(Radiographics. 2002;22:583-599.)
© RSNA, 2002
Contrast-enhanced MR Angiography of the Hand1
David A. Connell, FRANZCR,
George Koulouris, MB,BS,
Duncan A. Thorn, Dip App Sci and
Hollis G. Potter, MD
1 From the MRI Department, St Frances Xavier Cabrini Hospital, 183 Wattletree Rd, Malvern 3144, Victoria, Australia (D.A.C., G.K., D.A.T.); and the Department of Radiology/MR Imaging, Hospital for Special Surgery, New York, NY (H.G.P.). Received August 13, 2001; revision requested December 12 and received January 11, 2002; accepted January 16. Address correspondence to D.A.C. (e-mail: dconnell@netspace.net.au).
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Abstract
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Contrast material–enhanced magnetic resonance (MR) angiography of the hand noninvasively provides information comparable to that provided by conventional angiography. It is a quick and easy examination that takes less than 5 minutes to perform and produces high-quality images with use of a dedicated surface coil that provides a high signal-to-noise ratio, allowing small pixel size and high spatial resolution. Contrast-enhanced MR angiography requires intravenous injection of gadopentetate dimeglumine and acquisition of a volumetric slab of image data from the hand. This information is then projected with a maximum-intensity-projection algorithm. The technique is generally robust with reproducible findings. Image interpretation requires an understanding of (a) the normal vascular anatomy and anatomic variants of the hand and (b) common vascular diseases. MR angiography of the hand is commonly used to create an arterial "road map" prior to surgery, manage traumatic transection, and identify emboli. Vascular malformations are readily identified and connective tissue disorders including vasculitis are well demonstrated with this technique, which can also be used to assess bone viability following trauma to the carpus or to evaluate the viability of vascularized bone. Common artifacts may be secondary to contracture deformities or "wraparound" effect. However, most potential pitfalls can be avoided by being vigilant.
© RSNA, 2002
Index Terms: Fingers and toes • Hand, 43.92 • Hand, abnormalities, 43.30, 43.40, 43.60 • Hand, MR, 43.12142, 43.12143 • Magnetic resonance (MR), vascular studies, 43.12142, 43.12143 • Wrist, 43.92 • Wrist, MR, 43.12142, 43.12143
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LEARNING OBJECTIVES
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After reading this article and taking the test, the reader will be able to:
- Describe the normal vascular anatomy and anatomic variants of the hand.
- Identify vascular abnormalities of the hand.
- Describe the technique used in contrast-enhanced MR angiography of the hand and discuss associated pitfalls.
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Introduction
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Contrast material–enhanced magnetic resonance (MR) angiography is now a routine procedure in MR imaging departments. The technique is based on the principle of shortening the T1 relaxation time of blood by injecting a paramagnetic contrast material. This results in a significant difference in signal intensity between flowing blood and stationary tissue at heavily T1-weighted arterial-phase imaging.
Imaging the small vessels of the wrist and hand places special demands on this technique. High resolution is necessary to accurately depict the superficial and deep palmar arches and the digital vessels, which are often less than 1 mm in diameter. Because of the slow transit times of flowing blood in these distal vessels, bolus timing is not as critical for demonstrating these vessels as for demonstrating the aorta and the vessels of the arterial tree. However, acquisition time must be short enough to prevent venous contamination of the arterial anatomy. The challenge is to acquire high-resolution images in a short time and with an adequate signal-to-noise ratio while still covering the region of interest.
The availability of high-performance MR imaging gradient systems and high-quality receiver coils allows the acquisition of high-resolution arterial-phase images following intravenous administration of contrast agents. Contrast-enhanced MR angiographic findings are reproducible, and image quality is comparable to that of conventional angiography (1). We have performed more than 550 contrast-enhanced MR angiographic examinations of the hand at our two institutions, and this experience forms the basis for this article. We discuss and illustrate the normal anatomy and anatomic variants of the hand, contrast-enhanced MR angiographic technique, and the clinical utility and associated pitfalls of this imaging modality.
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Normal Anatomy
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The normal vascular anatomy of the hand is complex, with variants being the general rule. The most common pattern comprises deep and superficial palmar arches, which derive their main contributions from the radial and ulnar arteries, respectively, and give rise to the digital vessels (Fig 1).
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Figure 1. Drawing illustrates the normal arterial anatomy of the hand. The superficial palmar arch gives rise to the proper digital arteries (gray), and the deep palmar arch (black) supplies the thumb.
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The anastomosis between the termination of the radial artery and the palmar branch of the ulnar artery forms the deep palmar arch. The deep arch lies proximal to the superficial arch, crossing the bases of the metacarpal bones. Three palmar metacarpal branches are given off and span the deep and superficial arches. These vessels anastomose with the common palmar digital arteries from the superficial palmar arch and then bifurcate into the proper digital arteries. The deep arch also provides perforating vessels, which anastomose with the dorsal metacarpal arteries (2). The princeps pollicis and the first dorsal metacarpal artery both derive from the radial artery, which terminates into the deep palmar arch just proximal to these vessels, and are the main supply of the thumb. The arteria radialis indicis may combine with the princeps pollicis to form the first palmar metacarpal artery or may originate from the deep arch or the princeps pollicis itself. A complete deep palmar arch is seen in 97% of cases, with variations much less common than in the superficial arch (3).
