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Background: Computed tomography pulmonary angiography (CTPA) is a non-invasive imaging method that can quickly diagnose pulmonary embolism. This study aimed to compare test bolus and bolus track contrast enhancement protocols to determine the optimal technique for CTPA in the diagnosis of pulmonary embolism. Methods and Results: This retrospective study was conducted at the King Abdul-Aziz Specialist Hospital (KASH) in Taif city from September 2022 to March 2023. Ninety-eight patients with suspected PE were included in the study: underwent CTPA using the test bolus (TB) approach, and 49 patients underwent CTPA using the bolus tracking (BT) approach. The examination was performed using a 128-slice CT scanner. Densities of pulmonary arteries were measured based on the Hounsfield unit (HU) and compared between two groups (TB and BT) based on gender and age. The mean HU of the pulmonary arteries was significantly higher in the TB group than that of the BT group (392.06±110.77 HU and 298.9±93.098 HU, respectively, P=0.001). There was no statistically significant difference in the mean HU between females of the two groups [P=0.062]. In contrast, men in the TB group had a substantially greater density (384.7±116 HU) than men in the BT group (273.0±88.0 HU) [P=0.001]. There were no statistically significant differences between the two groups based on age except for the age subgroup 46-55 years; the TB group exhibited considerably higher density (421.54±138.148 HU) than the BT group (255.2±82.155 HU) [P=0.003]. The ANOVA test showed no statistically significant correlation between the effects of tracking systems, gender, and age on tracking intensity [P=0.640]. Conclusion: Both TB and BT procedures are accurate for diagnosing pulmonary embolism. A TB protocol results in significantly better opacification of the pulmonary arteries in men aged 46 to 55 than the BT protocol.

This study aimed to determine the scan delay for bolus tracking in the hepatic artery phase (HAP) of hepatic dynamic computed tomography (CT) using the cardiothoracic ratio (CTR) from CT scout images. We retrospectively studied 188 patients who underwent hepatic dynamic CT, 24 of whom had scan delays adjusted for CTR. The contrast enhancement of the abdominal aorta, portal vein, hepatic vein, and hepatic parenchyma was calculated for HAP. The adequacy of the scan timing for HAP was assessed using three classifications: early, appropriate, or late. The effect of HAP on scan timing adequacy was determined using multivariate logistic regression analysis, and the optimal cutoff value of CTR was evaluated using receiver operating characteristic analysis. The trigger times for bolus tracking (odds ratio: 1.58) and CTR (odds ratio: 1.23) were significantly affected by the appropriate scan timing of the HAP. The optimal cutoff value of CTR was 59.3%. The scan timing of HAP with a scan delay of 15 s was 14% of early and 86% of appropriate, and the proportion of early in CTR ≥ 60% (early, 52%; appropriate, 48%) was higher than that in CTR < 60% (early, 6%; appropriate, 94%). Adjusting the scan delay to 20 s in CTR ≥ 60% increased the proportion of appropriate (early, 4%; appropriate, 96%). The CTR of a CT scout image is an effective index for determining the scan delay for bolus tracking. Adjusting the scan delay by CTR can provide appropriate HAP images in more patients. Trial registration number: R-080; date of registration: 9 March 2023, retrospectively registered. [ABSTRACT FROM AUTHOR]

Background: Consistent coronary artery enhancement is essential to achieve accurate and reproducible quantification of coronary plaque composition. Purpose: To optimize coronary artery uniformity of enhancement using a bolus tracking technique with a dual region of interest (ROI) in coronary computed tomography angiography (CCTA) on a 320-detector CT scanner. Material and Methods: This prospective study recruited 100 consecutive patients who underwent CCTA and were randomly divided into two groups, namely, a manual trigger group (n = 50), in which a manual fast start technique was used to start the diagnostic scan with the visual evaluation of attenuation in the left atrium and left ventricle, and an automatic trigger group (n = 50), in which a bolus tracking technique was used to automatically start the breath-holding command and diagnostic scan with two ROIs placed in the right and left ventricles. Coronary artery image quality was assessed using quantitative and qualitative scores. The enhancement uniformity was characterized by attenuation variability of the ascending aorta (AAO) and coronary arteries. Results: No statistically significant differences in the image quality of the coronary arteries were observed between the two groups (all P > 0.05). The coefficients of variation (COVs) of arterial attenuation in the automatic trigger group were significantly smaller than in the manual trigger group (AAO: 9.89% vs. 17.93%; LMA: 10.35% vs. 18.98%; LAD proximal: 12.09% vs. 20.84%; LCX proximal: 11.85% vs. 20.95%; RCA proximal: 12.13% vs. 20.84%; all P < 0.05). Conclusion: The automatic trigger technique accompanied with dual ROI provides consistent coronary artery enhancement and optimizes coronary artery enhancement uniformity in CCTA on a 320-detector CT scanner. [ABSTRACT FROM AUTHOR]

