Книги по МРТ КТ на английском языке / MRI for Orthopaedic Surgeons Khanna ed 2010

Fig. 15.25 Ewing sarcoma. (A) An axial T1-weighted image shows a large low signal intensity soft-tissue mass originating from the right gluteal muscles (arrows). (B) An axial T2-weighted image shows ex-

tensive soft-tissue edema and a high signal intensity soft-tissue mass (arrows). The conventional radiographic findings and biopsy were conclusive for a diagnosis of Ewing sarcoma.

Fig. 15.26 Chondrosarcoma. (A) An axial T1-weighted image shows an aggressive, destructive lesion invading the right hemipelvis (arrows) and displacing the bladder. (B) An axial T2-weighted image

show a permeative, aggressive pattern of lytic destruction. The lesion has been described as occurring more commonly in the diaphysis.85,92

In most cases, an associated soft-tissue mass appears on MRI, which is seen best on T2-weighted, STIR, or contrast-en- hanced T1-weighted images.98 Bone destruction can be seen best on T1-weighted images, on which the lesion appears dark. Substantial surrounding edema can be seen on T2-weighted images and can suggest osteomyelitis (Fig. 15.25).85,99

Despite the aggressive nature of this disease, neoadjuvant chemotherapy has proved to be an e ective treatment adjunct. Given that this round-cell sarcoma is very sensitive to chemotherapy, large soft-tissue masses often involute after induction chemotherapy. As with osteosarcoma, MRI can assess the e ect of therapy on the lesion. With successful treatment, the lesion involutes and often has higher signal intensity on T2-weighted images, corresponding to necrosis.85,99,100

Chondrosarcoma

Chondrosarcoma, the second most common mesenchymal bone tumor, occurs most commonly in patients more than 40 years old. Chondrosarcoma occurs both as a primary lesion and as secondary lesion arising from other benign cartilage

shows a lobular pattern of growth by the chondrosarcoma (arrows), along with associated soft-tissue edema.

tumors such as enchondromas or osteochondromas. Chondrosarcomas can also occur as intramedullary and surface lesions, with growth rates varying from slow to aggressive. Radiographs show cortical destruction and the characteristic rings and stipples of cartilage calcification.

MRI assists with the evaluation of these tumors. Cartilaginous tumors, such as chondrosarcoma, have low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. One can often recognize a lobular growth pattern within the cartilage, with nodules separated by fibrous tissue (Fig. 15.26). Dynamic MRI is a new technique in which gadolinium contrast agent is administered and serial MR images of a given region are obtained over time to visualize the enhancement pattern. This method can di erentiate a low-grade chondrosarcoma from an enchondroma. The postgadolinium enhancement curve of a chondrosarcoma shows rapid enhancement and perfusion, whereas less active lesions (such as an endochondroma) show slower enhancement. As with other lesions, T1-weighted images show the anatomic detail of the lesion: cortical destruction and soft-tissue involvement. T2-weighted images show the cartilaginous nature of the lesion, as described above.101 Treatment of these lesions includes wide resection with or without irradiation. Chondrosarcoma has proved resistant to chemotherapy and adjuvant radiation treatment.102–104

1.Weiss SW, Goldblum JR. General considerations. In: Weiss SW, Goldblum JR, eds. Enzinger and Weiss’s Soft Tissue Tumors. St. Louis: Mosby; 2001:1–19

2.Yasko AW, Shreyaskumar RP, Pollack A, Pollock RE. Sarcomas of soft tissue and bone. In: Lenhard RE Jr, Osteen RT, Gansler T, eds. Clinical Oncology. Atlanta: American Cancer Society; 2001:611–631

3.Hanna SL, Fletcher BD. MR imaging of malignant soft-tissue tumors. Magn Reson Imaging Clin N Am 1995;3:629–650

4.Woertler K. Soft tissue masses in the foot and ankle: characteristics on MR Imaging. Semin Musculoskelet Radiol 2005;9:227–242

