Using the Flipped Classroom Model in Surgical Education: Efficacy and Trainee Perception.

OBJECTIVE: To describe the feasibility, efficacy, and learner perception of the flipped classroom model for teaching conferences within surgical training programs. DESIGN: For the flipped classroom conferences, video lectures were prepared by a faculty member, and sent to all attendees at least 2 days prior to lecture. The conference time was then spent going over cases and questions, rather than traditional lecture. We conducted a qualitative survey to assess learner's perceptions and pre-lecture quizzes to assess trainee preparedness. SETTING: The comparison of pre-conference quizzes between flipped classroom and traditional models was carried out at Brooke Army Medical Center (BAMC) in San Antonio, TX, a tertiary care facility with a general surgery residency program. The survey was conducted at BAMC and within the Complex General Surgical Oncology fellowship program at University of Texas MD Anderson Cancer Center, where a flipped classroom model was similarly employed. PARTICIPANTS: Surgical residents BAMC participated in pre-lecture quizzes. BAMC residents and MD Anderson fellows were invited to complete the online survey. RESULTS: Lecture videos did not increase mean preparation time (1.53 vs. 1.46 hours without vs. with video, p = 0.858), but did increase mean quiz scores from 67% to 80% (p = 0.031) with 32/35 learners utilizing videos. Videos increased the proportion of learners who self-reported preparing at all from 42% to 95% (p = 0.28), and preparing for at least one hour for conference from 23% to 49% (p = 0.014). Of survey respondents, 90% said videos were very helpful, 90% would use them weekly if available, and 90% prefer this format to traditional lecture. CONCLUSIONS: Utilization of a flipped classroom method was well received and preferred by surgical trainees, and it increased performance on pre-conference quizzes without increasing preparation time. Although creation of video lectures is work-intensive for lecturers, these results suggest it is more effective for learner preparation. These results could be generalizable to surgical residents nationwide as technology utilization increases in surgical education.

CT features and quantification of the characteristics of adrenocortical carcinomas on unenhanced and contrast-enhanced studies.

AIM: To describe the morphological and contrast-agent washout characteristics of adrenocortical carcinomas (ACCs) on computed tomography (CT). MATERIALS AND METHODS: Forty-one patients with histopathologically proven ACCs were retrospectively evaluated. The morphological characteristics of the ACCs were documented and compared with surgical and histopathological findings. The percentage of contrast agent enhancement washout (PEW) and relative PEW (RPEW) were calculated for 17 patients who had the combination of unenhanced, portal venous, and 15 min delayed phase images. RESULTS: Characteristic imaging findings of ACCs included large size (38 of 41 tumours were >6 cm), well-defined margin with a thin enhancing rim (25 patients), and central stellate area of low attenuation on contrast-enhanced CT images (21 patients). Tumour extension into the inferior vena cava (IVC) with associated thrombus was identified on CT in six (14.6%) patients. Of 17 tumours evaluated, 12 (71%) had a PEW value of ≤60%, and 14 (82%) had an RPEW value of ≤40%. CONCLUSION: Large size, a well-defined margin with a thin enhancing rim, central low attenuation, and a predilection for extension into the IVC are typical morphological characteristics of ACC on CT. The contrast-washout characteristics of ACCs, in concordance with their malignant nature, share those of non-adenomas rather than adenomas.

A current review of the etiology, diagnosis, and treatment of pediatric pheochromocytoma and paraganglioma.

