Bits and bytes: the future of radiology lies in informatics and information technology

Advances in informatics and information technology are sure to alter the practice of medical imaging and image-guided therapies substantially over the next decade. Each element of the imaging continuum will be affected by substantial increases in computing capacity coincident with the seamless integration of digital technology into our society at large. This article focuses primarily on areas where this IT transformation is likely to have a profound effect on the practice of radiology.

KEY POINTS

• Clinical decision support ensures consistent and appropriate resource utilization. • Big data enables correlation of health information across multiple domains. • Data mining advances the quality of medical decision-making. • Business analytics allow radiologists to maximize the benefits of imaging resources.

MR-guided percutaneous sclerotherapy of low-flow vascular malformations: Clinical experience using a 1.5 tesla MR system

PURPOSE

To demonstrate the feasibility, safety, and effectiveness of image-guided sclerotherapy of low-flow vascular malformations using a 1.5 Tesla (T) MR scanner with real-time imaging capability and in-suite fluoroscopy.

MATERIALS AND METHODS

Thirty-three procedures were performed with real-time 1.5T MR-guidance on 22 patients with a vascular malformation in the neck (n = 2), chest (n = 6), abdomen and pelvis (n = 15), and extremities (n = 11). Quantitative analysis was performed for changes in (a) planning time, (b) targeting time (interval between needle skin puncture and lesion access), (c) intervention time (interval between needle skin puncture and needle removal), and (d) total procedure time. Qualitative analysis was performed for (a) success of therapy and (b) occurrence of complications.

RESULTS

Technical success was achieved in 29 of 33 procedures. The average planning time did not significantly change between the first seven procedures and the last seven procedures (P = 0.447). The average targeting time decreased by 0:24:45 (hours:minutes:seconds) (P = 0.043), the average intervention time decreased by 0:26:58 (P = 0.022), and the average procedure time decreased by 0:28:41 (P = 0.046) when comparing the first seven procedures and the last seven procedures. Overall, there was an improvement in the patients' predominant symptoms following 82% of procedures, including a significant decrease in average pain following therapy (P < 0.001). There was a minor complication rate of 3% with no major complications.

CONCLUSION

MR-guided percutaneous sclerotherapy seems to be a safe, effective, and versatile technique for treating low-flow vascular malformations.

LEVEL OF EVIDENCE

3 J. Magn. Reson. Imaging 2017;45:1154-1162.

Comparing Preliminary and Final Neuroradiology Reports: What Factors Determine the Differences?

BACKGROUND AND PURPOSE

Trainees' interpretations of neuroradiologic studies are finalized by faculty neuroradiologists. We aimed to identify the factors that determine the degree to which the preliminary reports are modified.

MATERIALS AND METHODS

The character length of the preliminary and final reports and the percentage character change between the 2 reports were determined for neuroradiology reports composed during November 2012 to October 2013. Examination time, critical finding flag, missed critical finding flag, trainee level, faculty experience, imaging technique, and native-versus-non-native speaker status of the reader were collected. Multivariable linear regression models were used to evaluate the association between mean percentage character change and the various factors.

RESULTS

Of 34,661 reports, 2322 (6.7%) were read by radiology residents year 1; 4429 (12.8%), by radiology residents year 2; 3663 (10.6%), by radiology residents year 3; 2249 (6.5%), by radiology residents year 4; and 21,998 (63.5%), by fellows. The overall mean percentage character change was 14.8% (range, 0%-701.8%; median, 6.6%). Mean percentage character change increased for a missed critical finding (+41.6%, P < .0001), critical finding flag (+1.8%, P < .001), MR imaging studies (+3.6%, P < .001), and non-native trainees (+4.2%, P = .018). Compared with radiology residents year 1, radiology residents year 2 (-5.4%, P = .002), radiology residents year 3 (-5.9%, P = .002), radiology residents year 4 (-8.2%, P < .001), and fellows (-8.7%; P < .001) had a decreased mean percentage character change. Senior faculty had a lower mean percentage character change (-6.88%, P < .001). Examination time and non-native faculty did not affect mean percentage character change.

CONCLUSIONS

A missed critical finding, critical finding flag, MR imaging technique, trainee level, faculty experience level, and non-native-trainee status are associated with a higher degree of modification of a preliminary report. Understanding the factors that influence the extent of report revisions could improve the quality of report generation and trainee education.

Guidelines for Moderators: Roadmap to a Successful Conference

The ideal moderator of a conference session does more than simply introduce the speakers to the audience: a capable facilitator can do a great deal to lead the presenters and the participants on an informative journey. This article discusses expectations of a moderator and tips that can be applied to facilitate effective and efficient sessions at professional society meetings and to optimize the satisfaction of audience members. To assist first-time moderators become adept, these guidelines are comprehensive; however, even the most experienced moderators may benefit by reviewing this article.

Imaging in the Age of Precision Medicine: Summary of the Proceedings of the 10th Biannual Symposium of the International Society for Strategic Studies in Radiology

During the past decade, with its breakthroughs in systems biology, precision medicine (PM) has emerged as a novel health-care paradigm. Challenging reductionism and broad-based approaches in medicine, PM is an approach for disease treatment and prevention that takes into account individual variability in genes, environment, and lifestyle. It involves integrating information from multiple sources in a holistic manner to achieve a definitive diagnosis, focused treatment, and adequate response assessment. Biomedical imaging and imaging-guided interventions, which provide multiparametric morphologic and functional information and enable focused, minimally invasive treatments, are key elements in the infrastructure needed for PM. The emerging discipline of radiogenomics, which links genotypic information to phenotypic disease manifestations at imaging, should also greatly contribute to patient-tailored care. Because of the growing volume and complexity of imaging data, decision-support algorithms will be required to help physicians apply the most essential patient data for optimal management. These innovations will challenge traditional concepts of health care and business models. Reimbursement policies and quality assurance measures will have to be reconsidered and adapted. In their 10th biannual symposium, which was held in August 2013, the members of the International Society for Strategic Studies in Radiology discussed the opportunities and challenges arising for the imaging community with the transition to PM. This article summarizes the discussions and central messages of the symposium.

Expert witnesses: neuroradiologists' perspectives

PURPOSE

Physician malpractice expert witnesses may testify on behalf of physicians or patients. The goal of the study was to assess the experience of neuroradiologists as expert witnesses and their attitudes about such testimony.

METHODS

A survey was distributed to the 4,357 e-mail addresses of the members of the American Society of Neuroradiology with questions about expert witnesses.

