Role of Laser Pointer in Budgeting Fluoroscopy-Time and Radiation Exposure.

BACKGROUND: Literature on radiation exposure with use of the mini C-arm and value of having built-in laser guidance is limited. The purpose of this study was to determine whether laser guidance use on a mini C-arm fluoroscopy unit can reduce radiation exposure. METHODS: Surgeons (N = 25) performed the same simulated surgical task, which involved obtaining "perfect circle" views of 2 cannulated screws placed into a cadaveric wrist, done with and without C-arm laser guidance. The testing order was randomized. Main outcomes were time to complete the task, number of shots required to complete the task, number of blank shots taken, radiation exposure, total dose area product (DAP), and total exposure time. RESULTS: Laser guidance significantly reduced the percentage of surgeons who took blank shots, from 88% of the group without the laser to 12% of the group with the laser, and decreased the total average blank shots in the group from 3.5 to 0.1. While we found laser guidance led to shorter time to complete the task, decreased shots taken, and decreased exposure time and DAP, these findings only approached significance. CONCLUSION: While debate continues regarding whether mini or standard C-arm is safest, it is clear that decreasing the overall number of exposures limits potential adverse effects. Our study demonstrated that when using a mini C-arm, laser guidance decreases the number of exposures required to capture an image. These findings warrant a larger study to define the specific exposure savings and indicate potential benefit of mini C-arm use with laser guidance.

Effect of low and high dose melagatran and other antithrombotic drugs on platelet aggregation.

BACKGROUND: Thrombin-induced aggregation of human platelets can be completely inhibited by melagatran, the bioactive form of ximelagatran, an oral direct thrombin inhibitor. METHODS: The potential of melagatran to differentially inhibit alpha- and gamma-thrombins was tested with a synthetic thrombin substrate. Washed human platelets were also employed to determine if melagatran differentially inhibited alpha- and gamma-thrombin-induced platelet aggregation at distinct platelet thrombin receptors. In vitro studies were conducted with washed human platelets to determine thrombin-induced aggregation responses in the presence of varying doses of the anti-thrombotic drugs: melagatran, argatroban, heparin, and hirudin. RESULTS: Melagatran rapidly inhibits the hydrolysis of a thrombin chromogenic substrate within 0-1 min with alpha-, beta- and gamma-thrombin being equally inhibited by high dose melagatran while alpha-thrombin was significantly more sensitive at low doses. The maximum level of melagatran inhibition of alpha- and gamma-thrombin-induced platelet aggregation requires platelets to be pre-incubated with the drug for 10-30 min. Melagatran appears to have no direct effect on the PAR-1 receptor. It does appear to have a direct effect on the GPIbalpha thrombin receptor activity as well as the PAR-4 receptor. Inhibition of platelet aggregation is dose dependent, however, at low melagatran doses (0.01-0.04 nM) platelets aggregate at significantly (P < 0.05) higher levels. The lower the level of thrombin-induced aggregation that was observed with control samples (aggregations from 10% to 39%), corresponded with a higher observed melagatran-induced stimulation with drug-treated platelets. The range of stimulation varies between several hundred percent at approximately 10% aggregation to around 20% at about 20-39% aggregation. Preliminary studies indicate that this in vitro stimulatory effect is abrogated in platelets derived from volunteers who took aspirin (81 mg/day) for 7 days. Three other anti-thrombotic drugs, argatroban, heparin and hirudin, were tested with low drug levels but none were found to consistently stimulate the reaction. CONCLUSIONS: These results indicate that melagatran acts as both a direct thrombin inhibitor and indirectly by some interaction with the platelet membrane. While melagatran has been withdrawn from clinical use, its ability to differentially inhibit gamma-thrombin/PAR-4 versus alpha-thrombin/PAR-1 at low doses may warrant it, or less toxic analogs to be used in the future for as yet unknown disease states involving PAR-4.

Lumbar dural ectasia secondary to spinal fusion: a report of two cases.

Two cases of lumbar dural ectasia secondary to spinal fusion are presented. Background history of dural ectasia is discussed; computed tomography (CT) and MR imaging characteristics of dural ectasia are shown and possible causes are discussed.

Evaluation of platybasia with MR imaging.

