Magnetic Resonance N e u ro g r a p h y R e s e a rc h Evaluation of Its Effectiveness Gaurav K. Thawait, MDa, Avneesh Chhabra, MDb, John A. Carrino, MDa, John Eng, MDc,* KEYWORDS MR neurography Research Clinical outcome Nerve surgery
KEY POINTS Radiologists involved in magnetic resonance neurography (MRN) research should use appropriate methodology to evaluate the effectiveness of this imaging technique. Clinical research involving MRN has focused on establishing technical and diagnostic accuracy efficacy. Future research is needed to evaluate MRN with respect to the higher levels in the efficacy hierarchy: therapeutic, patient outcome, and societal. Data collection from the treating physician is necessary to address the higher levels in the efficacy hierarchy.
The rapid advent of new diagnostic techniques in radiology has led to the notion that these new technologies should be evaluated not only for optimal image quality and diagnostic accuracy but also for cost-effectiveness and ultimate improvement in patient care. In addition, in order for a modality to be considered appropriate, its value compared with current methods of diagnosis should be established. Taking these factors into consideration, the evaluation of a diagnostic technology can be complicated and, for a new technology to become a viable option for incorporation in a diagnostic algorithm, it should excel in multiple categories of diagnostic technology assessment. Extensive work has been done in the methodology of technology assessment. Fineberg and
colleagues,1 in 1977, described 4 levels of efficacy to evaluate the clinical effectiveness of a diagnostic procedure. Fryback and Thornbury,2 and later Thornbury,3 revised it to a 6-tiered model for efficacy. These models incorporate evaluation of both efficacy and effectiveness. The term efficacy defines the probability of benefit from the technology under ideal conditions of use, whereas the term effectiveness is used to reflect the performance in everyday clinical practice.4 Hunink and Krestin5 have argued that evaluation of a new diagnostic test on the 6-tier model might be challenging because of time and economic constraints. Magnetic resonance neurography (MRN) is a specialized technique that is rapidly becoming part of the diagnostic algorithm in the clinical evaluation of peripheral nerve injury. However, in order for this modality to be considered appropriate, its
Disclosures: A. Chhabra received patient research grants from Siemens, Integra Life Sciences and GE-AUR; J.A. Carrino received a patient research grant from Siemens. a Musculoskeletal Radiology Section, The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins Hospital, 601 North Caroline Street, JHOC 5168, Baltimore, MD 21202, USA; b University of Texas Southwestern, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA; c The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, Maryland 21287, USA * Corresponding author. E-mail address: [email protected] Neuroimag Clin N Am 24 (2014) 257–261 http://dx.doi.org/10.1016/j.nic.2013.03.030 1052-5149/14/$ – see front matter Ó 2014 Elsevier Inc. All rights reserved.
neuroimaging.theclinics.com
INTRODUCTION
258
Thawait et al value compared with current methods of diagnosis should be established. Therefore, radiologists involved in MRN research should use appropriate methodology to evaluate MRN’s effectiveness, ideally with a multidisciplinary approach. This article reviews the classic hierarchical model used in assessing diagnostic technologies along with a discussion of how this model can be applied to MRN. The article also emphasizes how to evaluate the impact of MRN on diagnostic thinking and therapeutic decisions.
currently performed at few centers in the country, and every center should optimize the imaging quality to obtain high-resolution and high-contrast twodimensional and three-dimensional imaging before they use the technique on their patients. The technical efficacy for images obtained by MRN has been successfully studied in some centers, and it continues to improve.6–9
Level 2: Diagnostic Accuracy Efficacy
The classic diagnostic efficacy model approximates the sequence of image generation and its use, so a brief review of the work flow is useful. An image is recorded by the imaging device and stored. This image is then interpreted by the radiologist who generates a report based on various normal and abnormal findings. The clinician uses this information to arrive at the final clinical diagnosis and drives the therapeutic decision-making process. The clinician’s treatment decisions affect the patient’s health outcome(s) and ultimately contribute to the economic and overall health outcomes at the societal level. The 6-tiered model of efficacy starts at the level of imaging quality with level 1, defined as technical efficacy; level 2, defined as diagnostic accuracy efficacy, relates to image interpretation; levels 3 and level 4, defined as diagnostic thinking efficacy and therapeutic efficacy, respectively, take into account the clinician’s decision making; level 5 is defined as patient outcome efficacy and describes the effect from a patient’s perspective; and level 6, societal efficacy, encompasses the effect on the health care system and society as a whole. In this hierarchical model, the relevance of higher levels depends on the proven efficacy at the lower levels. Also, an improvement at the lower levels of efficacy should be justified by a tangible effect on the higher levels. For example, there is no relevance of diagnostic accuracy efficacy until the technical efficacy is proved; in contrast, there may be more scope to improve the technical efficacy but it might not necessarily improve the diagnostic accuracy efficacy. The 6 levels of assessment are discussed in the following sections along with how they apply to the evaluation of MRN.