RESULTS

The survey found that 1,301 of 4,357 answered at least one survey question. Five hundred twenty seven of 1194 (44.1%) of respondents had experience as expert witnesses. Most offer to testify on behalf of both plaintiffs and defendant physicians (324 of 465; 69.7%). Some do not testify/review cases on behalf of a plaintiff because they do not think that physicians should testify against other physicians, even if negligence is a factor (40 of 198; 20.2%). This reason was the most common for not agreeing to be an expert witness for a plaintiff, for all age groups. Of those expressing an opinion, 312 of 874 (35.7%) of neuroradiologists feel negatively about expert witnesses, whereas 434 of 874 (49.6%) say they serve a purpose, and 105 of 874 (12.0%) feel they should be commended for their work on behalf of the justice system.

CONCLUSIONS

Of neuroradiologists answering the survey, nearly half have served as expert witnesses, and most feel comfortable testifying for both plaintiffs and defendants. Substantive negative perceptions (35.7%) of expert witnesses were found.

Critical findings: timing of notification in neuroradiology

BACKGROUND AND PURPOSE

Timely reporting of critical findings in radiology has been identified by The Joint Commission as one of the National Patient Safety Goals. Our aim was to determine the magnitude of delays between identifying a neuroradiologic critical finding and verbally notifying the caregiver in an effort to improve clinical outcomes.

MATERIALS AND METHODS

We surveyed the time of critical finding discovery, attempted notification, and direct communication between neuroradiologists and caregivers for weekday, evening, overnight, and weekend shifts during an 8-week period. The data were collected by trained observers and/or trainees and included 13 neuroradiology attendings plus fellows and residents. Critical findings were based on a previously approved 17-item list. Summary and comparative t test statistics were calculated, and sources of delays were identified.

RESULTS

Ninety-one critical findings were recorded. The mean time from study acquisition to critical finding discovery was 62.2 minutes, from critical finding discovery to call made 3.7 minutes, and from call made to direct communication, 5.2 minutes. The overall time from critical finding discovery to caregiver notification was within 10 minutes in 72.5% (66/91) and 15 minutes in 93.4% (85/91) of cases. There were no significant differences across shifts except for daytime versus overnight and weekend shifts, when means were 2.4, 5.6, and 8.7 minutes, respectively (P < .01). If >1 physician was called, the mean notification time increased from 3.5 to 10.1 minutes (P < .01). Sources of delays included inaccurate contact information, physician unavailability (shift change/office closed), patient transfer to a different service, or lack of responsiveness from caregivers.

CONCLUSIONS

Direct communication with the responsible referring physician occurred consistently within 10-15 minutes after observation of a critical finding. These delays are less than the average interval from study acquisition to critical finding discovery (mean, 62.2 minutes).

Expert witness blinding strategies to mitigate bias in radiology malpractice cases: a comprehensive review of the literature

Like all physicians, radiologists in the United States are subject to frequent and costly medical malpractice claims. Legal scholars and physicians concur that the US civil justice system is neither precise nor accurate in determining whether malpractice has truly occurred in cases in which claims are made. Sometimes, this inaccuracy is driven by biases inherent in medical expert-witness opinions. For example, expert-witness testimony involving "missed" radiology findings can be negatively affected by several cognitive biases, such as contextual bias, hindsight bias, and outcome bias. Biases inherent in the US legal system, such as selection bias, compensation bias, and affiliation bias, also play important roles. Fortunately, many of these biases can be significantly mitigated or eliminated through the use of appropriate blinding techniques. This paper reviews the major works on expert-witness blinding in the legal scholarship and the radiology professional literature. Its purpose is to acquaint the reader with the evidence that unblinded expert-witness testimony is tainted by multiple sources of bias and to examine proposed strategies for addressing these biases through blinding.

Continuous practice quality improvement initiative for communication of critical findings in neuroradiology

The authors examined faculty's compliance with a hospital-approved neuroradiology critical findings (CFs) policy, which requires urgent verbal communication with the clinical team when 17 specific critical pathologies are identified. During June 2011 to July 2013, 50 random neuroradiology reports were sampled monthly for the presence of CFs and appropriate action. Faculty were provided ongoing feedback, and at the end of 2 years, the medical records for cases with noncommunicated CFs were reviewed to identify potential adverse outcomes. Of the 1200 reviewed reports, 195 (16.3%) had and 1005 (83.8%) did not have a CF. A total of 176 of 195 (90.3%) cases with CFs were communicated, and compliance increased from 77.4% to 85.6% (P = .027) since the monthly sampling was instituted; 1 of 19 (5.3%) noncommunicated CFs resulted in a potential adverse event. The ongoing monthly feedback resulted in improved faculty compliance with the CF policy. However, a small number of cases with CFs are still not being communicated.

Attitudes about medical malpractice: an American Society of Neuroradiology survey

SUMMARY

The concern over medicolegal liability is pervasive among physicians. We sought, through an email survey to the members of the ASNR, to assess the experience with and attitudes about the medicolegal environment among neuroradiologists. Of 4357 physicians surveyed, 904 answered at least 1 of the questions in the survey; 449 of 904 (49.7%) had been sued: 180 (44.9%) had been sued once, 114 (28.4%) twice, 60 (15.0%) 3 times, and 47 (11.7%) more than 3 times. The payouts for suits were most commonly in the $50,000 to $150,000 range, except for interventional neuroradiologists, in whom the most common value was $600,000 to $1,200,000. Only 9 of 481 (1.9%) of suits returned a plaintiff verdict. Despite reported outcomes that favored physicians with respect to cases being dropped (270/481 = 56.1%), settled without a payment (11/481 = 2.3%), or a defense verdict (46/481 = 9.6), most respondents (81.1%, 647/798) believed that the medicolegal system was weighted toward plaintiffs. More than half of the neuroradiologists (55.2%, 435/787) reported being mildly to moderately concerned, and 19.1% (150/787) were very or extremely concerned about being sued.

MR-guided sclerotherapy of low-flow vascular malformations using T2 -weighted interrupted bSSFP (T2 W-iSSFP): comparison of pulse sequences for visualization and needle guidance

PURPOSE

Image-guided treatment of low-flow vascular (venous or lymphatic) malformations presents a challenging visualization problem, regardless of the imaging modality being used for guidance. The purpose of this study was to employ a new magnetic resonance imaging (MRI) sequence, T2 -weighted interrupted balanced steady-state free precession (T2 W-iSSFP), for real-time image guidance of needle insertion.

