Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3860_Библиотеки_им_академика_М_И_Перельмана
.pdf
A B
https://t.me/med1917
C D
FIGURE 5-16. Comparison of conventional angiography and two-dimensional time-of-flight (2-D TOF) magnetic resonance (MR)
angiography in a patient with severe aortoiliac occlusive disease and absent femoral pulses. A: Digital subtraction angiogram
(DSA) of the pelvis. The study was performed by translumbar puncture of the upper abdominal aorta (
Note the severe left common iliac artery stenosis (
from the same injection shows reconstitution of the right external iliac artery via the right hypogastric artery (
image from DSA of the femoral arteries in the same patient shows opacification of vessels on the left but not the right. D: Late
image from the same injection as C shows delayed faint opacification of the femoral vessels on the right. (
curved arrow
) and occlusion of the right common iliac artery. B: Delayed image
straight arrow
Continued
⫽ catheter).
arrow
). C: Early
)
MR and CT Angiography
https://t.me/med1917
45
E
FIGURE 5-16. (
shows severe stenosis of the left common iliac artery (
). Note the visualization of flow in the right iliac-circumflex artery (
arrow
open arrow
common iliac artery occlusion. F: Coronal MIP of the 2-D TOF MR angiogram of the same patient shows excellent bilateral
visualization of vessels.
renal artery stenosis, and evaluation of abdominal extension of aortic dissection.
tions include evaluation of renal artery anatomy in transplant donors, diagnosis of mesenteric ischemia resulting
from proximal superior mesenteric artery occlusion, and
depiction of hepatic artery anatomy in potential liver
transplant recipients.
tained for suspected acute rupture of an abdominal aortic aneurysm, as this diagnosis can be made most expedi-
Continued
) but not on the left. These vessels are seen because they act as collaterals to the right leg in this patient with right
)E:Coronal maximum intensity projection (MIP) of the 2-D TOF MR angiogram of the same patient
straight arrow
) and occlusion of the right common iliac artery (
large open arrow
) and right inferior epigastric artery (
curved
small
is not uncommon to miss small accessory renal arteries or
9,11,12,15,19,29
Additional indica-
subtle intimal abnormalities. MRA does not require iodinated contrast (and therefore can be used with impunity
in patients with renal failure or contrast allergies), but it
can be difficult to obtain because the number of MR
scanners is limited. CTA is more readily available and
16,25
Neither study should be ob-
easier to perform than MRA but it requires large volumes
of iodinated contrast (sometimes in excess of that used
for conventional angiography).
tiously by a noncontrast CT scan of the abdomen (the
presence of an abdominal aortic aneurysm and high attenuation blood in the retroperitoneum or peritoneum).
MRA and CTA are reported to be highly accurate in
the evaluation of the abdominal aorta and its branches,
although large prospective comparative studies are lack-
11–13,15,16,23,25
ing.
The image resolution of both tech-
niques is less than that of conventional angiography; so it
MRA
A complete MR examination of the abdominal aorta and
its branches requires both anatomic T1-weighted images
and flow-sensitive sequences.
11
The anatomic sequences
are essential for evaluation of vessel morphology and the
solid organs. Occasionally, important coincidental pa-
F
46 J. A. Kaufman
https://t.me/med1917
FIGURE 5-17. Coronal maximum intensity projection of a gadolinium enhanced three-dimensional magnetic resonance
angiogram of the aorta and pelvis in patient with a prior aortobiliac graft. A large left iliac artery anastomatic pseudoaneu-
arrow
rysm (
signal loss in this aneurysm.
) is clearly demonstrated. Note the absence of
thology such as renal carcinomas may be detected. Because background signal is suppressed in MRA, aneurysms lined with mural thrombus may be easily overlooked on flow sequences.
MRA of the abdominal aorta can be performed with
both TOF or PC sequences;
11,12
however, imaging of the
whole abdominal aorta can be time consuming and requires large fields of view in which loss of signal as a
result of saturation can be troublesome. Gadolinium-enhanced 3-D MRA obviates many of the limitations of
standard TOF and PC sequences in the abdomen.
15
This
technique permits image acquisition in the coronal
plane, with fields of view large enough to cover the area
from the diaphragm to the inguinal ligament (Fig. 5-17).