The ulnar artery terminates into the larger superficial palmar branch to form the superficial arch, whereas a smaller deep palmar branch contributes to the deep arch. The superficial palmar arch provides the three common palmar digital arteries, which anastomose with the metacarpal arteries as described earlier. Finally, the proper digital arteries provide dorsal branches for anastomosis with the dorsal digital arteries. The superficial arch also provides the proper digital artery to the fifth digit. The superficial arch has been described as complete in approximately 78% of cases (3). The prevalence of complete arches and their variants is subject to debate and largely depends on the degree of contribution from the ulnar artery in the case of the deep arch, with several subcategories described by various authors (3,4). Possible explanations for the variety of arterial configurations include failure of development in the embryonic period, retention of vessels that normally undergo regression (5), and even persistence of primitive patterns as seen in lower primates (6).
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Imaging Technique
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A high-field MR imager with good-quality receiver coils is necessary to perform contrast-enhanced MR angiography of the hand. We use either a wrist quadrature phased-array surface coil (ICG Medical Advances, Milwaukee, Wis) or a send-receive phased-array extremity coil (Medrad, Indianola, Pa). Although the wrist coil has a better signal-to-noise ratio, its field of view (maximum, 12 cm) does not always provide enough coverage for all diseases.
A 256 x 224 imaging matrix with a 15-cm rectangular field of view yields submillimeter pixel sizes. Section thickness is 0.8 mm, and summing of 44 partition images gives good resolution and a 35-mm-thick imaging slab, which is adequate to cover the arterial anatomy of most hands. The rectangular field of view reduces acquisition time, thereby preventing venous contamination. An adequate signal-to-noise ratio in conjunction with a short acquisition time can only be attained with a high-quality receiver coil and a fast three-dimensional (3D) spoiled gradient-echo sequence. Repetition time should be as short as possible (<10 msec) to minimize acquisition time. An echo time of less than 3 msec is used. A narrow bandwidth improves the signal-to-noise ratio but results in a slower scan. A wider receiver bandwidth allows a shorter echo time; we commonly use a bandwidth of 31.2 kHz. Acquisition time should be approximately 40 seconds.
The apparent resolution of the images can be improved with use of zero-filling interpolation. This technique expands k space by filling it with zeros at its periphery prior to performing Fourier transform to reconstruct the image. The image can then be displayed with a higher-resolution matrix than the one with which it was acquired. The technique is also useful for increasing the number of apparent sections in the 3D data set, thereby reducing partial volume errors.
The patient lies prone with the arm raised above the head, and the hand is placed in the center of the extremity coil. Alternatively, the patient may be placed supine with the arm at the side and the wrist positioned in a high-quality wrist coil. Feetfirst imaging is more suitable for claustrophobic patients, but headfirst imaging allows the injection site to be monitored and is therefore preferable. To reduce acquisition time, the hand must be positioned with no rotation so that the minimum number of thin sections can be used to cover the vascular anatomy of the wrist. The fingers must be spread slightly to prevent overlapping of the digital arteries. In cases of clinically suspected vasospasm, wrapping the hand in a warm towel may be helpful in depicting the peripheral digital vessels, and the fan is usually turned off.
The arrival of the bolus of paramagnetic contrast material must coincide with the filling of central k space to produce maximum vessel contrast. For most patients, a 15-second delay after the injection of a 30-mL bolus will be adequate to demonstrate the arteries of the hand. Elliptic-centric filling of k space will fill the central part of k space first when the concentration of contrast material is maximal and thus will produce high vessel contrast. The outer lines of k space are filled later when the bolus has tapered off. The elliptic-centric filling of k space also minimizes venous contamination and thus allows longer scan times, which in turn make greater spatial resolution possible. Care must be taken, however, not to begin the sequence too early so that the central portion of k space is filled prior to the arrival of the contrast material bolus (7).
A set of 3D precontrast "mask" images is acquired immediately prior to the intravenous administration of contrast material to limit artifacts due to patient motion between acquisition of the pre- and postcontrast data sets. Beginning 15 seconds after the completion of contrast material administration, the sequence can be performed up to four times to ensure visualization of the contrast material bolus and to demonstrate the arterial, capillary, and venous phases. The precontrast data set is then subtracted from each of the postcontrast data sets. The resultant subtracted images can be manipulated with a maximum-intensity-projection (MIP) algorithm to produce a 3D image of the arterial anatomy.
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Clinical Utility of Contrast-enhanced MR Angiography
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Arterial Mapping Prior to Surgery
Contrast-enhanced MR angiography is a robust technique that can be used as a preoperative adjunct to reconstructive surgery for congenital and acquired abnormalities of the hand as well as to delineate normal anatomy prior to surgical creation of an arteriovenous fistula. This is of particular benefit because no iodinated contrast material is required. Iodinated contrast material may be deleterious to patients with compromised renal function. The anatomy of both the radial and ulnar arteries and the integrity of the superficial and deep palmar arches can be demonstrated (Fig 2).
