Measuring the instructional validity of clinical simulation problems

Written clinical simulation problems in two formats--forced-choiced and essay--were used to test junior and senior medical students at the conclusion of their pediatric rotations. A comparison was made in the performance of students with varying levels of clinical experience. There seemed to be no consistent pattern of improvement with increased instructional time on the forced-choice management problems. Junior students did show improvement over time on the essay management problems, which also seemed to reflect the increased problem-solving and organizational skills of seniors in comparison to juniors. Correlations across problems and correlations between the clinical problem test and other measurement techniques were very weak, partly due to the low sampling reliability of clinical simulation problems. In this study, clinical simulation problems failed to demonstrate responsiveness to development and maturation in the problem-solving approach to patient care.     

Daily CT localization for correcting portal errors in the treatment of prostate cancer

Introduction: Improved prostate localization techniques should allow the reduction of margins around the target to facilitate dose escalation in high-risk patients while minimizing the risk of normal tissue morbidity. A daily CT simulation technique is presented to assess setup variations in portal placement and organ motion for the treatment of localized prostate cancer.

Methods and Materials: Six patients who consented to this study underwent supine position CT simulation with an alpha cradle cast, intravenous contrast, and urethrogram. Patients received 46 Gy to the initial Planning Treatment Volume (PTV₁) in a four-field conformal technique that included the prostate, seminal vesicles, and lymph nodes as the Gross Tumor Volume (GTV₁). The prostate or prostate and seminal vesicles (GTV₂) then received 56 Gy to PTV₂. All doses were delivered in 2-Gy fractions.

After 5 weeks of treatment (50 Gy), a second CT simulation was performed. The alpha cradle was secured to a specially designed rigid sliding board. The prostate was contoured and a new isocenter was generated with appropriate surface markers. Prostate-only treatment portals for the final conedown (GTV₃) were created with a 0.25-cm margin from the GTV to PTV. On each subsequent treatment day, the patient was placed in his cast on the sliding board for a repeat CT simulation. The daily isocenter was recalculated in the anterior/posterior (A/P) and lateral dimension and compared to the 50-Gy CT simulation isocenter. Couch and surface marker shifts were calculated to produce portal alignment. To maintain proper positioning, the patients were transferred to a stretcher while on the sliding board in the cast and transported to the treatment room where they were then transferred to the treatment couch. The patients were then treated to the corrected isocenter. Portal films and electronic portal images were obtained for each field.

Results: Utilizing CT–CT image registration (fusion) of the daily and 50-Gy baseline CT scans, the isocenter changes were quantified to reflect the contribution of positional (surface marker shifts) error and absolute prostate motion relative to the bony pelvis. The maximum daily A/P shift was 7.3 mm. Motion was less than 5 mm in the remaining patients and the overall mean magnitude change was 2.9 mm. The overall variability was quantified by a pooled standard deviation of 1.7 mm. The maximum lateral shifts were less than 3 mm for all patients. With careful attention to patient positioning, maximal portal placement error was reduced to 3 mm.

Conclusion: In our experience, prostate motion after 50 Gy was significantly less than previously reported. This may reflect early physiologic changes due to radiation, which restrict prostate motion. This observation is being tested in a separate study. Intrapatient and overall population variance was minimal. With daily isocenter correction of setup and organ motion errors by CT imaging, PTV margins can be significantly reduced or eliminated. We believe this will facilitate further dose escalation in high-risk patients with minimal risk of increased morbidity. This technique may also be beneficial in low-risk patients by sparing more normal surrounding tissue.     

A rating system for prompt clinical diagnosis of ischemic stroke

BACKGROUND: When a CT scan is not available, an early accurate clinical diagnosis of ischemic stroke is essential to initiate prompt therapy. Our objective was to construct a clinical index that is easy to use when stroke patients are first evaluated at the hospital, to identify those who probably are experiencing an acute ischemic episode. The study was conducted at a university-affiliated medical referral center and two community general hospitals in Mexico. METHODS: Clinical records were reviewed for 801 patients with sudden onset of a focal or global neurologic dysfunction, presumably of vascular origin lasting more than 24 h. Eligibility criteria for this study were admission to the hospital within the first 24 h after symptomatic onset, CT scan diagnosis between 24 and 72 h, and age >45 years. Ischemic stroke included cases of arterial brain infarction, while nonischemic stroke included subarachnoid or intraparenchymatous hemorrhage, mass lesion, venous infarction, and in cases without a CT scan evidence that could explain the clinical manifestations. Data excerpted for analysis were age, sex, history of diabetes mellitus or previous stroke/transient ischemic attack (TIA), time of onset of symptoms, presence of headache, vomiting, neck stiffness, hemiplegia, leukocytosis or atrial fibrillation, diastolic blood pressure, and Glasgow coma scale (GCS) rating. Two multivariable analyses were used: 1) step-wise multiple logistic regression (SMLR), and 2) conjunctive consolidation (CC). RESULTS: After appropriate exclusions, the study proceeded with 83 ischemic and 42 nonischemic stroke patients. With SMLR, six variables were selected as predictive for ischemic stroke, including neck stiffness, diastolic blood pressure, previous history of stroke/TIA, hemiplegia, GCS, and atrial fibrillation. An appropriate sum of weighted ratings had a positive predictive value (PPV) of 100% for ischemic stroke. With consolidated categories, the PPV was 97% when patients had the following: no neck stiffness; no atrial fibrillation but history of stroke/TIA and GCS > or =12, or no neck stiffness but atrial fibrillation. CONCLUSIONS: Among patients with acute stroke, clinical data can be used to identify a group with a high probability of ischemic stroke. There are slightly different results between both methods; while SMLR includes the four variables selected by CC, the latter included neither diastolic blood pressure nor hemiplegia/hemiparesia. However, CC results seem easier to understand and interpret than with SMLR.     