This is important in evaluation of aortic aneurysms or
dissections, because detection of both the proximal and
the distal extent of these lesions is crucial for management. With ultrafast pulse sequences, gadolinium-enhanced abdominal MRAs can be obtained in a single
breath-hold.
21
MRA of the renal and visceral arteries is a much more
focused examination than aortic studies. Usually, a T1weighted sequence is used to localize the vessels of interest (we find the sagittal plane is best). Whenever possible,
flow sequences are constructed with thin slices (1.5–2.0
mm), high-resolution matrices (256 ⫻ 256 or 512 ⫻ 512),
and a plane of acquisition that will maximize the likeli-
hood of including the entire vessel of interest. The most
widely used sequence is gadolinium-enhanced 3-D MRA
(Fig. 5-19) in the coronal plane. In general, the highest
accuracy of MRA is for proximal atherosclerotic disease
of the renal and visceral arteries.
Determination of the clinical importance of a renal
artery stenosis can be difficult, particularly when the lesion appears to be less than severe. One of the potential
advantages of MRA is that quantitative measurements of
flow can be used as adjuncts to angiographic images in
questionable cases.
30
CTA
CTA of the abdominal aorta and its visceral branches
provides information about vascular structures and adjacent organs with a single acquisition. In addition, vascular
calcification is readily visible on CTA source images, but
invisible on MR angiograms. This can be either a help or
a hindrance, because visualization of calcification may aid
in planning interventions, but it may obscure the origins
19,23
of small vessels.
A crucial prerequisite for high-quality
studies is the patient’s ability to suspend respiration for
20 to 40 sec., because the visceral vessels move with normal breathing. As always, careful attention must be given
to the delay between contrast injection and initiation of
the scan. For patients with normal renal function, CTA is
an excellent modality for evaluation of the abdominal
arteries (Fig. 5-20).
Studies of the abdominal aorta usually are designed
to use thin (3 mm) collimation at the level of the renal
and proximal visceral arteries, and thicker (5–7 mm)
collimation for the infrarenal aorta through the external
29
iliac arteries.
In most patients, it is not possible to scan
the abdominal aorta and iliac arteries with 3-mm collimation in a single breath-hold (even with a pitch of 2,
this would require a scan of 1.5–2 min.). Some scanners
are capable of variable pitch and collimation, whereas
others require interruption of the scan in the mid-abdomen to change parameters. Contrast (60% iodine)
should be injected at a rate of 3 to 5 mL/sec for a total
volume of 120 to 150 mL.
When the focus of the study is evaluation of the renal
and visceral branches of the aorta, extended anatomic
coverage is less important. In general, the pelvic arteries
do not need to be included in these acquisitions. Therefore, these studies can be tailored to maximize small-vessel detail with collimations of 3 mm and a pitch of 1 to
1.5.
19,23,25,29
Dense opacification with contrast is necessary to provide adequate visualization of the distal portions of vessels. If possible, contrast (60% iodine) should
be injected at a rate of 5 mL/sec for a total volume of 120
to 150 mL. An important pitfall of renal and visceral CTA
is densely calcified atherosclerotic plaque, which can
make grading of degree of luminal stenosis difficult.
MR and CT Angiography 47
https://t.me/med1917
A
B
FIGURE 5-18. Magnetic resonance (MR) venogram of
the pelvis in a patient with suspected right lower-extremity
deep vein thrombosis but a normal ultrasound examination.
A: Coronal maximum intensity projection (MIP) of a two-dimensional time-of-flight (2-D TOF) MR venogram. What do
you think? B: Right anterior oblique MIP of the same study.
Now what is your diagnosis? C: Axial source image from the
2-D TOF MR venogram shows an intraluminal filling defect in
the right external iliac vein (
arrow
) consistent with thrombus.
Note that the thrombus is completely surrounded by a bright
signal (i.e., flow), explaining why the thrombus is so hard to
see in the coronal projection. This case underscores the importance of reviewing source images to evaluate suspicious
C
findings.
48 J. A. Kaufman
https://t.me/med1917
FIGURE 5-19. Oblique restricted maximum-intensity projection of a gadolinium-enhanced three-dimensional time-of-flight
magnetic resonance angiogram of a transplanted kidney located in the right pelvis. There is moderate narrowing of the
renal artery anastomosis with the right hypogastric artery
(
straight arrow
(
curved arrow
). The origin of the hypogastric artery is patent
).