5.Hussein R, Smith MA. Soft tissue sarcomas: are current referral guidelines su cient? Ann R Coll Surg Engl 2005;87:171–173

6.Sim FH, Frassica FJ, Frassica DA. Soft-tissue tumors: diagnosis, evaluation, and management. J Am Acad Orthop Surg 1994;2:202–211

7.Frassica FJ, Khanna JA, McCarthy EF. The role of MR imaging in soft tissue tumor evaluation: perspective of the orthopedic oncologist

and musculoskeletal pathologist. Magn Reson Imaging Clin N Am 2000;8:915–927

8.Drevelegas A, Pilavaki M, Chourmouzi D. Lipomatous tumors of soft tissue: MR appearance with histological correlation. Eur J Radiol 2004;50:257–267

9.Bauland CG, van Steensel MAM, Steijlen PM, Rieu PNMA, Spauwen PHM. The pathogenesis of hemangiomas: a review. Plast Reconstr

Surg 2006;117:29e–35e

10.Murphey MD, Fairbairn KJ, Parman LM, Baxter KG, Parsa MB, Smith WS. From the archives of the AFIP. Musculoskeletal angiomatous lesions: radiologic-pathologic correlation. Radiographics 1995;15:893–917

11.Olsen KI, Stacy GS, Montag A. Soft-tissue cavernous hemangioma. Radiographics 2004;24:849–854

12.Frassica FJ, Thompson RC Jr. Evaluation, diagnosis, and classification of benign soft tissue tumors (Instructional Course Lectures, the American Academy of Orthopaedic Surgeons). J Bone Joint Surg Am 1996;78:126–140

13.Ostlere S, Graham R. Imaging of soft tissue masses. Imaging 2005;17:268–284

14.Feldman F, Johnston A. Intraosseous ganglion. Am J Roentgenol Radium Ther Nucl Med 1973;118:328–343

15.McCarthy CL, McNally EG. The MRI appearance of cystic lesions around the knee. Skeletal Radiol 2004;33:187–209

16.Bui-Mansfield LT, Youngberg RA. Intraarticular ganglia of the knee: prevalence, presentation, etiology, and management. AJR Am J Roentgenol 1997;168:123–127

17.Yilmaz E, Karakurt L, Ozercan I, Ozdemir H. A ganglion cyst that developed from the infrapatellar fat pad of the knee. Arthroscopy 2004;20:e65–e68

18.Tang P, Hornicek FJ, Gebhardt MC, Cates J, Mankin HJ. Surgical treatment of hemangiomas of soft tissue. Clin Orthop Relat Res 2002;399:205–210

19.Wahrman JE, Honig PJ. Hemangiomas. Pediatr Rev 1994;15:266–271

20.Baker WM. On the formation of the synovial cysts in the leg in connection with disease of the knee joint. St Bartholomew Hosp Rep. 1877;13:245–261

21.Fritschy D, Fasel J, Imbert JC, Bianchi S, Verdonk R, Wirth CJ. The popliteal cyst. Knee Surg Sports Traumatol Arthrosc 2006;14: 623–628

22.Zhang WW, Lukan JK, Dryjski ML. Nonoperative management of lower extremity claudication caused by a Baker’s cyst: case report and review of the literature. Vascular 2005;13:244–247

23.Miller TT, Staron RB, Koenigsberg T, Levin TL, Feldman F. MR imaging of Baker cysts: association with internal derangement, e usion, and degenerative arthropathy. Radiology 1996;201:247–250

24.Sansone V, De Ponti A. Arthroscopic treatment of popliteal cyst and associated intra-articular knee disorders in adults. Arthroscopy 1999;15:368–372

25.Kornaat PR, Bloem JL, Ceulemans RYT, et al. Osteoarthritis of the knee: association between clinical features and MR imaging findings. Radiology 2006;239:811–817

26.Reid JD, Kommareddi S, Lankerani M, Park MC. Chronic expanding hematomas. A clinicopathologic entity. JAMA 1980;244:2441–2442

