Magnetic resonance imaging of pelvic tumors in children.

Pelvic tumors in children may be large, complex and of unknown origin. Preoperative radiological information regarding tumor localization and extent becomes essential in these cases for proper staging and surgical planning. Magnetic resonance imaging (MRI) offers the ability to enhance the surgical preparation of children who present with a pelvic mass. Advantages of MRI over computerized tomography include improved soft tissue characterization, signal enhancement of neuroendocrine tumors and multiplanar imaging. These features better define the origin, size and extent of tumors. In addition, no ionizing radiation is required. Several examples of pelvic tumors are presented. The new anatomical information provided by MRI altered surgical planning previously based on computerized tomography findings alone.

Transcranial Doppler assessment of cerebral perfusion reserve in patients with carotid occlusive disease and no evidence of cerebral infarction.

Using transcranial Doppler ultrasound (TCD), we measured bilateral middle cerebral artery mean blood flow velocities (MCAVs) before and 10 minutes after intravenous infusion of 1 gram of acetazolamide in 20 patients without cerebral infarction. Seven patients had normal carotid arteries (group 1), seven had unilateral internal carotid artery (ICA) stenosis > or = 75% (group 2), and six had unilateral ICA occlusion (group 3). Before acetazolamide infusion, side-to-side differences in MCAV were 0.06 cm/sec in group 1 (p = 0.98), 4.3 cm/sec in group 2 (p = 0.36), and 15.0 cm/sec in group 3 (p = 0.02). Bilateral MCAV increased in all three groups after acetazolamide infusion, and the side-to-side differences in MCAV were 3.2 cm/sec in group 1 (p = 0.40), 11.4 cm/sec in group 2 (p = 0.04), and 27.6 cm/sec in group 3 (p = 0.03). Patients with carotid stenosis or occlusion and ipsilateral transient ischemic attacks (TIAs) had higher side-to-side differences in MCAV before (p = 0.03) and after (p = 0.01) acetazolamide than did asymptomatic patients with carotid disease. The association of impaired cerebral perfusion reserve and TIAs suggests that the TCD-acetazolamide test may enable identification of a subgroup of patients with carotid occlusive disease who are at higher risk for stroke.

Comparison of transcranial Doppler ultrasound and transesophageal contrast echocardiography in the detection of interatrial right-to-left shunts.

Transesophageal contrast echocardiography is an effective but semiinvasive technique for the detection of interatrial right-to-left shunts. Transcranial Doppler ultrasound is an alternative noninvasive method, but may be limited by false-positive diagnoses due to intrapulmonary shunting. This study examined the accuracy of transcranial Doppler for the detection of shunt lesions. Transcranial Doppler of the right middle cerebral artery was performed simultaneously with transesophageal and transthoracic contrast echocardiography in 32 patients using agitated saline contrast during normal respiration and Valsalva. Transesophageal contrast echocardiography diagnosed an interatrial right-to-left shunt in 13 patients and intrapulmonary shunting in 6 patients. Transcranial Doppler identified all 13 interatrial right-to-left shunts and an intrapulmonary shunt in 3 of 6 patients. Absence of a shunt was confirmed by transcranial Doppler in 12 of 12 patients. Transcranial Doppler had a sensitivity of 100% (13 of 13), specificity of 100% (18 of 18) and accuracy of 100% (31 of 31) for prediction of an interatrial right-to-left shunt by transesophageal contrast echocardiography. In comparison, transthoracic contrast echocardiography had a sensitivity of 54% (7 of 13), specificity of 94% (17 of 18) and accuracy of 77% (24 of 31). Thus, transcranial Doppler is highly accurate for detection of an interatrial right-to-left shunt and not compromised by physiologic intrapulmonary shunts, whereas transthoracic contrast echocardiography lacks sensitivity. Transcranial Doppler may be useful as an alternative to transesophageal study, where the primary indication for transesophageal echocardiography is exclusion of an interatrial right-to-left shunt.

Transcranial Doppler ultrasound identifies patients with right-to-left cardiac or pulmonary shunts.