Background: Cervicocerebral CT angiography (CTA) using the bolus tracking technique has been widely used for the assessment of cerebrovascular diseases. Regions of interest (ROI) can be placed in the descending aorta, ascending aorta, and the aortic arch. However, no study has compared the arteries and veins display when when the region of interest (ROI) is placed at different sites. In this study, we showed the impact of ROI positions on the image quality of cervicocerebral CTA. Methods: Two hundred and seventy patients who underwent cervicocerebral CTA with bolus tracking technique were randomly divided into three groups based on the position of the ROI placement: ascending aorta (Group 1, n = 90), aortic arch (Group 2, n = 90), and descending aorta (Group 3, n = 90). The scanning parameters and contrast agent injection protocols were consistent across all groups. Three observers independently assessed the objective image quality, while two observers jointly assessed the subjective image quality using a grade scale: poor (grade 1), average (grade 2), good (grade 3), and excellent (grade 4). The differences in intravascular CT values, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), AVCR (arterial venous contrast ratio), and subjective image quality scores were compared among the three groups. Results: The CT values of the intracranial veins (superior sagittal sinus, ethmoid sinus and great cerebral vein) in group 1 were significantly lower than those in group 3 (p

PurposeAcquisition timing and B1 calibration are two key factors that affect the quality and accuracy of hyperpolarized 13 C MRI. The goal of this project was to develop a new approach using regional bolus tracking to trigger Bloch-Siegert B1 mapping and real-time B1 calibration based on regional B1 measurements, followed by dynamic imaging of hyperpolarized 13 C metabolites in vivo.MethodsThe proposed approach was implemented on a system which allows real-time data processing and real-time control on the sequence. Real-time center frequency calibration upon the bolus arrival was also added. The feasibility of applying the proposed framework for in vivo hyperpolarized 13 C imaging was tested on healthy rats, tumor-bearing mice and a healthy volunteer on a clinical 3T scanner following hyperpolarized [1-13 C]pyruvate injection. Multichannel receive coils were used in the human study.ResultsAutomatic acquisition timing based on either regional bolus peak or bolus arrival was achieved with the proposed framework. Reduced blurring artifacts in real-time reconstructed images were observed with real-time center frequency calibration. Real-time computed B1 scaling factors agreed with real-time acquired B1 maps. Flip angle correction using B1 maps results in a more consistent quantification of metabolic activity (i.e, pyruvate-to-lactate conversion, kPL ). Experiment recordings are provided to demonstrate the real-time actions during the experiment.ConclusionsThe proposed method was successfully demonstrated on animals and a human volunteer, and is anticipated to improve the efficient use of the hyperpolarized signal as well as the accuracy and robustness of hyperpolarized 13 C imaging.

PurposeAcquisition timing and B1 calibration are two key factors that affect the quality and accuracy of hyperpolarized 13 C MRI. The goal of this project was to develop a new approach using regional bolus tracking to trigger Bloch-Siegert B1 mapping and real-time B1 calibration based on regional B1 measurements, followed by dynamic imaging of hyperpolarized 13 C metabolites in vivo.MethodsThe proposed approach was implemented on a system which allows real-time data processing and real-time control on the sequence. Real-time center frequency calibration upon the bolus arrival was also added. The feasibility of applying the proposed framework for in vivo hyperpolarized 13 C imaging was tested on healthy rats, tumor-bearing mice and a healthy volunteer on a clinical 3T scanner following hyperpolarized [1-13 C]pyruvate injection. Multichannel receive coils were used in the human study.ResultsAutomatic acquisition timing based on either regional bolus peak or bolus arrival was achieved with the proposed framework. Reduced blurring artifacts in real-time reconstructed images were observed with real-time center frequency calibration. Real-time computed B1 scaling factors agreed with real-time acquired B1 maps. Flip angle correction using B1 maps results in a more consistent quantification of metabolic activity (i.e, pyruvate-to-lactate conversion, kPL ). Experiment recordings are provided to demonstrate the real-time actions during the experiment.ConclusionsThe proposed method was successfully demonstrated on animals and a human volunteer, and is anticipated to improve the efficient use of the hyperpolarized signal as well as the accuracy and robustness of hyperpolarized 13 C imaging.

