Cranial arteriovenous malformations in neonates: color Doppler imaging with angiographic correlation

Five neonates with cranial arteriovenous malformations were studied with color Doppler sonography. Excellent correlation was found between sonography and subsequent angiography. In three patients with vein of Galen aneurysms, sonography showed a cystic structure with rapid or swirling flow. Careful adjustment of the color Doppler system was required to demonstrate flow in another patient with a dural arteriovenous malformation. An arteriovenous fistula in a fifth patient appeared as an area of increased flow. Arterial feeders and major draining veins were visualized in all five patients. Color Doppler imaging also was used to assess the effect of embolic or operative therapy in three of the patients. We conclude that color Doppler sonography is able reliably to characterize flow patterns in neonatal cranial arteriovenous malformations. Color Doppler imaging also is helpful in assessing flow after embolic or surgical therapy.     

MR imaging of dural arteriovenous malformations with ocular signs

Summary Four patients with dural arteriovenous malformation (AVMs) draining into the cavernous sinus, who presented ophthalmic manifestations, were studied by magnetic resonance (MR) imaging. In all patients signal decrease in the involved cavernous sinus was demonstrated in coronal spinecho (SE) imaging. It is attributable to rapid venous flow in the sinus, and this high velocity signal loss is a fairly pathognomonic finding in this condition. We stress the validity of MR imaging in the primary diagnosis of dural AVMs with ophthalmic symptoms.     

Pulmonary arteriovenous malformations: diagnosis by gradient-refocused MR imaging

Six known or suspected pulmonary arteriovenous malformations (AVMs) in four patients were evaluated with magnetic resonance (MR) imaging at 1.5 T. All lesions were imaged using a gradient-refocused echo pulse sequence with a 25/13 ms [repetition (TR)/echo (TE) times] and a 30 degrees flip angle, as well as with a cardiac-gated spin echo short TR/TE pulse sequence technique. Five of the lesions were vascular in nature based on their signal intensity characteristics, and one nonvascular lesion was a carcinoid tumor. On the spin echo images, the AVMs showed a central signal intensity void with a peripheral rim of intermediate signal intensity that was detectable for lesions greater than or equal to 1.5 cm in size. Smaller lesions were more difficult to distinguish from the surrounding air-filled lung, which normally generates no appreciable signal on MR images. The AVMs demonstrated uniform high signal intensity on the gradient echo pulse sequence and were more conspicuous, irrespective of size. With a single breath-hold scan, the vascular nature of the lesion could be rapidly confirmed with an acquisition time of 13 s. In three patients, the cine MR gradient echo images showed a pulsatile quality to the signal intensity in the lesion over the cardiac cycle similar to that within adjacent pulmonary vessels. The results of this study show a potential role for gradient echo MR imaging as a rapid, noninvasive method to evaluate the vascular nature of an atypical pulmonary nodule.     

Hepatocellular carcinoma: evaluation with color Doppler US and MR imaging.

Fifteen patients with hepatocellular carcinoma underwent examination with color Doppler ultrasound (US), magnetic resonance (MR) imaging, dynamic computed tomography (CT), and angiography. Doppler signals ranging from 0.22 to 3.48 kHz could be obtained from within the tumor in 14 of 15 patients. The resistive index was 0.38-0.77. Color Doppler signals were visualized in nine of 15 lesions with a Doppler shift greater than 0.7 kHz. The Doppler signals and the resistive index of the tumor vessels became lower as the vessels progressed into the center of the lesion. The appearance of tumor vessels recognized on MR images obtained with gradient-recalled acquisition in the steady state (GRASS) in 11 of 15 lesions was compared with that on CT scans and angiograms. Tumors that were hyperintense on GRASS images obtained with a flip angle of 15 degrees transmitted Doppler signals of considerably higher amplitude compared with the isointense lesions. Both color Doppler US and MR imaging provided useful information for characterizing intratumoral blood flow.     

Doppler US gating of cardiac MR imaging

RATIONALE AND OBJECTIVES: Electrocardiographic (ECG) gating of cardiac magnetic resonance (MR) imaging has been problematic for many reasons. The purpose of this study was to demonstrate the feasibility of using Doppler ultrasound (US) gating, either directly off the moving cardiac wall or the systolic upstroke of the arterial signal from the great vessels in neck, in alternative gating modes. MATERIALS AND METHODS: A 2.5-MHz, range-gated Doppler US device was used with A-mode guidance for gating directly off left ventricular wall motion. A 4- or 8.1-MHz, continuous-wave (CW) Doppler US device was used for gating off the systolic upstroke from the great vessels in the neck. The subject undergoing imaging held the transducer against his chest for range-gated Doppler US and against his neck for 8.1-MHz CW Doppler US. The 4-MHz transducer was strapped to the subject's neck. Modified Doppler signals were fed back into the gating circuitry of the MR imager to achieve cardiac synchrony. RESULTS: Cardiac gating was achieved by using both the range-gated technique directly off the cardiac wall and the CW method off blood flow from the great vessels. Problems occurred with radiofrequency shielding during the range-gated method; however, these problems were almost completely removed by use of the CW Doppler probes. CONCLUSION: Doppler US gating of MR images is possible and potentially could overcome many shortcomings of ECG gating. Subsequent embodiments of the technique will require improved radiofrequency shielding in the range-gated technique.     

