Jet Ventilation Decreases Target Motion and Increases Yield of ENB Especially in Lesions With Negative Bronchus Sign.

BACKGROUND: Electromagnetic navigational bronchoscopy (ENB) is used to obtain peripheral lung tissue samples for evaluation and staging of central and peripheral lung lesions. Jet ventilation delivers and maintains a sustained airway pressure at high frequency, chest wall and diaphragmatic movement is drastically reduced compared with traditional ventilation. The current study looks to examine the effectiveness of tissue sampling (diagnostic yield) while using jet ventilation on target-lesion movement when compared with traditional ventilation. METHODS: A total of 36 patients received total intravenous anesthesia with both jet and traditional ventilation during ENB procedure where sensor to lesion displacement was recorded. When planning the ENB procedure, the presence or absence of a viable airway to the lesion was recorded. Sensor to lesion movement was recorded and compared for significance using χ and t tests, utilizing stringent P-values. RESULTS: Overall patients with an airway to the lesion (n=23) had a higher proportion of successful diagnostic biopsies, 83% compared with those patients that lacked an airway to the lesion (n=13) 70% proportion of successful diagnostic biopsies. When using jet ventilation, the chance of nonzero displacement was 8.3% (0.14 mm), regardless of the presence of an airway. Compared with traditional ventilation, the chance of a nonzero displacement between the sensor and target-lesion was 83% (6.4 mm), independent of airway presence to the lesions. CONCLUSION: In patients without an airway, jet ventilation significantly decreased target displacement when compared with traditional ventilation (2 vs. 17 mm). In patients with direct airway to the lesion, jet ventilation did not significantly decrease target displacement when compared with the traditional approach.

Harmonic subtraction for evaluating right ventricle ejection fraction from planar equilibrium radionuclide angiography.

We report an initial investigation of a subtraction-based method to estimate right ventricle ejection fraction (RVEF) from ECG-gated planar equilibrium radionuclide angiography (ERNA) data. Twenty-six consecutive patients referred for scintigraphic evaluation of cardiac function prior to chemotherapy had ECG-gated first-pass (FP) imaging and ERNA imaging performed following the same radiotracer injection. RVEF was computed from FP images (RVEFFP) and separately from ERNA images (RVEFERNA). Standard methods for computing ejection fractions were used to obtain RVEFFP values. RVEFERNA values were obtained using harmonic subtraction of the left ventricular contribution from a biventricular region of interest contoured on the equilibrium images acquired in the shallow right anterior oblique projection. Clinically acquired chest CT data were used to derive information regarding the relative position of the left and right ventricle and about the presence of pulmonary artery enlargement. Computation of RVEFERNA was successful for each of the 26 patients. Computation of RVEFFP failed for four patients. For the 22 patients for which RVEF was computed using both methods, the average RVEFFP was 49% and the average RVEFERNA was 51%, with coefficients of variation of 11 and 7.5%, respectively. Low RVEFERNA values were associated with pulmonary artery dilation. Estimation of RVEFERNA, using a harmonic subtraction-based method of computation is clinically feasible and accurate in the patient population studied. The results support further investigation in patients with frank heart failure.

Clinical intervention for quality improvement of gastric-emptying studies.

UNLABELLED: Prompted by clinical concerns for false-negative tests, we implemented a clinical intervention consisting of a training session and an image-based verification procedure to document homogeneous radioactivity distribution in the radiolabeled meal (egg substitute per the guideline). METHODS: A technologist training session emphasized the importance of thorough mixing of (99m)Tc-sulfur colloid in the egg meal. For 6 mo after training, an image of the prepared mixed egg was acquired before patient ingestion. Consecutive gastric-emptying studies performed 6 mo before and after training were reviewed by 2 experienced physicians. RESULTS: There were 7 abnormal and 44 normal studies before and 15 abnormal and 29 normal studies after training (P < 0.05). Subjective evaluations of images for meal-mixing quality by 2 readers correlated with each other and with an objective measure of expected gastric-emptying physiology (correlation coefficients, 0.54 and 0.38, respectively). CONCLUSION: The described clinical intervention improved the accuracy of our gastric-emptying studies by decreasing false-negative studies.

Extravasation of a therapeutic dose of 131I-metaiodobenzylguanidine: prevention, dosimetry, and mitigation.

UNLABELLED: After the extravasation of a therapeutic dose of (131)I-metaiodobenzylguanidine that produced a radiation burn to a patient's forearm, we instituted a catheter placement verification protocol. METHODS: Before therapy infusion, proper placement is verified by administering 37 MBq of (99m)Tc-pertechnetate through the catheter, and monitoring activity at the administration site and on the contralateral extremity. A dosimetric model describing both high-rate and low-rate dose components was developed and predicted that the basal epidermal layer received a radiation dose consistent with the observed moist desquamation radiation skin toxicity. RESULTS: No extravasation incidents have occurred since the verification procedure was instituted. CONCLUSION: To protect against radiation injury from extravasation of therapeutic radionuclides, test administration of a small (99m)Tc dose with probe monitoring of comparable sites in both upper extremities appears to be an effective preventive measure.

Shortening the 4-hour gastric-emptying protocol.