This refers to image interpretation by the radiologist to make a diagnosis. Several descriptive statistics are used for this evaluation, such as sensitivity, specificity, positive and negative predictive values, and receiver operating characteristics (ROC) analysis. The diagnostic accuracy efficacy is a combined function of the image quality and observer interpretation. The observer interpretation is reader dependent. In MRN, the learning curve is steep and readers must learn normal nerve anatomy, anatomic variations, imaging pitfalls, nerve pathophysiology, and the wide spectrum of lesions encountered in a busy neuromuscular practice. To alleviate potential interpretation errors and to attain reasonable diagnostic performance, MRN readers must improve their interpretation skills by reading current articles and regularly participating in multidisciplinary conferences. In the literature, MRN has been shown to correlate with clinical, electrophysiological, and surgical findings, and good to excellent diagnostic accuracy and interobserver reproducibility has been observed in the evaluation of various small and large peripheral nerves.10–13 Chhabra and colleagues13 reported the optimal cutoff value of nerve/vessel signal intensity ratio for predicting sciatic neuropathy was 0.89, with sensitivity of 94.1% and specificity of 90.2% (area under the ROC curve, 0.963; 95% confidence interval, 0.886–0.994). Although anatomic MRN is practiced with good accuracy, functional diffusion tensor imaging (DTI) is also gaining acceptance. Andreisek and colleagues8 reported that there were no side-to-side statistically significant differences on fiber tracking of median nerves in healthy volunteers, reflecting the good precision of DTI. Guggenberger and colleagues14 showed the fractional anisotropy and apparent diffusion coefficient threshold values of normal and pathologic median nerves.
Level 1: Technical Efficacy
Level 3: Diagnostic Thinking Efficacy
Technical efficacy is under the physicist’s purview. It evaluates the technical characteristics of an image like signal, noise, quality, and spatial and contrast resolution. The technical efficacy is tested on phantoms and then on patients. MRN is
Diagnostic thinking efficacy measures the ability of a new technology to provide clinically useful information and alter the diagnostic algorithm. A diagnostic test might have high sensitivity and specificity, but it should be able to make a
SIX TIERS OF DIAGNOSTIC EFFICACY
Magnetic Resonance Neurography Research difference in establishing the diagnosis or affecting the diagnostic work-up. Diagnostic thinking efficacy can be evaluated by using questionnaires that are completed by clinicians before and after receiving the image interpretation results. The questionnaire may pertain to certainty of diagnosis or the physician’s confidence in certain clinical
Fig. 1. Survey questionnaire used in our MRN research.
findings, before and after imaging results. One such questionnaire used in our practice (Fig. 1) uses ordinal scales to simplify completion of the questionnaire. The physician reports on the specific nerve abnormality along with the degree of confidence before and after the imaging results. The change in degree of nerve injury is also
259
260
Thawait et al recorded. The ordinal scale provides a semiquantitative approach that reduces the quandary of subjectivity.
Level 4: Therapeutic Efficacy Therapeutic efficacy assesses the magnitude to which a diagnostic test affects the patient’s treatment plan. This efficacy can also be measured by using clinician questionnaires, as shown in Fig. 1. The physician records the change in degree of confidence in need for surgery, the anatomic approach to surgery, and the timing and duration of surgery. The questionnaire compares the preliminary treatment options before the diagnostic test result with the treatment plan after the test results are made available to the physician. The new diagnostic test is most efficacious if it completely changes the treatment plan for the patient. However, an argument can be made that, even if the new diagnostic test has no effect on the therapy, it helps in reassuring the clinician or affects the diagnostic certainty (measured by degree of confidence). This reassurance can be considered a beneficial effect. In 2008, Andreisek and colleagues15 conducted a successful study to show the value of MRN in influencing patient management.
