Optimization of Z-axis automatic exposure control for multidetector row CT evaluation of neck and comparison with fixed tube current technique for image quality and radiation dose.

BACKGROUND AND PURPOSE: Z-axis automatic exposure control (AEC) technique automatically adjusts tube current based on size of body region scanned. The purpose of the current study was to compare diagnostic acceptability, noise, and radiation exposure of multidetector row CT (MDCT) of neck performed with z-axis AEC and with fixed current. MATERIALS AND METHODS: Two study groups of 26 patients each underwent MDCT of neck using z-axis AEC with 8 noise index (NI), 150-440 mA, and 10 NI, 75-440 mA, respectively. A control group consisting of another 26 patients underwent MDCT of neck with fixed-current technique (300 mA). Objective noise and mean tube current-time products (mA . s) were recorded. Two radiologists evaluated images for diagnostic acceptability and subjective noise on a 5-point scale. RESULTS: All CT examinations of study and control groups were diagnostically acceptable, though objective noise was significantly more with z-axis AEC (shoulder: NI 8, 20.6 +/- 6.2 HU; NI 10, 22.2 +/- 4.6 HU) than with fixed current (16.2 +/- 6 HU) (P = .01). There was no significant difference between AEC and fixed current in diagnostic acceptability and subjective noise (P = .22-.42). AEC resulted in significant radiation dose reduction (NI 8, 186.3 +/- 20.5 mA . s; NI 10, 158.1 +/- 21.2 mA x s), compared with fixed current (235 +/- 21.8 mA x s). CONCLUSION: Z-axis AEC resulted in similar subjective noise and diagnostic acceptability, with radiation dose reduction of 21% for NI of 8 and 33% for NI of 10, respectively, for MDCT evaluation of neck, compared with those of fixed current technique.

Evaluation of left ventricular endocardial volumes and ejection fractions computed from gated perfusion SPECT with magnetic resonance imaging: comparison of two methods.

BACKGROUND: Two methods of computing left ventricular volumes and ejection fraction (EF) from 8-frame gated perfusion single photon emission computed tomography (SPECT) were compared with each other and with magnetic resonance (MR) imaging. METHODS AND RESULTS: Thirty-five subjects underwent 8-frame gated dual-isotope SPECT imaging and 12- to 16-frame gated MR imaging. Endocardial boundaries on short-axis MR images were hand traced by experts blinded to any SPECT results. Volumes and EF were computed with the use of Simpson's rule. SPECT images were analyzed for the same functional variables with the use of 2 automatic programs, Quantitative Gated SPECT (QGS) and the Emory Cardiac Toolbox (ECTb). The mean difference between MR and SPECT EF was 0.008 for ECTb and 0.08 for QGS. QGS showed a slight trend toward higher correlation for EF (r = 0.72, SE of the estimate = 0.08) than ECTb (r = 0.70, SE of the estimate = 0.09). For both SPECT methods, left ventricular volumes were similarly correlated with MR, although SPECT volumes were higher than MR values by approximately 30%. CONCLUSIONS: QGS and ECTb values of cardiac function computed from 8-frame gated perfusion SPECT correlate very well with each other and correlate well with MR. Averaged over all subjects, ECTb measurements of EF are not significantly different from MR values but QGS significantly underestimates the MR values.

In vitro effects of transcatheter injection on structure, cell viability, and cell metabolism in fibroblast-impregnated alginate microspheres.