Portal, splenic, and mesenteric veins
Imaging of the portal venous system is performed most
commonly for patency, involvement by malignant tu-
mors, or evidence of portal hypertension. Results with
both MR and CT portal venography have been excel-
6,25
lent;
however, it is important to keep in mind that
duplex color-flow ultrasound is an inexpensive and rapid
alternate method of assessing the portal venous system.
MR venography
The portal venous system is well suited to imaging with
MR techniques because portal blood flow is slow and
nonpulsatile. The entire portal venous system can be
imaged quickly with 2-D TOF, 2-D PC, and 3-D gadolinium-enhanced sequences, particularly when acquired in
the coronal plane. With PC sequences the V
should be
enc
between 10 and 30 cm/sec. The direction of flow in the
portal vein (important in patients with suspected portal
hypertension) can be determined from display of PC
images with directional encoding or with saturation
bands in TOF sequences.
6
Excellent results also have
been reported with gadolinium contrast-enhanced techniques.
31
CT venography
Portal venous imaging with helical CT scanners requires a
longer delay than arterialimaging, frequentlyas long as 60
sec. Contrast (60% iodine) is injected at a rate of 2 to 4
mL/sec, for a total volume of 100 to 150 mL. Scanning
should begin caudal and progress cephalad, as this is the
same direction asflow within the mesenteric veins. Breathholding is necessary to minimize motion artifact. A major
A B
FIGURE 5-20. Computed tomographic (CT) angiogram of a patient with a type III aortic dissection. A: Axial source image above
the level of the celiac artery shows contrast-enhanced flow on both sides of an intimal flap (
finding is diagnostic of dissection. B: Shaded surface display of the CT angiogram. The relationship of the dissection flap (
to the abdominal vessels is clearly demonstrated. The flap appears as a cleft in the contrast column because of the postprocessing algorithm used to create the surface display.
arrow
) in the abdominal aorta. This
arrow
)
advantage of CT is that the arterial phase can be imaged
https://t.me/med1917
with an initial scan using a 20-sec. delay. In addition, information about the periportal soft tissues can be obtained at
the same time, and the direction of portal flow has no
impact on venous opacification. The latter is also a disadvantage, as direction of flow cannot be determined from
CT data.
Thoracic aorta
The thoracic aorta is subject to a wide range of pathology,
including aneurysm formation, dissection, arteritis, traumatic transection, and congenital lesions such as coarctation. The mostappropriate imaging modality for a specific
patient depends on the suspected diagnosis, the clinical
status of the patient, and the information needed to make
a management decision. For example, an unstable patient
with a suspected ruptured thoracic aortic aneurysm may
be imaged initially with a noncontrast CT scanof the chest;
if an aneurysm is detected and blood is present in the
mediastinum or pleural cavity, no further workup may be
necessary. At the other end of the spectrum, a stable patient who is being monitored for a known dissection can
be imaged with MR or contrast-enhanced CT. In general,
MRI has no role in the patient with a suspected acute
traumatic aortic transection.
MRA
Most MRI of the thoracic aorta can be accomplished
using T1-weighted images in multiple planes (axial, coronal, sagittal, sagittal-oblique).
quences have a greater than 95% sensitivity and specificity for detection of aortic dissection (Fig. 5-21), and
the multiplanar acquisitions allow accurate determination of the relationship between the left subclavian artery and pathologic processes such as dissections and
descending aortic aneurysms.
piratory compensation should be used to maximize image quality.
MRA sequences are most useful in the thoracic aorta to
confirm flow in dissections or to diagnose occlusive disease of the great vessel origins. For example, flow in a
false lumen in a dissection may be so slow that it appears
gray on T1-weighted images. To distinguish between a
patent or thrombosed false lumen, a flow sensitive sequence is required. Cardiac gated axial 2-D PC sequences
with a V
set to detect slow flow (40 cm/sec) with flow
enc
encoding in the superior-inferior direction can answer
the question quickly. For occlusive disease of the great
vessel origins, 2-D and 3-D TOF, as well as 3-D PC sequences, all have been employed with success. One of the
challenges of thoracic aortic MRA is that flow is multidirectional and, in the presence of aneur ysms or dissections, slow and turbulent. Dynamic gadolinium contrast-
32
Nonangiographic se-
33
Cardiac gating and res-
MR and CT Angiography 49
FIGURE 5-21. Axial T1-weighted image from just below the
aortic arch in a patient with a type I aortic dissection. The
dissection flap (
ascending and the descending aorta. The flap is readily visible
in this anatomic (i.e., nonangiographic) study because the
flowing blood in the aorta exits the slice before it can be
imaged, and thus it appears black.
arrows
) is seen in the lumens of both the
enhanced 3-D techniques are useful in these cases because there is no loss of signal resulting from slow or
complex directional flow.