Increasing Valid Profiles in Phallometric Assessment of Sex Offenders with Child Victims: Combining the Strengths of Audio Stimuli and Synthetic Characters

Penile plethysmography (PPG) is a measure of sexual interests that relies heavily on the stimuli it uses to generate valid results. Ethical considerations surrounding the use of real images in PPG have further limited the content admissible for these stimuli. To palliate this limitation, the current study aimed to combine audio and visual stimuli by incorporating computer-generated characters to create new stimuli capable of accurately classifying sex offenders with child victims, while also increasing the number of valid profiles. Three modalities (audio, visual, and audiovisual) were compared using two groups (15 sex offenders with child victims and 15 non-offenders). Both the new visual and audiovisual stimuli resulted in a 13% increase in the number of valid profiles at 2.5 mm, when compared to the standard audio stimuli. Furthermore, the new audiovisual stimuli generated a 34% increase in penile responses. All three modalities were able to discriminate between the two groups by their responses to the adult and child stimuli. Lastly, sexual interest indices for all three modalities could accurately classify participants in their appropriate groups, as demonstrated by ROC curve analysis (i.e., audio AUC = .81, 95% CI [.60, 1.00]; visual AUC = .84, 95% CI [.66, 1.00], and audiovisual AUC = .83, 95% CI [.63, 1.00]). Results suggest that computer-generated characters allow accurate discrimination of sex offenders with child victims and can be added to already validated stimuli to increase the number of valid profiles. The implications of audiovisual stimuli using computer-generated characters and their possible use in PPG evaluations are also discussed.     

Revision Hip Arthroplasty with A Modular Cementless Stem: Mid-Term Follow Up

Despite the increasing volume of revision total hip arthroplasty (THA) being performed in the United States, there are few studies reporting mid-term clinical and radiographic outcomes of modular fully porous-coated femoral stems. We retrospectively studied a consecutive series of patients who underwent revision THA with a modular extensively porous-coated femoral component at a single institution and by a single surgeon. The final study group included 54 hips (52 patients) followed for an average of 84 months. Ten-year survival rates with revision for any reason and revision for femoral loosening as endpoints were 94% and 100%, respectively. No complications regarding the modular junction were encountered. Of the 50 hips with adequate radiographs, all showed proximal ingrowth and 42 (84%) had both proximal and distal ingrowth. The modular, fully porous-coated femoral stem studied demonstrated excellent survivorship and bone ingrowth at mid-term follow up.     

Medial Olivocochlear-Induced Transient-Evoked Otoacoustic Emission Amplitude Shifts in Individual Subjects

Activation of the medial olivocochlear reflex (MOCR) can be assessed indirectly using transient-evoked otoacoustic emissions (TEOAEs). The change in TEOAE amplitudes when the MOCR is activated (medial olivocochlear (MOC) shift) has most often been quantified as the mean value in groups of subjects. The usefulness of MOC shift measurements may be increased by the ability to quantify significant shifts in individuals. This study used statistical resampling to quantify significant MOC shifts in 16 subjects. TEOAEs were obtained using transient stimuli containing energy from 1 to 10 kHz. A nonlinear paradigm was used to extract TEOAEs. Transient stimuli were presented at 30 dB sensation level (SL) with suppressor stimuli presented 12 dB higher. Contralateral white noise, used to activate the MOCR, was presented at 30 dB SL and was interleaved on and off in 30-s intervals during a 7-min recording period. Confounding factors of middle ear muscle reflex and slow amplitude drifts were accounted for. TEOAEs were analyzed in 11 1/3-octave frequency bands. The statistical significance of each individual MOC shift was determined using a bootstrap procedure. The minimum detectable MOC shifts ranged from 0.10 to 3.25 dB and were highly dependent on signal-to-noise ratio at each frequency. Subjects exhibited a wide range of magnitudes of significant MOC shifts in the 1.0–3.2-kHz region (median?=?1.94 dB, range?=?0.34–6.51 dB). There was considerable overlap between the magnitudes of significant and nonsignificant shifts. While most subjects had significant MOC shifts in one or more frequency bands below 4 kHz, few had significant shifts in all of these bands. Above 4 kHz, few significant shifts were seen, but this may have been due to lower signal-to-noise ratios. The specific frequency bands containing significant shifts were variable across individuals. Further work is needed to determine the clinical usefulness of examining MOC shifts in individuals.     

Dengue Fever With Hemorrhagic Features in a Special Forces Soldier

Military operations are conducted in a variety of settings. Some settings provide significant U.S. resources for preventive, primary, urgent, andemergency or trauma care. Other operations consist of small numbers of personnel relying on limited internal, improvised, and/or host nation resources. Special Forces often conduct their missions in rural, austere, andremote settings with a small “medical footprint.” Often the supported government has difficulty providing essential services, including medical care. To address this, U.S. Special Forces select andtrain highly motivated individuals to perform medical duties in an exceptionally austere environment devoid of resources. This case highlights those services andthe medical decision-making process required to provide medical care to approach the standard of care in the United States. In this case, the affected individual had dengue fever.