We performed transcranial Doppler ultrasound (TCD) and transesophageal contrast echocardiography simultaneously in four patients. In one patient with a patent foramen ovale and another patient with pulmonary A-V fistulae, we detected micro air bubbles in the right middle cerebral artery three to five cardiac cycles after their appearance in the left atrium following intravenous injection of contrast. In two patients without right-to-left shunts, we did not detect air bubbles in the left atrium or middle cerebral artery following injection of contrast. These results show that TCD can identify patients with right-to-left cardiac or pulmonary shunts.

Magnetic resonance imaging of cutaneous neoplasms: clinicopathologic correlation.

Recently, magnetic resonance imaging (MRI) has been reported to be clinically useful, in selected cases, in patients with melanocytic skin lesions. This report describes good resolution, clinically useful MRI scans of squamous cell carcinoma, dermatofibroma, and primary cutaneous B-cell lymphoma. The tumor depth measured by MRI was in excellent correlation with Breslow's depth measurements, indicating that MRI is probably the radiologic technique of choice for preoperative evaluation of the extent and depth of primary and recurrent skin tumors. This report also provides the authors' recommendations for obtaining optimal MRI images of cutaneous lesions.

Magnetic resonance imaging for assessment of vena caval tumor thrombi: a comparative study with venacavography and computerized tomography scanning.

We assessed the accuracy of magnetic resonance imaging in demonstrating the presence and extent of vena caval tumor thrombi. The study group included 20 patients with vena caval thrombi from renal cell carcinoma (18), renal pelvic transitional cell carcinoma (1) and adrenal pheochromocytoma (1). Preoperative diagnostic studies included magnetic resonance imaging in all patients, inferior venacavography in 16 and computerized tomography scanning in 15. All patients underwent an operation in which the presence and extent of the vena caval thrombus were confirmed. Magnetic resonance imaging accurately delineated the presence and extent of the thrombus in all 20 patients (100%). Venacavography was accurate in 15 patients (94%) but 8 (50%) required a retrograde and antegrade study. Computerized tomography scanning demonstrated the presence of a tumor thrombus in all 15 patients but accurately delineated the cephalad extent of the thrombus in only 5 (33%). In patients with vena caval tumor thrombi magnetic resonance imaging can provide accurate information regarding the extent of vena caval involvement while avoiding the need for an invasive contrast imaging study.

Right renal mass with vena caval thrombus.

This case illustrates the difficulties that sometimes occur in the evaluation of patients with a nonfunctioning kidney. Because of the clinical presentation, suggestive of renal cell carcinoma, no urinary cytology study was obtained from the affected kidney. This study certainly would have led to the correct diagnosis. Despite this fact, the operative management would not have changed except for complete removal of the ureter. In our case we elected to follow the distal ureter by ureteral washings and ureteroscopy during follow-up cystoscopy studies to preclude a further operation. Although no data are available on the role of adjuvant therapy in these patients, because of the poor prognosis associated with such extensive disease we gave our patient 2 courses of M-VAC in an attempt to prevent progression of the disease.

Abdominal radiograph and renal ultrasound versus excretory urography in the evaluation of asymptomatic patients after extracorporeal shock wave lithotripsy.

A prospective study was done to compare the relative efficacy of an abdominal radiograph and renal ultrasound to excretory urography for the evaluation of asymptomatic patients 1 month after extracorporeal shock wave lithotripsy. We evaluated 101 renal units in 84 asymptomatic patients who had undergone extracorporeal shock wave lithotripsy 1 month previously with abdominal radiography, excretory urography and ultrasonography to evaluate the presence of retained stone fragments, dilatation of the collecting system and intrarenal or perirenal fluid collections or masses. The combination of abdominal radiography and ultrasonography identified retained fragments in 62 renal units, while excretory urography identified them in 54. Ultrasonography was less specific in identifying dilatation of part or all of the collecting system; proving falsely positive in 7 renal units and falsely negative in 14 compared to excretory urography. However, the case of obstruction was diagnosed correctly by both modalities. Finally, ultrasound appeared to be more specific and more sensitive in the evaluation of the presence of intrarenal or perirenal abnormalities. We conclude that a combination of abdominal radiography and ultrasonography is as good or better than excretory urography in identifying residual stone fragments and intrarenal or perirenal abnormalities. However, the finding of dilatation of all or part of the collecting system by ultrasonography is nonspecific and probably is better evaluated by excretory urography. We suggest that the routine radiological evaluation of asymptomatic patients 1 month after extracorporeal shock wave lithotripsy could be limited routinely to abdominal radiography and ultrasonography. However, when abnormalities of the collecting system are visualized on these studies excretory urography should be performed.