MATERIALS AND METHODS

T2 W-iSSFP uses variable flip angle balanced steady-state free precession (bSSFP, a.k.a. SSFP) to establish T2 -weighting and fat suppression. Swine (n = 3) and patients (n = 4, three female, all with venous malformations) were enrolled in the assessment. T2 -weighted turbo spin echo (T2 -TSE) with spectral adiabatic inversion recovery (SPAIR), SPAIR-T2 -TSE or T2 -TSE for short, was used as the reference. T2 -weighted half Fourier acquired single shot turbo spin echo (T2 -HASTE) with SPAIR (SPAIR-T2 -HASTE, T2 -HASTE for short), fat saturated bSSFP (FS-SSFP), and T2 W-iSSFP were imaged. Numeric metrics, namely, contrast-to-noise ratio (CNR) efficiency (CNR divided by the square root of acquisition time) and local sharpness (the reciprocal of edge width), were used to assess image quality. MR-guided sclerotherapy was performed on the same patients using real-time T2 W-iSSFP to guide needle insertion.

RESULTS

Comparing the visualization of needles in the images of swine, the local sharpness (mm(-1) ) was: 0.21 ± 0.06 (T2 -HASTE), 0.48 ± 0.02 (FS-SSFP), and 0.49 ± 0.03 (T2 W-iSSFP). T2 W-iSSFP is higher than T2 -HASTE (P < 0.001). For the patient images, their CNR efficiencies were: 797 ± 66 (T2 -HASTE), 281 ± 44 (FS-SSFP), and 860 ± 29 (T2 W-iSSFP). T2 W-iSSFP is higher than FS-SSFP (P < 0.02). The frame rate of T2 W-iSSFP was 2.5-3.5 frames per second. All MR-guided sclerotherapy procedures were successful, with all needles (six punctures) placed in the targets.

CONCLUSION

T2 W-iSSFP provides effective lesion identification and needle visualization. This new pulse sequence can be used for MR-guided sclerotherapy of low-flow vascular malformations. It may have potential use in other MR-guided procedures where heavily T2 -weighted real-time images are needed.

Determination and communication of critical findings in neuroradiology

PURPOSE

The aims of this study were to analyze reporting of critical findings among neuroradiologists in a university setting and to revise a list of critical findings reflecting an academic clinical practice as part of a practice quality improvement project.

MATERIALS AND METHODS

Neuroradiologic studies performed between January 1 and February 28, 2011, containing "critical finding" notations were searched. Reports were matched with an institutionally approved list of critical findings. These findings and unlisted items that were labeled critical were analyzed for frequency, clinical severity, and diagnosis category. The list was revised on the basis of frequency and severity results.

RESULTS

A total of 12,607 reports contained 871 critical findings, 608 of which (69.8%) matched the preexisting list. One-third of the findings (263 of 871) labeled critical were not found on the list. Facial, spinal, and calvarial fractures (76 of 263 [28.9%]) and neurovascular injuries (38 of 263 [14.4%]) were the most frequent unlisted findings. A revised list encompassed 86.7% of all communicated neuroradiologic critical findings.

CONCLUSIONS

Clinician-approved and neuroradiologist-approved standardized sets of critical findings can facilitate the communication of important results without "overcalling" and decreasing efficiency. Physician judgment of what constitutes a critical finding supersedes any such list, as clinical scenarios are highly variable from patient to patient. Critical findings lists require intermittent revision to reflect practice patterns and changing incidence of disease. Such a review can constitute a practice quality improvement initiative.

Neuroradiology critical findings lists: survey of neuroradiology training programs

BACKGROUND AND PURPOSE

The Joint Commission has identified timely reporting of critical results as one of the National Patient Safety Goals. We surveyed directors of neuroradiology fellowships to assess and compare critical findings lists across programs.

MATERIALS AND METHODS

A 3-question survey was e-mailed to directors of neuroradiology fellowships with the following questions: 1) Do you currently have a "critical findings" list that you abide by in your neuroradiology division? 2) How is that list distributed to your residents and fellows for implementation, if at all? and 3) Was this list vetted by neurology, neurosurgery, and otolaryngology departments? Programs with CF lists were asked for a copy of the list. Summary and comparative statistics were calculated.

RESULTS

Fifty-one of 89 (57.3%) programs responded. Twenty-one of 51 (41.2%) programs had CF lists. Lists were distributed during orientation, sent via Web sites and e-mails, and posted in work areas. Eleven of 21 lists were developed internally, and 5 of 21, with the input from other departments. The origin of 5 of 21 lists was unknown. Forty CF entities were seen in 20 submitted lists (mean, 9.1; range, 2-23). The most frequent entities were the following: cerebral hemorrhage (18 of 20 lists), acute stroke (15 of 20), spinal cord compression (15 of 20), brain herniation (12 of 20), and spinal fracture/instability (12 of 20). Programs with no CF lists called clinicians on the basis of "common sense" and "clinical judgment."

CONCLUSIONS

Less than a half (41.2%) of directors of neuroradiology fellowships that responded have implemented CF lists. CF lists have variable length and content and are predominantly developed by radiology departments without external input.

Unbiased review of digital diagnostic images in practice: informatics prototype and pilot study

RATIONALE AND OBJECTIVES

Clinical and contextual information associated with images may influence how radiologists draw diagnostic inferences, highlighting the need to control multiple sources of bias in the methodologic design of investigations involving radiologic interpretation. In the past, manual control methods to mask review films presented in practice have been used to reduce potential interpretive bias associated with differences between viewing images for patient care and reviewing images for the purposes of research, education, and quality improvement. These manual precedents from the film era raise the question whether similar methods to reduce bias can be implemented in the modern digital environment.

MATERIALS AND METHODS

A prototype application, CreateAPatient, was built for masking review case presentations within one institution's production radiology information system and picture archiving and communication system. To test whether CreateAPatient could be used to mask review images presented in practice, six board-certified radiologists participated in a pilot study. During pilot testing, seven digital chest radiographs, known to contain lung nodules and associated with fictitious patient identifiers, were mixed into the routine workloads of the participating radiologists while they covered general evening call shifts. The aim was to test whether it was possible to mask the presentation of these review cases, both by probing the interpreting radiologists to report detection and by conducting a forced-choice experiment on a separate cohort of 20 radiologists and information technology professionals.

RESULTS

None of the participating radiologists reported awareness of review activity, and forced-choice detection was less than predicted at chance, suggesting that radiologists were effectively blinded. In addition, no evidence was identified of review reports unsafely propagating beyond their intended scope or otherwise interfering with patient care, despite integration of these records within production electronic work flow systems.

