Hybrid Imaging Approach Research Articles

Whole-Body SPECT/CT: Protocol Variation and Technical Consideration-A Narrative Review.

Introducing a hybrid imaging approach, such as single-photon emission computerized tomography with X-ray computed tomography (SPECT)/CT, improves diagnostic accuracy and patient management. The ongoing advancement of SPECT hardware and software has resulted in the clinical application of novel approaches. For example, whole-body SPECT/CT (WB-SPECT/CT) studies cover multiple consecutive bed positions, similar to positron emission tomography-computed tomography (PET/CT). WB-SPECT/CT proves to be a helpful tool for evaluating bone metastases (BM), reducing equivocal findings, and enhancing user confidence, displaying effective performance in contrast to planar bone scintigraphy (PBS). Consequently, it is increasingly utilized and might substitute PBS, which leads to new questions and issues concerning the acquisition protocol, patient imaging time, and workflow process. Therefore, this review highlights various aspects of WB-SPECT/CT acquisition protocols that need to be considered to help understand WB-SPECT/CT workflow processes and optimize imaging protocols.

Advancements and Future Outlook of PET/CT-Guided Interventions

Advancements in minimally invasive technology, coupled with imaging breakthroughs, have empowered the field of interventional radiology to achieve unparalleled precision in image-guided diagnosis and treatment while simultaneously reducing periprocedural morbidity. Molecular imaging, which provides valuable physiological and metabolic information alongside anatomical localization, can expand the capabilities of image-guided interventions. Among various molecular imaging techniques, positron emission tomography (PET) stands out for its superior spatial resolution and ability to acquire quantitative data. PET has emerged as a crucial tool for oncologic imaging and plays a pivotal role in both staging and the assessment of treatment responses. Typically used in combination with computed tomography (CT) (PET/CT) and occasionally with magnetic resonance imaging MRI (PET/MRI), PET as a hybrid imaging approach offers enhanced insights into disease progression and response. In recent years, PET has also found its way into image-guided interventions, especially within the rapidly expanding field of interventional oncology. This review aims to explore the current and evolving role of metabolic imaging, specifically PET, in interventional oncology. By delving into the unique advantages and applications of PET in guiding oncological interventions and assessing response, we seek to highlight the increasing significance of this modality in the realm of interventional radiology.

Hybrid Autofluorescence and Optoacoustic Microscopy for the Label-Free, Early and Rapid Detection of Pathogenic Infections in Vegetative Tissues.

Agriculture plays a pivotal role in food security and food security is challenged by pests and pathogens. Due to these challenges, the yields and quality of agricultural production are reduced and, in response, restrictions in the trade of plant products are applied. Governments have collaborated to establish robust phytosanitary measures, promote disease surveillance, and invest in research and development to mitigate the impact on food security. Classic as well as modernized tools for disease diagnosis and pathogen surveillance do exist, but most of these are time-consuming, laborious, or are less sensitive. To that end, we propose the innovative application of a hybrid imaging approach through the combination of confocal fluorescence and optoacoustic imaging microscopy. This has allowed us to non-destructively detect the physiological changes that occur in plant tissues as a result of a pathogen-induced interaction well before visual symptoms occur. When broccoli leaves were artificially infected with Xanthomonas campestris pv. campestris (Xcc), eventually causing an economically important bacterial disease, the induced optical absorption alterations could be detected at very early stages of infection. Therefore, this innovative microscopy approach was positively utilized to detect the disease caused by a plant pathogen, showing that it can also be employed to detect quarantine pathogens such as Xylella fastidiosa.

Histopathology-validated lesion detection rates of clinically significant prostate cancer with mpMRI, [68Ga]PSMA-11-PET and [11C]Acetate-PET.

PET/CT and multiparametric MRI (mpMRI) are important diagnostic tools in clinically significant prostate cancer (csPC). The aim of this study was to compare csPC detection rates with [68Ga]PSMA-11-PET (PSMA)-PET, [11C]Acetate (ACE)-PET, and mpMRI with histopathology as reference, to identify the most suitable imaging modalities for subsequent hybrid imaging. An additional aim was to compare inter-reader variability to assess reproducibility. During 2016-2019, all study participants were examined with PSMA-PET/mpMRI and ACE-PET/CT prior to radical prostatectomy. PSMA-PET, ACE-PET and mpMRI were evaluated separately by two observers, and were compared with histopathology-defined csPC. Statistical analyses included two-sided McNemar test and index of specific agreement. Fifty-five study participants were included, with 130 histopathological intraprostatic lesions >0.05 cc. Of these, 32% (42/130) were classified as csPC with ISUP grade ≥2 and volume >0.5 cc. PSMA-PET and mpMRI showed no difference in performance (P = 0.48), with mean csPC detection rate of 70% (29.5/42) and 74% (31/42), respectively, while with ACE-PET the mean csPC detection rate was 37% (15.5/42). Interobserver agreement was higher with PSMA-PET compared to mpMRI [79% (26/33) vs 67% (24/38)]. Including all detected lesions from each pair of observers, the detection rate increased to 90% (38/42) with mpMRI, and 79% (33/42) with PSMA-PET. PSMA-PET and mpMRI showed high csPC detection rates and superior performance compared to ACE-PET. The interobserver agreement indicates higher reproducibility with PSMA-PET. The combined result of all observers in both PSMA-PET and mpMRI showed the highest detection rate, suggesting an added value of a hybrid imaging approach.