Adrenal imaging. Computed tomographic scanning and magnetic resonance imaging.

On the basis of this review and others, adrenal imaging using MRI requires functional biochemical data, such as scintigraphy (NP-59 and MIBG), for cortical adrenal assessment. For medullary hyperfunction such as intra-adrenal pheochromocytomas and neuroblastomas, MRI provides excellent staging and localization. Computed tomography is preferred for biochemically established hyperfunction such as Cushing's and Conn's syndromes.

Magnetic resonance imaging of cutaneous melanocytic lesions.

This is the first literature report on magnetic resonance imaging (MRI) examination of cutaneous melanocytic or any other type of skin lesions. Good resolution, clinically useful MRI scans of a congenital nevus and a metastatic melanoma to the skin are presented. The potential usefulness of MRI technique to physicians dealing with cutaneous disease is discussed.

The role of magnetic resonance imaging in the staging of bladder carcinoma.

The clinical staging of bladder carcinoma traditionally has relied on transurethral resection of the bladder tumor, urinary cytology, excretory urography and an examination with the patient under anesthesia. Recent evidence has shown magnetic resonance imaging to be effective in the staging of bladder cancer. Whether magnetic resonance imaging is more accurate than conventional clinical staging techniques has not been answered. To determine the usefulness of magnetic resonance imaging in this regard 34 patients with bladder carcinoma underwent staging by this technique before radical cystectomy. The magnetic resonance imaging stage and conventional clinical stage were compared to the final pathological stage. Magnetic resonance imaging had an over-all accuracy of 50 per cent versus 57 per cent for conventional staging techniques and it identified 2 of 5 patients with nodal disease. To date magnetic resonance imaging does not appear to be better than conventional clinical staging techniques in patients with bladder carcinoma.

The association of neuroblastoma with myoclonic encephalopathy of infants: the use of magnetic resonance as an imaging modality.

The association of neural crest tumors with myoclonic encephalopathy of infants has been well described. Since these tumors often are clinically occult the diagnostic modalities used to identify these lesions need to be sensitive. We describe a child with neuroblastoma associated with infantile myoclonic encephalopathy in whom magnetic resonance imaging identified the lesion while other techniques were unable to demonstrate a mass clearly. Magnetic resonance imaging should be considered as a diagnostic modality when adrenal lesions are suspected but not apparent with other imaging techniques.

Evolving focal cerebral ischemia in cats: spatial correlation of nuclear magnetic resonance imaging, cerebral blood flow, tetrazolium staining, and histopathology.

The spatial correlation of nuclear magnetic resonance imaging (NMRI) and cerebral blood flow (CBF) may improve our ability to identify ischemic brain lesions and may provide further insight into the pathophysiology of early cerebral ischemia. Eleven pentobarbital-anesthetized adult cats underwent exposure of the common carotid arteries bilaterally and the right middle cerebral artery through a transorbital approach. Baseline NMRI images were obtained with a single spin-echo, multislice technique using a 0.6-T field, 0.4-cm slice thickness, and a surface coil. Focal ischemia was produced with right middle cerebral artery occlusion and potentiated with bilateral common carotid artery ligation. Sequential NMRI studies were then performed at 1, 2, 4, 6, and 12 hours or until CBF was determined in the same cats using [14C]iodoantipyrine at either 2 (n = 2), 4 (n = 2), 6 (n = 2), or 12 (n = 1) hours after the time of occlusion. This protocol allowed temporal and spatial correlation of NMRI and CBF. Alternate 5-mm brain slices were incubated with 1% 2,3,5-triphenyltetrazolium chloride (TTC) for 45 minutes at 37-41 degrees C and frozen in liquid Freon for later autoradiographic CBF determination. Four cats were studied only with NMRI and TTC (not CBF). The correlation between areas of increased NMRI signal intensity observed in T2-weighted images (repetition time 2,000 msec, echo time 120 msec), vital staining with TTC, low CBF, and routine histology was evaluated. During the early phase (less than 6 hours), T2-weighted NMRI changes were localized to the central ischemic gray matter areas, as defined in the later CBF images, with no involvement of the white matter. By the twelfth hour the NMRI changes involved the entire ischemic area including gray and white matter. The initial visible changes seen on T2-weighted NMRI are suggestive of cellular edema, and the later changes are characteristic of vasogenic edema. The spread of NMRI changes compared with the ischemic area determined from autoradiographic CBF is consistent with the previously described biphasic evolution of ischemic injury. These data suggest that T2-weighted NMRI could be used clinically to delineate areas of acute ischemic stroke.