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Figure 2a. Normal arterial anatomy and variants of the hand. (a) MR angiogram demonstrates absence of the superficial arch. The deep arch gives rise to the princeps pollicis artery (curved arrow) and the second common digital artery (open arrow). The ulnar artery gives off a branch (large straight solid arrow) to complete the arch and directly supplies the common digital arteries to the third, fourth, and fifth digits (small straight solid arrows). (b) MR angiogram obtained in a different patient demonstrates how the common digital arteries (arrows) arise from the deep arch and in turn give rise to the radial and ulnar proper digital arteries. (c) MR angiogram obtained in a third patient demonstrates absence of the ulnar artery. The radial artery (curved arrow) feeds the superficial arch (straight arrows), which in turn gives rise to the common digital arteries. The patient was not thought to be a suitable candidate for arteriovenous fistulization.
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Figure 2b. Normal arterial anatomy and variants of the hand. (a) MR angiogram demonstrates absence of the superficial arch. The deep arch gives rise to the princeps pollicis artery (curved arrow) and the second common digital artery (open arrow). The ulnar artery gives off a branch (large straight solid arrow) to complete the arch and directly supplies the common digital arteries to the third, fourth, and fifth digits (small straight solid arrows). (b) MR angiogram obtained in a different patient demonstrates how the common digital arteries (arrows) arise from the deep arch and in turn give rise to the radial and ulnar proper digital arteries. (c) MR angiogram obtained in a third patient demonstrates absence of the ulnar artery. The radial artery (curved arrow) feeds the superficial arch (straight arrows), which in turn gives rise to the common digital arteries. The patient was not thought to be a suitable candidate for arteriovenous fistulization.
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Figure 2c. Normal arterial anatomy and variants of the hand. (a) MR angiogram demonstrates absence of the superficial arch. The deep arch gives rise to the princeps pollicis artery (curved arrow) and the second common digital artery (open arrow). The ulnar artery gives off a branch (large straight solid arrow) to complete the arch and directly supplies the common digital arteries to the third, fourth, and fifth digits (small straight solid arrows). (b) MR angiogram obtained in a different patient demonstrates how the common digital arteries (arrows) arise from the deep arch and in turn give rise to the radial and ulnar proper digital arteries. (c) MR angiogram obtained in a third patient demonstrates absence of the ulnar artery. The radial artery (curved arrow) feeds the superficial arch (straight arrows), which in turn gives rise to the common digital arteries. The patient was not thought to be a suitable candidate for arteriovenous fistulization.
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Management of Traumatic Transection
Traumatic transection of the hand vasculature as a result of penetrating trauma is often clinically apparent, although approximately one-third of patients present with delayed symptoms (8). Isolated laceration of either the radial or ulnar artery is usually not critical, given the rich collateral anastomoses found in the hand. Intervention with a view toward reconstruction is rare but is required if the injury is complicated by thrombus propagation with embolism or results in concomitant disruption to distal collateral flow (9). Neovascularization bypasses the interrupted flow caused by transection, and recanalization occurs (Figs 3, 4).
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Figure 3a. Traumatic transection in a 27-year-old cook who had sustained a deep cut to the palm of the hand. (a) Contrast-enhanced MR angiogram demonstrates abrupt termination of the left ulnar artery (arrow), with the radial artery supplying both the superficial and deep arches. (b) Contrast-enhanced MR angiogram obtained following conservative treatment shows a collateral vessel bridging the transected segment of the artery (arrow), a finding that is consistent with early recanalization and repair.
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Figure 3b. Traumatic transection in a 27-year-old cook who had sustained a deep cut to the palm of the hand. (a) Contrast-enhanced MR angiogram demonstrates abrupt termination of the left ulnar artery (arrow), with the radial artery supplying both the superficial and deep arches. (b) Contrast-enhanced MR angiogram obtained following conservative treatment shows a collateral vessel bridging the transected segment of the artery (arrow), a finding that is consistent with early recanalization and repair.
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Figure 4a. Traumatic transection in a 34-year-old carpenter who had sustained laceration of the second digit 3 months earlier. (a) Image from the unsubtracted data set shows nonfilling of a segment of the ulnar digital vessel at the level of the proximal interphalangeal joint of the second digit (arrow), a location that corresponds to the laceration site. (b) Subtracted contrast-enhanced MR angiogram demonstrates filling of the vessel distal to the laceration (arrow), presumably by collateral vessels that are not visualized.
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Figure 4b. Traumatic transection in a 34-year-old carpenter who had sustained laceration of the second digit 3 months earlier. (a) Image from the unsubtracted data set shows nonfilling of a segment of the ulnar digital vessel at the level of the proximal interphalangeal joint of the second digit (arrow), a location that corresponds to the laceration site. (b) Subtracted contrast-enhanced MR angiogram demonstrates filling of the vessel distal to the laceration (arrow), presumably by collateral vessels that are not visualized.
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Diagnosis of Pathologic Conditions
Aneurysms.—
True aneurysms typically result from repetitive trauma (eg, in baseball catchers and jackhammer workers) and are most commonly seen in the ulnar artery (Fig 5), often where it abuts the hook of the hamate bone and the superficial branch of the radial artery between the abductor pollicis brevis and opponens pollicis muscles (10). Other causes of aneurysms include atherosclerosis, infection, arteritis, and tumor infiltration (11). Contrast-enhanced MR angiography not only delineates the exact site and nature of the aneurysm, but also provides an anatomic "road map" of collateral branches. As in all other aneurysms, complications include rupture and thromboembolism. Aneurysms of the palmar arch, including the digital arteries, are rare (only 18 cases have been reported to date) and classically manifest as a painful pulsatile mass following trauma (12). They can also be secondary to an inflammatory process or atherosclerosis. Involvement of the digital vessels is usually due to a penetrating injury and typically results in formation of a pseudoaneurysm. Pseudoaneurysms may also result from fracture of the carpus (Fig 6).