The split-bolus method in computed tomography (CT) is the method used in the evaluation of renal dynamic enhancement stages and in the detection of pathologies. When designing the CT urography technique, there are several important options such as single-bolus and split bolus techniques. The single-bolus method consists of three separate post-contrast phases: arterial, nephrographic, and excretory (pyelogram), as a result raising the total radiation dose imparted to patients. On the other hand, in the split-bolus technique, the contrast dose is divided into several separate administrations to obtain the nephrographic and excretory phases simultaneously. With the split-bolus technique, by reducing the radiation dose and the number of phases that the patient will be exposed to, urinary system evaluation and the whole abdomen pathological evaluations can be performed. The device to be used in imaging must be a tomography device with at least 16 Multidetector CT sections. The bolus tracking method is one of the most accurate contrast delivery methods for renal dynamics and the split-bolus technique. Automatic dose calibration is used. [ABSTRACT FROM AUTHOR]

Background: Parathyroid lesions are identified by subjective enhancement and washout patterns on computed tomography (CT). We have previously proposed "percentage arterial enhancement" (PAE) as an objective index and now aim to validate its performance prospectively. Methods: Dual‐phase CT was performed in 40 consecutive primary hyperparathyroidism patients. PAE was calculated as [{arterial phase Hounsfield unit (HU)‐unenhanced phase HU}/unenhanced phase HU] × 100. PAE > 128.9% was considered parathyroid. Results: PAE had 94.2% sensitivity, 100% positive predictive value (PPV) in lateralization, and sensitivity and PPV of 93.9% in quadrant localization of single‐gland disease. PAE failed to identify two lesions: an intrathyroidal parathyroid carcinoma in the background of multinodular goiter and another lower enhancing cystic parathyroid adenoma. PAE had 60% sensitivity, and 100% PPV to identify multigland disease. The mean effective dose was 2.74 mSV. Conclusions: PAE is a specific CT index for parathyroid lesions with less radiation exposure. Areas of caution include intrathyroidal and cystic lesions. [ABSTRACT FROM AUTHOR]

Contrast-enhanced CT angiography (CTA) is a widely used, noninvasive imaging technique for evaluating cardiovascular structures. Contrast-induced nephrotoxicity is a concern in renal disease; however, the true nephrotoxic potential of iodinated contrast media (CM) is unknown. If a renal impaired patient requires CTA, it is important to protect the kidneys from further harm by reducing total iodinated CM volume while still obtaining diagnostic quality imaging. These same reduced volume CM techniques can also be applied to nonrenal impaired patients in times of CM shortage. This educational review discusses several modifications to CTA that can be adapted to both conventional 64-slice and the newer generation CT scanners which enable subsecond acquisition with a reduced CM volume technique. Such modifications include hardware and software adjustments and changes to both the volume and flow rate of administered CM, with the goal to reduce the dose of CM without compromising diagnostic yield. [ABSTRACT FROM AUTHOR]

PurposeA novel application of two-dimensional (2D) spatially selective radiofrequency (2DRF) excitation pulses in hyperpolarized 13C imaging is proposed for monitoring the bolus injection with highly efficient sampling of the initially polarized substrate, thus leaving more polarization available for detection of the subsequently generated metabolic products.MethodsA 2DRF pulse was designed with a spiral trajectory and conventional clinical gradient performance. To demonstrate the ability of our 2DRF bolus tracking pulse sequence, hyperpolarized [1-(13)ruvate in vivo imaging experiments were performed in normal rats, with a comparison to 1DRF excitation pulses.ResultsOur designed 2DRF pulse was able to rapidly and efficiently monitor the injected bolus dynamics in vivo, with an 8-fold enhanced time resolution in comparison with 1DRF in our experimental settings. When applied at the pyruvate frequency for bolus tracking, our 2DRF pulse demonstrated reduced saturation of the hyperpolarization for the substrate and metabolic products compared to a 1DRF pulse, while being immune to ±0.5 ppm magnetic field inhomogeneity at 3T.Conclusion2DRF pulses in hyperpolarized 13C imaging can be used to efficiently monitor the bolus injection with reduced hyperpolarization saturation compared to 1DRF pulses. The parameters of our design are based on clinical scanner limits, which allows for rapid translation to human studies.

