科手术治疗或活检。活检针为MR兼容性。结果 24例病人获得了组织病理学诊断(24／26)。在10例后来行外科手术治疗或活检的病人中，MR活检诊断与最终诊断基本符合(10／10)。未发现明显并发症。结论 介入性MR引导下骨骼肌肉系统病变的经皮活检是1种安全、准确的新技术。     

Dynamic contrast-enhanced T2*-weighted MR imaging of tumefactive demyelinating lesions.

PURPOSE: Dynamic contrast-enhanced T2*-weighted MR imaging has been helpful in characterizing intracranial mass lesions by providing information on vascularity. Tumefactive demyelinating lesions (TDLs) can mimic intracranial neoplasms on conventional MR images, can be difficult to diagnose, and often result in surgical biopsy for suspected tumor. The purpose of this study was to determine whether dynamic contrast-enhanced T2*-weighted MR imaging can be used to distinguish between TDLs and intracranial neoplasms that share common features on conventional MR images. METHODS: We retrospectively reviewed the conventional and dynamic contrast-enhanced T2*-weighted MR images and medical records of 10 patients with tumefactive demyelinating disease that was diagnosed by either biopsy or strong clinical suspicion supported by laboratory evaluation that included CSF analysis and evoked potential tests. Twelve TDLs in 10 patients and 11 brain tumors that appeared similar on conventional MR images were studied. Relative cerebral blood volume (rCBV) was calculated from dynamic MR data and was expressed as a ratio to contralateral normal white matter. rCBV values from 11 patients with intracranial neoplasms with very similar conventional MR imaging features were used for comparison. RESULTS: The rCBV values of TDLs ranged from 0.22 to 1.79 (n = 12), with a mean of 0.88 +/- 0.46 (SD). The rCBV values of intracranial neoplasms ranged from 1.55 to 19.20 (n = 11), with a mean of 6.47 +/- 6.52. The difference in rCBV values between the two groups was statistically significant (P =.009). The difference in rCBV values between TDLs and primary cerebral lymphomas (n = 4) was less pronounced but was statistically significant (P =.005). CONCLUSION: Dynamic contrast-enhanced T2*-weighted MR imaging is a useful diagnostic tool in differentiating TDLs from intracranial neoplasms and may therefore obviate unnecessary surgical biopsy.     

MR-guided core biopsies using a closed 1.0 T imager. First clinical results.

OBJECTIVE: High soft-tissue contrast and multiplanar imaging capabilities of MRI may be advantageous in biopsy guidance compared to CT. We report our first results with MR-guided core biopsies using a closed 1.0 T MR imager. METHODS AND PATIENTS: In ten patients, seven liver lesions and one lesion each in the muscle of the back, the gluteal muscle and in the breast were biopsied under MR guidance using MR-compatible needles (Tru-Cut type, 18G and 14G). For control scans T1-weighted turbo-spin-echo (TSE), gradient-echo and T2-weighted TSE sequences were used. RESULTS: In all patients, the suspicious lesions and the biopsy needle were exactly delineated in MR control scans. In nine out of ten patients, the suspicious lesion was clarified histologically. Controls of needle position in a second plane were performed twice. Pushing the inner stylet alone resulted in a distortion of the needle in several cases in its flat area. The small diameter of the MR gantry was inconvenient for a few patients. One complication (intrahepatic bleeding) was observed, which healed up without consequences. CONCLUSION: Using a closed 1.0 T MR imager MR-guided core biopsies can be conducted efficiently. Core biopsies should be taken by pulling and pushing the outer cannula. Advantageous compared to CT are the multiplanar imaging capabilities, while the smaller gantry is disadvantageous.     