34
CTA
Helical acquisition of thoracic aortic CT scans allows imaging from the thoracic inlet to the diaphragm in 20 to
40 secs. Furthermore, when imaging an unstable patient,
intensive care equipment such as monitors, respirators,
and infusion pumps is safe to use in the scanner room.
For these reasons, helical CT is the preferred modality for
unstable patients with suspected acute thoracic aortic
pathology. As with MRI, most diagnoses can be arrived at
from the axial source images. Multiplanar reconstructions usually supplement, rather than supplant, the axial
source images.
Contrast-enhanced CT has a greater than 95% sensitiv-
ity and specificity for aortic dissection and transec-
25,27
tion.
The diagnosis of dissection requires demonstration of blood (flowing or thrombosed) on both sides
of an intimal flap (Fig. 5-22). In many centers, no further
imaging of dissections is obtained if the CT is of high
quality. Traumatic aortic transection is implied from the
presence of a mediastinal hematoma adjacent to the
aortic arch, although pseudoaneurysms may be visualized
on contrast-enhanced studies. Stable patients with positive CT scans should undergo angiography to confirm
and localize the injury, because the sensitivities and specificities of CT (or transesophageal echo [TEE], an alter-
50 J. A. Kaufman
https://t.me/med1917
FIGURE 5-22. Axial image at the level of the aortic arch from
the same contrast enhanced computed tomographic angiogram of a type I aortic dissection seen in Fig. 5-11. The intimal
flap (
arrow
) is clearly visible because of the contrast-enhanced
blood in the surrounding lumen. Postprocessed images are not
necessary to make the diagnosis of dissection.
native technique for aortic imaging) for detection of
great vessel origin injuries and arch vessel anomalies such
as replacement of the left vertebral artery to the aortic
arch are unknown.
To image the entire thoracic aorta, a collimation of 3
27
to 7 mm with a pitch of 1 to 2 is necessary.
A collimation
of 7 mm may seem relatively thick, but it is important to
remember that the thoracic aorta and the great vessels
are large vascular structures. Cardiac pulsatility is an important source of artifacts on axial source images as well,
particularly in the region of the aortic root. Crescentic
linear artifacts can occur that may be confused with dissection flaps.
Contrast (60% iodine) injection rates should be 3 to 5
25,27
mL/sec for a total of 100 to 150 mL.
Although injection of contrast via an arm vein is typical, it may introduce
streak artifacts from intense opacification of the brachiocephalic veins and superior vena cava. In most cases, it is
not time efficient in an unstable patient to try to find a
suitable injection site in the lower extremities, and the
streak artifact is not severe enough to warrant such a
maneuver. A slightly shorter delay may be required than
for abdominal CTA but timing boluses should be used
whenever possible. Breath-holding is necessar y for optimum imaging.
Pulmonary arteries
An accurate, safe, and quick noninvasive technique to
diagnose pulmonary artery thromboembolism would be
a major advance in patient care. Pulmonar y embolism is
one of the most feared entities in clinical practice, and yet
it remains frequently an elusive diagnosis. Although the
morbidity of pulmonary angiography is in actuality low,
many clinicians are reluctant to pursue imaging beyond
ventilation/perfusion (V/Q) scans. One of the limitations of V/Q scans is that the results of scans for pulmonary embolism are expressed as a probability, rather than
a binary “yes”or “no” result. The promise of cross-sectional angiographic techniques is that a more definitive
diagnosis will be rendered.
MRA
MRA of the pulmonary arteries is challenging because
patients are frequently ill, the characteristics of flow are
complex in the pulmonary vasculature,and emboli vary in
size from several centimeters to several millimeters. Excellent preliminary results have been reported with a
number of techniques, including 2-D TOF, 2-D PC, and
3-D gadolinium-enhanced sequences.
used sequences are 3-D gadolinium-enhanced, with or
without breath-holding. An important advantage of MRA
in pulmonary embolism is that the lower extremities and
pelvis can be screened for DVT with MR venography at the
same time. A major limitation is that detection of small
peripheral emboli is poor with MRA. In general, pulmonary artery MRA as a clinical tool remains available at only
a limited number of institutions.