Level 5: Patient Outcome Efficacy This level of efficacy evaluation is the most important from the individual patient’s perspective. It measures the level of patient satisfaction and the change in level of functionality after the treatment. Many questionnaires are available that can be used for estimating the functional capacity/disability and quality of life. These questionnaires can be general or specific to different sites of involvement in the patient. For example, Disabilities of the Arm, Shoulder, and Hand (DASH) can be used for upper extremity neuropathies16; Foot and Ankle Ability Measure (FAAM) for foot and ankle neuropathies17; and Boston Carpal Tunnel Questionnaire (BCTQ), which is specific for carpal tunnel syndrome18. Techniques are also available for measuring less specific health outcomes such as Quality of Life (QOL) and Quality-adjusted Life Years (QALY).19,20 However, these measures can be difficult to accomplish because it requires the patient’s compliance and repeated follow-ups, which might be arduous for a busy radiologist/clinician.
Level 6: Societal Efficacy This final level of efficacy evaluation assesses the critical question of whether the new diagnostic technology leads to an efficient use of the health care resources and is beneficial to the society as a whole. The value (benefit/cost) is established
by cost-effectiveness analyses and modeling methods. A cost-effectiveness study remains to be performed for MRN’s societal impact, and the study design could be similar to other diseases/ modalities.
SUMMARY The past and recent literature on MRN has focused on the technical and diagnostic accuracy efficacy, leaving out the other levels in the 6-tier model. This focus has led to an insufficient assessment of this technology, because the clinical usefulness and its effect on patient clinical outcome have not been documented. As more and more institutions use MRN, the challenge is to adequately assess the technique while it is being accommodated into clinical practice. The technical effectiveness and diagnostic accuracy have been established,21,22 so researchers should now focus on the remaining tiers of efficacy assessment, which can be accomplished by using clinician and patient surveys as described earlier and by studying homogenous populations of specific neuropathy sites or particular causes of neuropathy. Valid clinical studies of the higher levels of efficacy that can be generalized require collaboration between imaging researchers and the clinicians who are directly taking care of these patients. It is imperative to determine the clinical impact of MRN. The prospective research should focus on the assessment of MRN’s effect on clinicians’ diagnostic thinking and therapeutic decision making as well as patient outcomes. Institutions currently using MRN as a diagnostic tool should conduct more studies relating to diagnostic, treatment, and societal outcomes.
REFERENCES 1. Fineberg HV, Bauman R, Sosman M. Computerized cranial tomography. Effect on diagnostic and therapeutic plans. JAMA 1977;238(3):224–7. 2. Fryback DG, Thornbury JR. The efficacy of diagnostic imaging. Med Decis Making 1991;11(2):88–94. 3. Thornbury JR. Intermediate outcomes: diagnostic and therapeutic impact. Acad Radiol 1999;6(Suppl 1): S58–65 [discussion: S66–8]. 4. Brook RH, Lohr KN. Efficacy, effectiveness, variations, and quality. Boundary-crossing research. Med Care 1985;23(5):710–22. 5. Hunink MG, Krestin GP. Study design for concurrent development, assessment, and implementation of new diagnostic imaging technology. Radiology 2002;222(3):604–14. 6. Howe FA, Filler AG, Bell BA, et al. Magnetic resonance neurography. Magn Reson Med 1992;28(2):328–38.
Magnetic Resonance Neurography Research 7. Zhang Z, Meng Q, Chen Y, et al. 3-T imaging of the cranial nerves using three-dimensional reversed FISP with diffusion-weighted MR sequence. J Magn Reson Imaging 2008;27(3):454–8. 8. Andreisek G, White LM, Kassner A, et al. Evaluation of diffusion tensor imaging and fiber tractography of the median nerve: preliminary results on intrasubject variability and precision of measurements. AJR Am J Roentgenol 2010;194(1):W65–72. 9. Chhabra A, Subhawong TK, Bizzell C, et al. 3T MR neurography using three-dimensional diffusionweighted PSIF: technical issues and advantages. Skeletal Radiol 2011;40(10):1355–60. 10. Thawait SK, Chaudhry V, Thawait GK, et al. Highresolution MR neurography of diffuse peripheral nerve lesions. AJNR Am J Neuroradiol 2011;32(8): 1365–72. 11. Viallon M, Vargas MI, Jlassi H, et al. High-resolution and functional magnetic resonance imaging of the brachial plexus using an isotropic 3D T2 STIR (Short Term Inversion Recovery) SPACE sequence and diffusion tensor imaging. Eur Radiol 2008;18(5): 1018–23. 12. Vargas MI, Viallon M, Nguyen D, et al. New approaches in imaging of the brachial plexus. Eur J Radiol 2010;74(2):403–10. 13. Chhabra A, Chalian M, Soldatos T, et al. 3-T highresolution MR neurography of sciatic neuropathy. AJR Am J Roentgenol 2012;198(4):W357–64. 14. Guggenberger R, Markovic D, Eppenberger P, et al. Assessment of median nerve with MR neurography by using diffusion-tensor imaging: normative and
15.