CONTEXT: Pheochromocytomas and paragangliomas (PHEO/PGL) are neuroendocrine tumors that arise from sympathetic and parasympathetic paraganglia. Diagnosed rarely during childhood, PHEO/PGL are nonetheless important clinical entities, particularly given our evolving understanding of their pathophysiology. EVIDENCE ACQUISITION: We identified articles through the U.S. National Library of Medicine by using the search terms pheochromocytoma and paraganglioma. Results were narrowed to manuscripts that included children and studies related to the genetics of PHEO/PGL. Web-based resources for genetic disorders were also used. For all articles, we performed subsequent reference searches and verification of source data. EVIDENCE SYNTHESIS: Up to 20% of PHEO/PGL are diagnosed in children. Most are functional tumors, and clinical presentation includes symptoms related to catecholamine hypersecretion and/or tumor mass effect. Increasingly, PHEO/PGL are identified during presymptomatic screening in children with genetic syndromes associated with PHEO/PGL (multiple endocrine neoplasia type 2, von Hippel-Lindau disease, and the paraganglioma syndromes). Plasma and/or urine metanephrines are the best diagnostic test for a functional tumor, and the management of pediatric patients is similar to adults. Genetic counseling should be undertaken in all cases. Although most pediatric PHEO/PGL are benign, these tumors can occasionally metastasize, a condition for which no curative treatment exists. CONCLUSIONS: Although PHEO/PGL are rarely diagnosed during childhood, the pediatric provider should be able to recognize and screen for such tumors, particularly in the context of a known genetic predisposition. Optimal care of these children includes a multidisciplinary team approach at centers experienced in the evaluation and treatment of these uncommon yet fascinating endocrine neoplasms.

Acute cord occlusion increases blood ionized magnesium concentration in preterm fetal sheep during maternal magnesium sulfate exposure.

This study tested the hypothesis that a pathophysiologic insult to the fetus that decreases pH (umbilical cord occlusion) produces an increase in physiologically active (i.e., ionized) magnesium concentration. Preterm pregnant sheep (n = 7) were instrumented with maternal and fetal catheters and an inflatable vascular occluder was placed around the umbilical cord. After a 2-day recovery period, each ewe received a 4-g loading dose, followed by continuous intravenous infusion of 1 g magnesium sulfate/h. After 48 h, an episode of acute fetal distress was produced by inflation of the umbilical occluder for 10 min. Maternal and fetal arterial blood samples were collected at regular intervals to quantitate ionized magnesium concentration and monitor physiologic status. Magnesium sulfate infusion increased maternal and fetal blood ionized magnesium concentration. In vitro blood analysis demonstrated that there was a linear inverse correlation (r2 = 0.99) between fetal sheep blood pH and ionized magnesium concentration. In vivo, 10 min of umbilical cord occlusion produced an increase in fetal blood ionized magnesium concentration in all animals (P = 0.02) that was temporally related to the decrease in fetal blood pH. Whether this increase in physiologically active magnesium concentration is beneficial (via neuroprotection) or deleterious (via suppression of stress response) to the distressed fetus remains to be determined.

Computed tomography with a linear accelerator with radiotherapy applications.

An earlier paper [Simpson et al., Med. Phys. 9, 574 (1982)] described a computed tomography (CT) scanner that was constructed by adding a detector array to a 4-MV isocentric linear accelerator. Since the previous article, the detector array has been improved and we now demonstrate better than 3-mm spatial resolution and better than 1% relative electron density discrimination. A series of pictures from volunteer patients is included. Normal anatomy is visualized with bone, muscle, fat, and air being clearly delineated.

A 4-MV CT scanner for radiation therapy: the prototype system.

A Varian 4-MV isocentric therapy accelerator has been modified to perform also as a CT scanner. The goal is to provide a computed tomography capability for use in radiotherapy at low cost. We envision three principal uses for the system. These are (i) to provide two and three-dimensional maps of electron density distribution for CT assisted therapy planning; (ii) to aid in patient set up by providing sectional views of the treatment volume and high contrast scout-mode verification images; and (iii) to provide a means for periodically checking the patients anatomical conformation against that which was used to generate the original therapy plan. The machine was modified by mounting an array of detectors on a frame that is bolted to the counterweight end of the gantry in such a manner as to define a "third generation" CT scanner geometry. Details of the detectors and data acquisition electronics are provided. We present results of phantom studies which demonstrate that this prototype system has a spatial resolution of 4 mm and the ability to discriminate electron density differences of less than 1%. We also show that the system is exactly linear over a wide range of electron densities corresponding to those found in body tissues.