27.Aoki T, Nakata H, Watanabe H, et al. The radiological findings in chronic expanding hematoma. Skeletal Radiol 1999;28:396–401

28.Liu PT, Leslie KO, Beauchamp CP, Cherian SF. Chronic expanding hematoma of the thigh simulating neoplasm on gadolinium-enhanced MRI. Skeletal Radiol 2006;35:254–257

29.Keenan S, Bui-Mansfield LT. Musculoskeletal lesions with fluid-fluid level: a pictorial essay. J Comput Assist Tomogr 2006;30:517–524

30.Imaizumi S, Morita T, Ogose A, et al. Soft tissue sarcoma mimicking chronic hematoma: value of magnetic resonance imaging in di erential diagnosis. J Orthop Sci 2002;7:33–37

31.Hait G, Boswick JA Jr, Stone NH. Heterotopic bone formation secondary to trauma (myositis ossificans traumatica). J Trauma 1970;10:405–411

32.Parikh J, Hyare H, Saifuddin A. The imaging features of posttraumatic myositis ossificans, with emphasis on MRI. Clin Radiol 2002;57:1058–1066

33.Beiner JM, Jokl P. Muscle contusion injury and myositis ossificans traumatica. Clin Orthop Relat Res 2002; 403(suppl):S110–S119

34.Khoury NJ, El-Khoury GY, Kathol MH. MRI diagnosis of diabetic muscle infarction: report of two cases. Skeletal Radiol 1997;26:122– 127

35.Bunch TJ, Birskovich LM, Eiken PW. Diabetic myonecrosis in a previously healthy woman and review of a 25-year Mayo Clinic experience. Endocr Pract 2002;8:343–346

36.Kattapuram TM, Suri R, Rosol MS, Rosenberg AE, Kattapuram SV. Idiopathic and diabetic skeletal muscle necrosis: evaluation by magnetic resonance imaging. Skeletal Radiol 2005;34:203–209

37.Bjornskov EK, Carry MR, Katz FH, Lefkowitz J, Ringel SP. Diabetic muscle infarction: a new perspective on pathogenesis and management. Neuromuscul Disord 1995;5:39–45

38.Keller DR, Erpelding M, Grist T. Diabetic muscular infarction. Preventing morbidity by avoiding excisional biopsy. Arch Intern Med 1997;157:1611–1612

39.Jelinek JS, Murphey MD, Aboulafia AJ, Dussault RG, Kaplan PA, Snearly WN. Muscle infarction in patients with diabetes mellitus: MR imaging findings. Radiology 1999;211:241–247

40.Theos A, Korf BR. Pathophysiology of neurofibromatosis type 1. Ann Intern Med 2006;144:842–849

41.Kostelic JK, Haughton VM, Sether LA. Lumbar spinal nerves in the neural foramen: MR appearance. Radiology 1991;178:837–839

42.Lim R, Jaramillo D, Poussaint TY, Chang Y, Korf B. Superficial neurofibroma: a lesion with unique MRI characteristics in patients with neurofibromatosis type 1. AJR Am J Roentgenol 2005;184:962–968

43.Temple HT, Mizel MS, Murphey MD, Sweet DE. Osteoblastoma of the foot and ankle. Foot Ankle Int 1998;19:698–704

44.Peterson L, Stener B. Old total rupture of the adductor longus muscle. A report of seven cases. Acta Orthop Scand 1976;47:653–657

45.Rubin SJ, Feldman F, Staron RB, Zwass A, Totterman S, Meyers SP. Magnetic resonance imaging of muscle injury. Clin Imaging 1995;19:263–269

46.Al-Nakshabandi NA, Ryan AG, Choudur H, et al. Pigmented villonodular synovitis. Clin Radiol 2004;59:414–420

47.Tyler WK, Vidal AF, Williams RJ, Healey JH. Pigmented villonodular synovitis. J Am Acad Orthop Surg 2006;14:376–385

