HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Myung, J. S. Articles by Kang, H. S. Search for Related Content PubMed PubMed Citation Articles by Myung, J. S. Articles by Kang, H. S. Social Bookmarking                      What's this? Hotlight (NEW!) What's Hotlight?

MR Diskography and CT Diskography with Gadodiamide–Iodinated Contrast Mixture for the Diagnosis of Foraminal Impingement

¹ Department of Radiology, Seoul National University Bundang Hospital, 300 Gumi-Dong, Bundang-Gu, Seongnam-si, Gyeonggi-Do 463-707, Korea.
² Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Gyeonggi-Do, Korea.
³ Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.

Received September 13, 2007; accepted after revision March 19, 2008.

 
Address correspondence to J. W. Lee (joonwoo2{at}gmail.com).

Abstract

Top Abstract Introduction Subjects and Methods Results Discussion References

 
OBJECTIVE. This study was designed to investigate whether the use of MR diskography would result in improved reader confidence over the use of CT diskography alone for evaluating foraminal impingement causing lumbar radiculopathy.

SUBJECTS AND METHODS. Sixteen disk levels in 14 consecutive patients with suspected foraminal impingement causing lumbar radiculopathy were prospectively included in the study. A mixture of diluted gadodiamide and iodinated contrast material was injected at each disk level. After diskography, a CT scan (CT diskography) and T1-weighted fat-suppressed MR image (MR diskography) were obtained. Two spine radiologists and an orthopedic spine surgeon independently scored CT diskography and MR diskography for foraminal evaluation on a 3-point scale: 1, low confidence; 2, moderate confidence; and 3, high confidence. Each reader also assessed whether MR diskography showed an additional benefit over CT diskography with regard to the depiction of foraminal abnormalities only. Another radiologist reviewed conventional MR images focused on disk height and morphology.

RESULTS. The reviewers' confidence scores for MR diskography were superior to those for CT diskography (reader 1, p = 0.00008; reader 2, p = 0.0008; reader 3, p = 0.0015) (p < 0.05). MR diskography was considered beneficial in 13 of 16 disk levels (reader 1), 14 of 16 (reader 2), and 14 of 16 (reader 3). MR diskography increased the confidence scores for the detection of foraminal impingement, especially in cases of severe disk degeneration, but did not show additional benefits in cases of an extensive vacuum in the disk or large disk extrusion.

CONCLUSION. Simultaneous MR diskography and CT diskography with a mixture of gadodiamide and iodinated contrast material may be beneficial for evaluating foraminal impingement causing lumbar radiculopathy.

Keywords: CT diskography • disk degeneration • disk herniation • foraminal impingement • intervertebral vacuum • MR diskography • osteophyte • radiculopathy

Introduction

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Disk herniations and osteophytes are common causes of foraminal impingement causing radiculopathy. MRI is now widely used as a standard method for evaluating spine abnormalities and diseases, but Van de Kelft et al. [1] reported that MRI showed relatively low specificity for the detection of foraminal lesions; in addition, those researchers found that MRI could not accurately differentiate disk herniations from osteophytes [1]. Precise, detailed anatomic evaluation of neural foraminal impingement may be important to surgeons to plan operations [2]. Hamasaki et al. [3] reported that CT diskography can be useful for evaluating pure foraminal disk herniation. However, clear visualization of a herniated disk on CT is difficult because the attenuation of iodinated contrast material on CT is similar to that of an adjacent vertebral body endplate or an osteophyte. Performing postdiskographic MRI (i.e., MR diskography) could solve the difficulty by providing excellent contrast.

Most of the studies in the literature documenting MR diskography performance have focused on it as an alternative use for patients with allergies to iodinated contrast agents [4–7]. For evaluation of the shoulder and ankle joints, researchers have reported that simultaneous MR arthrography and CT arthrography with a mixture of gadodiamide and iodinated contrast material can aid in diagnosis of joint disorders [8, 9]. Our hypothesis was that simultaneous MR diskography and CT diskography with a mixture of gadodiamide and iodinated contrast material would be useful for evaluating foraminal lesions and for clearly differentiating disk herniations from osteophytes because gadodiamide is clearly visible on fat-saturated T1-weighted images. To the best of our knowledge, no study has been reported to date that focuses on the role of MR diskography in evaluating foraminal impingement.

The current study was designed to test the hypothesis that performing MR diskography results in improved reader confidence over performing CT diskography alone for evaluating foraminal impingement causing lumbar radiculopathy.