CONCLUSIONS

Information technology can facilitate the design of unbiased methods involving professional review of digital diagnostic images.

Percutaneous punctures with MR imaging guidance: comparison between MR imaging-enhanced fluoroscopic guidance and real-time MR Imaging guidance

PURPOSE

To evaluate and compare the technical accuracy and feasibility of magnetic resonance (MR) imaging-enhanced fluoroscopic guidance and real-time MR imaging guidance for percutaneous puncture procedures in phantoms and animals.

MATERIALS AND METHODS

The experimental protocol was approved by the institutional animal care and use committee. Punctures were performed in phantoms, aiming for markers (20 each for MR imaging-enhanced fluoroscopic guidance and real-time MR imaging guidance), and pigs, aiming for anatomic landmarks (10 for MR imaging-enhanced fluoroscopic guidance and five for MR imaging guidance). To guide the punctures, T1-weighted three-dimensional (3D) MR images of the phantom or pig were acquired. Additional axial and coronal T2-weighted images were used to visualize the anatomy in the animals. For MR imaging-enhanced fluoroscopic guidance, phantoms and pigs were transferred to the fluoroscopic system after initial MR imaging and C-arm computed tomography (CT) was performed. C-arm CT and MR imaging data sets were coregistered. Prototype navigation software was used to plan a puncture path with use of MR images and to superimpose it on fluoroscopic images. For real-time MR imaging, an interventional MR imaging prototype for interactive real-time section position navigation was used. Punctures were performed within the magnet bore. After completion, 3D MR imaging was performed to evaluate the accuracy of insertions. Puncture durations were compared by using the log-rank test. The Mann-Whitney U test was applied to compare the spatial errors.

RESULTS

In phantoms, the mean total error was 8.6 mm ± 2.8 with MR imaging-enhanced fluoroscopic guidance and 4.0 mm ± 1.2 with real-time MR imaging guidance (P < .001). The mean puncture time was 2 minutes 10 seconds ± 44 seconds with MR imaging-enhanced fluoroscopic guidance and 37 seconds ± 14 with real-time MR imaging guidance (P < .001). In the animal study, a tolerable distance (<1 cm) between target and needle tip was observed for both MR imaging-enhanced fluoroscopic guidance and real-time MR imaging guidance. The mean total error was 7.7 mm ± 2.4 with MR imaging-enhanced fluoroscopic guidance and 7.9 mm ± 4.9 with real-time MR imaging guidance (P = .77). The mean puncture time was 5 minutes 43 seconds ± 2 minutes 7 seconds with MR imaging-enhanced fluoroscopic guidance and 5 minutes 14 seconds ± 2 minutes 25 seconds with real-time MR imaging guidance (P = .68).

CONCLUSION

Both MR imaging-enhanced fluoroscopic guidance and real-time MR imaging guidance demonstrated reasonable and similar accuracy in guiding needle placement to selected targets in phantoms and animals.

Sponges and incorrect sponge count: Minor contributions to the process of detecting retained foreign bodies

Background: Postoperative retained foreign bodies [RFBs] can be a serious event, but they are rare. The x-ray is the current gold standard to detect RFBs. There has been scant research on the process of detection as opposed to the consequence of RFBs. Surgical sponges incorporating automatic data identity capture technology (radiofrequency tags, barcodes) have been proposed to detect RFBs. Because resources in healthcare are scarce, careful consideration needs to be given to developing the right technology in order to maximize the process of RFB elimination. There have been few studies that identify factors contributing to the process of RFB detection. Study design: Our goal was to determine the frequency with which x-rays were ordered to detect abdominal surgery post operative RFBs and the indications for ordering them. We reviewed the Johns Hopkins Hospital's Department of Radiology database to retrospectively study the demographic and radiologic data on patients who underwent exploratory surgery for RFBs following abdominal procedures performed between April 2004 and April 2008. Results: Of the 13,335 portable abdominal x-rays taken during the period, 203 (1.5%) were ordered to assess patients for the presence of an RFB. Of these, 57 (28%) were taken because no RFB count was made (e.g., for emergency procedures), 57 (28%) were taken per procedure or protocol, 51 (25%) were taken because of an incorrect instrument count, and 39 (19%) were taken because of an incorrect sponge count. Of the 203 x-rays, 192 (95%) were negative for RFBs, 11 (5%) were positive or had suspicious findings, and of these 3 (2%) revealed more than 1 RFB. The 11 patients with positive or suspicious findings underwent exploratory procedures immediately during the same operation; of these, 8 (72%) actually had an RFB and 3 (28%) had a negative result at exploration. Conclusion: Multiple pathways lead to the decision to obtain X-rays for RFBs, of which sponges/Incorrect sponge counts make up only one in five. Therefore, technology that focuses on sponges alone may not majorly impact clinical outcome because x-rays will still be required in the majority of cases of suspected high risk.

Quality control in neuroradiology: impact of trainees on discrepancy rates

BACKGROUND AND PURPOSE

Prior studies have found a 2%-8% clinically significant error rate in radiology practice. We compared discrepancy rates of studies interpreted by subspecialty-trained neuroradiologists working with and without trainees.

MATERIALS AND METHODS

Subspecialty-trained neuroradiologists reviewed 2162 studies during 41 months. Discrepancies between the original and "second opinion" reports were scored: 1, no change; 2, clinically insignificant detection discrepancy; 3, clinically insignificant interpretation discrepancy; 4, clinically significant detection discrepancy; and 5, clinically significant interpretation discrepancy. Faculty alone versus faculty and trainee discrepancy rates were calculated.

RESULTS

In 87.6% (1894/2162), there were no discrepancies with the original report. The neuroradiology division had a 1.8% (39/2162; 95% CI, 1.3%-2.5%) rate of clinically significant discrepancies. In cases reviewed solely by faculty neuroradiologists (16.2% = 350/2162 of the total), the rate of discrepancy was 1.7% (6/350). With fellows (1232/2162, 57.0% of total) and residents (580/2162, 26.8% of total), the rates of discrepancy were 1.6% (20/1232) and 2.2% (13/580), respectively. The odds of a discrepant result were 26% greater (OR = 1.26; 95% CI, 0.38-4.20) when reading with a resident and 8% less (OR = 0.92; 95% CI, 0.35-2.44) when reading with a fellow than when reading alone.