16.
17.
18.
19.
20. 21.
22.
pathologic diffusion values. Radiology 2012;265(1): 194–203. Andreisek G, Burg D, Studer A, et al. Upper extremity peripheral neuropathies: role and impact of MR imaging on patient management. Eur Radiol 2008; 18(9):1953–61. Jester A, Harth A, Wind G, et al. Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire: determining functional activity profiles in patients with upper extremity disorders. J Hand Surg Br 2005;30(1):23–8. Martin RL, Irrgang JJ, Burdett RG, et al. Evidence of validity for the Foot and Ankle Ability Measure (FAAM). Foot Ankle Int 2005;26(11):968–83. Padua L, Padua R, Aprile I, et al. Boston Carpal Tunnel Questionnaire: the influence of diagnosis on patient-oriented results. Neurol Res 2005;27(5): 522–4. Bleichrodt H, Johannesson M. The validity of QALYs: an experimental test of constant proportional tradeoff and utility independence. Med Decis Making 1997;17(1):21–32. Padilla GV. Validity of health-related quality of life subscales. Prog Cardiovasc Nurs 1992;7(1):13–20. Chhabra A, Subhawong TK, Williams EH, et al. Highresolution MR neurography: evaluation before repeat tarsal tunnel surgery. AJR Am J Roentgenol 2011;197(1):175–83. Ba¨umer P, Dombert T, Staub F, et al. Ulnar neuropathy at the elbow: MR neurography–nerve T2 signal increase and caliber. Radiology 2011; 260(1):199–206.
261
KEY POINTS Radiologists involved in magnetic resonance neurography (MRN) research should use appropriate methodology to evaluate the effectiveness of this imaging technique. Clinical research involving MRN has focused on establishing technical and diagnostic accuracy efficacy. Future research is needed to evaluate MRN with respect to the higher levels in the efficacy hierarchy: therapeutic, patient outcome, and societal. Data collection from the treating physician is necessary to address the higher levels in the efficacy hierarchy.
The rapid advent of new diagnostic techniques in radiology has led to the notion that these new technologies should be evaluated not only for optimal image quality and diagnostic accuracy but also for cost-effectiveness and ultimate improvement in patient care. In addition, in order for a modality to be considered appropriate, its value compared with current methods of diagnosis should be established. Taking these factors into consideration, the evaluation of a diagnostic technology can be complicated and, for a new technology to become a viable option for incorporation in a diagnostic algorithm, it should excel in multiple categories of diagnostic technology assessment. Extensive work has been done in the methodology of technology assessment. Fineberg and
colleagues,1 in 1977, described 4 levels of efficacy to evaluate the clinical effectiveness of a diagnostic procedure. Fryback and Thornbury,2 and later Thornbury,3 revised it to a 6-tiered model for efficacy. These models incorporate evaluation of both efficacy and effectiveness. The term efficacy defines the probability of benefit from the technology under ideal conditions of use, whereas the term effectiveness is used to reflect the performance in everyday clinical practice.4 Hunink and Krestin5 have argued that evaluation of a new diagnostic test on the 6-tier model might be challenging because of time and economic constraints. Magnetic resonance neurography (MRN) is a specialized technique that is rapidly becoming part of the diagnostic algorithm in the clinical evaluation of peripheral nerve injury. However, in order for this modality to be considered appropriate, its
Disclosures: A. Chhabra received patient research grants from Siemens, Integra Life Sciences and GE-AUR; J.A. Carrino received a patient research grant from Siemens. a Musculoskeletal Radiology Section, The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins Hospital, 601 North Caroline Street, JHOC 5168, Baltimore, MD 21202, USA; b University of Texas Southwestern, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA; c The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, Maryland 21287, USA * Corresponding author. E-mail address: [email protected] Neuroimag Clin N Am 24 (2014) 257–261 http://dx.doi.org/10.1016/j.nic.2013.03.030 1052-5149/14/$ – see front matter Ó 2014 Elsevier Inc. All rights reserved.
