MO-D-217A-01: Optimizing Dose in the Interventional Suite: Do You Really Need That Image Quality?

The imaging equipment used to guide interventions has evolved significantly in the recent past. As a result, the equipment has become more complex to operate. This evolution has left many operators ill equipped to fully optimize the radiation dose delivered, as they are often more focused on the technical skills required to complete the case rather than balancing image quality and radiation dose. In addition, they are usually better trained in these technical skills than in the delivery of optimal dose. Interventionalists are faced with dose optimization in two main venues: the angiography suite and the CT suite. In the angiographic suite, the operator has the ability to manipulate very simple parameters which can optimize dose. These, in combination with geometric and protective barrier techniques, can create a safe and efficient environment for patients, staff and operators. In addition, with the assistance of a medical physicist, operators can become more facile with their equipment and help to develop local protocols for their institution. In the CT suite, a similar approach can be applied. While the operator is more dependent on the technologist to manipulate the parameters during a case, the two can work together to optimize the dose for CT-guided procedures. Knowledge of the key variable parameters is paramount to developing this team approach. This course will review simple techniques that operators can employ to optimize dose during both fluoroscopically- and CT- guided procedures, and will examine the question, "Do you really need that image quality?" LEARNING OBJECTIVES: 1. Gain a better appreciation of the clinical perspective and need for operator education. 2. Identify simple techniques which can be employed to optimize dose with both fluoroscopically- and CT-guided interventions. 3. Discuss the importance of the question, "Do you really need that image quality?"

Transcutaneous pacing in a hypothermic-dog model.

STUDY OBJECTIVE: To evaluate the hemodynamic response to transcutaneous pacing (TCP) during rewarming from hypothermia. METHODS: We conducted a prospective, controlled laboratory investigation using 20 mongrel dogs. The animals were anesthetized, intubated, and mechanically ventilated. Arterial pressure, core temperature, and cardiac rhythm were continuously monitored. All dogs were cooled to a core temperature of 27 degrees C; experimental animals were then subjected to TCP with active rewarming, and control animals underwent sham transcutaneous pacing and rewarmed in the same manner. Serial hemodynamic measurements, time to rewarming, and cardiac isoenzyme concentrations were analyzed. RESULTS: Rewarming was accomplished significantly faster in the paced group (171.5 +/- 31.5 minutes) than in the control group (254 +/- 55.9 minutes, P < .05). After rewarming, the mean cardiac index in the paced dogs returned to 84% of baseline, compared with 63% of baseline in the nonpaced group (P < .05). None of the paced animals demonstrated significant hemodynamic deterioration, potentially lethal arrhythmias, or other evidence of myocardial injury. CONCLUSION: TCP is safe, effective and easily implemented in dogs. In this small series of dogs, TCP restored and maintained hemodynamic stability and allowed the hypothermic animals to rewarm in half the time required by their nonpaced counterparts.

Myelin basic protein in the optic nerve of the developing albino rat: an immunoperoxidase study of paraffin embedded tissue.

The distribution of myelin basic protein (MBP) was determined by application of the unlabeled peroxidase-anti-peroxidase method to sections of paraffin embedded optic nerve taken from the developing albino rat. MBP was not detected in optic nerves from animals younger than 90 hours postnatum. MBP staining presented first as faint, diffuse deposits of chromagen which were found in approximately one-third of the 90 hour subjects. The number of MBP positive regions and the intensity of staining of these regions increased rapidly with age. There was no obvious radial gradient in the distribution of MBP in cross sections of developing optic nerves, nor were smooth central/peripheral gradients apparent in longitudinal sections.

Processing techniques for the demonstration of myelin basic protein in paraffin-embedded optic nerve: an immunoperoxidase study of the developing albino rat.

A comparison was made of the effects of various fixation and processing conditions upon the antigenicity of myelin basic protein (MBP) in sections of paraffin-embedded optic nerve from the developing albino rat as judged by the unlabeled peroxidase-antiperoxidase technique. The fixatives used were: Perfix, 4% and 2% buffered paraformaldehyde (pH 7.4), 10% buffered formalin (pH 7.4); Bouin's, Clark's, and Carnoy's fixatives, and 20% formalin in a solution of HgCl2 that had been saturated at 1 degrees C. Perfix appeared to be the best fixative for the preservation of morphology and MBP antigenicity during the early stages of myelinogenesis but was not satisfactory during the later stages. The buffered aldehydes were slightly more destructive of MBP antigenicity than was Perfix, but they produced satisfactory results following the first postnatal week. Bouin's fixative was similar in effect to the buffered aldehydes, but nonspecific background staining was higher. HgCl2/formalin, Clark's and Carnoy's fixatives were unsuitable. No differences were noted in staining between material processed for embedding using 5, 30, or 60 min schedules.