This study aimed to determine the optimal placement of the region of interest (ROI) among four anatomical sites--pulmonary artery (PA), pulmonary vein (PV), aortic arch (AA), and carotid artery (CA)--in computed tomography (CT) brain angiography with automatic bolus tracking in healthy beagle dogs. Six beagles were included, and CT brain angiography was performed four times for each dog, to cover each ROI. The scan parameters, amount, and injection rate of the contrast medium were the same. The major intracranial arteries were selected for quantitative and qualitative evaluation: caudal cerebellar artery (CcA), basilar artery (BA), rostral cerebellar artery (RcA), caudal cerebral artery (CCA), middle cerebral artery (MCA), and rostral cerebral artery (RCA). Quantitative evaluation showed significantly higher CT attenuation values for the RcA, CCA, and MCA in the PA group and RcA and MCA in the PV group than in the CA group. Qualitative analysis revealed significantly higher scores for the BA, CCA, and MCA in the PA and PV groups than in the CA group. Venous contamination did not differ significantly among the ROIs, but the mean scores of the AA and CA groups were higher than those of the PA and PV groups. CT brain angiography using bolus tracking in the beagle dogs showed that the ROI should be placed at the PA or PV rather than at the CA for optimal images with strong contrast enhancement of the BA, RcA, CCA, and MCA and minimal venous contamination. [ABSTRACT FROM AUTHOR]

Background: Cervicocerebral CT angiography (CTA) using the bolus tracking technique has been widely used for the assessment of cerebrovascular diseases. Regions of interest (ROI) can be placed in the descending aorta, ascending aorta, and the aortic arch. However, no study has compared the arteries and veins display when when the region of interest (ROI) is placed at different sites. In this study, we showed the impact of ROI positions on the image quality of cervicocerebral CTA., Methods: Two hundred and seventy patients who underwent cervicocerebral CTA with bolus tracking technique were randomly divided into three groups based on the position of the ROI placement: ascending aorta (Group 1, n = 90), aortic arch (Group 2, n = 90), and descending aorta (Group 3, n = 90). The scanning parameters and contrast agent injection protocols were consistent across all groups. Three observers independently assessed the objective image quality, while two observers jointly assessed the subjective image quality using a grade scale: poor (grade 1), average (grade 2), good (grade 3), and excellent (grade 4). The differences in intravascular CT values, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), AVCR (arterial venous contrast ratio), and subjective image quality scores were compared among the three groups., Results: The CT values of the intracranial veins (superior sagittal sinus, ethmoid sinus and great cerebral vein) in group 1 were significantly lower than those in group 3 (p < 0.001). However, no significant differences were observed in CT values, SNR and CNR in the internal carotid artery and middle cerebral artery among the three groups. The proportion of images with grade 4 was significantly higher in group 1 than group 2 and 3 (41.1% vs 15.6% and 13.3%, p < 0.001). The proportion of images with grade 1 was significantly lower in group 1 than group 2 and 3 (1.1% vs 6.6% and 17.8%, p < 0.001)., Conclusion: The ROI positions for cervicocerebral CTA did not affect the arterial image quality, but venous structures imaging was affected when the ROI was placed in the ascending aorta., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Purpose: This study aims to prove that the test bolus technique provides a better selective imaging study of the pulmonary arterial system in comparison to the automatic bolus-tracking technique. Method: A prospective study included 600 patients, classified into 2 groups where each group consisted of 300 patients. In group A, we used the bolus tracking technique with 80−100 ml of contrast while in group B test bolus technique was used with 50 mL of contrast. Results: It was clear that the Main PA average density was 260.5 HU in group A and increased to 320 HU in group B with P value < 0.002. The Ascending aorta average density decreased from 250 HU in group A to 130 HU in group B with P value