Soft-tissue tumors: value of static and dynamic gadopentetate dimeglumine-enhanced MR imaging in prediction of malignancy

PURPOSE: To prospectively evaluate static and dynamic gadopentetate dimeglumine-enhanced magnetic resonance (MR) imaging relative to nonenhanced MR imaging in differentiation of benign from malignant soft-tissue lesions and to evaluate which MR imaging parameters are most predictive of malignancy, with associated interobserver variability. MATERIALS AND METHODS: One hundred forty consecutive patients (78 male patients [median age, 51 years], 62 female patients [median age, 53 years]) with a soft-tissue mass underwent nonenhanced static and dynamic contrast material-enhanced MR imaging. Diagnosis was based on histologic findings in surgical specimens (86 of 140), findings at core-needle biopsy (43 of 140), or results of all imaging procedures with clinical follow-up (11 of 140). Multivariate logistic regression analysis was used to identify the best combination of MR imaging parameters that might be predictive of malignancy. Subjective overall performance of two observers was evaluated with receiver operating characteristic analysis. RESULTS: For subjective overall diagnosis, area under the receiver operating characteristic curve, a measure for diagnostic accuracy, was significantly larger for combined nonenhanced and contrast-enhanced MR imaging than it was for nonenhanced MR imaging alone, with no significant difference between observers. Multivariate analysis of all lesions revealed that combined nonenhanced static and dynamic contrast-enhanced MR imaging parameters were significantly superior to nonenhanced MR imaging parameters alone and to nonenhanced MR imaging parameters combined with static contrast-enhanced MR imaging parameters in prediction of malignancy. The most discriminating parameters were presence of liquefaction, start of dynamic enhancement (time interval between start of arterial and tumor enhancement), and lesion size (diameter). Results for extremity lesions were the same, with one exception: With dynamic contrast-enhanced MR imaging parameters, diagnostic performance of one observer did not improve. CONCLUSION: Static and dynamic contrast-enhanced MR imaging, when added to nonenhanced MR imaging, improved differentiation between benign and malignant soft-tissue lesions.     

MRI引导下骨骼肌肉病变活检的应用价值

目的：介绍iPath200辅助MPI引导下骨骼肌肉系统活检的技术操作方法，并评价其应用价值。方法：24例骨骼肌肉系统病变患者，均在iPath200辅助MPI引导下进行经皮活检。所用设备为Philips公司生产的开放式0．23T。常导磁共振检查仪(Proview)，并配有iPath200光学引导系统。活检针采用德国Daum公司的磁共振兼容性活检针。24例病人中的6例在活检中行Nil对比增强检查。所用对比剂为Gd-DTPA。24例病人中的10例后来行外科手术治疗或活检。结果：MPI引导活检取得足够的标本，所有的病例均获得了组织病理学诊断(24／PA)。在10例后来行外科手术治疗或活检的病人中，初步诊断与最终诊断基本符合(10／10)。未发现明显并发症如严重出血及神经损害等。结论：iPath200辅助MPI引导下的骨骼肌肉系统病变的经皮活检是一种安全、准确的新技术。     

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

Thirty magnetic resonance (MR)-guided biopsies were obtained from 20 skeletal and 10 soft-tissue lesions in 31 patients using an open 0.2 T MR system equipped with interventional accessories. The results from aspiration (N = 3), core biopsy (N = 15), and transcortical trephine biopsy (N = 12) were evaluated for accuracy and clinical efficacy. Specimens were successfully obtained from 29 patients. Results were clinically effective in 23 patients, rated definitive in 16, nonconclusive in 9, and unspecific in 2 patients. A false diagnosis due to sampling error occurred in 2 patients, and biopsy sampling was impossible in one case. The best diagnostic yield was achieved from nontranscortical biopsies of osteolytic or soft-tissue masses. Results from transcortical biopsies were less specific due to the predominance of benign lesions. MR fluoroscopy for needle guidance was applied in 13 patients. Complete needle placement inside the magnet could be performed in 16 patients. MR-guided biopsy using an open low-field MR imager is feasible and clinically effective and will become a valuable tool in the management of musculoskeletal lesions. J. Magn. Reson. Imaging 2001;13:761-768.     

Breast lesions: evaluation with dynamic contrast-enhanced T1-weighted MR imaging and with T2*-weighted first-pass perfusion MR imaging