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Figure 5a. Aneurysm in a 43-year-old builder who presented with a pulsatile mass of the ulnar aspect of the wrist. (a) Contrast-enhanced MR angiogram demonstrates a saccular aneurysm (arrow) that arises from the ulnar artery adjacent to the ulnar styloid process. The precontrast data set has not been subtracted from the postcontrast data set, so that the relationship of the aneurysm to the bone structures could be appreciated. (b) Subtracted image clearly demonstrates the aneurysm (arrow).
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Figure 5b. Aneurysm in a 43-year-old builder who presented with a pulsatile mass of the ulnar aspect of the wrist. (a) Contrast-enhanced MR angiogram demonstrates a saccular aneurysm (arrow) that arises from the ulnar artery adjacent to the ulnar styloid process. The precontrast data set has not been subtracted from the postcontrast data set, so that the relationship of the aneurysm to the bone structures could be appreciated. (b) Subtracted image clearly demonstrates the aneurysm (arrow).
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Figure 6a. Pseudoaneurysm in a 23-year-old cricket player who had fallen on an outstretched hand. (a) Axial MR image of the wrist shows a fracture of the hook of the hamate bone (arrows). (b) Contrast-enhanced MR angiogram demonstrates a poorly defined lesion at the junction of the ulnar artery and the deep arch (arrow), a finding that is consistent with pseudoaneurysm formation resulting from vascular injury.
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Figure 6b. Pseudoaneurysm in a 23-year-old cricket player who had fallen on an outstretched hand. (a) Axial MR image of the wrist shows a fracture of the hook of the hamate bone (arrows). (b) Contrast-enhanced MR angiogram demonstrates a poorly defined lesion at the junction of the ulnar artery and the deep arch (arrow), a finding that is consistent with pseudoaneurysm formation resulting from vascular injury.
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Emboli.—
Emboli to the upper limb account for 15%–20% of all peripheral emboli and typically originate from the heart (70% of cases) secondary to conditions such as cardiac arrhythmias (most commonly atrial fibrillation), ventricular aneurysms, myocardial infarction, blood dyscrasias, paradoxical emboli, and bacterial endocarditis (13–15). The remaining 30% of cases result from proximal upper limb vascular abnormalities (eg, aneurysms [most commonly involving the subclavian artery] secondary to thoracic outlet compression with poststenotic dilatation, anomalous first rib, scalene fascial bands, occlusion of a bypass graft, and nonunited fractures of the clavicle. Emboli of cardiac origin tend to be larger and as such will occlude the larger proximal vessels, with the brachial artery bifurcation being the most common site in the upper extremity (16). In contrast, emboli to the hand and wrist tend to be a result of microembolic showers; as such, they rarely threaten limb viability and are transient in nature, although it has been shown that early intervention is pivotal in achieving the best outcome. Microemboli to the arteries of the hand typically produce segmental occlusions of the common and proper digital arteries with abrupt termination of blood flow (Fig 7). Contrast-enhanced MR angiography is a simple way to monitor patients following thrombolysis and is sensitive in the detection of collateral vessel filling.
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Figure 7a. Microemboli in a 53-year-old man with sudden onset of ischemia in the left fourth and fifth digits. (a) Angiogram demonstrates abrupt occlusion of the proper digital arteries to the fourth and fifth digits (arrows), a finding that is consistent with peripheral emboli. Other images (not shown) demonstrated thrombosis partially occluding the left subclavian artery. (b) Contrast-enhanced MR angiogram obtained to monitor patient response following urokinase injection also shows abrupt termination of the proper digital vessels of the fourth and fifth digits (arrows).
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Figure 7b. Microemboli in a 53-year-old man with sudden onset of ischemia in the left fourth and fifth digits. (a) Angiogram demonstrates abrupt occlusion of the proper digital arteries to the fourth and fifth digits (arrows), a finding that is consistent with peripheral emboli. Other images (not shown) demonstrated thrombosis partially occluding the left subclavian artery. (b) Contrast-enhanced MR angiogram obtained to monitor patient response following urokinase injection also shows abrupt termination of the proper digital vessels of the fourth and fifth digits (arrows).
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Arteriovenous Malformations.—
Congenital vascular tumors involve the hand in 30%–60% of cases (14). Classification is based on endothelial characteristics, treatment, and prognosis (17). Arteriovenous malformations (AVMs) consist of a network of dilated, tortuous vessels with abnormal communications between arteries and veins that infiltrate and often replace surrounding normal tissue. At histologic analysis, AVMs demonstrate endothelial mitotic activity and a combination of capillary, venous, arterial, and lymphatic beds. They are congenital abnormalities that grow at the same rate as the patient, and, unlike hemangiomas, they do not regress with age (18). Occasionally, they can increase in size during puberty and in patients experiencing altered hormonal states such as pregnancy. Rarely, cardiac decompensation secondary to high output failure may occur, most commonly in children, which is also an indication for treatment. However, most AVMs are sporadic and can be associated with systemic angiodysplasia (eg, Klippel-Trenaunay-Weber syndrome) (19).