CTA
Helical CTA for pulmonary embolism has been embraced
enthusiastically because of the simplicity of the technique
and the wide availability of helical CT scanners. Central
emboli are detected with a greater than 95% sensitivity
and specificity, although the sensitivity for small peripheral emboli is much lower.
unresolved question becomes, What represents a clinically “significant” pulmonary embolism? If one accepts
that allpulmonary emboli are important, whether peripheral or central, massive or small, then pulmonary angiography should be considered in patients with negative
helical scans. CT for pulmonary embolism has a potential
role as a first line imaging test for patients with suspected
pulmonary embolism and normal renal function. This
modality will not be appropriate for patients with tenuous
or compromised renal function.
As with CTA of the thoracic aorta, the axial images are
frequently diagnostic in helical CTA of the pulmonary
arteries. The diagnostic feature of pulmonar y embolus is
an intraluminal filling defect within a pulmonary artery
(Fig. 5-23). Interbronchial lymph nodes can result in
35
35
The most widely
35
22
Given this limitation, the
MR and CT Angiography
https://t.me/med1917
A B
FIGURE 5-23. Diagnosis of pulmonary embolism by computed tomographic (CT) angiography. A: Axial slice from a CT
angiogram shows an intraluminal filling defect (
lower lobe atelectasis and a left pleural effusion. B: Conventional selective left pulmonary angiogram on the same patient
confirms the large embolus (
arrow
) in the left lower lobe pulmonary artery.
arrow
) in the left lower lobe pulmonary artery. Note that there is also partial left
51
false-positive readings because of their proximity to interlobar pulmonary arteries, and interpretation in areas of
pulmonary atelectasis or consolidation can be diffi-
22,35
cult.
Postprocessing such as oblique sagittal reformations or MIPs may help clarify questionable findings. A
major advantage of helical CT for pulmonar y embolism
is that alternative thoracic pathology may be discovered
that explains the patient’s symptoms. Typical helical CT
protocols for pulmonary embolism use injection rates of
3 to 5 mL/sec for 150 mL and lower concentrations of
iodine to avoid streak artifact from dense opacification of
the superior vena cava.
22
Other parameters include 3- to
5-mm collimation, a pitch of 1 to 1.7, and a 10- to 15-sec.
delay, depending on the patient’s hemodynamic status.
Breath-holding is essential to minimize motion artifact.
Thoracic veins
Occlusion of the central veins of the chest can occur as a
result of extrinsic compression by malignancy or inflammatory processes, invasion by tumor, or iatrogenic causes
such as central venous access catheters or pacemakers.
Patients may present with swelling localized to one arm
when the occlusion is limited to the subclavian/brachiocephalic veins or facial swelling when the superior vena
cava is involved. Although ultrasound is useful for the
axillary, subclavian, and jugular veins, it cannot visualize
the more central thoracic veins. Conventional upper-extremity venography is an excellent modality for evaluation of the patency of the peripheral and central veins,
but it provides no information about structures extrinsic
to the veins. MRI and CT of the chest can provide both
flow and anatomic information.
MR venography
The most widely used MR venographic technique for the
thoracic veins is 2-D TOF, because of the sensitivity of the
pulse sequence for slow flow and the short acquisition
14
times.
Gadolinium-enhanced 3-D acquisitions show
great promise in evaluation of the thoracic veins. Images
can be acquired in any plane, although the axial and
coronal planes are generally preferred. Relative to arterial studies, the slices for thoracic venography can be
thick (2–4 mm), as the goal of the study is to image the
large venous structures. Conventional T1-weighted images in the axial and coronal planes are important to
permit evaluation of the perivascular tissues.
CT venography
CT evaluation of central venous occlusion provides information about both vascular patency and adjacent soft
tissues with one acquisition but may require contrast injection into both upper extremities for complete evaluation. Dilute contrast (30%) should be used to minimize
streak artifacts, and injection rates should be lower than
for arterial studies (1–2 mL/sec for 80 mL). The base of
the neck should be included in the area scanned to
evaluate the patency of the jugular veins. Collimation of
5 to 7 mm, a pitch of 1 to 1.5, and a delay of 20 to 30 is
sufficient for most patients.