48.Stubbs AJ, Higgins LD. Pigmented villonodular synovitis of the knee: disease of the popliteus tendon and posterolateral compartment. Arthroscopy 2005;21:893.e1–893.e5

49.Cheng XG, You YH, Liu W, Zhao T, Qu H. MRI features of pigmented villonodular synovitis (PVNS). Clin Rheumatol 2004;23:31–34

50.Bouali H, Deppert EJ, Leventhal LJ, Reeves B, Pope T. Pigmented villonodular synovitis: a disease in evolution. J Rheumatol 2004;31: 1659–1662

51.García-Porrúa C, González-Gay MA, Vázquez-Caruncho M. Tophaceous gout mimicking tumoral growth. J Rheumatol 1999;26:508–509

52.Floemer F, Morrison WB, Bongartz G, Ledermann HP. MRI characteristics of olecranon bursitis. AJR Am J Roentgenol 2004;183: 29–34

53.Mutlu H, Sildiroglu H, Pekkafali Z, Kizilkaya E, Cermik H. MRI appearance of retrocalcaneal bursitis and rheumatoid nodule in a patient with rheumatoid arthritis. Clin Rheumatol 2006;25:734–736

54.Rennie WJ, Saifuddin A. Pes anserine bursitis: incidence in symptomatic knees and clinical presentation. Skeletal Radiol 2005;34: 395–398

55.Dawn B, Williams JK, Walker SE. Prepatellar bursitis: a unique presentation of tophaceous gout in an normouricemic patient. J Rheumatol 1997;24:976–978

56.Kato T, Takagi H, Sekino S, et al. Dorsalis pedis artery true aneurysm due to atherosclerosis: case report and literature review. J Vasc Surg 2004;40:1044–1048

57.Tatli S, Lipton MJ, Davison BD, Skorstad RB, Yucel EK. From the RSNA refresher courses: MR imaging of aortic and peripheral vascular disease. Radiographics 2003;23:S59–S78

58.Kars HZ, Topaktas S, Dogan K. Aneurysmal peroneal nerve compression. Neurosurgery 1992;30:930–931

59.Katz SG, Kohl RD, Razack N. Bilateral infrapopliteal artery aneurysms. Ann Vasc Surg 1992;6:168–170

60.Wright LB, Matchett WJ, Cruz CP, et al. Popliteal artery disease: diagnosis and treatment. Radiographics 2004;24:467–479

61.Weiss SW, Goldblum JR. Liposarcoma. In: Weiss SW, Goldblum JR, eds. Enzinger and Weiss’s Soft Tissue Tumors. St. Louis: Mosby; 2001:641–693

62.Sung MS, Kang HS, Suh JS, et al. Myxoid liposarcoma: appearance at MR imaging with histologic correlation. Radiographics 2000;20:1007–1019

63.Spillane AJ, A’Hern R, Judson IR, Fisher C, Thomas JM. Synovial sarcoma: a clinicopathologic, staging, and prognostic assessment. J Clin Oncol 2000;18:3794–3803

64.Olsen KM, Chew FS. Tumoral calcinosis: pearls, polemics, and alternative possibilities. Radiographics 2006;26:871–885

65.Cadman NL, Soule EH, Kelly PJ. Synovial sarcoma: an analysis of 134 tumors. Cancer 1965;18:613–627

66.Abboud JA, Beredjiklian PK, Donthineni-Rao R. Forearm mass in an adolescent. Clin Orthop Relat Res 2004;428:302–307

67.Coindre JM, Pelmus M, Hostein I, Lussan C, Bui BN, Guillou L. Should molecular testing be required for diagnosing synovial sarcoma? A prospective study of 204 cases. Cancer 2003;98:2700–2707

68.Link TM, Haeussler MD, Poppek S, et al. Malignant fibrous histiocytoma of bone: conventional X-ray and MR imaging features. Skeletal Radiol 1998;27:552–558