Subjects and Methods

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Patients
From March 2006 to December 2006, 27 patients were referred to our department for lumbar diskography. Among them, patients with suspected foraminal impingement causing radi culopathy were enrolled in this prospective study after providing informed consent. In total, 16 disks in 14 patients were included in this study. The patients included seven men and seven women ranging in age from 44 to 73 years (mean, 63.5 years). Among them, six patients underwent surgery: diskectomy in three and laminectomy in three. Our institutional review board approved this prospective study.

Technique
Diskography was performed via a postero lateral approach using a 22-gauge coaxial Chiba needle (Cook Inc., USA) under fluoroscopy guidance (Integris Allura, Philips Healthcare) [10]. One of four radiologists, who had 3–9 years' experience in spine inter vention, performed diskography after informing patients of the risks and benefits of diskography. A mixture of 1.5 mL of iodinated contrast agent (iohexol [Omnipaque 300, GE Healthcare]), 0.01 mmol of gadodiamide (Omniscan, GE Healthcare, 0.5 mmol/mL concentration), and 0.333 g of cefazolin (Cefazolin, Chong Gun Dang; 1 g of powder) was made [4, 5, 7] (Appendix 1). After the appropriate needle placement had been confirmed in two planes, the solution was placed in 3-mL syringes for individual disk injections and diskography was performed. From 1 to 2.5 mL of the mixture was injected into each nucleus to be studied. During injection at each disk level, the patient's pain responses were recorded.

Patients were transported immediately after injection to a 1.5-T MRI unit (Gyroscan Intera, Philips Healthcare) and a 16-MDCT unit (MX-IDT8000, Philips Healthcare) to avoid diffusion of the contrast media. The imaging protocol for MR diskography consisted of axial and coronal T1-weighted fat-saturated sequences (TR/TE, 598/9.2; field of view, 320 mm; matrix, 512 x 512; number of signals acquired, 3; number of excitations, 3; slice thickness, 4 mm; gap, 0.4 mm; flip angle, 90°). The axial images were acquired with angulations through each disk to allow true transverse images to be obtained. CT scans were obtained using contiguous 3-mm axial sections and sagittal and coronal reformations were obtained (Fig. 1A, 1B, 1C, 1D).

View larger version (144K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A —Simultaneous MR diskography and CT diskography performed in 60-year-old woman with pain radiating to left leg. Axial fat-saturated T1-weighted image shows excellent contrast between gadodiamide of bright signal intensity and adjacent tissues. Note bright signal intensity of gadodiamide shows protruded disk extending to left foraminal zone (arrow) at L4–5.

View larger version (157K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B —Simultaneous MR diskography and CT diskography performed in 60-year-old woman with pain radiating to left leg. Coronal fat-saturated T1-weighted image reveals left foraminal disk protrusion (long arrow); protruding disk directly abuts left L4 nerve root (short arrow) at L4–5.

View larger version (91K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C —Simultaneous MR diskography and CT diskography performed in 60-year-old woman with pain radiating to left leg. Simultaneous postdiskographic CT images reveal no visible disk protrusion at left foraminal zone of L4–5 (arrow) where protrusion is accurately shown on previous MR diskography images (A and B).

View larger version (100K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1D —Simultaneous MR diskography and CT diskography performed in 60-year-old woman with pain radiating to left leg. Simultaneous postdiskographic CT images reveal no visible disk protrusion at left foraminal zone of L4–5 (arrow) where protrusion is accurately shown on previous MR diskography images (A and B).

Imaging Analysis
Two spine radiologists (readers 1 and 2), who had 7 and 9 years' experience, respectively, at the time of the study in MRI interpretation, and an orthopedic spine surgeon (reader 3), who had 9 years' experience in spine surgery, independently reviewed CT diskography and MR diskography of selected cases.

During the first interpretation session, each reader independently scored CT diskography and MR diskography with regard to foraminal evaluation using the following 3-point scale: 1, low confidence; 2, moderate confidence; and 3, high confidence. CT diskography and MR diskography images were randomly numbered and were evaluated on separate days 1 week apart. The analysis focused on the relation of the affected nerve root and the surrounding structures in the neural foramen. If the structures compressing the nerve root could be clearly seen with high confidence, the score was 3; with moderate confi dence, 2; or with low confidence, 1.

During the second interpretation session, each reader independently evaluated CT diskography and MR diskography on the same day. Each reader mentioned whether MR diskography showed additional findings over CT diskography only.