PURPOSE: To evaluate the diagnostic value of an imaging protocol that combines dynamic contrast-enhanced T1-weighted magnetic resonance (MR) imaging and T2*-weighted first-pass perfusion imaging in patients with breast tumors and to determine if T2*-weighted imaging can provide additional diagnostic information to that obtained with T1-weighted imaging. MATERIALS AND METHODS: One hundred thirty patients with breast tumors underwent MR imaging with dynamic contrast-enhanced T1-weighted imaging of the entire breast, which was followed immediately with single-section, T2*-weighted imaging of the tumor. RESULTS: With T2*-weighted perfusion imaging, 57 of 72 carcinomas but only four of 58 benign lesions had a signal intensity loss of 20% or more during the first pass, for a sensitivity of 79% and a specificity of 93%. With dynamic contrast-enhanced T1-weighted imaging, 64 carcinomas and 19 benign lesions showed a signal intensity increase of 90% or more in the first image obtained after the administration of contrast material, for a sensitivity of 89% and a specificity of 67%. CONCLUSION: T2*-weighted first-pass perfusion imaging can help differentiate between benign and malignant breast lesions with a high level of specificity. The combination of T1-weighted and T2*-weighted imaging is feasible in a single patient examination and may improve breast MR imaging.     

肝细胞癌射频治疗后的磁共振表现

目的：评价MRI平扫及Gd-DTPA动态增强对射频治疗肝细胞癌疗效随访的价值。材料和方法：回顾性分析了55例RF术前及术后的MRI表现,并与活检及长期随访结果进行对照。结果：RF术前病灶在T1加权上多呈相对低信号、T2加权像上呈相对高信号,RF术后病灶转变成T1加权较高信号、T2加权均匀一致的等低信号,残存的癌结节表现为病灶周围包膜不规整或周边小结节并在动态增强时呈单峰型“快进快出”强化表现,活检提示癌灶残存。结论：MR平扫评价RF的疗效基本可靠,动态增强能进一步提高评价信心及准确率。RF术后定期MR随访具有重要意义。     

MR-guided interventional breast procedures considering vacuum biopsy in particular

Histologic work-up of just MR-detected breast lesions has become essential with increasing use of contrast-enhanced MR imaging. In the present article an overview is given about the different MR-guided breast interventions, performed since 1990. Presently, for reasons of costs and image quality closed magnets are most widely used. The following approaches have been described: MR-guided freehand localization in supine position, stereotaxic localization in supine position and most frequently used localization in the prone position by means of a compression device that immobilises the breast to prevent tissue shift during intervention. Only limited experience exists with interventions on open magnets. MR-guided wire localization is a well-established procedure. Recently, percutaneous vacuum biopsy of enhancing breast lesions has become possible under MR guidance. The new system allows accurate and safe access to lesions in any location of the breast and direct check-up of representative excision by visualisation of the cavity. Thus reliable histologic evaluation of lesions smaller than 10 mm is possible with this approach.     

MR imaging-detected breast lesions: histopathologic correlation of lesion characteristics and signal intensity data

OBJECTIVE: The aim of our study was to differentiate benign from malignant breast lesions that had been detected exclusively on MR imaging by analyzing qualitative and quantitative lesion characteristics. MATERIALS AND METHODS: We performed 51 MR imaging-guided breast interventions (41 preoperative lesion localizations and 10 large-core needle biopsies) in 45 patients with exclusively MR imaging-detected lesions. All patients had previously undergone diagnostic dynamic contrast-enhanced MR imaging of the breast with a double breast coil at 1.0 T (n = 36) or 1.5 T (n = 15). The diagnostic MR images were evaluated on a workstation. Lesion morphology (size, shape, margin type, enhancement pattern), signal intensity parameters (time to peak enhancement, maximum slope of enhancement curve, washout, relative water content), and scores analogous to the Breast Imaging Reporting and Data System (BI-RADS) categories were correlated with histology. RESULTS: Histology revealed malignancy in 37.3% (19/51) of the lesions. The positive predictive value for malignancy of exclusively MR imaging-detectable lesions increased as the analogous BI-RADS category increased. Late inhomogeneous contrast enhancement was the only morphologic criterion that was statistically significantly correlated with malignancy. Malignant and benign lesions did not differ significantly in any of the quantitatively evaluated signal intensity parameters. Carcinomas showed a tendency toward faster and stronger enhancement and stronger washout. CONCLUSION: The classification of exclusively MR imaging-detectable breast lesions according to a combination of morphologic and perfusion parameters including the late enhancement pattern helps identify the lesions for which interventional MR imaging is required. Quantitative signal intensity data alone do not suffice.     

