Matthew S. Johnson

Physician assistants in interventional radiology practice.

Interventional radiology (IR) is a clinical subspecialty; as such, there is a large amount of direct patient care. However, until recently, this topic has not been a major focus in radiology training programs. Additionally, as interventional radiologists develop busier and busier practices, there is less time to spend with individual patients. Physician extenders such as physician assistants (PAs) represent an excellent way to improve clinical patient care. This article describes what PAs are and how they work together with physicians. It illustrates differences between PAs and other physician extenders and describes the duties that may be delegated to PAs in the IR setting.

Kinetics of release of heparin from alginate hydrogel.

PURPOSEnInjected sodium alginate may be a useful perivascular drug delivery vehicle. This study was performed to determine the release rates of heparin from sodium alginate hydrogels cross-linked with varying amounts of calcium gluconate.nnnMATERIALS AND METHODSnSix hydrogels, composed of 0.16 mEq sodium alginate and 4,000 units unfractionated heparin, were cross-linked with calcium gluconate to yield ion equivalence (IE) ratios (calcium:alginate) of 0.2, 0.4, 0.58, 0.8, 1.0, or 1.2. Two milliliters of normal saline was placed on top of each gel and allowed to remain in contact for up to 10 days. At set time intervals, the amount of heparin in the eluent was determined with use of high-performance liquid chromatography.nnnRESULTSnGels with 0.2 and 0.4 IE were partially liquid at 24 hours; the other gels solidified within 10 minutes. The 0.58 IE gel was slowest to solidify but immobilized the most heparin and released heparin slowest over 10 days. At 10 days, between 5.5% and 9.8% of the heparin immobilized was retained in the gel.nnnCONCLUSIONnThis hydrogel shows promise as a vehicle for in vivo perivascular heparin delivery. The 0.58:1 IE ratio hydrogel has slowest release rate and the greatest immobilization despite its longer cross-linking time.

Percutaneous Management of Hemangiomas and Vascular Malformations

As discussed, the most useful classification of vascular malformations to date is the one by Mulliken and Glowaki. The majority of vascular malformations can be diagnosed clinically with MRI now the gold standard to delineate the extent of the lesion or in cases where the diagnosis is in doubt.