Background: Brachycephalic dogs with pulmonary stenosis are known to have a higher incidence of concurrent coronary artery abnormalities than non‐brachycephalic breeds, which increases risk when performing balloon valvuloplasty. The use of ECG‐gated CT angiography has been reported for the evaluation of coronary arteries in normal dogs and dogs with pulmonary stenosis. The purpose of this study was to report findings of coronary artery origination and morphology of main branches using ECG‐gated CT angiography in brachycephalic dogs with pulmonary stenosis. Methods: An ECG‐gated CT angiographic protocol was used to image coronary artery anatomy in nine brachycephalic dogs with pulmonary stenosis. Images were assessed for quality as well as coronary artery morphology by one veterinary radiologist, one veterinary cardiologist and one veterinary radiology resident. Results: All nine dogs had good to excellent image quality. Coronary artery anomalies were identified in three of nine dogs: one R2A anomaly, one L2A anomaly and one L2C anomaly. Two dogs were assessed to be poor balloon valvuloplasty candidates based on CT angiographic images. Limitation: Coronary artery morphology was not confirmed via postmortem examination in all patients. Conclusion: ECG‐gated CT angiography is a minimally invasive imaging modality capable of diagnosing various coronary artery anomalies in brachycephalic dogs with pulmonary stenosis and aiding in the determination of patient candidacy for balloon valvuloplasty. [ABSTRACT FROM AUTHOR]

Purpose: Acquisition timing and B1 calibration are two key factors that affect the quality and accuracy of hyperpolarized 13C MRI. The goal of this project was to develop a new approach using regional bolus tracking to trigger Bloch‐Siegert B1 mapping and real‐time B1 calibration based on regional B1 measurements, followed by dynamic imaging of hyperpolarized 13C metabolites in vivo. Methods: The proposed approach was implemented on a system which allows real‐time data processing and real‐time control on the sequence. Real‐time center frequency calibration upon the bolus arrival was also added. The feasibility of applying the proposed framework for in vivo hyperpolarized 13C imaging was tested on healthy rats, tumor‐bearing mice and a healthy volunteer on a clinical 3T scanner following hyperpolarized [1‐13C]pyruvate injection. Multichannel receive coils were used in the human study. Results: Automatic acquisition timing based on either regional bolus peak or bolus arrival was achieved with the proposed framework. Reduced blurring artifacts in real‐time reconstructed images were observed with real‐time center frequency calibration. Real‐time computed B1 scaling factors agreed with real‐time acquired B1 maps. Flip angle correction using B1 maps results in a more consistent quantification of metabolic activity (i.e, pyruvate‐to‐lactate conversion, kPL). Experiment recordings are provided to demonstrate the real‐time actions during the experiment. Conclusions: The proposed method was successfully demonstrated on animals and a human volunteer, and is anticipated to improve the efficient use of the hyperpolarized signal as well as the accuracy and robustness of hyperpolarized 13C imaging. [ABSTRACT FROM AUTHOR]

Background The importance of bolus tracking (BT) regarding total effective radiation dose (ERD) in the era of advanced coronary computed tomography angiography (CTA) has been ignored. We aimed to investigate whether adjusting BT parameters reduces ERD. Methods Adults consecutively referred to CTA (n = 289) in a 320 detector-row scanner were distributed into four BT protocols according to delay time and time between intermittent scans, as follows: A (n = 70, delay 10s, intermittent scans 1s); B (n = 79, delay 10s, intermittent scans 2s); C (n = 68, delay 15s, intermittent scans 1s); and D (n = 72, delay 15s, intermittent scans 2s). Image quality was assessed. Results The overall ERD in BT and AP were 0.32 ± 0.14 mSv and 6.06 ± 0.66 mSv, respectively. ERD in BT was different among protocols (A:0.44 ± 0.14 mSv; B:0.32 ± 0.10 mSv; C:0.28 ± 0.14 mSv; D:0.23 ± 0.09 mSv; p < 0.001), with no loss in image quality. Adjusted for potential confounders (heart rate, tube current and acquisition window), protocol D provided the highest reduction in total ERD (β = −0.33, p = 0.004). Conclusion Delaying initiation of BT images (and acquiring them less frequently) reduces radiation dose and does not impair image quality. [ABSTRACT FROM AUTHOR]