MR imaging of liposarcomas: correlation of MR features and histology

The magnetic resonance (MR) imaging features of liposarcoma were correlated with histology in 15 patients. The MR findings for liposarcoma were not specific. The six myxoid liposarcomas and two atypical lipomatous tumors, however, had distinctive MR features, i.e., nodular masses of slightly heterogeneous intermediate to high signal intensity (SI), intermingled with high SI septa on T1-weighted images. The T2-weighted images demonstrated the relative reversal of these regional SI characteristics. Additionally, MR correctly identified the presence of fat in all eight cases in which it was pathologically present. The fat in two atypical lipomatous tumors was inseparable on MR from the subcutaneous fat. Magnetic resonance appears useful for preoperative staging and follow-up studies of liposarcomas. It may be helpful in identifying patients with myxoid liposarcoma and atypical lipomatous tumors who have longer survival times.     

子宫腺肌症的MRI表现及其病理学对照研究

目的：研究MRI在子宫腺肌症诊断中的应用价值。方法：对30例子宫腺肌症患者行矢状面快速自旋回波（Turbo SE)T1WI,T2TI,T1和T2频谱预饱和翻转恢复序列（T1SPIR和T2SPIR）扫描，必要时辅以横断面或冠状面扫描。所有病例均经手术病理证实。结果：弥漫型子宫腺肌症12例，在T2WI上表现为子宫结合带弥漫性增厚，厚度10－35mm，平均18mm，6例病变呈均匀低信号；6例病变内有散在的点高信号区，其中5例在T1WI仍表现为高信号。局限型子宫腺肌症（腺肌瘤）18例共23个病灶，在T2WI上表现为肌层内卵圆形，不规则形或类圆形肿块，呈与结合带信号相近的低信号，直径2．0－7.5cm，平均3.9cm，除1个病灶与周围肌组织有较清楚的界限外，其余病灶均与周围肌组织分界不清，15个病灶内有散在点状高信号区，其中12个在T1WI上也呈高信号，MRI上弥漫增厚的结合带和局限性低信号肿块，病理学上为异位内膜岛周围增生肥大的平滑肌，其内散在的点状信号区异异位内膜岛。仅在T2WI表现高信号的为示出血的内膜岛，在T1WI和T2WI均为高信号的为出血的内膜岛。结论：MRI是诊断子宫腺肌症的优越的无创性检查方法，T2WI最佳扫描序列，T2WI与T1WI，T1SPIR，T2SPIR4种序列相结合可大大提高断诊准确率。     

Uterine arteriovenous malformations: primary treatment with therapeutic embolization.

Uterine arteriovenous malformations are rare lesions that can cause massive vaginal bleeding and spontaneous abortions. The majority are either congenital or related to gestational trophoblastic disease. Hysterectomy has been the treatment with symptomatic uterine arteriovenous malformations by means of transcatheter embolization; three of the lesions were related to gestational trophoblastic disease and one was congenital. All were supplied by the uterine arteries that were subselectively embolized with particulate material. This resulted in prompt cessation of uterine hemorrhage. There were no complications, and one pregnancy was achieved. The three other women have normal menstruation and no recurrence of bleeding at follow-up 10-48 months after treatment. On the basis of this experience and that of others, embolotherapy should be the treatment of first choice in these lesions, as it appears safe and effective. Additionally, uterine function is preserved in patients who are usually reproductively active.     

Renal arteriovenous malformations: CT features

The CT and clinical features of six patients with congenital renal arteriovenous malformation (RAVM) were reviewed to determine the characteristics of this condition. The most common symptom was hematuria. The CT images were characterized by masses of vascular density located in the renal sinus and surrounding the pelvicaliceal system with or without dilated renal veins. The exact size of the RAVM and the relation to the pelvicaliceal system were well demonstrated by delayed images or drip infusion technique, whereas the bolus injection technique was essential to document the vascular nature. The potential pitfalls in diagnosis that can occur if only an infusion study is performed are discussed.     