Another radiologist also reviewed conventional radiographs, conventional MR images, and medical records of the patients in the study group. On radiography, the reviewers assessed whether vacuum or severe disk degeneration was present. On conventional MRI, disk morphology and disk height were evaluated. Disk morphology was classified as protrusion, extrusion, or diffuse bulging according to the recommendations of the American Society of Neuroradiology [11]. Disk height was classified as showing severe disk degeneration or not. Severe disk degeneration was defined as present if a disk was less than half the height of an adjacent normal disk [12]. From the medical records, the reviewers noted pain provocation responses during diskography, operative findings, and postoperative clinical improvement in terms of radiculopathy.

After a consensus meeting, the three readers evaluated cases in which MR diskography did not show findings that yielded additional gain over CT diskography alone or vice versa. For differences between confidence scores of CT diskography and MR diskography assigned by each reviewer, the Wilcoxon's matched-pairs signed rank test was used. The analysis was performed using statistics software (GraphPad InStat, version 3.05, GraphPad Software).

Results

Top Abstract Introduction Subjects and Methods Results Discussion References

 
The results are summarized in Tables 1 and 2. For all readers, the mean difference between the confidence score of MR diskography and that of CT diskography was 0.875 and the confidence scores of MR diskography were significantly higher than those of CT diskography (reader 1, p = 0.00008; reader 2, p = 0.0008; reader 3, p = 0.0015) (p < 0.05). The clinical significance of this difference is that the confidence of the readers in MR diskography (mean = 2.79) was almost a full point higher than their confidence in CT diskography (mean = 1.92). This corresponds to an increase from almost moderate confidence (CT) to almost high confidence (MR). MR diskography was considered to provide additional findings in 13 of 16 disk levels (81.3%, reader 1), 14 of 16 disk levels (87.5%, reader 2), and 14 of 16 disk levels (87.5%, reader 3). MR diskography showed additional gain in two of three patients with severe disk degeneration (Fig. 2A, 2B).

View larger version (155K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A —68-year-old woman with pain radiating to right leg. Coronal MR diskography scan shows disk protrusion (arrow) accurately. Disk height is less than half that of adjacent normal disk, which suggests severe disk degeneration.

View larger version (109K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B —68-year-old woman with pain radiating to right leg. CT diskography scan reveals no visible disk protrusion. It is difficult to differentiate protruded disk from vertebral osteophyte on CT diskography.

However, in two disk levels (L3–4 disk in patient 1 and L5–S1 disk in patient 6) all three readers determined that MR diskography afforded no additional gain compared with CT diskography alone. In patient 1, the L3–4 disk protruded to the left foraminal and extraforaminal zone distinctively and disk herniation was clearly certified on CT diskography (Fig. 3A, 3B). In patient 6, the L5–S1 disk had a vacuum that interfered with the depiction of disk morphology on MR diskography (Fig. 4A, 4B).

View larger version (139K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A —66-year-old woman with pain radiating to right leg. Coronal MR diskography scan reveals right foraminal disk protrusion (arrow) at L5–S1 level. Although foraminal disk protrusion is also clearly certified on CT diskography (B), contrast between protruded disk filled with gadodiamide and adjacent vertebra is excellent on MR diskography.

View larger version (106K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B —66-year-old woman with pain radiating to right leg. Reformatted coronal CT diskography image reveals right foraminal disk protrusion (arrow) at L5–S1 level.

View larger version (132K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4A —64-year-old woman with pain radiating to left leg. L5–S1 disk has vacuum (arrow) that interfered with depiction of disk morphology and detailed foraminal structure on axial MR diskography scan.

View larger version (105K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4B —64-year-old woman with pain radiating to left leg. Axial CT diskography image shows intervertebral vacuum (short arrow). Difference between vertebral margin (long arrow) and vacuum is clearly seen when compared with MR diskography.

Discussion

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Foraminal stenosis is frequently found to result from disk height loss, osteophytes, and facet arthrosis in old age [17]. When compression to the nerve root is suspected on MRI, whether the cause of foraminal impingement is a herniated disk or an osteophyte is difficult to clearly distinguish. From the operator's point of view, having detailed anatomic information about foraminal lesions is helpful to plan surgery. In cases of foraminal impingement, MRI in the axial view is noted to have low specificity, and whether the cause of foraminal impingement is a herniated disk or an osteophyte is difficult to clearly discern.

CT diskography is widely used and allows excellent delineation and exact localization of both disk degeneration and annular tears, as well as the identification of disk herniation and other abnormalities [10, 13]. Hamasaki et al. [3] reported that CT diskography could be a useful technique for the detection of pure foraminal disk herniation. However, clear visualization of a herniated disk is difficult because the attenuation of iodinated contrast material on CT is similar to that of an adjacent vertebral body endplate or an osteophyte. MR diskography could solve this difficulty by providing excellent contrast.

