Optimization of Iodinated Contrast Media Inventory Management: Effect of Inventory Diversification on Waste Reduction.

PURPOSE: Iodinated contrast medium (ICM) is available in single- and multiuse vials of varying sizes, but CT departments often preferentially stock only a single or a limited number of vial sizes. The aims of this study were to assess actual ICM waste at a large safety-net hospital and to compare with estimated waste if single-use vials in a variety of vial sizes or multiuse vials were used. METHODS: ICM administrations were retrospectively reviewed for all CT examinations performed in 2021 in a department that stocked only 100-mL ICM vials. Administered ICM dose, opened ICM volume and number of vials, and wasted ICM were compared with hypothetical models using optimally sized single-use vials and multiuse vials. Contrast use was also compared by patient class. RESULTS: In total, 40,393 ICM administrations over 49,670 CT examinations among 26,028 patients were reviewed, totaling 4,168,335 mL of contrast media. The mean dose was 103 mL, with mode of 100 mL. Exclusive use of 100-mL vials resulted in 1,006,165 mL waste (mean waste, 26 mL/administration). Optimally sized single-use vials resulted in 436,515 mL waste (mean waste, 11 mL/administration). Multiuse vials resulted in 537,074 mL waste (mean waste, 13 mL/administration). The distribution of optimal single-use vial size differed significantly by patient class (P < .001), with inpatient examinations more amenable to the use of smaller single-use vials. CONCLUSIONS: Optimizing ICM inventory can reduce contrast waste by 50% to 59%. Regular monitoring of contrast use may help optimize inventory selection across care settings. This retrospective review supports scrutiny of ICM inventory management to reduce waste, save costs, and mitigate the impacts of supply-chain disruptions.

Nontraditional Uses of US Contrast Agents in Abdominal Imaging and Intervention.

With the increasing availability of contrast-enhanced US (CEUS) worldwide and in the United States, the potential applications of this modality in abdominal imaging and intervention are continuing to expand. CEUS leverages the many inherent benefits of US with a safe and unique microbubble contrast agent. When injected intravenously, US contrast agents (UCAs) function as a pure blood pool agent, augmenting diagnostic US examinations such as vascular imaging. In the procedure suite, UCA can be used to improve needle visualization and depict active extravasation. UCA may also be injected through needles and tubes into various body spaces, allowing the assessment of the urinary system, indwelling catheters, and other tracts and cavities. Some venous and lymphatic lesions may be diagnosed with the direct injection of a UCA into these lesions. The authors highlight some of the many applications that are relevant to the abdominal imaging professional and interventional radiologist but should not be considered a complete list, and users of UCAs should continue to consider uses beyond those traditionally highlighted in recent literature. Online supplemental material is available for this article. ©RSNA, 2022.

Safety of Radioembolization in the Setting of Angiographically Apparent Arterioportal Shunting.

PURPOSE: To retrospectively analyze adverse events (AE) in patients with hepatocellular carcinoma (HCC) treated with yttrium-90 radioembolization in the setting of angiographically apparent arterioportal shunts (APSs). MATERIALS AND METHODS: Thirty-two patients with HCC underwent radioembolization with APSs from January 2011 to September 2016, totaling 34 administrations using resin (6) and glass (28) microspheres. APSs were graded angiographically as segmental (9), ipsilobar (15), contralobar (7), or main portal (2), according to portal perfusion. Tumors were categorized as solitary (9), multifocal (7), or infiltrative (16). Both unilobar (25) and bilobar (7) disease was treated. Child Pugh Score was A (22), B (10), or C (2), with a median Model for End-Stage Liver Disease (MELD)/Na-MELD of 8/8.5. Median procedure dose was 132.6 Gy. AEs were graded using Combined Terminology Criteria for Adverse Events (CTCAE) version 4.0. Tumor response was assessed using the modified Response Evaluation Criteria in Solid Tumors (mRECIST). RESULTS: CTCAE grade ≥3 AEs were observed in 22% of patients. Barcelona Clinic Liver Cancer (BCLC) C patients with nonsegmental shunts who received lobar administrations had a grade ≥3 AE rate of 38% compared with the remaining cohort, which was 12% (P = .076). No events were reported in patients with segmental shunts (P = .023). Imaging analysis revealed mRECIST complete response (17), partial response (13), stable disease (3), and progressive disease (1). Overall survival at 6 months and 12 months was 72% and 57%, respectively. CONCLUSIONS: Radioembolization in the setting of APS may have a higher AE profile than reported literature when BCLC-C patients with nonsegmental shunts receive lobar administrations. Segmental shunts are generally well tolerated.

Manifestations of sickle cell disease on thoracic imaging.

Sickle cell disease is an inherited hemolytic disease with systemic complications. These complications significantly impact the patients' quality of life. There are characteristic radiological findings that can aid in the diagnosis and management of common sequelae of sickle cell disease. In this review, we will discuss the thoracic imaging findings of common complications of sickle cell disease in an organ-based approach and provide imaging examples of them.

Use of dMLC for implementation of dynamic respiratory-gated radiation therapy.

