Performance of the Tachyon Time-of-Flight PET Camera.

We have constructed and characterized a time-of-flight Positron Emission Tomography (TOF PET) camera called the Tachyon. The Tachyon is a single-ring Lutetium Oxyorthosilicate (LSO) based camera designed to obtain significantly better timing resolution than the ~ 550 ps found in present commercial TOF cameras, in order to quantify the benefit of improved TOF resolution for clinically relevant tasks. The Tachyon's detector module is optimized for timing by coupling the 6.15 × 25 mm2 side of 6.15 × 6.15 × 25 mm3 LSO scintillator crystals onto a 1-inch diameter Hamamatsu R-9800 PMT with a super-bialkali photocathode. We characterized the camera according to the NEMA NU 2-2012 standard, measuring the energy resolution, timing resolution, spatial resolution, noise equivalent count rates and sensitivity. The Tachyon achieved a coincidence timing resolution of 314 ps +/- ps FWHM over all crystal-crystal combinations. Experiments were performed with the NEMA body phantom to assess the imaging performance improvement over non-TOF PET. The results show that at a matched contrast, incorporating 314 ps TOF reduces the standard deviation of the contrast by a factor of about 2.3.

Effect of 176Lu background on singles transmission for LSO-based PET cameras.

We explore how the radioactive background from naturally occurring 176Lu affects single photon transmission imaging for lutetium orthosilicate (LSO) scintillator-based PET cameras by estimating the transmission noise equivalent count rate (NECR) including this background. Assuming a typical PET camera geometry (80 cm detector ring diameter), we use a combination of measurement and analytic computation to estimate the counting rates due to transmission, scatter and background events as a function of singles transmission source strength. We then compute a NECR for singles transmission. We find that the presence of radiation from the naturally occurring 176Lu reduces the NECR by 60% or higher for source strengths less than 10 mCi, and that a 25% reduction of the NECR can occur even with a source strength of 40 mCi.

Spinal cord stimulation in severe, inoperable peripheral vascular disease.

Objective. To assess the effect of spinal cord stimulation in patients with severe, inoperable peripheral vascular disease, and uncontrolled pain. Patients and methods. A case study of 20 patients with end-stage peripheral vascular disease, either Fontaine Class 3 or 4 limb ischemia. All 20 patients implanted with spinal cord stimulation devices with follow-up from one to five years (mean, 32 months) performed in a multidisciplinary pain treatment center. Results. In the 20 patients implanted with a spinal cord stimulator for peripheral vascular disease, overall there was 75% limb salvage; with Fontaine Class 3 patients there was 86% and with Fontaine Class 4 patients, 69% limb salvage of the treated limbs. Conclusions. Twenty patients with end-stage peripheral vascular disease were implanted with spinal cord stimulators and followed for five years, until amputation or end of life, showing excellent results for limb salvage and minimal complications. The current literature regarding the use of spinal cord stimulation for peripheral vascular disease is reviewed, supporting its benefit for limb salvage and pain relief.

Percutaneous transjejunal biliary dilatation: alternate management for benign strictures.

Since 1980, 23 patients with diffuse benign biliary strictures underwent percutaneous retrograde biliary dilatation through a surgically created jejunal access route. Bile ducts of 15 patients with sclerosing cholangitis, five with traumatic strictures, and three with strictures of diverse etiology were dilated with 25-atm balloons during 88 separate sessions. Individual dilatation intervals ranged between 2 and 36 months. Three patients with sclerosing cholangitis died. One uncomplicated bile duct rupture occurred in the trauma group because of balloon oversizing. Our 5-year experience indicates that bile duct patency can be safely maintained by repeated retrograde dilatations without the need for biliary catheters or stents.

Nonsurgical drainage of appendiceal abscesses.

Five patients with abdominal abscesses complicating appendicitis were successfully treated by catheter drainage. In two patients, the percutaneous procedure was performed after incomplete surgical drainage; in three patients it was used as the only means of initial drainage. No interval appendectomy was required and no complications were associated with the procedure. Percutaneous management of appendiceal abscesses can be proposed as an alternative to surgical drainage.