According to the results of our study, MR diskography showed a significantly higher confidence score than CT diskography alone and was considered beneficial in the evaluation of most disk levels. MR diskography allowed clear differentiation of the intervertebral disk from the vertebral endplate or an osteophyte in most cases. However, MR diskography did not show additional gain in cases of a large extruded disk herniation or an extensive vacuum. MR diskography was likely to give more confident information about the structure causing foraminal impingement in a disk with severe disk degeneration than CT diskography only.

To date, MR diskography has been reported to be a suitable substitute in patients who have allergic reactions to iodinated contrast agents [4, 5, 18, 19]. As well as serving as a substitute imaging technique for evaluating patients with adverse reactions, MR diskography can provide more detailed anatomic information than CT diskography through its multiplanar capability and excellent soft-tissue contrast, especially for visualization of the nerve root [4, 7, 20, 21]. Kluner et al. [21] also performed MRI-based diskography with a mixture of iodine contrast material and gadolinium-based contrast material and found that obtaining additional coronal and sagittal views was advantageous and allowed easier identification of nerve structures.

Diluted gadodiamide has been used as a contrast agent in multiple joints, including the shoulder, knee, and ankle [8, 9, 22]. The use of full-strength gadodiamide does not suffice for evaluating disk morphology in MR diskography because the disk will actually be dark on T1-weighted sequences. Full-strength gadodiamide can be used with CT diskography and other percutaneous spine interventions [6, 23] because gadodiamide is visible on both fluoroscopy and CT. It is ambiguous what effect full-strength gadodiamide will have on the disks. Although a deleterious response seems unlikely, a diluted gadodiamide mixture is suitable and is safer than full strength. In this study, the dilution of gadodiamide (1:250 with normal saline) was injected into each disk level because that concentration is lower than the concentration previously reported to be safe [5].

Intradiskal administration of only gadodiamide has procedural drawbacks. The injection of gadodiamide into the disk cannot be observed under fluoroscopy at low concentrations (i.e., at and below 1:150). In addition, researchers have reported that gadodiamide cannot reach the intrathecal space inadvertently [5]. Huang et al. [4] reported that the mixture of iodinated contrast material with gadolinium did not interact or adversely affect the MR images obtained as long as a small amount of iodinated contrast material was used. The authors also used a mixture of iodinated contrast agent with gadodiamide. In that study, intradiskal needle placement was confirmed by first injecting a small amount of mixture solution, which was simple and markedly safe. We found that during routine CT diskography, simultaneous MR diskography with a single intradiskal injection of the mixture solution can provide supplementary anatomic information for foraminal lesions, especially in ambiguous cases, without additional invasiveness.

We acknowledge as a limitation of our study that surgery was available in only approximately half (six of 14) of our patients. However, surgery is not necessarily mandatory for treatment. Second, we examined the benefit in terms of additional diagnostic confidence of MR diskography over CT diskography alone, but we did not compare MR diskography with standard MRI and CT. The aim of the study was not clarification of the superiority of MR diskography over MRI but evaluation of whether simultaneous MR diskography during CT diskography offers additional benefits. That is the reason that we did not compare MR diskography with MRI and CT. Third, bone and root in the foramen could be evaluated using sagittal images, but scanning in the sagittal plane was not achieved in all patients; in fact, sagittal scanning was achieved tentatively in only one patient. However, coronal scanning was sufficient in the evaluation of the foramen and nerve root. The other shortcoming of our study is the low number of patients in the study population. However, this study is a preliminary study and further investigation is needed.

In conclusion, simultaneous MR diskography and CT diskography with a mixture of gadodiamide and iodinated contrast material may be beneficial for evaluating foraminal impingement causing lumbar radiculopathy.

References

Top Abstract Introduction Subjects and Methods Results Discussion References

 