Renal allograft rejection: evaluation by Doppler US and MR imaging

A prospective study compared the efficacy of Doppler ultrasonography (US) and magnetic resonance (MR) imaging in evaluating 38 renal allografts, with specific attention to transplant rejection. Forty-three Doppler US and 42 MR examinations were performed and interpreted. Histologic correlation was obtained from 22 biopsy or nephrectomy specimens. Clinical correlation or a response to instituted therapy was used as confirmation in the remaining allografts. Accuracy in identifying cyclosporine toxicity or acute tubular necrosis could not be evaluated because there were few such cases, with concomitant rejection in most. The ability to predict and identify presence or absence of rejection was not affected by different serum creatinine values. Doppler US was significantly superior to MR imaging in identifying allograft rejection, demonstrating a higher sensitivity (95% vs. 70%), specificity (95% vs. 73%), and accuracy (95% vs. 71%). Because of its low cost and accessibility, Doppler US should become the primary modality for renal transplant screening.     

Uterine junctional zone: correlation between histologic findings and MR imaging.

Uterine zonal anatomy as visualized on T2-weighted (repetition time, 2,500 msec; echo time, 80 msec) magnetic resonance (MR) images consists of a high-intensity central (endometrial) zone, a subjacent low-intensity junctional zone of myometrium, a moderately intense zone of myometrium, and a thin, low-intensity subserosal zone of myometrium. To better define the histologic correlates of these diagnostically significant zones, T2-weighted MR images of 17 in vivo and 13 extirpated human uteri were compared with histologic sections of 17 uteri stained with hematoxylin-eosin, Mallory trichrome, and immunofluorescence staining for actin. Morphometric and electron microscopic observations of uterine surgical specimens were also made. The observations indicate that both the junctional zone and the subserosal zone consist of compact smooth muscle fibers with little extracellular matrix compared with the myometrium proper. Also, the junctional zone is divided into a compact region and a transitional region. The compact region correlates well with the hypointense MR appearance of the junctional zone.     

Contrast-enhanced MR perfusion imaging and MR angiography: utility for management of pulmonary arteriovenous malformations for embolotherapy

Objective: The purpose of this study was to assess the capability of MR perfusion imaging and angiography (MRA) for management of pulmonary arteriovenous malformation (PAVM). Methods and patients: Eight patients, having 15 PAVMs underwent pulmonary angiography (PAG), CT, MR perfusion imaging and MRA. For the pretherapeutic management, MRA was compared with PAG and CT regarding detectability and diameter of vasculature. For post-therapeutic management, the change in size of aneurysmal sac, any residual contrast-enhancement and the blood supply within the sac were evaluated. Results: All PAVMs with aneurysmal sac, feeding artery and draining vein diameters of equal to or more than 3 mm, were identified and measured with similar results by all modalities. On follow-up studies, 7 (58.4%) out of 12 treated PAVMs showed a decrease in size and residual contrast-enhancement. The residual contrast-enhancement was considered as bronchial artery-to-pulmonary artery collateral flow by MR perfusion imaging. Conclusion: MR perfusion imaging and MRangiography are useful for management of PAVMs over 3 mm in diameter.     

Uterine neoplasms: MR imaging

Magnetic resonance (MR) studies were performed on 20 healthy volunteers and 41 patients with proved cervical and uterine neoplasms. MR imaging demonstrated normal uterine landmarks in all patients. On T2-weighted images, the normal uterine wall could be differentiated into three distinct layers: a central high-intensity zone, a junctional low-intensity band, and a peripheral medium-intensity area. While most of the normal cervices had only two distinct zones (central high-intensity zone and peripheral low-intensity zone), a small percentage had three layers of signal intensity, similar to the uterine body. Primary cervical and uterine neoplasms could be identified on MR images. In 18 of 22 patients with proved carcinoma, a mass with a signal intensity higher than that of normal cervical lips was seen on T2-weighted images. Endometrial carcinoma was most often identified as expansion of the central high-intensity area; discrete tumor nodules were visible in nine of 15 patients. Mixed müllerian sarcoma appeared as a large pelvic mass with complete obliteration of normal uterine landmarks. MR imaging delineates primary cervical and endometrial carcinoma better than computed tomography does.     

Measurement of aortic blood flow with MR imaging: comparative study with Doppler US

An innovative magnetic resonance imaging technique was applied to the measurement of blood flow in the abdominal aorta. The technique combines selective excitation and visualization from an orthogonal view. The distance that fluid has moved is directly visualized. The blood flow velocity at every 50 msec throughout the cardiac cycle was measured in a short time (about 4 minutes) using electrocardiographic gating and repeated excitations in each cycle. Measurements were compared with those obtained by Doppler ultrasound (US) as a reference. The pulsatile change of flow velocity in the cycle correlated well with the Doppler US recording. Two flow velocity indexes, peak flow velocity and the velocity integral, also showed good correlation (r = .98 for both). This method is applicable for clinical use and is useful for measurement of high flow rates, as found in arteries.