CONCLUSIONS

There was a 1.8% rate of clinically significant detection or interpretation discrepancy among academic neuroradiologists. The difference in the discrepancy rates between faculty only (1.7%), fellows and faculty (1.6%), and residents and faculty (2.2%) was not statistically significant but showed a trend indicating that reading with a resident increased the odds of a discrepant result.

White Paper Report of the 2010 RAD-AID Conference on International Radiology for Developing Countries: identifying sustainable strategies for imaging services in the developing world

The 2010 RAD-AID Conference on International Radiology for Developing Countries was a multidisciplinary meeting to discuss data, experiences, and models pertaining to radiology in the developing world, where widespread shortages of imaging services reduce health care quality. The theme of this year's conference was sustainability, with a focus on establishing and maintaining imaging services in resource-limited regions. Conference presenters and participants identified 4 important components of sustainability: (1) sustainable financing models for radiology development, (2) integration of radiology and public health, (3) sustainable clinical models and technology solutions for resource-limited regions, and (4) education and training of both developing and developed world health care personnel.

Modified map-seeking circuit: use of computer-aided detection in locating postoperative retained foreign bodies

BACKGROUND

More than 98% of intra-operative X-rays taken to search for postoperative retained foreign bodies (RFBs) have negative findings; in over 30% of cases of such X-rays, the finding is a false negative. Newer technologies created to find RFBs must not only reduce the false-negative rate, but also must not increase the burden of detecting RFBs. We have introduced the use of computer-aided detection (CAD) to facilitate the detection of RFBs on X-rays utilizing a modified version of map-seeking circuit (MSC) algorithm the referenced map-seeking circuit (RMSC), for our proof-of-concept study for detection of needles in plain abdominal X-rays.

METHODS

Images were obtained by using a portable cassette-based X-ray machine and a C-arm (digital) machine, both of which are commonly used in the operating room. The images obtained using these machines were divided into subimages of approximately 250 × 250 pixels each, for a total of 455 subimages from the cassette-based machine (A) and 365 from the digital machine (B) for use as test samples. Images obtained from A and B were analyzed separately using our modified MSC algorithm with a minimum (τ = 0) and a maximum threshold (τ = 0.5).

RESULTS

The automated detection rate (positive predictive value) was 86%, with a false positive/negative rate of 10% to 15% when τ was zero.

CONCLUSION

The CAD-based RMSC algorithm has the potential to improve the accuracy with which RFBs can be found in X-rays. Further research is needed to optimize the detection rate and to identify a wider range of RFBs.

MR monitoring of NaCl-enhanced radiofrequency ablations: observations on low- and high-field-strength MR images with pathologic correlation

PURPOSE

To test the hypothesis that magnetic resonance (MR) imaging can be used to monitor both intraparenchymal injection of NaCl solution and subsequent radiofrequency ablation (RFA) within tissues pretreated with NaCl, report the low- and high-field-strength MR appearance of NaCl-enhanced RFAs, and compare MR findings with pathologic findings.

MATERIALS AND METHODS

Ten ex vivo calf liver specimens were injected with saturated NaCl (seven were mixed with methylene blue during MR fluoroscopic monitoring) and reexamined with fast imaging with steady-state progression (FISP), true FISP, reversed FISP (PSIF), and fast spin-echo T2-weighted MR sequences. The NaCl-to-liver contrast-to-noise ratio (CNR) was calculated for various sequences, and CNRs were compared with the Student t test. Distribution on MR images was compared with the results of pathologic analysis. Forty additional in vivo monopolar RFAs were performed in paraspinal muscles of seven minipigs after animal care committee approval (10 standard control ablations, 30 were preceded by direct injection of saturated NaCl at various volumes [3-9 mL] and rates [1 or 6mL/min]). Postablation low-field-strength (n = 20) and high-field-strength (n = 20) MR examinations consisted of T2-weighted imaging, short inversion time inversion-recovery (STIR) imaging, and contrast material-enhanced T1-weighted imaging. Ablation shape, conspicuity, volume, and signal intensity were compared between the two groups and with the results of pathologic analysis. The difference in volumes with and without NaCl injection was evaluated by using two-way analysis of variance.

RESULTS

Mean CNR was highest on fast spin-echo T2-weighted images and was significantly higher for PSIF than for FISP (P < .0001) or true FISP (P = .003). NaCl distribution on MR images corresponded with the results of pathologic analysis in ex vivo livers. Interactive in vivo monitoring of NaCl injection and electrode placement was feasible. NaCl-enhanced ablations had irregular shapes, a higher CNR, and significantly larger volumes (F = 22.0; df = 1, 90; P < .00001). All ablations had intermediate or low signal intensity with high-signal-intensity rims on all images. Fluid signals overlaid NaCl-enhanced ablations on fast spin-echo T2-weighted and STIR images, particularly on high-field-strength MR images.

CONCLUSION

MR imaging can be used to reliably monitor the distribution of injected NaCl solution in tissues. Interventional MR imaging techniques can be used to guide and monitor RFAs within NaCl pretreated tissues, with good correlation with pathologic results.

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.

Model-free parameters from dynamic contrast-enhanced-MRI: sensitivity to EES volume fraction and bolus timing

PURPOSE

To quantify the unknown relative sensitivities of semiquantitative measures from dynamic contrast-enhanced (DCE) MRI to variations in the volume fraction V(e) of the extravascular extracellular space (EES), and the duration of the contrast injection.

MATERIALS AND METHODS

Tissue-uptake curves were simulated across various values of F, PS, V(e), and bolus timings, with and without additive noise and at different image reacquisition rates. From each, the peak of the first derivative (G(peak)), the total uptake after the rapid first phase (CE), and the IAUC were calculated and plotted against F for each experimental condition. Relationships between each measure and the corresponding quantitative measure K(trans) were also examined, particularly for linearity.

RESULTS

The highest sensitivity to flow was achieved for shorter bolus timings for G(peak), CE, and IAUC. G(peak) and IAUC were most linearly related to K(trans). The sensitivity to V(e) was lowest for G(peak), followed by IAUC and CE. Long sampling intervals resulted in severe underestimation of G(peak), while IAUC was unaffected provided that the limits of integration were properly applied. G(peak) could not be properly calculated in the presence of noise without a prior smoothing of the acquired curves, while IAUC was again unaffected by noise.

CONCLUSION

G(peak) and IAUC are both useful model-free analogs of blood flow (i.e., K(trans)) for pre- and posttreatment comparisons. G(peak) may be the better choice in cases where larger changes in V(e) are likely, but only if sufficient noise reduction and fast image sampling are applied. If V(e) is expected to remain stable, IAUC is superior to G(peak) by virtue of its stability in the face of noise and more reliable estimation over a wider range of sampling rates.