Object: We aimed to modify our previously published method for arterial input function measurements for evaluation of cerebral perfusion (dynamic susceptibility contrast MRI) such that it can be applied in humans in a clinical setting.Materials and methods: Similarly to our previous work, a conventional measurement sequence for dynamic susceptibility contrast MRI is extended with an additional measurement slice at the neck. Measurement parameters at this slice were optimized for the blood signal (short echo time, background suppression, magnitude and phase images). Phase-based evaluation of the signal in the carotid arteries is used to obtain quantitative arterial input functions.Results: In all pilot measurements, quantitative arterial input functions were obtained. The resulting absolute perfusion parameters agree well with literature values (gray and white matter mean values of 46 and 24 mL/100 g/min, respectively, for cerebral blood flow and 3.0% and 1.6%, respectively, for cerebral blood volume).Conclusions: The proposed method has the potential to quantify arterial input functions in the carotid arteries from a direct measurement without any additional normalization. [ABSTRACT FROM AUTHOR]

This study was performed to optimize scan delays for canine kidney by using a bolus-tracking technique. In six beagle dogs, computed tomography (CT) of the kidney was performed three times in each dog with different scan delays after a bolus-tracking trigger of 100 Hounsfield units (HU) of aortic enhancement. Delays were 5, 20, 35, and 50 sec for the first scan, 10, 25, 40, and 55 sec for the second scan, and 15, 30, 45, and 60 sec for the third scan. The renal artery-to-vein contrast difference peaked at 5 sec, and the renal cortex-to-medulla contrast difference peaked at 10 sec. The renal cortex-to-medulla contrast difference approached zero at a scan delay of 30 sec after the bolus trigger. For the injection protocol used in this study, the optimal scan delay times for renal arterial, corticomedullary, and nephrographic phases were 5, 10, and 30 sec after triggering at 100 HU of aortic enhancement using the bolus-tracking technique. The bolus-tracking technique is useful in multi-phase renal CT study as it compensates for different transit times to the kidney among different animals, requires a small dose of contrast media, and does not require additional patient radiation exposure. [ABSTRACT FROM AUTHOR]

Multidetector computed tomography angiography (MDCTA) has become a well-established modality for limb angiography for a variety of indications. The technique of MDCTA depends on the scanner features including the number of detector rows, rotation speeds and single or dual source energy. Integral to a diagnostic quality CTA is the acquisition timing. Various techniques are available for determining the appropriate timing of scan acquisition which includes fixed delay, test bolus and the bolus tracking technique. The transit times of contrast from the aorta to the peripheral arteries shows a wide variability and is dependent upon the inter individual hemodynamic states. The bolus tracking technique is the most preferred one which allows reliable scan timing with acceptable contrast volume and radiation dose. Pitfalls with all these techniques are well described and we report one such technical pitfall in a case of left foot arteriovenous malformation (AVM) where the bolus tracking technique employed for scan triggering failed to initiate acquisition.

The purpose of this study was to optimize the monitoring dose, obtained using the conventional filtered back projection (FBP) method and iterative reconstruction algorithms, for the bolus tracking technique. A phantom study was performed to assess the effect of the scan start time in patients grouped according to different body weights. An oval torso phantom was used for simulating the time enhancement curve of the bolus tracking technique. To reproduce image noise levels in the two body weight groups, the phantom diameter was adjusted with a water-equivalent material. The tube currents were 10, 20, 30, and 50 mA. The monitoring scan was performed with the conventional FBP method and real-time adaptive iterative dose reduction by three-dimensional processing (AIDR 3D). The results at different doses were compared with those at 50 mA. The volume computed tomography dose index was 1.31, 2.65, 3.93, and 6.56 mGy at tube currents of 10, 20, 30, and 50 mA, respectively. The scan start time, reconstructed using FBP, was significantly faster at 10 and 20 mA in group A (50-59 kg) and at 20 mA in group B (≥80 kg). The CT values in the region of interest could not be measured at 10 mA because of artifacts. With real-time AIDR 3D, both groups showed no significant differences between the measurements obtained at 30 or 20 mA and those obtained at 50 mA. Our study demonstrated that the real-time AIDR 3D algorithm improved the accuracy of the CT measurements with the bolus tracking technique. [ABSTRACT FROM AUTHOR]