MR-guided core biopsy with MR fluoroscopy using a short, wide-bore 1.5-Tesla scanner: feasibility and initial results

PURPOSE: To evaluate MR fluoroscopy in a short, wide-bore 1.5T MRI suitable for near real-time biopsy guidance. MATERIALS AND METHODS: A total of eight consecutive patients underwent MR-guided core biopsy in a 1.5T system with a 70 cm bore diameter. A total of five biopsies were performed in focal liver lesions, three biopsies in soft-tissue tumors. Before biopsy, three different fast MR sequences were compared for image quality (anatomical visibility, lesion visibility, and artifacts), and signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. In all cases, an MR-compatible guidance needle was positioned under MR fluoroscopy using the most suitable sequence. RESULTS: In each patient the guidance needle could be placed accurately under MR fluoroscopy without having to remove the patient from the isocenter of the magnet during needle movement. All biopsies were technically successful and appropriate specimens could be obtained. In prebiopsy imaging, a T2-weighted single shot turbo spinecho sequence (half-Fourier acquisition single-shot turbo spin-echo [HASTE]) achieved the best rating for lesion visibility and superior SNR and CNR values. CONCLUSION: Findings of this study demonstrate that MR fluoroscopy for biopsy guidance in a short, wide-bore 1.5T scanner is feasible. This scanner combines the patient access advantages of an open-bore system with the superior image quality and speed of a high-field scanner. In our series, the HASTE sequence was best suited for MR-guidance of biopsies.     

Prostate cancer transrectal HIFU ablation: detection of local recurrences using T2-weighted and dynamic contrast-enhanced MRI

The objective was to evaluate T2-weighted (T2w) and dynamic contrast-enhanced (DCE) MRI in detecting local cancer recurrences after prostate high-intensity focused ultrasound (HIFU) ablation. Fifty-nine patients with biochemical recurrence after prostate HIFU ablation underwent T2-weighted and DCE MRI before transrectal biopsy. For each patient, biopsies were performed by two operators: operator 1 (blinded to MR results) performed random and colour Doppler-guided biopsies (“routine biopsies”); operator 2 obtained up to three cores per suspicious lesion on MRI (“targeted biopsies”). Seventy-seven suspicious lesions were detected on DCE images (n?=?52), T2w images (n?=?2) or both (n?=?23). Forty patients and 41 MR lesions were positive at biopsy. Of the 36 remaining MR lesions, 20 contained viable benign glands. Targeted biopsy detected more cancers than routine biopsy (36 versus 27 patients, p?=?0.0523). The mean percentages of positive cores per patient and of tumour invasion of the cores were significantly higher for targeted biopsies (p?<?0.0001). The odds ratios of the probability of finding viable cancer and viable prostate tissue (benign or malignant) at targeted versus routine biopsy were respectively 3.35 (95% CI 3.05–3.64) and 1.38 (95% CI 1.13–1.63). MRI combining T2-weighted and DCE images is a promising method for guiding post-HIFU biopsy towards areas containing recurrent cancer and viable prostate tissue.     

New Trends in Musculoskeletal Interventional Radiology: Percutaneous, MR_Guided Skeletal Biopsy

Several different types of magnetic resonance (MR) scanners that allow access to the patient during image acquisition and thus permit MR-guided biopsies have been introduced. A variety of MR-compatible biopsy needles and a prototype coaxial drill system, powered either by hand or an optional motor, are presently available for sampling skeletal lesions. In a small study population of 28 patients in our hospital who required a biopsy of a skeletal lesion, all but five biopsy procedures could be completed within the MR unit. In one patient who required a transpedicular approach to a lumbar vertebra, we decided to switch to computed tomography (CT) guidance. Four patients needed general anesthesia, which is currently not available in our interventional MR suite. Those procedures were also performed under CT guidance. In 18 of the 23 MR-guided cases, the samples were sufficient and the histopathologic diagnoses were confirmed by surgery or the clinical course. Three biopsies contained an adequate volume in the sample, but the contents were either unrepresentative of the final pathology or distorted beyond recognition by the biopsy drill. Two others revealed insufficient material. No procedural complications occurred. Percutaneous biopsy of skeletal lesions performed under MR guidance seems to be a safe procedure and reasonably accurate given the fact that it is still in an early stage of development. MR imaging may be used as an alternative to CT, but its role vis-vis CT has yet to be ascertained.