In vivo cardiovascular catheterization under real-time MRI guidance

PURPOSE

To test the hypothesis that cardiac and coronary catheterization can be successfully performed under real-time MR guidance using a conventional x-ray angiographic catheter.

MATERIALS AND METHODS

Cardiac and coronary catheterization was conducted on eight farm pigs using a real-time True FISP sequence. A pigtail catheter was used for both left- and right-heart catheterizations performed on all eight animals, while an Amplatz or Judkins catheter was used for the right coronary catheterization that was attempted on five animals. The intravascular devices were visualized by means of their native susceptibility artifacts. For right coronary artery catheterizations, 25% diluted gadolinium (Gd) contrast material was injected to confirm engagement of the right coronary artery.

RESULTS

Cardiac catheterization of both the right- and left-heart chambers was successfully performed in all eight pigs. In addition, right coronary catheterization was successfully completed in four of the five pigs in which it was attempted. The procedure time for cardiac catheterization was one minute, while the time range required for coronary catheterization was 32-91 minutes.

CONCLUSION

This work demonstrates that MRI-guided cardiac catheterization using conventional X-ray angiographic catheters is feasible; however, coronary catheterization with this passive-tracking technique is limited.

Image-guided and -monitored renal artery stenting using only MRI

PURPOSE

To demonstrate the ability of a unique interventional MR system to be used safely and effectively as the only imaging modality for all phases of MR-guided stent-supported angioplasty.

MATERIALS AND METHODS

An experimental disease model of renal stenosis was created in six pigs. An interventional MR system, which employed previously reported tools for real-time catheter tracking with automated scan-plane positioning, adaptive image parameters, and radial true-FISP imaging with steady-state precession (True-FISP) imaging coupled with a high-speed reconstruction technique, was then used to guide all phases of the intervention, including: guidewire and catheter insertion, stent deployment, and confirmation of therapeutic success. Pre- and postprocedural X-ray imaging was used as a gold standard to validate the experimental results.

RESULTS

All of the stent-supported angioplasty interventions were a technical success and were performed without complications. The average postoperative residual stenosis was 14.9%. The image guidance enabled the stents to be deployed with an accuracy of 0.98 +/- 0.69 mm. Additionally, using this interventional MRI system to guide renal artery stenting significantly reduces the procedure time, as compared to using X-ray fluoroscopy.

CONCLUSION

This study has clearly demonstrated the first successful treatment of renal artery stenting in an experimental animal model solely under MRI guidance and monitoring.

CT assessment of vocal cord medialization

BACKGROUND AND PURPOSE

Unilateral vocal cord paralysis (UVCP) occurs after iatrogenic injury or disease process and is associated with dysphonia and aspiration. Various surgical options are available for treatment of UVCP, including vocal cord medialization thyroplasty and injection laryngoplasty. These augmentative procedures improve phonation and airway protection. Our purpose was to demonstrate the CT appearance of implants used for the treatment of UVCP.

METHODS

Twelve patients treated surgically for UVCP were studied with helical CT. The vocal cords were augmented by using Silastic implants (n = 7), polytetrafluoroethylene (Gore-Tex) implants (n = 2), Teflon injections (n = 2), or fat injection (n = 1). Augmented vocal cords were characterized by size, shape, and Hounsfield units (HU). Two other patients with failed medialization thyroplasty were evaluated for the position of the extruded implant relative to the paralyzed vocal cord.

RESULTS

The 7 Silastic implants were triangular and hyperattenuated (293.4 +/- 90.4 HU). The 2 Gore-Tex implants were heterogeneous with lobulated medial margins and were hyperattenuating (320 and 414 HU). The injected materials demonstrated ovoid/masslike configurations: the 2 Teflon injections were hyperattenuated (107 and 429 HU), and the fat injection was hypoattenuated (-102 HU). Inferior displacement of the implant was demonstrated relative to the true vocal cord in 2 patients with failed Silastic thyroplasties.

CONCLUSION

CT can distinguish various types of vocal cord augmentation. Silastic implants are recognized by their characteristic triangular configuration. The Gore-Tex implants had unique heterogeneous attenuation with lobulated medial margins. Fat and Teflon injections both appear ovoid/masslike. Teflon injection should not be mistaken for tumor.

An Augmented Reality System for MR Image–guided Needle Biopsy: Initial Results in a Swine Model

PURPOSE

To evaluate an augmented reality (AR) system in combination with a 1.5-T closed-bore magnetic resonance (MR) imager as a navigation tool for needle biopsies.

MATERIALS AND METHODS

The experimental protocol had institutional animal care and use committee approval. Seventy biopsies were performed in phantoms by using 20 tube targets, each with a diameter of 6 mm, and 50 virtual targets. The position of the needle tip in AR and MR space was compared in multiple imaging planes, and virtual and real needle tip localization errors were calculated. Ten AR-guided biopsies were performed in three pigs, and the duration of each procedure was determined. After successful puncture, the distance to the target was measured on MR images. The confidence limits for the achieved in-plane hit rate and for lateral deviation were calculated. A repeated measures analysis of variance was used to determine whether the placement error in a particular dimension (x, y, or z) differed from the others.

RESULTS

For the 50 virtual targets, a mean error of 1.1 mm +/- 0.5 (standard deviation) was calculated. A repeated measures analysis of variance indicated no statistically significant difference (P > .99) in the errors in any particular orientation. For the real targets, all punctures were inside the 6-mm-diameter tube in the transverse plane. The needle depth was within the target plane in 11 biopsy procedures; the mean distance to the center of the target was 2.55 mm (95% confidence interval: 1.77 mm, 3.34 mm). For nine biopsy procedures, the needle tip was outside the target plane, with a mean distance to the edge of the target plane of 1.5 mm (range, 0.07-3.46 mm). In the animal experiments, the puncture was successful in all 10 cases, with a mean target-needle distance of 9.6 mm +/- 4.85. The average procedure time was 18 minutes per puncture.

CONCLUSION

Biopsy procedures performed with a combination of a closed-bore MR system and an AR system are feasible and accurate.

Toward rapid high resolution in vivo intravascular MRI: evaluation of vessel wall conspicuity in a porcine model using multiple imaging protocols

PURPOSE

To assess magnetic resonance (MR) pulse sequences for high resolution intravascular imaging.