PURPOSE: To determine if microsphere-encapsulated cell preparations can be delivered through a microcatheter without compromising microsphere structure, cell viability, or metabolism. MATERIALS AND METHODS: Fibroblast-impregnated microspheres were fabricated by using 1.0% alginate and rabbit synovial fibroblasts. Fibroblast-impregnated alginate microspheres injected through microcatheters were analyzed in parallel with identical noninjected microspheres. The effects of transcatheter injection on structure and cell viability (percentage of viable cells per microsphere) were correlated with microsphere size. Structural effects were analyzed by using light microscopy, and 7-day percentage (ratio of live cells to dead cells) cell viability was assessed with confocal microscopy and fluorescent staining. In a second series of experiments, the metabolism of small microspheres was studied during a course of 7 days by using a spectrophotometric bioanalyzer. RESULTS: Transcatheter injection caused fracturing and/or fragmentation of large (800-1,000 microm) and medium (500-750 microm) microspheres, while small (250-400 microm) microspheres were structurally unaffected by transcatheter injection. Fracturing and fragmentation were associated with cell release from the alginate matrix. Although transcatheter injection reduced cell viability by 17%-23% in all size categories, it did not cause a detectable alteration in the rate of glucose metabolism. CONCLUSION: Transcatheter injection was physiologically well tolerated by fibroblasts encapsulated in alginate microspheres; however, when microsphere diameter exceeded the catheter diameter, fracturing and fragmentation of microspheres compromised the sequestration function of the microsphere vector.

Career advancement of men and women in academic radiology: is the playing field level?

RATIONALE AND OBJECTIVES: The authors' purposes were to determine if there are gender differences in the speed of promotion and/or academic productivity in academic radiology and if this situation had changed since a previous study was performed in 1987. MATERIALS AND METHODS: Surveys were distributed to faculty members of academic radiology departments in May 1997. A total of 707 surveys were analyzed according to gender for time at rank for assistant and associate professor levels, in relation to publication rate, grant funding rate, and distribution of professional time. RESULTS: There was no difference between genders in the time at assistant professor rank. Among all current professors, women had been associate professors longer than men, but there was no difference between genders for those who had been in academic radiology for less than 15 years. There was no gender difference at any rank in the rate of publishing original articles. There was no difference in funding rates, although men had more total grant support. Male associate professors reported spending more time in administration and slightly more time in total hours at work than did their female colleagues, and male professors spent slightly more time teaching residents. Otherwise, there is no difference in how men and women at any rank spend their professional time. There are, however, lower percentages of women in tenured positions and in the uppermost levels of departmental administration. CONCLUSION: The time at rank for men and women and their rate of publication appear to have equalized. Women still are underrepresented at the uppermost levels of departmental administration, however, and are less likely than men to hold tenured positions.

The road to success: factors affecting the speed of promotion of academic radiologists.

RATIONALE AND OBJECTIVES: The authors' purpose was to determine the factors influencing the speed of promotion of academic radiologists. MATERIALS AND METHODS: Three hundred forty-three surveys from faculty members of academic radiology departments with continuous academic careers were analyzed for time in rank at assistant and associate professor levels in relation to publication rate, grant funding rate, and distribution of professional time. Individuals promoted faster than the median time (6 years for assistant professors, 5 years for associate professors) were considered "fast track" and were compared with the remainder of the group. RESULTS: At the assistant professor level, fast track individuals had significantly higher rates of total publications and original articles than did others. At the level of associate professor, fast track individuals had significantly faster rates of publication of original articles, but no significant difference existed in total publication rate. No significant difference was found in the rate of founding of fast track individuals and others. Those with funding were not more likely to be on a fast track than those without funding. Fast track individuals spent significantly more time in administration at the assistant professor level than did other faculty, but no other significant differences were discovered in time distribution at the assistant or associate professor level. CONCLUSIONS: The rate of publishing original articles at the assistant and associate professor levels and the rate of overall publication at the assistant professor level were the most important parameters in predicting speed of promotion.

Treatment of brain tumors in children is associated with abnormal MR spectroscopic ratios in brain tissue remote from the tumor site.

