Optical Control of a Single Nuclear Spin in the Solid State.

We demonstrate a novel method for coherent optical manipulation of individual nuclear spins in the solid state, mediated by the electronic states of a proximal quantum emitter. Specifically, using the nitrogen-vacancy (NV) color center in diamond, we demonstrate control of a proximal ^{14}N nuclear spin via an all-optical Raman technique. We evaluate the extent to which the intrinsic physical properties of the NV center limit the performance of coherent control, and we find that it is ultimately constrained by the relative rates of transverse hyperfine coupling and radiative decay in the NV center's excited state. Possible extensions and applications to other color centers are discussed.

Phonon-induced population dynamics and intersystem crossing in nitrogen-vacancy centers.

We report direct measurement of population dynamics in the excited state manifold of a nitrogen-vacancy (NV) center in diamond. We quantify the phonon-induced mixing rate and demonstrate that it can be completely suppressed at low temperatures. Further, we measure the intersystem crossing (ISC) rate for different excited states and develop a theoretical model that unifies the phonon-induced mixing and ISC mechanisms. We find that our model is in excellent agreement with experiment and that it can be used to predict unknown elements of the NV center's electronic structure. We discuss the model's implications for enhancing the NV center's performance as a room-temperature sensor.

Quantum interference of single photons from remote nitrogen-vacancy centers in diamond.

We demonstrate quantum interference between indistinguishable photons emitted by two nitrogen-vacancy centers in distinct diamond samples separated by two meters. Macroscopic solid immersion lenses are used to enhance photon collection efficiency. Quantum interference is verified by measuring a value of the second-order cross-correlation function g((2))(0)=0.35±0.04<0.5. In addition, optical transition frequencies of two separated nitrogen-vacancy centers are tuned into resonance with each other by applying external electric fields. An extension of the present approach to generate entanglement of remote solid-state qubits is discussed.

Experimental catheter obstruction of the gastric coronary vein. Possible technique for percutaneous intravascular tamponade of the gastroesophageal varices.

Experimental catheter obstruction of the left gastric (coronary) vein was explored in 10 dogs. Using a transjugular approach, the liver was punctured and the portal vein catheterized. Coaxially introduced catheters were then used to catheterize selectively and produce an intravascular obstruction (tamponade) of the gastric coronary vein. Ballon catheters were used for a temporary occlusion. Injection of a tissue adhesive, isobutyl 2-cyanoacrylate, was used for a definitive obliteration. The achieved results show the anatomical feasibility of this approach and give good perspective for development of a clinical method for percutaneous intravascular tamponade of the bleeding gastroesophageal varices in cirrhotics.

Gallstone susceptibility to in vitro fragmentation by a 480-nm pulsed dye laser. Correlation with computed tomography characteristics.

The object of this investigation was to determine gallstone susceptibility to laser lithotripsy and to discover whether this susceptibility is related to the computed tomography (CT) appearance of gallstones. Gallstones collected from surgery were scanned by CT and classified as homogeneously dense (greater than 90 Hounsfield units [HU]), homogeneously faint (30-60 HU), or rimmed. Sixty stones were subjected to laser energy at 20, 40, 60, 80, or 100 mJ. Fracture and fragmentation (all particles less than 2 mm) were assessed in relation to the energy level setting and number of laser pulses delivered. The authors found that a 480-nm, flashlamp-pumped pulsed dye laser can fragment completely all the types of human gallstones that were tested, although there is significant variability in gallstone susceptibility to laser lithotripsy. This susceptibility varies with CT appearance: dense stones require fewer pulses and lower energies for fracture and fragmentation, compared to faint or rimmed stones. The authors anticipate that CT characterization of gallstones may be a clinically useful screening tool before laser lithotripsy.

Gastric infarction after therapeutic embolization.

A case of extensive gastric necrosis after therapeutic transcatheter embolization of the left gastric artery with fragments of gelatin sponge for recurrent massive upper gastrointestinal hemorrhage is reported. Although future modifications in technique and in choice of embolic agents undoubtedly will be forthcoming, postembolic ischemic necrosis may prove to be a major limitation of this technique. Until more widespread experience is accumulated and the frequency of postembolic ischemic necrosis is known, it would seem prudent to reserve this procedure for those patients presenting prohibitive surgical risks.

Renal vascular hypertension during pregnancy.

We report two women with renal artery stenosis in pregnancy. The first patient presented with severe hypertension in the first and second trimesters characterized by an extremely high vascular resistance (maximum 2455 dyne.second.cm-5). Transluminal angioplasty was performed at 20 weeks' gestation, resulting in resolution of the patient's hypertension. After angioplasty, her vascular resistance fell to 1600 dyne.second.cm-5, but did not reach normal pregnant levels. The pregnancy was carried to term without complication. The second patient's hypertension improved during pregnancy, and she delivered at term without complication. Twelve weeks postpartum, the patient again became severely hypertensive, and transluminal angioplasty was performed.

Transcatheter embolization of renal arteriovenous fistula.

A patient with malignant hypertension and acute renal failure underwent percutaneous renal biopsy which resulted in the creation of an arteriovenous fistula that communicated with the renal pelvis. Successful segmental embolization with gelatin sponge (Gelfoam) was achieved via a transcatheter approach.

Epinephrine renal venography.

Experience with the use of epinephrine renal venography in 60 patients with various renal disease is reviewed. The technique offers an important supplement to selective arteriography. It is of particular value in the diagnosis of avascular infiltrative tumors of the renal parenchyma and pelvis. Further, it is of value in the detailed demonstration of renal vein thrombosis and in seeking the cause of unexplained gross hematuria. It can also aid in evaluating expansile avascular renal masses and renal parenchymal disease. The authors found only a relatively low value for epinephrine renal venography in the diagnosis of hypervascular renal tumors and the early detection of venous extension of hypernephromas.