52 J. A. Kaufman
https://t.me/med1917
Extracranial carotid arteries
Accurate imaging of the extracranial carotid arteries is a
major priorityin the management of patients at risk for,or
with symptoms of, cerebrovascular disease. The importance of carotid artery imaging has been emphasized by
recent studies suggesting that aggressive surgical treatment of internal carotid stenoses of 60 to 70% or greater
reduction in diameter prevents stroke.
rotid noninvasive studies (CNIS) with duplex colorflow ultrasound are the most widely available and cost efficient
means of carotid artery evaluation, MRA and CTA have
major roles in carotid imaging. MRA andCTA may be used
to confirm the results of CNIS oras a primar y means of imaging the carotids in patients already undergoing MR or
CT evaluation for cerebral ischemia. In many institutions
conventional carotid angiography is now performed only
to resolve disagreements between CNIS and MRA or CTA.
MRA
MRA of the carotids is one of the most widely accepted
applications of this technique.
38
superficial, reliable in location, and subject to a limited
range of pathology (primarily occlusive disease or dissection). These characteristics allow imaging with specialized coils designed to capitalize on the proximity of the
carotid arteries to the anterior tissues of the neck. Typically, the “workhorse” sequence of carotid MRA is 2-D
TOF (1.5-mm slices, with a superior saturation band to
eliminate venous signal). Imaging of the carotid arteries
from the level of the thoracic inlet to the petrous portion
of the carotid is quick (7–9 mins.) using 2-D TOF MRA.
Numerous studies have shown a 75 to 95% agreement
between MRA and conventional angiography, and surgery can be performed safely on the basis of concordant
high-quality CNIS and MR angiograms.
There are several limitations to 2-D TOF MRA of the
extracranial carotid and vertebral circulation. The general tendency to overestimate the degree of stenosis is a
concern in situations in which surger y may be decided
purely on the severity of the stenosis.
area of signal loss is indicative of a 70% or greater reduction in luminal diameter; however, extremely slow flow in
an other wise patent vessel (such as distal to a critical
internal carotid artery stenosis) will appear as a complete
occlusion due to saturation. Lastly, the superior saturation band will mask reversed arterial flow such as in the
vertebral artery in the presence of a severe subclavian
artery origin occlusive disease.
40
Alternative MRI strategies of the carotid arteries include 3-D TOF and PC sequences, as well as gadoliniumenhanced 3-D TOF. The thinner partitions used with 3-D
sequences reduce signal loss in areas of turbulence and
improve the characterization of lesions. The amount of
anatomic coverage is limited with non-contrast 3-D acqui-
36,37
Although ca-
The carotid arteries are
39
27
In general, a focal
sitions because of long acquisition times and saturation
of flow in large volumes. Strategies for increasing the area
imaged include multiple overlapping thin 3-D TOF slabs
and the use of gadolinium contrast agents. Gadoliniumenhanced 3-D studies are immune to signal loss from slow
or turbulent flow and therefore permit more accurate
grading of lesions. When reversal of flow in an artery is
suspected as the cause of signal loss on a 2-D TOF study,
a single 2-D PC slice with a V
of 40 to 80 cm/sec and
enc
flow encoding in the superior-inferior direction can be
used to confirm the diagnosis.
CTA
Evaluation of the carotid arteries with CTA is quick and
simple because of the limited number of imaging strategies available with CT (contrast enhancement) and the
small area of anatomic coverage (the neck). In comparison to MRA, there is no signal loss in areas of slow or
turbulent flow vascular, and calcification is readily apparent. The latter may be a helpful feature when planning
carotid surgery.
A collimation of 1 to 3 mm with a pitch of 1 usually
provides excellent images. Contrast should be injected at
2 to 3 mL/sec for a total of 100 to 120 mL. A delay of 1220
secs. is adequate if a timing bolus is not used. Swallowing
should be suspended for the duration of the 30- to 60-second scan.
29
Although the results of early comparative studies (conventional angiography versus CTA) were mixed, the simplicity of this technique has resulted in widespread clinical implementation.
41
This technique is particularly
valuable when flow is extremely slow, as vessel patency still
can be demonstrated. In patients with renal insufficiency
or contrast allergies, an alternative imaging modality such
as MRA should be considered.
