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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.

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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.

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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.

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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.

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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.

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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.

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Studies in 28 traumatized cats showed the following acute changes after spinal cord compression in the cord segment below the trauma: 1) increase in size of the spinal cord evoked potential; 2) increase in size of the electrospinogram; and 3) increase in frequency of the electrospinogram.

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