PURPOSE: Children who have brain tumors are at risk for a variety of treatment-related sequelae, including neuropsychological and cognitive impairment, neurologic deficits, and neuroendocrinologic disturbances. We sought to determine the value of proton MR spectroscopy in assessing brain tissue remote from the tumor site to ascertain the effects of chemotherapy and radiation treatment in these patients. METHODS: Single-voxel proton MR spectra from 70 patients (111 spectra) and 11 healthy volunteers (11 spectra) were analyzed. NAA/Cr, NAA/Cho, and Cho/Cr ratios based on peak areas were obtained from nonneoplastic regions of the frontal lobe. The relationship between MR spectroscopic ratios and treatment was determined. RESULTS: NAA-containing ratios were decreased in patients as compared with control subjects. The presence of gadolinium-based contrast material did not cause significant changes in the ratios as compared with precontrast data. When chemotherapy was a component of a child's treatment protocol, we found a significant decline in NAA/Cr ratios. Patients who underwent both chemotherapy and radiation therapy showed a trend toward lower NAA-containing ratios if the chemotherapy was administered before the radiation therapy. Patients receiving whole-brain radiation had a trend toward lower NAA-containing ratios than did those who had only focal tumor treatment. CONCLUSION: In children with brain tumors, MR spectroscopy of brain tissue remote from the tumor reveals treatment-related biochemical changes.

MR of the brain in children.

MR imaging has firmly established its place as the cornerstone of pediatric neuroimaging. Recent advances in MR imaging have led to decreased imaging time, high resolution studies, and new methods for obtaining tissue contrast. Magnetic resonance angiography (MRA) now obviates the need for angiography in some children, although its extended role is still to be defined. Normal and abnormal development and myelination patterns have been further defined with MR imaging. The patterns of brain injury resulting from hypoxia and ischemia vary with the degree of the insult as well as the gestational age of the child. These patterns of hypoxic-ischemic encephalopathy can be analyzed to determine when the insult occurred. Neuronal migration disorders and phakomatoses can be diagnosed with confidence at an early age, thus facilitating genetic counseling. MR imaging can detect the most common lesions associated with childhood epilepsy, such as hippocampal sclerosis, focal cortical dysplasias, and low-grade tumors. Other areas, including pediatric AIDS, toxicity-related injury, metabolic/mitochondrial conditions, and disorders associated with iatrogenic injury, can be diagnosed with MR. Spectroscopy provides information that should prove useful in evaluating and monitoring neuronal and other brain tissue disorders in children.

Analysis of allogeneic and syngeneic rat heart transplants using 23Na magnetic resonance spectroscopy.

This study defines the total sodium-23 magnetic resonance spectroscopy (23Na MRS) signal from in vivo heterotopic rat heart transplants in the early post-transplant period and examines the utility of this noninvasive method for monitoring allograft rejection. Measurements were performed at 4.7 T. Syngeneic (n = 6) and allogeneic (n = 6) donor hearts were transplanted into the neck of recipient rats. There were 27 MRS observations between days 0 and 29 post-transplant. Heart grafts were excised at various intervals post-transplant for histologic examination. Allogeneic heart grafts rejected between days 4 and 5 post-transplant while syngeneic grafts continued to beat. All hearts showed ischemic damage. Allogeneic hearts showed cellular rejection by Day 1. 23Na MRS showed a steady elevation in signal in the 3 days prior to rejection and a sharp rise after rejection. 23Na MRS accurately identified full rejection and was also sensitive to the rejection process.

Patients' perceptions of increased pharmacy contact.

This prospective, randomized study was conducted to determine if increased patient contact between pharmacists and patients would result in greater patient awareness and satisfaction with their hospital stay and particularly with pharmacists and pharmacy services. Eligible patients were randomized to receive either the usual pharmacy care with minimum contact with the pharmacist, or expanded services based on increased contact with the pharmacist. A questionnaire was used to determine patient awareness and satisfaction. Statistically significant differences were found between the groups on awareness and satisfaction with pharmacy services scales as well as total scores. Total patient scores were highly reliable, with an alpha coefficient of 0.87. In addition, comments by patients in the group with increased contact were overwhelmingly positive, in contrast to those receiving usual care. Patients desire and appreciate greater contact with pharmacists.