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.

Comparison of metal artifact reduction using single-energy CT and dual-energy CT with various metallic implants in cadavers.

OBJECTIVES: The purpose of this study was to compare the effectiveness of metal artifact reduction using Single Energy Metal Artifact Reduction (SEMAR) and Dual Energy CT (DECT). MATERIALS AND METHODS: Six cadavers containing metal implants in the head, neck, abdomen, pelvis, and extremities were scanned with Standard, SEMAR, and DECT protocols on a 320-slice CT scanner. Four specialized radiologists blinded to acquisition methods rated severity of metal artifacts, visualization of anatomic structures, diagnostic interpretation, and image preference with a 5-point grading scale. RESULTS: Scores were significantly better for SEMAR than Standard images in the hip, knee, pelvis, abdomen, and maxillofacial scans (3.25 ±â€¯0.88 versus 2.14 ±â€¯0.93, p < 0.001). However, new reconstruction artifacts developed in SEMAR images that were not present in Standard images. Scores for severity of metal artifacts and visualization of smooth structures were significantly better for DECT than Standard images in the cervical spine (3.50±0.50 versus 2.0±0.58, p < 0.001) and was preferred over Standard images by one radiologist. In all other cases, radiologists preferred the Standard image over the DECT image due to increased image noise and reduced low-contrast resolution with DECT. In all cases, SEMAR was preferred over Standard and DECT images. CONCLUSION: SEMAR was more effective at reducing metal artifacts than DECT. Radiologists should be aware of new artifacts and review both the original and SEMAR images. When the anatomy or implant is relatively small, DECT may be superior to SEMAR without additional artifacts. However, radiologist should be aware of a reduction in soft tissue contrast.

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.

Comparison of implanted fiducial markers and self-expandable metallic stents for pancreatic image guided radiation therapy localization.

PURPOSE: The delivery of high-quality radiation therapy to pancreatic adenocarcinoma requires accurate localization. Radiopaque implanted fiducial markers (IFM) and self-expandable metallic stents (SEMS) have both been proposed as means of achieving accurate localization in image guided radiation therapy (IGRT). The suitability of IFM and SEMS for localization were evaluated in this study based on geometric and dosimetric surrogates. METHODS AND MATERIALS: In a retrospective study of 54 patients with pancreatic cancer who underwent tumor-directed IGRT, 9 were identified as having both IFM and SEMS. For each patient, cone beam computed tomography (CT) scans from each of 6 weeks of treatment were selected for review and comparison with the simulation CT. The centroids of both the IFM and SEMS on each cone beam CT were aligned with those on the planning CT to quantify geometric differences between IFM- and SEMS-based localization. This difference was used to mark the isocenter displacement from the original IFM-localized treatment plan to evaluate the dosimetric implications of SEMS localization. IFM were used as the localization standard given their intratumoral location, and the stability of IFM was evaluated by variability of intrafiducial distance. The original treatment plan was computed on the planning CT at the isocenter shifted by the determined displacement, and dose-volume histograms were calculated for the target volume and organs at risk. RESULTS: The average displacement for SEMS localization over all fractions in all patients was 7.7 mm. Planning target volume coverage by 90% of prescription dose was significantly reduced (mean, 11.1%; range, 0.5% to -46.6%) for SEMS compared with IFM localization (P < .05). Dose tolerances were exceeded for stomach, duodenum, and small bowel for 3, 3, and 5 of 9 patients, respectively, when SEMS localization was used. CONCLUSIONS: SEMS-based compared with IFM-based localization results in significant variability of radiation therapy localization for pancreatic cancer. IFM-based localization should be considered the standard of care for tumor-directed pancreatic cancer IGRT.

Evolution of the global burden of viral infections from unsafe medical injections, 2000-2010.