MATERIALS AND METHODS

Intravascular imaging of the abdominal aorta and iliac arteries was performed in vivo in a porcine model at 1.5 T using catheter-mounted micro-receive coils. Ten protocols, including spin-echo (SE)-echo planar imaging (SE-EPI), segmented EPI, half-Fourier single-shot turbo spin-echo (HASTE), fast imaging with steady-state free precession (TrueFISP), turbo spin-echo (TSE), and SE acquisition schemes were employed in 13 trials. Images were analyzed by six expert raters with respect to wall-conspicuity, wall-to-lumen/tissue contrast, visible layers of the arterial wall, anticipated clinical usefulness, and overall image quality. Mean differences between sequence-types were evaluated using analysis of variance (ANOVA) between groups with planned comparisons.

RESULTS

The vessel wall was delineated in almost all protocols. Motion artifacts from physiological and device motion were reduced in fast techniques. The best contrast between the wall and surrounding tissue was provided by a HASTE protocol. Anatomic layers of the vessel wall were best depicted on dark blood T2-weighted TSE. Overall, TrueFISP was ranked highest on the remaining measures.

CONCLUSION

Dedicated catheter-coils combined with fast sequences have potential for in vivo characterization of vessel walls. TrueFISP offered the best overall image quality and acquisition speed, but suffered from the inability to delineate the multiple layers of the wall, which seems associated with dark blood- and T2-weighted contrast. We believe future intra-arterial trials should proceed from this study in normal artery imaging and initially focus on fast T2-weighted dark blood techniques in trials with pathology.

Three-dimensional comparison of interventional MR radiofrequency ablation images with tissue response

OBJECTIVE

Solid tumors are being treated using radiofrequency (RF) ablation under interventional magnetic resonance imaging (MRI) guidance. We are investigating the ability of MRI to monitor ablation treatments by comparing MR images of thermal lesions to histologically assayed tissue damage.

MATERIAL AND METHODS

An open MRI system was used to guide an ablation electrode into five rabbit thigh muscles and acquire post-ablation MR image volumes. We developed a methodology using a 3D computer registration to make spatial correlations. After MR and histology images were registered with an accuracy of 1.32+/-0.39 mm (mean+/-SD), a boundary of necrosis identified in the histology was compared with the outer boundary of the hyperintense region in MR images.

RESULTS

For 14 T2-weighted MR images, the absolute distance between boundaries was 0.96+/-0.34 mm (mean+/-SD). Since the small discrepancy between boundaries is comparable to our registration accuracy, the boundaries may match exactly. Similar correlations to histology were obtained with a deformable model segmentation method.

CONCLUSIONS

This is good evidence that MR thermal lesion images can be used during RF ablation treatments to accurately localize the zone of necrosis at the lesion margin.

Use of intra-articular carbon dioxide and air for MR arthrography: a feasibility study

During animal experiments, carbon dioxide (CO(2)) and air were used as a novel contrast agent for direct magnetic resonance arthrography (MRAr). MRAr was performed after injection of CO(2) and air in the knee joints of two pigs. MR images of phantoms containing air, CO(2) and nitrogen were compared. After intra-articular injection, both present as a signal void on various sequences and permit sharp delineation of cartilage and other adjacent structures. Despite the potential for artefact generation, only a slight susceptibility artefact was seen after injection of CO(2) and air. In phantom experiments, air, CO(2) and nitrogen demonstrated identical slight regular susceptibility artefacts at the phantom margins. CO(2) MRAr can yield high contrast between cartilage, ligaments and synovium relative to the joint compartment. Therefore, this technique might be useful as an investigational method for the evaluation of cartilage surface lesions and possibly as an alternative contrast agent for clinical use.

A new type of susceptibility-artefact-based magnetic resonance angiography: intra-arterial injection of superparamagnetic iron oxide particles (SPIO) A Resovist® in combination with TrueFisp imaging: a feasibility study

The goal of this study was to evaluate the use of super paramagnetic particles of iron oxide (SPIO) as a dark blood contrast agent, in combination with a bright blood steady-state free precession sequence for magnetic resonance angiography (MRA), in an animal model. The original concentration of the SPIO of 500 mmol Fe/l and dilutions to 250, 125, 60, 30, 10 and 5 mmol Fe/l were intra-arterially injected into the aorta of a pig. Then the dilution of 10 mmol Fe/l was chosen for repeated intra-arterial injections into two pigs. During these intra-arterial SPIO injections MR images were acquired with a 1.5 T scanner. Signal intensity measurements were performed in the aorta. The signal-to-noise ratio during SPIO bolus passage was significantly less than during baseline conditions (Fisher's F-ratio 159.8, p < 0.005) or the recovery signal-to-noise ratio (Fisher's F-ratio 144.6, p < 0.005). Also, confirmation of flow distal to the catheter-tip position was possible. The use of SPIO as a dark blood agent in combination with a bright blood MR imaging sequence is feasible. Temporary loss of intraluminal signal occurs due to local decrease of the signal because of induction of local inhomogeneities after mixture the present blood and SPIO solution. It provides immediate information about blood flow distal to the catheter and is a potentially useful to guide intravascular MR-interventional procedures.

Semiautomatic parametric model-based 3D lesion segmentation for evaluation of MR-guided radiofrequency ablation therapy

RATIONALE AND OBJECTIVES

Interventional magnetic resonance imaging (iMRI) allows real-time guidance and optimization of radiofrequency ablation of pathologic tissue. For many tissues, resulting lesions have a characteristic two-boundary appearance featuring an inner region and an outer hyper-intense margin in both T2 and contrast-enhanced (CE) T1-weighted MR images. We created a geometric model-based semiautomatic method to aid in real-time lesion segmentation, cross-sectional/three-dimensional visualization, and intra/posttreatment evaluation.

MATERIALS AND METHODS

Our method relies on a 12-parameter, 3-dimensional, globally deformable model with quadric surfaces that describe both lesion boundaries. We present an energy minimization approach to quickly and semiautomatically fit the model to a gray-scale MR image volume. We applied the method to in vivo lesions (n = 10) in a rabbit thigh model, using T2 and CE T1-weighted MR images, and compared the results with manually segmented boundaries.

RESULTS

For all lesions, the median error was < or =1.21 mm for the inner region and < or =1.00 mm for the outer hyper-intense region, values that favorably compare to a voxel width of 0.7 mm and distances between the borders manually segmented by the two operators.

CONCLUSION

Our method provides a precise, semiautomatic approximation of lesion shape for ellipsoidal lesions. Further, the method has clinical applications in lesion visualization, volume estimation, and treatment evaluation.