neuroimaging.theclinics.com
INTRODUCTION
258
Thawait et al value compared with current methods of diagnosis should be established. Therefore, radiologists involved in MRN research should use appropriate methodology to evaluate MRN’s effectiveness, ideally with a multidisciplinary approach. This article reviews the classic hierarchical model used in assessing diagnostic technologies along with a discussion of how this model can be applied to MRN. The article also emphasizes how to evaluate the impact of MRN on diagnostic thinking and therapeutic decisions.
currently performed at few centers in the country, and every center should optimize the imaging quality to obtain high-resolution and high-contrast twodimensional and three-dimensional imaging before they use the technique on their patients. The technical efficacy for images obtained by MRN has been successfully studied in some centers, and it continues to improve.6–9
Level 2: Diagnostic Accuracy Efficacy
The classic diagnostic efficacy model approximates the sequence of image generation and its use, so a brief review of the work flow is useful. An image is recorded by the imaging device and stored. This image is then interpreted by the radiologist who generates a report based on various normal and abnormal findings. The clinician uses this information to arrive at the final clinical diagnosis and drives the therapeutic decision-making process. The clinician’s treatment decisions affect the patient’s health outcome(s) and ultimately contribute to the economic and overall health outcomes at the societal level. The 6-tiered model of efficacy starts at the level of imaging quality with level 1, defined as technical efficacy; level 2, defined as diagnostic accuracy efficacy, relates to image interpretation; levels 3 and level 4, defined as diagnostic thinking efficacy and therapeutic efficacy, respectively, take into account the clinician’s decision making; level 5 is defined as patient outcome efficacy and describes the effect from a patient’s perspective; and level 6, societal efficacy, encompasses the effect on the health care system and society as a whole. In this hierarchical model, the relevance of higher levels depends on the proven efficacy at the lower levels. Also, an improvement at the lower levels of efficacy should be justified by a tangible effect on the higher levels. For example, there is no relevance of diagnostic accuracy efficacy until the technical efficacy is proved; in contrast, there may be more scope to improve the technical efficacy but it might not necessarily improve the diagnostic accuracy efficacy. The 6 levels of assessment are discussed in the following sections along with how they apply to the evaluation of MRN.
This refers to image interpretation by the radiologist to make a diagnosis. Several descriptive statistics are used for this evaluation, such as sensitivity, specificity, positive and negative predictive values, and receiver operating characteristics (ROC) analysis. The diagnostic accuracy efficacy is a combined function of the image quality and observer interpretation. The observer interpretation is reader dependent. In MRN, the learning curve is steep and readers must learn normal nerve anatomy, anatomic variations, imaging pitfalls, nerve pathophysiology, and the wide spectrum of lesions encountered in a busy neuromuscular practice. To alleviate potential interpretation errors and to attain reasonable diagnostic performance, MRN readers must improve their interpretation skills by reading current articles and regularly participating in multidisciplinary conferences. In the literature, MRN has been shown to correlate with clinical, electrophysiological, and surgical findings, and good to excellent diagnostic accuracy and interobserver reproducibility has been observed in the evaluation of various small and large peripheral nerves.10–13 Chhabra and colleagues13 reported the optimal cutoff value of nerve/vessel signal intensity ratio for predicting sciatic neuropathy was 0.89, with sensitivity of 94.1% and specificity of 90.2% (area under the ROC curve, 0.963; 95% confidence interval, 0.886–0.994). Although anatomic MRN is practiced with good accuracy, functional diffusion tensor imaging (DTI) is also gaining acceptance. Andreisek and colleagues8 reported that there were no side-to-side statistically significant differences on fiber tracking of median nerves in healthy volunteers, reflecting the good precision of DTI. Guggenberger and colleagues14 showed the fractional anisotropy and apparent diffusion coefficient threshold values of normal and pathologic median nerves.