■ Conclusion
MRA and CTA have the potential to assume many of the diagnostic functions of conventional angiography. Much
work is required to determine and validate the best applications of these two techniques. MRA is the least invasive
and will be particularly valuable in the imaging of patients
who have renal failure and contrast allergies. CTA is easier
and likely to be more accessible (many more practices
have CT scanners than MR scanners), but it will always require radiation and iodinated contrast. A working knowledge of both techniques is important for all persons interested in the care of patients withvascular diseases.
REFERENCES
1. Egglin TK, O’Moore PV, Feinstein AR, et al. Complications of
peripheral arteriography: a new system to identify patients at increased risk. J Vasc Surg 1995;22:787–794.
MR and CT Angiography
https://t.me/med1917
53
2. Mistretta CA. Relative characteristics of MR angiography and competing vascular imaging modalities. J Magn Reson Imaging 1993;3:
685–698.
3. Jolesz FA, Blumenfeld SM. Interventional uses of magnetic resonance imaging. Magn Reson Q 1994;10:85–96.
4. Wedeen VJ, Meuli RA, Edelman RR, et al. Projectile imaging of
pulsatile flow with magnetic resonance. Science 1985;230:946–948.
5. Baum RA, Rutter CM, Sunshine JH, et al. Multicenter trial to evaluate vascular magnetic resonance angiography of the lower extremity. JAMA 1995;274:875–880.
6. Finn J, Kane R, Edelman R, et al. Imaging of the portal venous
system in patients with cirrhosis: MR angiography vs duplex doppler sonography. AJR Am J Roentgenol 1993;161:989–994.
7. Drutman J, Gyorke A, Davis WL, et al. Evaluation of subclavian steal
with two-dimensional phase contrast and two-dimensional time-offlight MRangiography. Am J Neuroradiol 1994;15:1642–1645.
8. Carpenter JP, Holland GA, Baum RA, et al. Magnetic resonance
venography for the detection of deep venous thrombosis: comparison with contrast venography and duplex Doppler ultrasonography. J Vasc Surg 1993;18:734–741.
9. Fellner C, Strotzer M, Geissler A, et al. Renal arteries: evaluation
with optimized 2D and 3D time-of-flight MR angiography. Radiology
1995;196:681–687.
10. Finn JP, Zisk JHS, Edelman RR, et al. Central venous occlusion: MR
angiography. Radiology 1993;187:245–251.
11. Kaufman JA, Geller SC, Petersen MJ, et al. MR imaging (including
MR angiography) of abdominal aortic aneur ysms: comparison with
conventional angiography. AJR Am J Roentgenol 1994;163:203–210.
12. Kim D, Edelman RR, Kent KC, et al. Abdominal aorta and renal
artery stenosis: evaluation with MR angiography. Radiology
1990;174:727–731.
13. Krebs TL, Daly B, Wong JJ, et al. Vascular complications of pancreatic transplantation: MR evaluation. Radiology 1995;196:793–798.
14. Rose SC, Gomes AS, YoonHC. MR angiography for mapping potential central venous access sites in patients with advanced venous
occlusive disease. Am J Roentgenol 1996;166:1181–1187.
15. Prince MR. Gadolinium-enhanced MR aortography. Radiology
1994;191:155–164.
16. Alfrey EJ, Rubin GD, Kuo PC, et al. The use of spiral computed
tomography in the evaluation of living donors for kidney transplantation. Transplantation 1995;59:643–645.
17. Baldt MM, Zontsich T, Stumpflen A, et al. Deep venous thrombosis
of the lower extremity: efficacy of spiral CT venography compared
with conventional venography in diagnosis. Radiology 1996;200:
423–428.
18. Brink JA, Lim JT, Wang G, et al. Technical optimization of spiral CT
for depiction of renal artery stenosis: in vitro analysis. Radiology
1995;194:157–163.
19. Galanski M, Prokop M, Chavan A, et al. Renal artery stenoses: spiral
CT angiography. Radiology 1993;189:185–192.
20. Gavant ML, Menke PG, Fabian T, et al. Blunt traumatic aortic
rupture: detection with helical CT of the chest. Radiology
1995;197:125–133.