MR-guided endovascular interventions: device visualization, tracking, navigation, clinical applications, and safety aspects

Reliable visualization and tracking are essential for guiding endovascular devices within blood vessels. The most commonly used methods are susceptibility artifact-based tracking that relies on the artifact created within the image by the device and microcoil- or antenna-based tracking that uses the high signal generated by small MR endovascular receive coils when the transmit coil emits a nonselective radiofrequency pulse. To date, the use of endovascular MR guidance techniques has primarily been confined to animal experiments. There are only a few reports on MR-guided endovascular applications in patients. Therefore, access to the patient within the scanner, dedicated devices, and safety issues remain major challenges. To face these challenges, attention from all radiologists, especially interventional radiologists, is required to make MR-guided endovascular procedures a clinical reality.

MR imaging-guided percutaneous angioplasty and stent placement in a swine model comparison of open- and closed-bore scanners

RATIONALE AND OBJECTIVES

The purpose of this study is to compare the feasibility and precision of renal artery angioplasty and stent placement using two different MR scanners.

MATERIALS AND METHODS

MR imaging-guided angioplasty and stent placements were performed on seven pigs using 0.2 and 1.5 T scanners (Magnetom Open and Magnetom Sonata, Siemens Medical Solutions, Erlangen, Germany). For guidance of catheters, guide wires and stents susceptibility artifact-based tracking was used. The end point of each intervention was to position a stent in the renal artery with its proximal end at the level of the aortic wall. Procedure time and stent position were evaluated.

RESULTS

Catheterization, angioplasty, and stent placement were feasible using MRI guidance at both 0.2 and 1,5 Tesla. At 1.5 T all catheter manipulations and interventions were performed in less than 30 minutes. At 0.2 T the interventions took up to 90 minutes. No significant difference in the stent deviation was noted between the two scanners.

CONCLUSION

The use of a high-performance 1.5 T scanner helped to reduce the procedure time to half of that of a low-field system. Since no difference in stent placement precision was noted, a dedicated MR-stent might be mandatory for more precise stent placement.

The Interventional MR Imaging Suite: Magnet Designs and Equipment Requirements

Soon after the introduction of MR imaging as an imaging tool, researchers began to investigate its capabilities to guide interventional minimally invasive procedures, such as biopsies. These early efforts have encouraged vendors and numerous research groups worldwide to identify clinical problems in the field of image-guided intervention, for which MR imaging is beneficial as an imaging modality, and to develop and refine soft-ware and hardware components to meet the specific requirements of interventional MR imaging. Over nearly 20 years, continuous advances in magnet and system design have accelerated the progress of MR-guided intervention.

Radiofrequency Thermal Ablation: The Role of MR Imaging in Guiding and Monitoring Tumor Therapy

Performing RFA procedures under MR imaging involves two distinct processes: interactive guidance of the RF electrode into the targeted tumor and monitoring the effect of therapy. The justification for using MR imaging for electrode guidance is quite similar to its use to guide biopsy and aspiration procedures, where MR imaging offers advantages related to superior soft tissue contrast, multiplanar capabilities, and high vascular conspicuity that facilitate safe and accurate guidance in selected lesions. The major contribution of MR imaging to thermal ablation procedures is its ability to monitor tissue changes associated with the heating process instantaneously, an attribute that is not paralleled by any other currently available imaging modality. Such ability facilitates a controlled approach to ablation by helping to detect inadequately treated tumor foci for subsequent interactive repositioning of the RF electrode during therapy. As such, MR imaging guidance and monitoring enable treatment of the entire tumor on a single-visit basis while avoiding undue overtreatment and preserving often critically needed organ function. Although knowledge of interventional MR imaging concepts and familiarity with its technology and with the related safety issues are indispensable for interventional radiologists attempting thermal ablation procedures in the MR imaging environment, understanding the tissue basis of necrosis imaging is becoming an essential part of the knowledge base for the larger sector of general radiologists who are required to interpret the follow-up MR imaging scans of the increasing number of thermal ablation patients.

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.

MR-Guided Percutaneous Sclerotherapy of Low-Flow Vascular Malformations in the Head and Neck

MR-guided sclerotherapy is an excellent approach for the treatment of the predominant symptoms of congenital low-flow vascular malformations in the head and neck. In the authors' experience, this mode of treatment appears to be safe and efficient and allows the quantitative verification of therapeutic success during follow-up examinations.

MR imaging follow-up after percutaneous radiofrequency ablation of renal cell carcinoma: findings in 18 patients during first 6 months

PURPOSE

To prospectively evaluate the magnetic resonance (MR) imaging findings seen within the first 6 months after radiofrequency (RF) thermal ablation of renal cell carcinoma (RCC).

MATERIALS AND METHODS

After providing written informed consent, 18 patients (17 men, one woman; mean age, 71.2 years) with RCC underwent MR imaging-guided percutaneous RF thermal ablation, which was performed by using protocols approved by a comprehensive cancer center protocol committee and the institutional review board for human investigation. The study was Health Insurance Portability and Accountability Act compliant. Follow-up unenhanced T2-weighted MR images and unenhanced and gadolinium-enhanced T1-weighted MR images were acquired immediately, 2 weeks, 3 months, and 6 months after ablation. Thermal ablation zone size was analyzed, and contrast-to-noise ratios (CNRs) were calculated from the signal amplitudes of the thermal ablation zone, perirenal fat, and normal renal cortex on the MR images. Statistical analyses were performed by using the paired Student t test. P < .05 was considered to indicate statistical significance.

RESULTS

The mean follow-up time was 16.1 months (range, 6.0-41.2 months). The mean sizes of the thermal ablation zones were 6.8, 7.0, 6.1, and 4.7 cm2, respectively, at immediate, 2-week, 3-month, and 6-month follow-up MR imaging examinations. Thermal ablation zones were uniformly hypointense and had a surrounding bright rim on T2-weighted images and were predominantly hyperintense on T1-weighted images. Thin rim enhancement with central hypointensity was noted on the gadolinium-enhanced images. Gadolinium-enhanced T1-weighted and unenhanced T2-weighted MR images showed significantly higher CNRs than unenhanced T1-weighted MR images. Residual tumor was detected after RF thermal ablation in two cases and was best seen on unenhanced T2-weighted and gadolinium-enhanced T1-weighted MR images.

CONCLUSION

After initially increasing in size within the first 2 weeks, renal RF thermal ablation zones involuted during the remainder of the MR imaging follow-up period.