MR imaging provides excellent contrast resolution between ligament, muscle, bone, vessels, and fat and can delineate the relationship between an AVM and the surrounding vasculature to allow effective management planning and, if necessary, surgical planning (20). Contrast-enhanced MR angiography can supplement this information by demonstrating the anatomy and extent (localized versus diffuse) of the AVM, its flow characteristics (high- versus low-flow states), the relevant feeding vessels, and the degree of vascularity (Fig 8). In addition to possibly exacerbating vasospasm, conventional angiography is often unsatisfactory in demonstrating lesions with high flow velocities and often leads to underestimation of the amount of abnormal tissue (21). Knowledge of the precise size, extent, and location of the AVM and of the number of connections will allow effective pretreatment planning. In many centers, this information is gleaned prior to embolization, although it is also useful for surgical planning.
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Figure 8a. Arteriovenous malformation in a 28-year-old man with vascular deformity of the hand. (a) Partition image demonstrates a fusiform abnormality encasing the flexor tendons (arrows). (b) MIP image produced by summing approximately 45 partition images demonstrates an arteriovenous malformation with large draining veins tracking along the ulnar (curved arrow) and radial (straight arrow) sides of the wrist.
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Figure 8b. Arteriovenous malformation in a 28-year-old man with vascular deformity of the hand. (a) Partition image demonstrates a fusiform abnormality encasing the flexor tendons (arrows). (b) MIP image produced by summing approximately 45 partition images demonstrates an arteriovenous malformation with large draining veins tracking along the ulnar (curved arrow) and radial (straight arrow) sides of the wrist.
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Furthermore, the capacity of contrast-enhanced MR angiography to help determine whether a lesion is associated with an arteriovenous fistula provides a further advantage in that this information is an important determinant of resectability and a predictor of surgical outcome (22,23). Because many conservatively managed AVMs require monitoring for further growth or recur following surgery, contrast-enhanced MR angiography has an advantage over conventional angiography in its ease of repetition without the inherent invasive risks or problems related to vasospasm. This is of particular importance because complete resection or definitive cure is seen in only small and well-demarcated lesions.
Hemangiomas.—
Cavernous hemangiomas are vascular lesions characterized by large, endothelium-lined venous channels at histologic analysis. They are larger and have thicker walls than capillary hemangiomas (24). Cavernous hemangiomas are rarely congenital and are characterized by increased mitotic activity. They first appear in the neonatal period and grow rapidly; however, they regress with age, so that 50% of lesions have regressed by 5 years of age and 70% by 7 years (24). Residual lesions (noninvoluting hemangioma) may occasionally persist, demonstrating fibrofatty infiltration (17). They are invariably associated with and sustained by arteriovenous fistulas (14). Differentiation between a hemangioma and a vascular malformation is made based on a pathologic finding of mast cells. It is difficult to discriminate between the two entities on the basis of imaging criteria alone. Because highly vascular soft-tissue tumors cannot be differentiated from hemangiomas at nuclear medicine studies, MR imaging and contrast-enhanced MR angiography have now superseded this modality (25) and are used with a frequency and success comparable to those of conventional angiography (17,26,27). Contrast-enhanced MR angiography demonstrates the size, extent, and vascular supply of the lesion. These findings are best appreciated on sequential MIP images (Fig 9).
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Figure 9a. Hemangioma in a 15-year-old boy with a pulsatile mass on the volar side of the proximal third digit. (a) Contrast-enhanced MR angiogram shows the common and proper digital arteries to the second, third, and fourth digits (thick arrows). Note also the lobulated foci of enhancement around the base of the third digit (thin arrow). (b) Image from the second data set acquired 45 seconds later shows a hemangioma and its relationship to the proper digital vessels of the third digit (arrow).
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Figure 9b. Hemangioma in a 15-year-old boy with a pulsatile mass on the volar side of the proximal third digit. (a) Contrast-enhanced MR angiogram shows the common and proper digital arteries to the second, third, and fourth digits (thick arrows). Note also the lobulated foci of enhancement around the base of the third digit (thin arrow). (b) Image from the second data set acquired 45 seconds later shows a hemangioma and its relationship to the proper digital vessels of the third digit (arrow).
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Benign and Malignant Tumors.—
Soft-tissue tumors of the hand and wrist comprise approximately 15% and 4% of all benign and malignantsoft-tissue lesions, respectively (28), although the MR imaging appearance of malignant tumors is nonspecific and therefore cannot reliably help distinguish between the two. Benign lesions include glomus tumors (Fig 10), tendon giant cell tumors, ganglia, and Dupuytren contracture. Malignant tumors include chondrosarcoma, osteosarcoma, synovial sarcoma (Fig 11), fibrosarcoma, and malignant vascular tumors. When used in conjunction with MR imaging, contrast-enhanced MR angiography can help detect lesion extension, infiltrative borders, and invasion of neurovascular structures and can be used for staging when the lesion is proximal to the arterial system.
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Figure 10. Glomus tumor in a 37-year-old woman with a painful focus in the pulp of the right second digit. Contrast-enhanced MR angiogram shows the proper digital vessels, with the ulnar artery to the second digit (straight arrow) coursing toward a small enhancing lesion in the fingertip (curved arrow). A glomus tumor was confirmed at surgery.