BACKGROUND AND PURPOSE: Platybasia, or abnormal obtuseness of the basal angle, was first measured on plain skull images. At present, evaluation of the brain and skull more commonly involves CT and MR imaging. We evaluated a new MR imaging method of evaluating platybasia. METHODS: We retrospectively evaluated midline sagittal MR images in 200 adults and 50 children. The basal angle of the skull base was measured by using two methods: The standard MR imaging technique measured the angle formed by two lines-one joining the nasion and the center of the pituitary fossa connected by a line joining the anterior border of the foramen magnum and center of the pituitary fossa. The modified technique measured the angle formed by a line across the anterior cranial fossa and dorsum sellae connecting a line along the clivus. RESULTS: With the standard MR imaging technique, we obtained mean angles of 129 degrees +/- 6 degrees for adults and 127 degrees +/- 5 degrees for children, compared with 135.3 degrees (composite mean) in previous series. The modified technique produced values of 117 degrees +/- 6 degrees for adults and 114 degrees +/- 5 degrees for children, which were significantly lower that those of standard MR imaging and traditional radiography (P <.05). CONCLUSION: Both the standard and modified MR imaging techniques produced basal angles lower than those previously reported with standard radiography. The modified technique uses clearly featured landmarks that can be reproduced consistently on midline sagittal T1 images. This technique and its corresponding values can be used as the new standard for evaluating the basal angle.

Improvement in sensitivity of allele-specific PCR facilitates reliable noninvasive prenatal detection of cystic fibrosis.

BACKGROUND: Cell-free fetal DNA circulating in maternal blood has potential as a safer alternative to invasive methods of prenatal testing for paternally inherited genetic alterations, such as cystic fibrosis (CF) mutations. METHODS: We used allele-specific PCR to detect mutated CF D1152H DNA in the presence of an excess of the corresponding wild-type sequence. Pfx buffer (Invitrogen) containing replication accessory proteins and Taq polymerase with no proofreading activity was combined with TaqMaster PCR Enhancer (Eppendorf) to suppress nonspecific amplification of the wild-type allele. The procedure was tested on DNA isolated from plasma drawn from 11 pregnant women (gestational age, 11-19.2 weeks), with mutation confirmation by chorionic villus sampling. RESULTS: The method detected 5 copies of the CF D1152H mutant allele in the presence of up to approximately 100,000 copies of wild-type allele without interference from the wild-type sequence. The D1152H mutation was correctly identified in one positive sample; the only false-positive result was seen in a mishandled sample. CONCLUSIONS: This procedure allows for reliable detection of the paternally inherited D1152H mutation and has potential application for detection of other mutations, which may help reduce the need for invasive testing.

Multidrug resistance protein attenuates gemtuzumab ozogamicin-induced cytotoxicity in acute myeloid leukemia cells.

Gemtuzumab ozogamicin (GO) is a novel immunoconjugate therapy for acute myeloid leukemia (AML). P-glycoprotein (Pgp) confers resistance to GO and is associated with a worse clinical response. To address whether multidrug resistance protein (MRP) affects GO susceptibility, we characterized Pgp, MRP1, and MRP2 expression in CD33+ cell lines and CD33+ AML samples and analyzed the effect of the Pgp inhibitor cyclosporine (CSA) and the MRP inhibitor MK-571 on GO-induced cytotoxicity. MRP1, but not MRP2, expression correlated with MRP activity. MK-571 enhanced GO-induced cytotoxicity in Pgp-negative/MRP-positive NB4 and HL-60 cells. CSA, but not MK-571 alone, restored GO susceptibility in Pgp-positive/MRP-positive TF1 cells; however, MK-571 enhanced cytotoxicity in the presence of CSA. All patient samples exhibited MRP activity, and 17 of 23 exhibited Pgp activity. CSA increased GO-induced cytotoxicity in 12 Pgp-positive samples, whereas MK-571 alone was effective in only one sample with minimal Pgp activity. In 3 Pgp-positive/MRP-positive samples, MK-571 enhanced GO-induced cytotoxicity in the presence of CSA. Thus, MRP1 may attenuate susceptibility to GO. This effect was comparatively less than that for Pgp and required the inhibition of Pgp for detection in cells that coexpressed both transporters. Because MK-571 and CSA failed to affect cytotoxicity in a portion of Pgp-positive/MRP-positive AML samples, additional resistance mechanisms are likely important.