Glial fibrillary acidic protein in the optic nerve of the developing albino rat: an immunoperoxidase study of paraffin-embedded tissue.

The unlabeled peroxidase-anti-peroxidase method was used to stain glial fibrillary acidic (GFA) protein in the optic nerve of the developing albino rat. Optic nerves from animals ranging in age from the day of birth to adulthood were embedded in paraffin following fixation with various agents for times ranging from 30 minutes to 48 hours. GFA protein activity was demonstrable at birth in large astrocytic processes following fixation with alcohols or with Perfix for short intervals, but not with 4% or 2% buffered paraformaldehyde solutions. With increasing age, GFA protein could be demonstrated using higher aldehyde concentrations, longer fixation times, and longer paraffin embedding schedules. At all ages GFA protein activity was greater following treatment with nonaldehyde fixatives rather than those containing formaldehyde or glutaraldehyde. At birth the majority of GFA protein-containing processes were confined to planes which were perpendicular to the axons of the optic nerve. With increasing age, tangential and longitudinal processes became more numerous until, in the mature optic nerve, astrocytic processes were best characterized as being multidirectional.

Post-embedding immunoperoxidase staining of glial fibrillary acidic protein for light and electron microscopy.

Post-embedding peroxidase-antiperoxidase methods to stain glial fibrillary acidic (GFA) protein in Araldite-embedded sections for light and electron microscopy were developed. The Jimpy mouse spinal cord was used because it is gliotic and contains abundant glial filaments and GFA protein. For light microscopy, specific staining was obtained in thick and in ultrathin sections mounted on glass following removal of the plastic with sodium ethoxide. Consistent specific staining for GFA protein in ultrathin sections mounted on nickel grids required partial removal of the plastic with 1% sodium ethoxide and further treatment with 2% sodium dodecyl sulfate (SDS).

Glial fibrillary acidic protein in the retina of the developing albino rat: an immunoperoxidase study of paraffin-embedded tissue.

The peroxidase-anti-peroxidase method was used on paraffin-embedded material to demonstrate the distribution of glial fibrillary acidic (GFA) protein, an astrocyte-specific protein, in the developing retina of the albino rat. At birth activity was scant and was confined to scattered, poorly differentiated cells in the inner retinal layers near the optic disc. At 3 days primitive astrocytes which displayed GFA protein activity were confined to the stratum opticum near the optic disc. With increasing age these cells were found at greater distances from the optic disc and began to assume the appearance of typical fibrous astrocytes. By 30 days the perikarya of these cells were confined almost exclusively to the region between the nerve fiber layer and the inner limiting membrane. The processes of these cells terminated either in suckerlike end-feet upon blood vessels or, to a lesser extent, ended in relation to axon fascicles of the nerve fiber layer. A second population of GFA protein-active cells existed as perivascular glia which were found upon vessels in the inner portion of the stratum opticum in young animals. In the mature retina perivascular glia were found on vessels throughout the stratum opticum and in the inner portion of the inner plexiform layer. Unequivocal staining of Müller cells or their processes was not obtained. The best staining was obtained with fixatives containing minimal concentrations of aldehydes, especially in tissue from younger animals. The fixative which gave the best preservation of cellular structure along with preservation of GFA protein antigenicity was Perfix (Fischer Scientific Company).

Automation of long-path absorption cell measurements.

Recent advances have been made in the operation of long-path absorption cells which make them easier to align and improve the accuracy of measurements made with them. Only one person is required now for routine measurements of low absorption coefficients of atmospheric absorbers. Unique gear designs for the adjustment of the cell mirrors are described which utilize low-torque linear drives and make possible rapid changes in pathlength and precision repositioning of the cell output beam at long pathlengths. Automation of cell operation by the use of remote Selsyn controls is described. Several techniques are discussed for precision optical alignment of long-path absorption cells, including the use of infrared radiation sources. The system accuracy which results from these refinements in operation is included.

Simple template method for targeting brain loci in small animal stereotaxy.

A simple and reliable method for stereotaxic approach at any angle is described. The presentation of the coordinate on a template replaces calculation of stereotaxic coordinates.