PURPOSE: A standardized 4-hour gastric-emptying protocol has been recommended by a consensus panel. However, a study length of 4 hours may be inconvenient. The purpose of this investigation was to determine if the percent emptying at 2 hours could predict abnormal or normal results at 4 hours. METHODS: Our data consist of 2 distinct patient groups, containing 174 and 158 patients, respectively. All patients were given a standardized meal according to the Tougas et al protocol. Percent gastric emptying was measured at 1, 2, 3, and 4 hours (or until gastric emptying was equal to or more than 90%). The sensitivity, specificity, and the likelihood ratios of the 2-hour cutoffs were determined using the 4-hour data as the standard. We have estimated the accuracy and percent of studies stopped at 2 hours, resulting from various "definitely normal" and "definitely abnormal" threshold combinations. RESULTS: Using gastric emptying of less than 35% at 2 hours for diagnosis of delayed gastric emptying, and emptying at 2 hours greater than 55% for a diagnosis of normal gastric emptying yielded accuracies of 0.966 and 0.949 in the 2 datasets, respectively, compared with the Tougas standard values. The observed 2-hour gastric-emptying values would have allowed early termination in 79% and 78% of the studies, respectively. CONCLUSION: Adopting criteria for the termination of gastric-emptying study at 2 hours in selected patients yields significant reductions in the average length of a gastric-emptying study, while maintaining study accuracy.

Overcorrection of iodinated contrast attenuation in SPECT-CT: phantom studies.

PURPOSE: The authors investigated the effects of iodinated contrast agents on the quantification of radioactivity obtained using a combined single photon emission tomography (SPECT) and high resolution 16 slice computed tomography (CT) scanner. METHODS: Two conditions were evaluated: Contrast media mixed with radioisotope and the contrast media, and the radioisotope solution confined in adjacent but distinct volumes. Phantoms containing combinations of 99mTc, 111In, and 131I solutions in normal saline and contrast solutions in normal saline corresponding to the two conditions were prepared and scanned. Images were reconstructed by iterative reconstruction (ordered subset expectation maximization), with and without CT-derived attenuation maps. The reconstructed counts encoded in the reconstructed images were compared. RESULTS: Compared to normal saline, the presence of an iodinated contrast agent resulted in the underestimation of reconstructed counts in all nonattenuation corrected SPECT images. Compared to normal saline, the presence of a contrast agent resulted in the overestimation of reconstructed counts in all attenuation corrected SPECT images. The largest underestimation of reconstructed counts was 12.8% and the largest overestimation value was 35.9%. CONCLUSIONS: High concentrations of a contrast agent caused errors in the measurement of actual radiotracer reconstructed counts in phantoms. These errors could have important consequences for the use of oral and intravenous contrast in both diagnostic (qualitative) and dosimetric (quantitative) SPECT-CT imaging. The authors' findings suggest that noncontrast imaging or alternative contrast-specific attenuation correction approaches should be considered for optimal SPECT activity quantification.

Experience with a simplified, standardized 4-hour gastric-emptying protocol.

UNLABELLED: Gastric-emptying studies have no accepted standard methodology or reference values. A simplified standardized protocol with a large reference database has been proposed, with imaging obtained at only 0, 1, 2, and 4 h. The rationale for its 4-h length is data suggesting that delayed emptying is detected with higher sensitivity at 4 h than at 2 h. The purpose of the current investigation was to review our 2-y experience using this protocol, to determine the added value of 4-h imaging, and to determine whether the lag phase can predict delayed emptying. METHODS: After ingesting a sandwich made with (99m)Tc-sulfur colloid egg substitute, 175 patients were imaged immediately, every 10 min for 1 h, and then at 2, 3, and 4 h. Percentage retention was calculated for each interval. Sensitivities, specificities, predictive values, and receiver operating characteristic (ROC) curves were computed for the 1-, 2-, and 3-h intervals on the basis of normal 4-h values. Data were analyzed to determine the added value of the 4-h study. Thresholds were sought that optimized accuracy. ROC analysis was used to determine the predictive value of the lag phase. RESULTS: Gastric emptying was delayed in 20% of patients at 2 h and in 26% at 4 h, a 29% increase in abnormal studies (P < 0.02). Of those normal at 2 h, 13% became abnormal at 4 h. Of those with delayed emptying at 2 h, 24% normalized at 4 h. Compared with the study at 4 h, the study at 2 h had a 59% sensitivity, 94% specificity, 76% PPV, and 87% NPV. ROC analysis showed that the areas under the ROC curve (AUC) were 0.75, 0.93, and 0.97 at 1, 2, and 3 h, respectively. The threshold for optimal accuracy for 3-h data was estimated to be greater than 30% retention. The accuracy of this threshold was 91%. The lag phase AUC for predicting delayed emptying at 4 h was 0.60. CONCLUSION: This first investigation of a large referral patient population using a standardized protocol found that abnormal emptying is detected with greater sensitivity at 4 h than at 2 h and that the lag phase is not predictive of delayed emptying.

Setup errors in patients treated with intensity-modulated whole pelvic radiation therapy for gynecological malignancies.

Intensity-modulated whole pelvic radiation therapy (IM-WPRT) has decreased the incidence of gastrointestinal complications by reducing the volume of normal tissue irradiated in gynecologic patients. However, IM-WPRT plans result in steep dose gradients around the target volume, and thus accurate patient setup is essential. To quantify the accuracy of our patient positioning, we examined the weekly portal films of 46 women treated with IM-WPRT at our institution. All patients were positioned using a customized immobilization device that was indexed to the treatment table. Setup errors were evaluated by comparing portal images to simulation images using an algorithm that registers user-defined open curve segments drawn on both sets of film. The setup errors, which were separated into systematic and random components, ranged from 1.9 to 3.7 mm for the translations and 1.3 degrees to 4.4 degrees for the 2 in-plane translations. The systematic errors were all less than the respective random errors, with the largest error in the anterior/posterior direction. In addition, there was no correlation between the magnitude of these errors and patient-specific factors (age, weight, height). In the future, we will investigate the effect of these setup errors on the delivered dose distribution.