21. Lawrence JA, Kim D, Kent KC, et al. Lower extremity spiral CT
angiography versus catheter angiography. Radiology 1995;194:
903–908.
22. Remy-Jardin M, Remy J, Deschildre F, et al. Diagnosis of pulmonary
embolism with spiral CT: comparison with pulmonary angiography
and scintigraphy. Radiology 1996;200:699–706.
23. Rubin GD, Walker PJ, Napel S, et al. Spiral CT of renal artery
stenosis: comparison of three-dimensional rendering techniques.
Radiology 1994;190:181–189.
24. Sostman HD, Layish DT, Tapson VF, et al. Prospective comparison
of helical CT and MR imaging in clinically suspected acute pulmonary embolism. J Magn Reson Imaging 1996;6:275–281.
25. Winter TC III, Freeny PC, Nhgiem HV, et al. Hepatic arterial anatomy in transplantation candidates: evaluation with three-dimensional CT arteriograms. Ra
26. Zeman RK, Berman PM, Silverman PM, et al. Diagnosis of aortic
dissection: value of helical CT with multiplanar reformation and
three-dimensional rendering. AJR Am J Roentgenol 1995;164:1375–
1380.
27. Anderson CM, Saloner D, Tsuruda JS, et al. Artifacts in maximumintensity-projection display of MR angiograms. Am J Roentgenol
1990;154:623–629.
28. Leung DA, McKinnon GC, Davis CP, et al. Breath-hold, contrastenhanced, three-dimensional MR angiography. Radiology 1996;
201:569–571.
29. Stehling MK, Lawrence JA, Weintraub JL, et al. CT angiography:
expanded clinical applications. Am J Roentgenol 1994;163: 947–955.
30. Laissey JP, Faraggi M, Lebtahi R, et al. Functional evaluation of
normal and ischemic kidney by means of gadolinium-DOTA enhanced TurboFLASH MR imaging: a preliminary comparison with
99
Tc-MAG3 dynamic scintigraphy. Magn Reson Imaging 1994;12:
13–19.
31. Rodgers PM, Ward J, Baudouin CJ, et al. Dynamic contrast-enhanced MR imaging of the portal venous system: comparison with
x-ray angiography. Radiology 1994;191:741– 745.
32. Hartnell GG, Finn JP, Zennie M, et al. MR imaging of the thoracic
aorta: comparison of spin-echo, angiographic, and breath-hold
techniques. Radiology 1994;191:697–704.
33. Nienaber CA, von Kodolitsch Y, Nicolas V, et al. The diagnosis of
thoracic aortic dissection by noninvasive imaging procedures. N
Engl J Med 1993;328:1–9.
34. Krinsky G, Rofsky N, Flyer M, et al. Gadolinium-enhanced three
dimensional MR angiography of acquired arch vessel disease. AJR
Am J Roentgenol 1996;167:981–987.
35. Gefter WB, Hatabu H, Holland GA, et al. Pulmonar y thromboembolism: recent developments in diagnosis with CT and MR imaging.
Radiology 1995;197:561– 574.
36. Executive Committee for the Asymptomatic Carotid Atherosclerosis
Study. Endarterectomy for asymptomatic carotid artery stenosis.
JAMA 1995;273:1421–1428.
37. Ferguson GG. Current status of prospective, randomized trials of
symptomatic carotid bifurcation disease. Semin Vasc Surg 1995;
8:46–54.
38. Patel MR, Kuntz KM, Klufas RA, et al. Preoperative assessment of
the carotid bifurcation: can magnetic resonance imaging and duplex ultrasonography replace contrast angiography? Stroke 1995;
26:1753–1758.
39. Lustgarten JH, Solomon RA, Quest DO, et al. Carotid endarterectomy after noninvasive evaluation by duplex ultrasonography and
magnetic resonance angiography. Neurosurgery 1994;34:612–618.
40. Drutman J, Gyorke A, Davis WL, et al. Evaluation of subclavian steal
with two-dimensional phase contrast and two-dimensional time-offlight MR angiography. Am J Neuroradiol 1994;15: 1642–1645.
41. Link J, Brossman J, Grabener M, et al. Spiral CT angiography and
selective digital subtraction angiography of internal carotid artery
stenosis. Am J Neuroradial 1996;17:89–94.
diology 199
5;195:363–370.
Соседние файлы в папке Библиотека им академика М.И. Перельмана