1. Van de Kelft E, van Vyve M. Diagnostic imaging algorithm for cervical soft disc herniation. J Neurol Neurosurg Psychiatry 1994; 57:724 –728[Abstract/Free Full Text]
2. Macnab I. Negative disc exploration: an analysis of the causes of nerve-root involvement in sixty-eight patients. J Bone J Surg 1971; 53:891 –903[Abstract/Free Full Text]
3. Hamasaki T, Baba I, Tanaka S, et al. Clinical characterizations and radiologic findings of pure foraminal-type cervical disc herniation: CT discography as a useful adjuvant in its precise diagnosis. Spine 2005; 30:E591 –E596[CrossRef][Medline]
4. Huang TS, Zucherman JF, Hsu KY, Shapiro M, Lentz D, Gartland J. Gadopentetate dimeglumine as an intradiscal contrast agent. Spine 2002; 27:839 –843[CrossRef][Medline]
5. Slipman CW, Rogers DP, Isaac Z, et al. MR lumbar discography with intradiscal gadolinium in patients with severe anaphylactoid reaction to iodinated contrast material. Pain Med2002; 28:23 –29
6. Falco FJ, Moran JG. Lumbar discography using gadolinium in patients with iodine contrast allergy followed by postdiscography computed tomography scan. Spine 2003;28 : E1–E4[CrossRef][Medline]
7. Wagner AL. Gadolinium diskography. Am J Neuroradiol 2004; 25:1824 –1827[Medline]
8. Kopka L, Funke M, Fischer U, Keating D, Oestmann J, Grabbe E. MR arthrography of the shoulder with gadopentetate dimeglumine: influence of concentration, iodinated contrast material, and time on signal intensity. AJR 1994; 163:621 –623[Abstract/Free Full Text]
9. Schmid MR, Pfirrmann CWA, Hodler J, Vienne P, Zanetti M. Cartilage lesions in the ankle joint: comparison of MR arthrography and CT arthrography. Skeletal Radiol 2003;32 : 259–265[Medline]
10. Tehranzadeh J. Discography 2000. Radiol Clin North Am 1998; 36:463 –495[CrossRef][Medline]
11. Fardon DF, Milette PC; Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology. Nomenclature and classification of lumbar disc pathology. Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology. Spine 2001;26 : E93–E113[CrossRef][Medline]
12. Goffin J, Geusens E, Vantomme N, et al. Long-term follow-up after interbody fusion of the cervical spine. J Spinal Disord Tech 2004; 17:79 –85[Medline]
13. Sachs BL, Vanharanta H, Spivey MA, et al. Dallas discogram description: a new classification of CT/discography in low-back disorders. Spine 1987; 12:287 –294[Medline]
14. Vanharanta H, Guyer RD, Ohnmeiss DD, et al. Disc deterioration in low-back syndromes: a prospective, multi-center CT/discography study. Spine 1988; 13:1349 –1351[CrossRef][Medline]
15. Vanharanta H, Sachs BL, Spivey M, et al. A comparison of CT/discography, pain response and radiographic disc height. Spine 1988; 13:321 –324[CrossRef][Medline]
16. Vanharanta H, Sachs BL, Ohnmeiss DD, et al. Pain provocation and disc deterioration by age: a CT/discography study in a low-back pain population. Spine 1989;14 : 420–423[CrossRef][Medline]
17. Matsumoto M, Fujimura Y, Suzuki N, et al. MRI of cervical intervertebral discs in asymptomatic subjects. J Bone Joint Surg Br 1998; 80:19 –24[CrossRef][Medline]
18. Bernard TN. Lumbar discography followed by computed tomography: refining the diagnosis of low-back pain. Spine1990; 15:690 –707[CrossRef][Medline]
19. Schreck RI, Manion WL, Kambin P, Sohn M. Nucleus pulposus pulmonary embolism: a case report. Spine 1995;20 :2463 –2466[Medline]
20. Kakitsubata Y, Theodorou DJ, Theodorou SJ, et al. Magnetic resonance discography in cadavers: tears of the annulus fibrosus. Clin Orthop Relat Res 2003;407 : 228–240[CrossRef][Medline]
21. Kluner C, Kivelitz D, Rogalla P, Putzier M, Hamm B, Enzweiler C. Percutaneous discography: comparison of low-dose CT, fluoroscopy and MRI in the diagnosis of lumbar disc disruption. Eur Spine J2006; 15:620 –626[CrossRef][Medline]
22. Hodler J. Rotator cuff disease: assessment with MR arthrography versus standard MR imaging in 36 patients with arthroscopic confirmation. Radiology 1992;182 : 431–436[Abstract/Free Full Text]
23. Safriel Y, Ali M, Hayt M, Ang R. Gadolinium use in spine procedures for patients with allergy to iodinated contrast: experience of 127 procedures. Am J Neuroradiol 2006;27 :1194 –1196[Abstract/Free Full Text]

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Myung, J. S. Articles by Kang, H. S. Search for Related Content PubMed PubMed Citation Articles by Myung, J. S. Articles by Kang, H. S. Social Bookmarking                      What's this? Hotlight (NEW!) What's Hotlight?