Level 1: Technical Efficacy
Level 3: Diagnostic Thinking Efficacy
Technical efficacy is under the physicist’s purview. It evaluates the technical characteristics of an image like signal, noise, quality, and spatial and contrast resolution. The technical efficacy is tested on phantoms and then on patients. MRN is
Diagnostic thinking efficacy measures the ability of a new technology to provide clinically useful information and alter the diagnostic algorithm. A diagnostic test might have high sensitivity and specificity, but it should be able to make a
SIX TIERS OF DIAGNOSTIC EFFICACY
Magnetic Resonance Neurography Research difference in establishing the diagnosis or affecting the diagnostic work-up. Diagnostic thinking efficacy can be evaluated by using questionnaires that are completed by clinicians before and after receiving the image interpretation results. The questionnaire may pertain to certainty of diagnosis or the physician’s confidence in certain clinical
Fig. 1. Survey questionnaire used in our MRN research.
findings, before and after imaging results. One such questionnaire used in our practice (Fig. 1) uses ordinal scales to simplify completion of the questionnaire. The physician reports on the specific nerve abnormality along with the degree of confidence before and after the imaging results. The change in degree of nerve injury is also
259
260
Thawait et al recorded. The ordinal scale provides a semiquantitative approach that reduces the quandary of subjectivity.
Level 4: Therapeutic Efficacy Therapeutic efficacy assesses the magnitude to which a diagnostic test affects the patient’s treatment plan. This efficacy can also be measured by using clinician questionnaires, as shown in Fig. 1. The physician records the change in degree of confidence in need for surgery, the anatomic approach to surgery, and the timing and duration of surgery. The questionnaire compares the preliminary treatment options before the diagnostic test result with the treatment plan after the test results are made available to the physician. The new diagnostic test is most efficacious if it completely changes the treatment plan for the patient. However, an argument can be made that, even if the new diagnostic test has no effect on the therapy, it helps in reassuring the clinician or affects the diagnostic certainty (measured by degree of confidence). This reassurance can be considered a beneficial effect. In 2008, Andreisek and colleagues15 conducted a successful study to show the value of MRN in influencing patient management.
Level 5: Patient Outcome Efficacy This level of efficacy evaluation is the most important from the individual patient’s perspective. It measures the level of patient satisfaction and the change in level of functionality after the treatment. Many questionnaires are available that can be used for estimating the functional capacity/disability and quality of life. These questionnaires can be general or specific to different sites of involvement in the patient. For example, Disabilities of the Arm, Shoulder, and Hand (DASH) can be used for upper extremity neuropathies16; Foot and Ankle Ability Measure (FAAM) for foot and ankle neuropathies17; and Boston Carpal Tunnel Questionnaire (BCTQ), which is specific for carpal tunnel syndrome18. Techniques are also available for measuring less specific health outcomes such as Quality of Life (QOL) and Quality-adjusted Life Years (QALY).19,20 However, these measures can be difficult to accomplish because it requires the patient’s compliance and repeated follow-ups, which might be arduous for a busy radiologist/clinician.
Level 6: Societal Efficacy This final level of efficacy evaluation assesses the critical question of whether the new diagnostic technology leads to an efficient use of the health care resources and is beneficial to the society as a whole. The value (benefit/cost) is established
by cost-effectiveness analyses and modeling methods. A cost-effectiveness study remains to be performed for MRN’s societal impact, and the study design could be similar to other diseases/ modalities.
SUMMARY The past and recent literature on MRN has focused on the technical and diagnostic accuracy efficacy, leaving out the other levels in the 6-tier model. This focus has led to an insufficient assessment of this technology, because the clinical usefulness and its effect on patient clinical outcome have not been documented. As more and more institutions use MRN, the challenge is to adequately assess the technique while it is being accommodated into clinical practice. The technical effectiveness and diagnostic accuracy have been established,21,22 so researchers should now focus on the remaining tiers of efficacy assessment, which can be accomplished by using clinician and patient surveys as described earlier and by studying homogenous populations of specific neuropathy sites or particular causes of neuropathy. Valid clinical studies of the higher levels of efficacy that can be generalized require collaboration between imaging researchers and the clinicians who are directly taking care of these patients. It is imperative to determine the clinical impact of MRN. The prospective research should focus on the assessment of MRN’s effect on clinicians’ diagnostic thinking and therapeutic decision making as well as patient outcomes. Institutions currently using MRN as a diagnostic tool should conduct more studies relating to diagnostic, treatment, and societal outcomes.