Cranial postoperative site: MR imaging appearance.

The ability to diagnose adverse postcraniotomy or postcraniectomy events is essential for proper postoperative care. The importance of identifying postoperative changes on CT has previously been shown. The purpose of this study is to assess the normal and abnormal MR changes that may be seen in the postcraniotomy/postcraniectomy period. The postoperative MR, CT, and medical records of 41 postcraniotomy patients and 26 postcraniectomy patients were reviewed. Reasons for choosing craniectomy over craniotomy included decompression, infected flap, bony involvement by tumor, and posttraumatic skull. In general, the postoperative normal anatomy was better seen with MR. Postoperative events included hemorrhage (two), infection (five), cyst formation (10), and recurrent tumor (five). In general, MR was found to be more useful than CT for the detection of hemorrhage and infection after craniotomy or craniectomy and for the proper localization of postoperative cysts. MR proved to be a useful method for following postoperative sites in the skull.

Magnetic resonance signal intensity patterns obtained from continuous and pulsatile flow models.

The purpose of this investigation was to extend previous steady state flow studies with magnetic resonance (MR) to pulsatile flow measurements obtained with gated cardiac techniques in man with a pulsatile artificial heart device. Bovine blood and a solution of MnCl2 were studied. Correlation was made with complex and time-varying MR signals observed in the descending aorta on cardiac gated images obtained through the midthorax. MR signals from flowing fluids represent velocity distribution as shown in a velocity profile, and laminar flow is distinguished from nonlaminar. At very slow flow rates, signal intensity is lower than background. As the rate is increased, paradoxical enhancement occurs followed by loss of signal, which is complete at 7 liters per minute with fluid and 15 liters per minute with blood. These areas correspond to maximum fluid velocities of 41 and 88 cm/sec, respectively.

Intracranial pressure telemetry system. I. Hardware development.

Results in the development of intracranial pressure(ICP) telemetry systems are reported. Included are a single-channel ICP system and a two-channel ICP and temperature system. The unit used hybrid-integrated circuits housed in a Kovar flatpack and packaged with polyurethane or Hysol epoxy. Battery and radio frequency (RF) induction power supplies were tested. The two-channel systems used RF power at 3.5 MHz and transmitted signals around 120 MHz. The package measures 3 x 2 x 0.8 cm and weighs 9 g. The pressure range is -20 to +100 mm Hg with accuracy to 1.0 mm Hg. The implant measures absolute pressure and has a baseline stability of better than +/- 2 mm Hg/month. 17 dogs and 4 goats were used for in vivo evaluation. A summary of results is presented. Detailed evaluation is given in section II of this paper.

Intracranial pressure telemetry system. II. Animal testing.

A small, implantable, telemetric device for the long-term monitoring of intracranial pressure has been described in part I of this article. This portion of the study is designed to demonstrate the in vivo operational characteristics of that implant device in experimental animals. Results indicate that this system can provide long-term in vivo operation with rapid and accurate responses to acute changes in pressure. Data also indicate some drift in the baseline measurement of pressure. No signs of abnormal body reactions to the units were observed.