Background: Bolus tracking can optimize the time delay between contrast injection and diagnostic scan initiation in contrast-enhanced computed tomography (CT), yet the procedure is time-consuming and subject to inter- and intra-operator variances which affect the enhancement levels in diagnostic scans. The objective of the current study is to use artificial intelligence algorithms to fully automate the bolus tracking procedure in contrast-enhanced abdominal CT exams for improved standardization and diagnostic accuracy while providing a simplified imaging workflow., Methods: This retrospective study used abdominal CT exams collected under a dedicated Institutional Review Board (IRB). Input data consisted of CT topograms and images with high heterogeneity in terms of anatomy, sex, cancer pathologies, and imaging artifacts acquired with four different CT scanner models. Our method consisted of two sequential steps: (I) automatic locator scan positioning on topograms, and (II) automatic region-of-interest (ROI) positioning within the aorta on locator scans. The task of locator scan positioning is formulated as a regression problem, where the limited amount of annotated data is circumvented using transfer learning. The task of ROI positioning is formulated as a segmentation problem., Results: Our locator scan positioning network offered improved positional consistency compared to a high degree of variance in manual slice positionings, verifying inter-operator variance as a significant source of error. When trained using expert-user ground-truth labels, the locator scan positioning network achieved a sub-centimeter error (9.76±6.78 mm) on a test dataset. The ROI segmentation network achieved a sub-millimeter absolute error (0.99±0.66 mm) on a test dataset., Conclusions: Locator scan positioning networks offer improved positional consistency compared to manual slice positionings and verified inter-operator variance as an important source of error. By significantly reducing operator-related decisions, this method opens opportunities to standardize and simplify the workflow of bolus tracking procedures for contrast-enhanced CT., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-22-686/coif). The authors have no conflicts of interest to declare., (2023 Quantitative Imaging in Medicine and Surgery. All rights reserved.)

Background: With fast computed tomography (CT), it is possible for the scanning to outpace the contrast medium bolus during aortic CT angiography (CTA). Purpose: To evaluate the effectiveness of a new method for reducing the risk of outpacing in which the scan start timing (ST) and speed can be estimated from the peak enhancement time measured at the femoral artery using a single test-bolus injection (femoral artery test injection method [FTI method]). Material and Methods: In 30 cases of aortic CTA, we measured the time to peak enhancement at the femoral artery (TPF) and the ascending aorta (TPA) with test-bolus injection performed twice in each examination. From the resultant linear relationship between TPF and transit time (TT = TPF - TPA), we developed a method for determining the ST and TT from TPF. One hundred patients were assigned to two groups: FTI and bolus tracking (BT), each with 50 patients. CT values were measured in main vessels (ascending aorta, descending aorta, femoral artery). The CT values of the vessels and the rate of cases with more than 300 HU (good cases) were compared between the two groups. Results: The enhancement in the FTI method was significantly higher than that of the BT method (average CT values: FTI, 388.3 ± 52.4; BT, 281.2 ± 59.1; P < 0.001). The rates of good cases for FTI and BT were 86.0% and 46.0%, respectively. Conclusion: The FTI method was very effective in reducing the risk of outpacing of the contrast medium transit in aortic CTA without the need for an additional contrast medium dose. [ABSTRACT FROM AUTHOR]

Background: The aim of the work is the application of a bolus tracking technique for tomographic evaluation of the uretero-vesicular junction in dogs. Ten adult dogs (8-14 years) with variable body weight (2,8-32 kg) were enrolled in the prospective study. The patients were placed in sternal recumbency with a 10° elevated pelvis and the visualization of the uretero-vesicular junction was obtained with the bolus tracking technique after intravenous administration of non-ionic contrast medium. In the post-contrast late phase a region of interest was placed within the lumen of the distal ureters and the density values were monitored before starting the helical scan. Results: The uretero-vesicular junction was clearly visible in 100 % of patients with the visualization of the endoluminal ureteral contrast enhancement and bladder washout. At the end of the tomographic study an evaluation of the dose records was performed and compared to human exposures reported in literature for the pelvic region. The effective dose estimated for each patient (37,5-138 mSv) proved to be elevated, when compared to those reported in human patients. Conclusion: The bolus tracking technique could be applied for the visualization of the uretero-vesicular junction in non-pathological patients, placing the region of interest in the distal ureters. The high effective doses recorded in our study support the need of specific thresholds for veterinary patients, pointing out the attention for paediatric patient's exposure also in veterinary imaging. [ABSTRACT FROM AUTHOR]