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Figure 11. Synovial sarcoma in a 47-year-old man with an enlarging mass in the proximal left thumb. Contrast-enhanced MR angiogram shows a vividly enhancing lesion (arrow) surrounded by a network of vessels. The lesion was resected and subsequently shown to be a synovial sarcoma.
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Raynaud Disease.—
Vasospastic disorders such as Raynaud disease result from an inappropriate arterial response to a stimulus that induces vasoconstriction. These disorders can be primary (idiopathic) or secondary (underlying systemic disorder). The clinical sign of bilateral characteristic color changes and autonomic dysfunction is known as Raynaud phenomenon. Unilateral disease should be considered suspicious for a superimposed thromboembolic event (29). The goal of diagnostic testing is to allow differentiation of Raynaud disease from other vaso-occlusive conditions and to help distinguish between primary and secondary Raynaud disease. Conventional angiography poses a specific risk in that contrast material may further exacerbate vasospasm. Furthermore, it invariably requires the use of vasodilators, which results in underestimation of the true extent of vasospasm. Secondary Raynaud disease may be due to many conditions, in particular connective tissue, immunoglobulin, and myeloproliferative disorders; occupational exposure; medications; and neoplasms (30). Contrast-enhanced MR angiographic findings in vasospastic disorders tend to be descriptive rather than pathognomonic and are characterized by gradual narrowing and tapering of the proper digital vessels, often with capillary congestion in the fingertips (Fig 12). Contrast-enhanced MR angiography is not usually necessary to establish the diagnosis because cold water testing or other provocative maneuvers are usually diagnostic.
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Figure 12. Raynaud disease in a 39-year-old man with cold-induced vasospasm. Contrast-enhanced MR angiogram demonstrates gradual tapering of the digital vessels with capillary congestion in the tips of the first and fifth digits, findings that are compatible with Raynaud disease.
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Vasculitides (Connective Tissue Disorders).—
Vasculitides, or connective tissue disorders, are a heterogeneous group of disease entities with considerable overlap that are characterized by tapering of the ulnar, radial, and proper digital arteries, often with superimposed vasospasm, and areas of narrowing interspersed with normal segments (29). Connective tissue disorders result in segmental occlusion of vessels secondary to antibody-antigen complex deposition, resulting in endothelial damage, fibrinoid thickening, and intimal hyperplasia. This ultimately leads to an obliterative endarteritis of the digital vessels. The vasculitides include polyarteritis nodosa (PAN), systemic lupus erythematosus, scleroderma, Sjögren syndrome, Henoch-Schönlein purpura, Wegener granulomatosis, giant cell arteritis, and dermatomyositis.
PAN is a rare disease with a male predilection that is characterized by progressive necrotizing inflammation of small to medium-sized arteries. The resulting exudations contribute to the formation of palpable nodules and to irregularity throughout the course of the vessel. Fibrinoid necrosis of the media is the pathologic hallmark. Although the causes of PAN are unclear, immune-mediated damage to the vasculature is thought to be the underlying process (31). At pathologic analysis, vascular abnormalities manifest as aneurysms, necrosis, and hemorrhage.
Vascular lesions in PAN are typically focal in distribution, demonstrate varying stages of development, and have a predilection for bifurcation points (29,32). Characteristic lesions of the hand include multiple short-segment stenoses of the proper and common digital arteries (29). Angiography is an important tool in the diagnosis of PAN, with a reported sensitivity and specificity as high as 89% and 90%, respectively (33). Without angiographic confirmation, the diagnosis can be made only in the 20%–30% of cases in which the results of tissue biopsies of skin nodules or muscle are positive (34). Contrast-enhanced MR angiography cannot reliably help differentiate PAN from other vasculitides; however, the gradual narrowing of irregular digital vessels with abrupt occlusion and the formation of digital aneurysms is suspicious for PAN (Fig 13).
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Figure 13a. PAN in a 47-year-old metal worker with ischemia of the second and third digits. (a) Conventional angiogram demonstrates occlusion of the proper digital vessels of the second, third, and fourth digits (arrows), a finding that suggests the presence of emboli. The patient was further evaluated with contrast-enhanced MR angiography. (b) MIP image demonstrates segmental narrowing of the proper digital vessels with numerous small aneurysms (short arrows). Occlusion of the proper digital vessels of the second and third digits is also seen (long arrows). Subsequent serologic testing and biopsy showed that the patient had PAN.
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Figure 13b. PAN in a 47-year-old metal worker with ischemia of the second and third digits. (a) Conventional angiogram demonstrates occlusion of the proper digital vessels of the second, third, and fourth digits (arrows), a finding that suggests the presence of emboli. The patient was further evaluated with contrast-enhanced MR angiography. (b) MIP image demonstrates segmental narrowing of the proper digital vessels with numerous small aneurysms (short arrows). Occlusion of the proper digital vessels of the second and third digits is also seen (long arrows). Subsequent serologic testing and biopsy showed that the patient had PAN.