69.Munk PL, Sallomi DF, Janzen DL, et al. Malignant fibrous histiocytoma of soft tissue imaging with emphasis on MRI. J Comput Assist Tomogr 1998;22:819–826

70.Grote HJ, Braun M, Kalinski T, et al. Spontaneous malignant transformation of conventional giant cell tumor. Skeletal Radiol 2004;33:169–175

71.Sheppard DG, Libshitz HI. Post-radiation sarcomas: a review of the clinical and imaging features in 63 cases. Clin Radiol 2001;56: 22–29

72.Capanna R, Bertoni F, Bacchini P, Bacci G, Guerra A, Campanacci M. Malignant fibrous histiocytoma of bone. The experience at the Rizzoli Institute: report of 90 cases. Cancer 1984;54:177–187

73.Herr MJ, Harmsen WS, Amadio PC, Scully SP. Epithelioid sarcoma of the hand. Clin Orthop Relat Res 2005;431:193–200

74.Hurtado RM, McCarthy E, Frassica F, Holt PA. Intraarticular epithelioid sarcoma. Skeletal Radiol 1998;27:453–456

75.Chase DR, Enzinger FM. Epithelioid sarcoma. Diagnosis, prognostic indicators, and treatment. Am J Surg Pathol 1985;9:241–263

76.Woertler K, Blasius S, Brinkschmidt C, Hillmann A, Link TM, Heindel W. Periosteal chondroma: MR characteristics. J Comput Assist Tomogr 2001;25:425–430

77.Nomikos GC, Murphey MD, Kransdorf MJ, Bancroft LW, Peterson JJ. Primary bone tumors of the lower extremities. Radiol Clin North Am 2002;40:971–990

78.Pettersson H, Gillespy T III, Hamlin DJ, et al. Primary musculoskeletal tumors: examination with MR imaging compared with conventional modalities. Radiology 1987;164:237–241

79.Wenaden AET, Szyszko TA, Saifuddin A. Imaging of periosteal reactions associated with focal lesions of bone. Clin Radiol 2005;60: 439–456

80.Hosalkar HS, Garg S, Moroz L, Pollack A, Dormans JP. The diagnostic accuracy of MRI versus CT imaging for osteoid osteoma in children. Clin Orthop Relat Res 2005;433:171–177

81.Gaeta M, Minutoli F, Pandolfo I, Vinci S, D’Andrea L, Blandino A. Magnetic resonance imaging findings of osteoid osteoma of the proximal femur. Eur Radiol 2004;14:1582–1589

82.Nakatani T, Yamamoto T, Akisue T, et al. Periosteal osteoblastoma of the distal femur. Skeletal Radiol 2004;33:107–111

83.Oxtoby JW, Davies AM. MRI characteristics of chondroblastoma. Clin Radiol 1996;51:22–26

84.Lin PP, Thenappan A, Deavers MT, Lewis VO, Yasko AW. Treatment and prognosis of chondroblastoma. Clin Orthop Relat Res 2005;438:103–109

85.Miller SL, Ho er FA. Malignant and benign bone tumors. Radiol Clin North Am 2001;39:673–699

86.Woertler K. Benign bone tumors and tumor-like lesions: value of cross-sectional imaging. Eur Radiol 2003;13:1820–1835

87.Antonio ZP, Alejandro RM, Luis MRJ, José GR. Femur ostochondroma and secondary pseudoaneurysm of the popliteal artery. Arch Orthop Trauma Surg 2006;126:127–130

88.Jee WH, Choi KH, Choe BY, Park JM, Shinn KS. Fibrous dysplasia: MR imaging characteristics with radiopathologic correlation. AJR Am J Roentgenol 1996;167:1523–1527

89.James SLJ, Davies AM. Giant-cell tumours of bone of the hand and wrist: a review of imaging findings and di erential diagnoses. Eur Radiol 2005;15:1855–1866

90.Vidyadhara S, Rao SK. Techniques in the management of juxtaarticular aggressive and recurrent giant cell tumors around the knee. Eur J Surg Oncol 2007;33:243–251