BACKGROUND: In 2000, the World Health Organization estimated that, in developing and transitional countries, unsafe injections accounted for respectively 5%, 32% and 40% of new infections with HIV, hepatitis B virus (HBV) and hepatitis C virus (HCV). Safe injection campaigns were organized worldwide. The present study sought to measure the progress in reducing the transmission of these viruses through unsafe injections over the subsequent decade. METHODS: A mass action model was updated, to recalculate the number of injection-related HIV, HCV and HBV infections acquired in 2000 and provide estimates for 2010. Data about the annual number of unsafe injections were updated. HIV prevalence in various regions in 2000 and 2010 were calculated from UNAIDS data. The ratio of HIV prevalence in healthcare settings compared to the general population was estimated from a literature review. Improved regional estimates of the prevalence of HCV seropositivity, HBsAg and HBeAg antigenemia were used for 2000 and 2010. For HIV and HCV, revised estimates of the probability of transmission per episode of unsafe injection were used, with low and high values allowing sensitivity analyses. RESULTS: Despite a 13% population growth, there was a reduction of respectively 87% and 83% in the absolute numbers of HIV and HCV infections transmitted through injections. For HBV, the reduction was more marked (91%) due to the additional impact of vaccination. While injections-related cases had accounted for 4.6%-9.1% of newly acquired HIV infections in 2000, this proportion decreased to 0.7%-1.3% in 2010, when unsafe injections caused between 16,939 and 33,877 HIV infections, between 157,592 and 315,120 HCV infections, and 1,679,745 HBV infections. CONCLUSION: From 2000 to 2010, substantial progress was made in reducing the burden of HIV, HCV and HBV infections transmitted through injections. In some regions, their elimination might become a reasonable public health goal.

Evolution of the global use of unsafe medical injections, 2000-2010.

OBJECTIVE: Since 1999, substantial efforts have been made by the international community to reduce the risks associated with unsafe injections, through ministries of health, international donors, the World Health Organization and the Safe Injection Global Network. The present study attempted to measure the progress, or lack thereof, made over the 2000-2010 decade in reducing unsafe injections in ten regions of the world corresponding to developing and transitional economies. METHODS: Data about the number of injections per person per year and the proportion of re-use of syringes and needles were obtained for 2010, mainly from population surveys, and compared with previous estimates for 2000 which had used various sources of information including injection safety assessments, population surveys and published studies on injection practices. RESULTS: From 2000 to 2010, in developing countries and transitional economies, the average number of injections per person per year decreased from 3.40 to 2.88, while the proportion of re-use of injection devices dropped from 39.8% to 5.5%. Combining both factors the number of unsafe injections per person per year decreased from 1.35 to 0.16. Even if substantial progress has been made, the Eastern Mediterranean region remains problematic, with 0.57 unsafe injections per person per year. In sub-Saharan Africa and Latin America, people now receive on average only 0.04-0.05 unsafe injections per year. CONCLUSION: Substantial progress has been made in reducing the number of unsafe injections in developing countries and transitional economies, essentially through a reduction in the re-use of injection devices. In some regions, elimination of unsafe injections might become a reasonable goal.

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.

Dose correction in lung for HDR breast brachytherapy.

PURPOSE: To evaluate the dosimetric impact of lung tissue in Ir-192 APBI. MATERIAL AND METHODS: In a 40 × 40 × 40 cm(3) water tank, an Accelerated Partial Breast Irradiation (APBI) brachytherapy balloon inflated to 4 cm diameter was situated directly below the center of a 30 × 30 × 1 cm(3) solid water slab. Nine cm of solid water was stacked above the 1 cm base. A parallel plate ion chamber was centered above the base and ionization current measurements were taken from the central HDR source dwell position for channels 1, 2, 3 and 5 of the balloon. Additional ionization data was acquired in the 9 cm stack at 1 cm increments. A comparable data set was also measured after replacing the 9 cm solid water stack with cork slabs. The ratios of measurements in the two phantoms were calculated and compared to predicted results of a commercial treatment planning system. RESULTS: Lower dose was measured in the cork within 1 cm of the cork/solid water interface possibly due to backscatter effects. Higher dose was measured beyond 1 cm from the cork/solid water interface, increasing with path length up to 15% at 9 cm depth in cork. The treatment planning system did not predict either dose effect. CONCLUSIONS: This study investigates the dosimetry of low density material when the breast is treated with Ir-192 brachytherapy. HDR dose from Ir-192 in a cork media is shown to be significantly different than in unit density media. These dose differences are not predicted in most commercial brachytherapy planning systems. Empirical models based on measurements could be used to estimate lung dose associated with HDR breast brachytherapy.

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.