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The term systemic scleroderma refers to a variety of disorders characterized by arteriolosclerosis and varying degrees of extracellular collagen accumulation, ultimately leading to tissue and visceral fibrosis. Several subcategories exist, including systemic sclerosis (diffuse scleroderma), CREST syndrome (calcinosis cutis, Raynaud phenomenon, esophageal dysfunction, sclerodactyly, telangiectasia) (localized scleroderma), scleroderma variants, and the overlap syndromes (35). Raynaud phenomenon occurs frequently and usually precedes the onset of scleroderma. In fact, its presence with no apparent cause warrants greater concern and closer follow-up for the development of cancer or connective tissue disease—in particular, scleroderma (36,37).
The proximal vessels of the upper extremity are more often involved than those of the hand. The ulnar artery is occluded in slightly over one-third of cases; in contrast, the radial artery is invariably patent (38,39). As with the other vasculitides, the proper digital arteries are the most commonly affected vessels, probably due to increased shear stress because the proper digital arteries are located near the metacarpophalangeal and interphalangeal joints (Fig 14) (39,40).
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Figure 14. Systemic scleroderma in a 42-year-old woman who had undergone resection of the right fifth digit. MR angiogram demonstrates absence of the ulnar artery. The radial artery supplies the deep arch, which in turn gives rise to the common digital arteries (solid arrows) and princeps pollicis artery (open arrow). Note the absence of the proper digital vessels.
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Inflammation or Synovitis.—
Rheumatoid arthritis is a chronic multisystem inflammatory disease characterized chiefly by synovitis, vasculitis, serositis, and nodule formation. It classically affects the small joints of the hand symmetrically and is characterized at histologic analysis by a proliferative synovitis with hyperplasia (pannus formation). Inflammatory mediators are responsible for the vascularization of the pannus, which results in progressive joint destruction and ankylosis (41). Pannus can be demonstrated with contrast-enhanced MR angiography and is characterized by a proliferative network of fine vessels in a periarticular distribution. Approximately 44 partition images (Fig 15a) make up each MIP image (Fig 15b) and can be viewed independently to further assess pannus and cortical erosions. Other connective tissue diseases such as systemic lupus erythematosus, Sjögren syndrome, and psoriatic arthropathy (Fig 16) show considerable overlap at pathologic analysis. Synovitis associated with reflex sympathetic dystrophy can also be demonstrated (Fig 17).
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Figure 15a. Pannus disease in a 49-year-old woman with long-standing rheumatoid arthritis. (a) Partition image obtained following intravenous injection of gadopentetate dimeglumine shows vivid enhancement of the synovium around the carpal, metacarpophalangeal, and proximal interphalangeal joints. (b) MIP image clearly demonstrates widely distributed synovial proliferation and enhancement, a finding that suggests the presence of active pannus disease.
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Figure 15b. Pannus disease in a 49-year-old woman with long-standing rheumatoid arthritis. (a) Partition image obtained following intravenous injection of gadopentetate dimeglumine shows vivid enhancement of the synovium around the carpal, metacarpophalangeal, and proximal interphalangeal joints. (b) MIP image clearly demonstrates widely distributed synovial proliferation and enhancement, a finding that suggests the presence of active pannus disease.
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Figure 16. Psoriatic arthropathy in a 42-year-old woman who presented with wrist pain and swelling. Contrast-enhanced MR angiogram demonstrates a normal vascular arch but marked synovial thickening and enhancement of the carpal bones, findings that are compatible with synovial disease.
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Figure 17. Synovitis in a 51-year-old woman who had fallen on an outstretched hand 6 weeks earlier. MR angiogram shows vivid synovial enhancement around the radiocarpal joint but absence of synovial disease around the metacarpal or interphalangeal joints, findings that are compatible with posttraumatic synovitis.
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Other Applications
Assessment of Bone Viability.—
Avascular necrosis of the carpal bones, notably the scaphoid bone (due to trauma or idiopathic Preiser disease) (42) and lunate bone (43), has been well documented at conventional MR imaging. The capacity to help detect early-stage avascular necrosis, and therefore to alter therapeutic management and ultimately affect clinical outcome, has significantly empowered MR imaging as an important diagnostic tool in disorders of the hand. The presence of avascular necrosis is a critical issue in patient outcome following surgical intervention for nonunion (44–46). In the setting of avascular necrosis, MR imaging has been shown to have a specificity of 100%, with 89% specificity at T1-weighted MR imaging (47).
MR imaging has also been used as an adjunct to clinical assessment in documenting the vascularity of the scaphoid bone before and after treatment on the basis of changes in bone marrow signal intensity and the presence of a surrounding zone of hyperemia (45,47,48). The standard of reference in the assessment of vascularity of the proximal pole is the visualization of punctate bleeding of cancellous bone at surgery (46,49,50). Gadolinium-enhanced fat-suppressed T1-weighted MR imaging clearly demonstrates the disparity in bone marrow enhancement because the only additional measurable increase in signal intensity is due to vascular perfusion. In postoperative patients, accurate assessment of scaphoid bone vascularity is more difficult. The treatment of choice is bone grafting with internal fixation, with reported success rates greater than 80% (50). Gadolinium-enhanced MR angiography can also improve diagnostic yield by helping document the presence or absence of neovascularization (Fig 18) and may, therefore, play an important role in postoperative patients in particular.