91.Mendenhall WM, Zlotecki RA, Gibbs CP, Reith JD, Scarborough MT, Mendenhall NP. Aneurysmal bone cyst. Am J Clin Oncol 2006;29:311–315

92.Ho er FA. Primary skeletal neoplasms: osteosarcoma and Ewing sarcoma. Top Magn Reson Imaging 2002;13:231–239

93.McCarthy EF, Frassica FJ. Pathology of Bone and Joint Disorders: With Clinical and Radiographic Correlation. Philadelphia: WB Saunders; 1998

94.Jee WH, Choe BY, Kang HS, et al. Nonossifying fibroma: characteristics at MR imaging with pathologic correlation. Radiology 1998;209:197–202

95.Onikul E, Fletcher BD, Parham DM, Chen G. Accuracy of MR imaging for estimating intraosseous extent of osteosarcoma. AJR Am J Roentgenol 1996;167:1211–1215

96.Murphey MD, Jelinek JS, Temple HT, Flemming DJ, Gannon FH. Imaging of periosteal osteosarcoma: radiologic-pathologic comparison. Radiology 2004;233:129–138

97.Murphey MD, wan Jaovisidha S, Temple HT, Gannon FH, Jelinek JS, Malawer MM. Telangiectatic osteosarcoma: radiologic-pathologic comparison. Radiology 2003;229:545–553

98.van der Woude HJ, Bloem JL, Hogendoorn PCW. Preoperative evaluation and monitoring chemotherapy in patients with high-grade osteogenic and Ewing’s sarcoma: review of current imaging modalities. Skeletal Radiol 1998;27:57–71

99.Grier HE. The Ewing family of tumors. Ewing’s sarcoma and primitive neuroectodermal tumors. Pediatr Clin North Am 1997;44:991–1004

100.Kau man WM, Fletcher BD, Hanna SL, Meyer WH. MR imaging findings in recurrent primary osseous Ewing sarcoma. Magn Reson Imaging 1994;12:1147–1153

101.Verstraete KL, Lang P. Bone and soft tissue tumors: the role of contrast agents for MR imaging. Eur J Radiol 2000;34:229–246

102.Lee FY, Mankin HJ, Fondren G, et al. Chondrosarcoma of bone: an assessment of outcome. J Bone Joint Surg Am 1999;81:326–338

103.Rizzo M, Ghert MA, Harrelson JM, Scully SP. Chondrosarcoma of bone: analysis of 108 cases and evaluation for predictors of outcome. Clin Orthop Relat Res 2001;391:224–233

104.Terek RM. Recent advances in the basic science of chondrosarcoma. Orthop Clin North Am 2006;37:9–14

Imaging of the musculoskeletal system typically begins with radiographs, CT, or conventional MRI. Several advanced MRI techniques have proven useful for the evaluation of subtle and complex pathology, such as early manifestations of disease, preoperative planning, and postoperative analysis. In addition, advanced MRI techniques may be helpful in narrowing a di erential diagnosis, addressing a specific clinical question, or evaluating a finding detected on another imaging study. This chapter addresses techniques in musculoskeletal MRI that are increasingly used to assist clinical problem-solving.

■ MR Arthrography

Although conventional MRI often detects complex joint pathology with high sensitivity, MR arthrography is useful for the depiction of intraarticular structures that may be subtle or incompletely seen on a routine study. MR arthrography is especially useful for postoperative patients and for the evaluation of suspected ligamentous, cartilaginous, or labral injury. Arthrography relies on distention or enhancement of the joint with contrast medium to separate or enhance structures e ectively, thereby defining joint pathology with increased clarity.1 Direct and indirect methods of MR arthrography are commonly used.