Correction of hypersplenism without splenectomy.

Permanent interruption of splenic artery blood flow to the spleen was accomplished in a 4.5-yr-old girl with significant hypersplenism secondary to biliary cirrhosis. The splenic artery was successfully occluded by transfemoral catheterization and selective instillation of bucrylate tissue adhesive.

Computed tomography of the skeletal system.

Because of its sensitivity to minor variations in radiographic density and its ability to eliminate overlapping because of the cross-sectional display, computed tomography (CT) of the skeletal system may yield valuable information that may not be apparent on plain film or radionclide examination of bone lesions. The authors present five case illustrations in which CT examination of bone was particularly helpful in the evaluation of the patient.

Percutaneous transhepatic T-tube placement for antegrade biliary drainage: a new technique.

The authors describe a method involving percutaneous transhepatic placement of T tubes for patients with jaundice due to a malignant obstruction. These rubber tubes have a larger caliber than standard polyethylene catheters and consequently, provide better drainage, thus minimizing the the occurrence of cholangitis due to debris obstructing the drainage tube.

Epidural venography in the diagnosis of lumbar spinal stenosis.

Epidural venography is valuable in diagnosing lumbar spinal stenosis. It shows anterior displacement of the posterior medial longitudinal intervertebral veins at the level of the lamina and the superior and inferior articular facets. This results in decreased distance between and sometimes overlapping of the posterior and anterior medial longitudinal intervertebral veins. Three cases of spinal stenosis diagnosed by epidural venography are presented.

Instant selective arterial occlusion with isobutyl 2-cyanoacrylate.

Isobutyl 2-cyanoacrylate (IBC) delivered selectively in small doses produced immediate occlusion of the injected arteries in dogs without significant undesired sequelae. In one patient, pelvic hemorrhage was promptly stopped by a similar technique. In another patient, who was on chronic renal dialysis and judged too ill for nephrectomy, IBC occluded both renal arteries and terminated a life-threatening renal protein loss.

Transjugular obliteration of the gastric coronary vein.

The feasibility of transjugular entry into the portal vein for catheterization and obliteration of the left gastric vein is demonstrated in a human. This technique may play a significant role in the nonsurgical management of bleeding esophageal varices.

Complete interruption of the aorta in Noonan's syndrome.

A patient is presented who lived to age 60 with complete interruption of the aorta associated with Noonan's syndrome. On chest x-ray there were calcified mediastinal masses and bilateral rib notching. Angiography demonstrated complete interruption of the aorta with markedly dilated tortuous intercostal arteries. The roentgenographic studies are correlated with the surgical and pathological findings. Noonan's syndrome is discussed.

The role of duplex scanning in the selection of patients for transluminal angioplasty.

As part of our initial evaluation to determine whether patients with lower extremity ischemia are candidates for intervention, arterial duplex examinations are performed in the noninvasive vascular laboratory. Patients with isolated short stenoses on the duplex examination are referred for transluminal angioplasty. One hundred thirty-four arteriograms were performed for ischemic peripheral vascular disease in 122 patients between July 1987 and March 1990. One hundred ten (82%) of the arteriograms were preceded by a lower extremity arterial duplex evaluation. Fifty cases (45%) were scheduled for transluminal angioplasty based on the findings of the duplex examination. Transluminal angioplasty was performed in 47 of 50 cases (94%). No significant differences in age, sex, or diabetes were found between the patients who were referred for transluminal angioplasty and those who were not. These data demonstrate that duplex scanning of the lower extremities allows the detection of lesions that will be amenable to transluminal angioplasty. We think that duplex scanning should become the standard screening tool for detection of treatable lower extremity lesions.

Treatment of acute renal artery occlusion after percutaneous transluminal angioplasty.

Four patients with occlusive complications after percutaneous transluminal renal artery angioplasty (PTA) have been treated from July 1, 1984, to March 14, 1988. During this interval such renal artery angioplasties were performed in 44 patients. Two resulted in complete main renal artery occlusion, one angioplasty resulted in occlusion of a stenotic renal artery bypass graft, and one renal PTA resulted in segmental branch renal artery narrowing, which was thought to represent a dissection. The latter segmental renal artery narrowing was treated expectantly with good long-term results. One of the main renal artery occlusions was treated by radiologic means by reentry and repeat transluminal dilation. The other two acute complete occlusions, one of an autogenous artery and the other of an aortorenal bypass graft, were treated by aortorenal or ileorenal bypass grafting, respectively. The overall incidence of main renal artery occlusion (including the bypass graft occlusion) after PTA requiring operative intervention was 4.5% (2/44). Revascularization was accomplished after 6 and 8 hours of renal ischemia time for the two surgical procedures. Despite this, the bypass grafts done emergently remain patent, and the involved kidneys appear to be functional. The incidence of main renal artery occlusion after PTA is not as low as would be apparent from a review of the literature. It is proposed that main renal artery occlusion after PTA can be treated successfully by surgical and interventional radiologic techniques because of the presence of protective renal collateral circulation whose formation was stimulated by the renal artery lesion that prompted PTA.

Transcatheter therapeutic embolization in the management of massive upper gastrointestinal bleeding.

Two methods of controlling life-threatening hemorrhage are infusion of vasospastic agents and embolization of the bleeding vessel. Gelfoam powder, Gelfoam sponge, and isobutyl cyanoacrylate have been used to control severe arterial and variceal hemorrhage from the upper gastrointestinal tract. The authors summarize their results and discuss gastric necrosis, a serious complication.