PURPOSE: To simulate and evaluate the use of dynamic multileaf collimators (dMLC) in respiratory gating to compensate for baseline drift. METHODS: Tumor motion tracking data from 30 lung tumors over 322 treatment fractions was analyzed with the finite state model. A dynamic respiratory gating window was established in real-time by determining the average positions during the previous two end-of-expiration breathing phases and centering the dMLC aperture on a weighted average of these positions. A simulated dMLC with physical motion constraints was used in dynamic gating treatment simulations. Fluence maps were created to provide a statistical description of radiation delivery for each fraction. Duty cycle was also calculated for each fraction. RESULTS: The average duty cycle was 2.3% greater under dynamic gating conditions. Dynamic gating also showed higher fluences and less tumor obstruction. Additionally, dynamic gating required fewer beam toggles and each delivery period was longer on average than with static gating. CONCLUSIONS: The use of dynamic gating showed better performance than static gating and the physical constraints of a dMLC were shown to not be an impediment to dynamic gating.

Correlation and prediction uncertainties in the cyberknife synchrony respiratory tracking system.

PURPOSE: The CyberKnife uses an online prediction model to improve radiation delivery when treating lung tumors. This study evaluates the prediction model used by the CyberKnife radiation therapy system in terms of treatment margins about the gross tumor volume (GTV). METHODS: From the data log files produced by the CyberKnife synchrony model, the uncertainty in radiation delivery can be calculated. Modeler points indicate the tracked position of the tumor and Predictor points predict the position about 115 ms in the future. The discrepancy between Predictor points and their corresponding Modeler points was analyzed for 100 treatment model data sets from 23 de-identified lung patients. The treatment margins were determined in each anatomic direction to cover an arbitrary volume of the GTV, derived from the Modeler points, when the radiation is targeted at the Predictor points. Each treatment model had about 30 min of motion data, of which about 10 min constituted treatment time; only these 10 min were used in the analysis. The frequencies of margin sizes were analyzed and truncated Gaussian normal functions were fit to each direction's distribution. The standard deviation of each Gaussian distribution was then used to describe the necessary margin expansions in each signed dimension in order to achieve the desired coverage. In this study, 95% modeler point coverage was compared to 99% modeler coverage. Two other error sources were investigated: the correlation error and the targeting error. These were added to the prediction error to give an aggregate error for the CyberKnife during treatment of lung tumors. RESULTS: Considering the magnitude of 2sigma from the mean of the Gaussian in each signed dimension, the margin expansions needed for 95% modeler point coverage were 1.2 mm in the lateral (LAT) direction and 1.7 mm in the anterior-posterior (AP) direction. For the superior-inferior (SI) direction, the fit was poor; but empirically, the expansions were 3.5 mm. For 99% modeler point coverage, the AP margin was 3.6 mm and the lateral margin was 2.9 mm. The SI margins for 99% modeler point coverage were highly variable. The aggregate error at 95% was 6.9 mm in the SI direction, 4.6 mm in the AP direction, and 3.5 in the lateral direction. CONCLUSIONS: The Predictor points follow the Modeler points closely. Margins were found in each clinical direction that would provide 95% modeler point coverage for 95% of the models reviewed in this study. Similar margins were found in two clinical directions for 99% modeler point coverage in 95% of models. These results can offer guidance in the selection of CTV margins for treatment with the CyberKnife.

Dynamic gating window for compensation of baseline shift in respiratory-gated radiation therapy.

PURPOSE: To analyze and evaluate the necessity and use of dynamic gating techniques for compensation of baseline shift during respiratory-gated radiation therapy of lung tumors. METHODS: Motion tracking data from 30 lung tumors over 592 treatment fractions were analyzed for baseline shift. The finite state model (FSM) was used to identify the end-of-exhale (EOE) breathing phase throughout each treatment fraction. Using duty cycle as an evaluation metric, several methods of end-of-exhale dynamic gating were compared: An a posteriori ideal gating window, a predictive trend-line-based gating window, and a predictive weighted point-based gating window. These methods were evaluated for each of several gating window types: Superior/inferior (SI) gating, anterior/posterior beam, lateral beam, and 3D gating. RESULTS: In the absence of dynamic gating techniques, SI gating gave a 39.6% duty cycle. The ideal SI gating window yielded a 41.5% duty cycle. The weight-based method of dynamic SI gating yielded a duty cycle of 36.2%. The trend-line-based method yielded a duty cycle of 34.0%. CONCLUSIONS: Dynamic gating was not broadly beneficial due to a breakdown of the FSM's ability to identify the EOE phase. When the EOE phase was well defined, dynamic gating showed an improvement over static-window gating.

Site-specific volumetric analysis of lung tumour motion.

The treatment of lung cancer with radiation therapy is hindered by respiratory motion. Real-time adjustments to compensate for this motion are hampered by mechanical system latencies and imaging-rate restrictions. To better understand tumour motion behaviour for adaptive image-guided radiation therapy of lung cancer, the volume of a tumour's motion space was investigated. Motion data were collected by tracking an implanted fiducial using fluoroscopy at 30 Hz during treatment sessions. A total of 637 treatment fractions from 31 tumours were used in this study. For each fraction, data points collected from three consecutive breathing cycles were used to identify instantaneous tumour location. A convex hull was created over these data points, defining the tumour motion envelope. The study sought a correlation between the tumour location in the lung and the convex hull's volume and shape. It was found that tumours located in the upper apex had smaller motion envelopes (<50 mm(3)), whereas tumours located near the chest wall or diaphragm had larger envelopes (>70 mm(3)). Tumours attached to fixed anatomical structures had small motion spaces. Three general shapes described the tumour motion envelopes: 50% of motion envelopes enclosed largely 1D oscillation, 38% enclosed an ellipsoid path, 6% enclosed an arced path and 6% were of hybrid shape. This location-space correlation suggests it may be useful in developing a predictive model, but more work needs to be done to verify it.