Direct Arthrography

This technique is a sterile, minimally invasive procedure in which dilute gadolinium or saline is directly injected into the joint of interest under fluoroscopic guidance, followed by immediate MRI. Although gadolinium-based contrast agents have not been approved by the FDA for intraarticular injection, they are commonly used clinically under the doctrine of the practice of medicine. The optimal gadolinium concentration for adequate signal intensity is 2 mmol/L, which is achieved by dilution with normal saline; this solution then is combined with iodinated contrast material and 1% lidocaine before joint injection.2 The total amount of dilute gadolinium injected varies by joint and patient size (Table 16.1).3 To prevent suboptimal joint distention and additional dilution of gadolinium, imaging of the joint should be performed no later than 30 minutes after injection.

Although conventional MRI is often useful, direct arthrography o ers improved sensitivity for the detection of many OCDs and other ligamentous, articular, and synovial defects. In the shoulder, partial-thickness rotator cu tears are seen more clearly when there is filling of focal cu defects with gadolinium solution. Anatomic variants of the shoulder that may otherwise be mistaken for pathology are often better defined with arthrography. Labral tears of the glenoid and hip are sometimes di cult to di erentiate from normal anatomic structures (Fig. 16.1) and may be more clearly seen when contrast extends into the labral substance (Fig. 16.2). Recurrent or residual meniscal tears in the knee may be seen more clearly with arthrography because a normal postoperative meniscus has an abnormal configuration that may exhibit abnormal signal.4 Arthrography o ers additional detail in the evaluation of injury to the lateral ligaments of the ankle, especially the calcaneofibular ligament. Partial undersurface tears of the UCL and RCL in the elbow may not be clearly seen without arthrography (Fig. 16.3). TFCC and intrinsic intercarpal ligamentous abnormalities may be more conspicuous with MR arthrography. Direct arthrography is particularly useful for the detection of intraarticular loose bodies and OCDs.

Indirect Arthrography

This technique requires the uptake of intravenous gadolinium by highly vascular synovial membranes, which di uses

Table 16.1 Recommended Volume of Dilute Contrast per Joint for Direct MR Arthrography

Source: Adapted from Sahin G, Demirtas M. An overview of MR arthrography with emphasis on the current technique and applicational hints and tips. Eur J Radiol 2006;58:416–430. Adapted by permission.

Fig. 16.1 This coronal oblique fat-suppressed T1-weighted image of a SLAP lesion in the left shoulder was obtained after the intraarticular injection of a dilute gadolinium solution posterior to the biceps attachment to the glenoid. This direct MR arthrogram shows an irregular collection of contrast material (arrow) extending into the superior labrum with partial detachment.

into existing joint fluid, creating the “arthrographic e ect.” The main benefit of this method is that intraarticular structures may be visualized without percutaneous access to a joint, which may be traumatic, time-consuming, or logistically di cult. Once gadolinium (0.1 mmol/kg) is injected intravenously, the patient must gently exercise the joint in question for approximately 10 to 15 minutes to increase vascular perfusion and joint pressure, improving the gadolinium’s di usion. Imaging is performed 5 to 30 minutes after contrast injection, depending on the joint.

The success of indirect arthrography is limited for noninflamed joints because noninflamed synovium does not enhance well. Additionally, indirect enhancement may not be helpful for large joints that require a greater amount of distention or for patients with tense joint e usions. Indirect arthrography is therefore best suited for smaller joints. Subtle cartilage defects, loose bodies, and hyperemic tendons and sheaths in the wrist, elbow, ankle, and knee may also be seen more clearly with contrast compared with conventional MRI techniques (Fig. 16.4). For example, recurrent tears in a postoperative knee may exhibit synovial hyperemia with joint fluid infiltrating a tear. Unfortunately, many normal and postoperative structures enhance with gadolinium, so enhancement does not necessarily reflect an abnormality. Indirect arthrography o ers a better depiction of extraarticular osseous and soft-tissue abnormalities than does direct arthrography.5

Fig. 16.2 This sagittal fat-suppressed T1-weighted image of the hip obtained after the intraarticular injection of a dilute gadolinium solution (direct MR arthrography) depicts contrast material through the anterior labral substance (arrow), reflecting a tear. Overall, the labrum maintains its triangular shape.