REFERENCES 1. Fineberg HV, Bauman R, Sosman M. Computerized cranial tomography. Effect on diagnostic and therapeutic plans. JAMA 1977;238(3):224–7. 2. Fryback DG, Thornbury JR. The efficacy of diagnostic imaging. Med Decis Making 1991;11(2):88–94. 3. Thornbury JR. Intermediate outcomes: diagnostic and therapeutic impact. Acad Radiol 1999;6(Suppl 1): S58–65 [discussion: S66–8]. 4. Brook RH, Lohr KN. Efficacy, effectiveness, variations, and quality. Boundary-crossing research. Med Care 1985;23(5):710–22. 5. Hunink MG, Krestin GP. Study design for concurrent development, assessment, and implementation of new diagnostic imaging technology. Radiology 2002;222(3):604–14. 6. Howe FA, Filler AG, Bell BA, et al. Magnetic resonance neurography. Magn Reson Med 1992;28(2):328–38.
Magnetic Resonance Neurography Research 7. Zhang Z, Meng Q, Chen Y, et al. 3-T imaging of the cranial nerves using three-dimensional reversed FISP with diffusion-weighted MR sequence. J Magn Reson Imaging 2008;27(3):454–8. 8. Andreisek G, White LM, Kassner A, et al. Evaluation of diffusion tensor imaging and fiber tractography of the median nerve: preliminary results on intrasubject variability and precision of measurements. AJR Am J Roentgenol 2010;194(1):W65–72. 9. Chhabra A, Subhawong TK, Bizzell C, et al. 3T MR neurography using three-dimensional diffusionweighted PSIF: technical issues and advantages. Skeletal Radiol 2011;40(10):1355–60. 10. Thawait SK, Chaudhry V, Thawait GK, et al. Highresolution MR neurography of diffuse peripheral nerve lesions. AJNR Am J Neuroradiol 2011;32(8): 1365–72. 11. Viallon M, Vargas MI, Jlassi H, et al. High-resolution and functional magnetic resonance imaging of the brachial plexus using an isotropic 3D T2 STIR (Short Term Inversion Recovery) SPACE sequence and diffusion tensor imaging. Eur Radiol 2008;18(5): 1018–23. 12. Vargas MI, Viallon M, Nguyen D, et al. New approaches in imaging of the brachial plexus. Eur J Radiol 2010;74(2):403–10. 13. Chhabra A, Chalian M, Soldatos T, et al. 3-T highresolution MR neurography of sciatic neuropathy. AJR Am J Roentgenol 2012;198(4):W357–64. 14. Guggenberger R, Markovic D, Eppenberger P, et al. Assessment of median nerve with MR neurography by using diffusion-tensor imaging: normative and
15.
16.
17.
18.
19.
20. 21.
22.
pathologic diffusion values. Radiology 2012;265(1): 194–203. Andreisek G, Burg D, Studer A, et al. Upper extremity peripheral neuropathies: role and impact of MR imaging on patient management. Eur Radiol 2008; 18(9):1953–61. Jester A, Harth A, Wind G, et al. Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire: determining functional activity profiles in patients with upper extremity disorders. J Hand Surg Br 2005;30(1):23–8. Martin RL, Irrgang JJ, Burdett RG, et al. Evidence of validity for the Foot and Ankle Ability Measure (FAAM). Foot Ankle Int 2005;26(11):968–83. Padua L, Padua R, Aprile I, et al. Boston Carpal Tunnel Questionnaire: the influence of diagnosis on patient-oriented results. Neurol Res 2005;27(5): 522–4. Bleichrodt H, Johannesson M. The validity of QALYs: an experimental test of constant proportional tradeoff and utility independence. Med Decis Making 1997;17(1):21–32. Padilla GV. Validity of health-related quality of life subscales. Prog Cardiovasc Nurs 1992;7(1):13–20. Chhabra A, Subhawong TK, Williams EH, et al. Highresolution MR neurography: evaluation before repeat tarsal tunnel surgery. AJR Am J Roentgenol 2011;197(1):175–83. Ba¨umer P, Dombert T, Staub F, et al. Ulnar neuropathy at the elbow: MR neurography–nerve T2 signal increase and caliber. Radiology 2011; 260(1):199–206.
261