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Figure 18a. Neovascularization in a 22-year-old man with a history of nonunion of a right scaphoid bone fracture treated with bone grafting. (a) Partition image demonstrates neovascularization with blood vessels that arise from the radial artery (arrow) and course toward the distal pole of the grafted scaphoid bone. (b) MIP image also demonstrates the vessels as they arise from the radial artery and neovascularization around the site of the bone graft (arrow). (c) Venous-phase MIP image shows contrast enhancement around the area of the bone graft (arrow), a finding that is compatible with synovitis and proximal leakage of contrast material. Follow-up imaging showed healing of the graft.
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Figure 18b. Neovascularization in a 22-year-old man with a history of nonunion of a right scaphoid bone fracture treated with bone grafting. (a) Partition image demonstrates neovascularization with blood vessels that arise from the radial artery (arrow) and course toward the distal pole of the grafted scaphoid bone. (b) MIP image also demonstrates the vessels as they arise from the radial artery and neovascularization around the site of the bone graft (arrow). (c) Venous-phase MIP image shows contrast enhancement around the area of the bone graft (arrow), a finding that is compatible with synovitis and proximal leakage of contrast material. Follow-up imaging showed healing of the graft.
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Figure 18c. Neovascularization in a 22-year-old man with a history of nonunion of a right scaphoid bone fracture treated with bone grafting. (a) Partition image demonstrates neovascularization with blood vessels that arise from the radial artery (arrow) and course toward the distal pole of the grafted scaphoid bone. (b) MIP image also demonstrates the vessels as they arise from the radial artery and neovascularization around the site of the bone graft (arrow). (c) Venous-phase MIP image shows contrast enhancement around the area of the bone graft (arrow), a finding that is compatible with synovitis and proximal leakage of contrast material. Follow-up imaging showed healing of the graft.
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Visualization of the Scaphoid Bone Vasculature.—
The location of the scaphoid and lunate bones in the radiocarpal joint results in large segments of hyaline cartilage covering the external surfaces, which is important for stress bearing and ligamentous insertion for joint stability. These external surfaces cannot be penetrated by nutrient vessels (51). Thus, few insertion points remain to provide a periosteum for sensation and sites of attachment for the feeding neurovascular bundle. This accounts for often delayed clinical presentation and diagnosis. Pain is often vague and nonspecific, vascularity has long been disrupted, and necrosis is well established.
The scaphoid bone usually derives its vascularity from three branches of the radial artery that commonly branch from the superficial palmar arch: the laterovolar, dorsal, and distal branches, so named for to their origins from the radial artery and their areas of osseous insertion. The high prevalence of avascular necrosis reflects the internal osseous vascular network, whereby the blood supply of the proximal pole is derived from the vessels that enter distally. The laterovolar group enters at a site on the volar aspect proximal to the tuberosity, the dorsal branch enters adjacent to the insertion of the dorsal radiocarpal ligament, and the distal branch enters along the lateral radiocarpal ligament. The first two branches anastomose freely, with the laterovolar group being the main nutrient vessel and the distal branch supplying only the tuberosity. Rarely, there is a fourth vessel that inserts on the proximal surface. The laterovolar, dorsal, and distal branches can be visualized with contrast-enhanced MR angiography, as can the new vessels attempting to supply the bone by entering the insertion points formerly occupied by the nutrient arteries.
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Imaging Pitfalls
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Contrast-enhanced MR angiography is generally a robust technique with reproducible findings. However, studies may be suboptimal if there are severe contracture deformities such as those seen in rheumatoid arthritis. If the digits cannot be straightened, it can be difficult to include the entire arterial tree in the imaging volume. Abrupt cutoff of a vessel may be seen if the arterial anatomy is not completely covered by the volume localizer. This can occur with contractures or with poor positioning of the hand within the coil. The palm must lie flat with the fingers slightly spread and the volume localizer placed on the volar surface (the arterial supply to the hand is volar). The dorsal surface represents mostly venous drainage and does not need to be included in the scan.
Aliasing artifact is caused by "wrapping" of parts of the hand to the opposite side of the image. This occurs when the field of view is too small, resulting in the phase encoding of signal that lies outside the selected field of view and its superimposition on the image (52). The anatomic area not included in the field of view wraps around to the opposite side of the image, thereby masking arterial anatomy (Fig 19). The artifact can be reduced by increasing the field of view, although this compromises the spatial resolution of the study. Oversampling by doubling the number of phase-encoding steps is an unsatisfactory method of overcoming wraparound because it doubles scanning time, resulting in venous contamination (53). A rectangular field of view can help eliminate wraparound artifact. Also, switching the frequency- and phase-encoding directions may be useful because wrapping is minimized in the frequency-encoding direction with consistent oversampling.
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Figure 19. Wraparound artifact in a 47-year-old man with suspected vasculitis. On an MIP image, the fourth and fifth digits have wrapped to the opposite side of the image and overlie the thumb.
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Conclusions
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Contrast-enhanced MR angiography of the hand noninvasively provides information comparable to that provided by conventional angiography. It is a quick and easy examination that takes less than 5 minutes to perform and produces high-quality images with use of a dedicated surface coil that provides a high signal-to-noise ratio, allowing small pixel size and high spatial resolution.
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Acknowledgments
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The authors thank Judy Tan for typing the manuscript.
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Footnotes
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Abbreviations: AVM = arteriovenous malformation,
MIP = maximum intensity projection,
PAN = polyarteritis nodosa,
3D = three-dimensional
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References
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Abstract
LEARNING OBJECTIVES