■ Magnets and Imaging Equipment

3.0-T Magnets

High field strength MRI systems are becoming widely available in the clinical setting, typically with magnetic field strengths of 3.0 T. The higher intrinsic signal-to-noise ratio of high field strength MRI can be used to improve imaging speed or resolution, but there are changes in relaxation time at 3.0 T and increased artifacts to consider. Nevertheless, 3.0- T MRI o ers the opportunity to explore physiologic imaging of joints and anatomy with greater definition.

Intrinsic signal-to-noise ratio is a function of the strength of the magnetic field, the volume of the tissue being imaged, and the RF coils used. All else being equal, 3.0 T should provide twice the intrinsic signal-to-noise ratio of 1.5 T, but this goal is not achieved clinically for several reasons. The FDA and manufacturers have mandated the use of power-monitoring systems for 3.0-T MRI systems because of the increased risk of RF burns. The more problematic sequences are FSE/turbospin and short TR SE (T1-weighted) sequences. Because motion, chemical shift, and susceptibility artifacts from metallic implants are increased at 3.0 T, postoperative imaging may be more problematic at higher field strengths.

Imaging speed is improved with higher field strength; therefore, it is theoretically possible to acquire images up

B

Fig. 16.3 Direct MR arthrography of the elbow. The T1-weighted coronal oblique (prescribed as a plane bisecting the humeral condyles) images obtained after the intraarticular injection of a dilute gadolinium solution show (A) the normal intact anterior bundle of the UCL (arrow), which is firmly a xed to the medial margin of the ulna (arrowhead), and (B) a partial articular surface tear as detachment (arrow) of the deep portion of the distal anterior bundle of the UCL from the medial margin of the ulna (arrowhead). Note that the contrast remains contained by the intact superficial layer of the UCL without extraarticular extravasation. This finding has been described as the “T” sign.

to four times faster at 3.0 T than at 1.5 T while maintaining a comparable signal-to-noise ratio. In actuality, given the number of di erent considerations, it is typical to image only twice as fast with 3.0 T as with 1.5 T. Image acquisition time at 3.0 T may be optimized by minimizing the number of signal averages, increasing TR to account for longer T1 relaxation, use of a higher receiver bandwidth for non-FSE sequences, and use of small echo spacing for FSE/turbo-spin sequences. As mentioned above, the increase in signal-to- noise ratio at 3.0 T may be used to improve spatial resolution of images acquired by producing thinner and more numerous sections (Fig. 16.5).6–8

Fig. 16.4 This T1-weighted coronal oblique image of the wrist (indirect MR arthrography) shows multicompartment enhancement of the carpus and distal radioulnar joint. Findings of ulnocarpal abutment with a TFCC tear (arrow) are present.

Parallel Imaging

Parallel imaging is a relatively new class of techniques capable of substantially increasing the imaging speed of MRI. Parallel imaging involves using spatial information inherent in the elements of an RF coil array to allow a reduction in the number of time-consuming, phase-encoded steps required during a scan. Parallel imaging, therefore, imposes particular hardware requirements. Coil arrays must be used with separate preamplifiers and receivers for each individual element and with appropriate decoupling networks to decrease cross-talk between elements. Although these techniques may be used to some degree with existing coil arrays, many tailored array geometries have been designed specifically for parallel imaging. Parallel imaging techniques may be applied to any existing pulse sequence to reduce imaging time or increase spatial resolution. Resultant time savings can then be used to add modifications that would otherwise prohibitively lengthen a pulse sequence. Recent technical advances and increased availability have placed parallel imaging in widespread clinical use.

Increased imaging speeds do come with a well-defined signal-to-noise ratio penalty, which must be taken into account when developing protocols. Nevertheless, for sequences with su cient baseline signal-to-noise ratio, parallel imaging can o er substantial benefits. There is great synergy with 3D volumetric acquisitions and high field