Neovascularization, vascular mimicry and molecular exchange: The imaging of tumorous tissue aggressiveness based on tissue perfusion

Angiogenesis in healthy tissue and within malignant tumors differs on many levels, which may partly be explained by vascular mimicry formation resulting in altered contrast material or different radiopharmaceuticals distributions.Failed remodulation results in changes in the molecular exchange through the capillary wall and those consequences affect the behavior of contrast agents and radiopharmaceuticals. One of the most indicative signs of malignant tissue is the increased permeability and the faster molecular exchange that occurs between the extracellular and intravascular spaces.Dynamic imaging can help to assess the changed microenvironment. The fast-distribution of molecules reflects newly developed conditions in blood-flow redistribution inside a tumor and within the affected organ during the early stages of tumor formation.Tumor development, as well as aggressiveness, can be assessed based on the change to the vascular bed development, the level of molecular exchange within the tissue, and/or indicative distribution within the organ. The study of the vascular network organization and its impact on the distribution of molecules is important to our understanding of the image pattern in several imaging methods, which in turn influences our interpretation of the findings.A hybrid imaging approach (including PET/MRI) allows the quantification of vascularization and/or its pathophysiological impressions in structural and metabolic images. It might optimize the evaluation of the pretreatment imaging, as well as help assess the effect of therapy targeting neovascularization; antiVEGF drugs and embolization-based therapies, for example.

Volumetric tri-modal imaging with combined photoacoustic, ultrasound, and shear wave elastography.

Photoacoustic imaging is a hybrid imaging approach that combines the advantages of optical and ultrasonic imaging in one modality. However, for comprehensive tissue characterization, optical contrast alone is not always sufficient. In this study, we combined photoacoustic imaging with high-resolution ultrasound and shear wave elastography. The multi-modal system can calculate optical absorption, acoustic reflection, and stiffness volumetrically. We constructed a multi-modal phantom with contrast for each imaging modality to test the system's performance. Experimental results indicate that the system successfully visualizes the embedded structures. We envision that the system will lead to more comprehensive tissue characterization for cancer screening and diagnosis.

Unobtrusive Measurement of Physiological Features Under Simulated and Real Driving Conditions

Objective: For driver state estimation, physiological features might be promising input parameters. As cable-bound sensing of these parameters is impractical for ubiquitous monitoring, the measurement certainly has to be based on unobtrusive and contact-free technologies. In this work, unobtrusive methods for heart rate (HR) and respiration rate (RR) monitoring, including a hybrid imaging approach, are evaluated under simulated and real driving conditions. Methods: The feasability of unobtrusive methods was tested by comparing measurements from unobtrusive sensors to reference sensors. Under laboratory conditions, magnetic induction and photoplethysmography, both integrated into the seat belt, and hybrid imaging, combining visual and thermal imaging, were evaluated for RR sensing. In real driving, creating an urban and a rural scenario, sensing of RR by hybrid imaging and sensing of HR by a seat-integrated capacitive ECG were evaluated. Results: Under laboratory conditions, a reliable RR detection was possibly using all three sensor technologies. In real-world driving, a reliable HR and RR detection was possible during the rural scenario. In the urban scenario, only the RR detection was feasible. Due to motion artifacts, the capacitive ECG was disturbed and the HR detection impaired. Conclusion: The evaluated unobtrusive measurement systems can monitor physiological parameters during e.g. long-time driving on highways, but may not yet be feasible for monitoring during agile inner-city driving situations, due to motion artifacts. Therefore, future work should focus on artifact reduction. Significance: Physiological features might be used as input parameters for driver state estimation systems. This work presents unobtrusive sensing methods for these parameters.

Elucidating the complementarity of resting-state networks derived from dynamic [18F]FDG and hemodynamic fluctuations using simultaneous small-animal PET/MRI

Functional connectivity (FC) and resting-state network (RSN) analyses using functional magnetic resonance imaging (fMRI) have evolved into a growing field of research and have provided useful biomarkers for the assessment of brain function in neurological disorders. However, the underlying mechanisms of the blood oxygen level-dependant (BOLD) signal are not fully resolved due to its inherent complexity. In contrast, [18F]fluorodeoxyglucose positron emission tomography ([18F]FDG-PET) has been shown to provide a more direct measure of local synaptic activity and may have additional value for the readout and interpretation of brain connectivity. We performed an RSN analysis from simultaneously acquired PET/fMRI data on a single-subject level to directly compare fMRI and [18F]FDG-PET-derived networks during the resting state. Simultaneous [18F]FDG-PET/fMRI scans were performed in 30 rats. Pairwise correlation analysis, as well as independent component analysis (ICA), were used to compare the readouts of both methods. We identified three RSNs with a high degree of similarity between PET and fMRI-derived readouts: the default-mode-like network (DMN), the basal ganglia network and the cerebellar-midbrain network. Overall, [18F]FDG connectivity indicated increased integration between different, often distant, brain areas compared to the results indicated by the more segregated fMRI-derived FC. Additionally, several networks exclusive to either modality were observed using ICA. These networks included mainly bilateral cortical networks of a limited spatial extent for fMRI and more spatially widespread networks for [18F]FDG-PET, often involving several subcortical areas.This is the first study using simultaneous PET/fMRI to report RSNs subject-wise from dynamic [18F]FDG tracer delivery and BOLD fluctuations with both independent component analysis (ICA) and pairwise correlation analysis in small animals. Our findings support previous studies, which show a close link between local synaptic glucose consumption and BOLD-fMRI-derived FC. However, several brain regions were exclusively attributed to either [18F]FDG or BOLD-derived networks underlining the complementarity of this hybrid imaging approach, which may contribute to the understanding of brain functional organization and could be of interest for future clinical applications.

Noninvasive multiparametric characterization of mammary tumors with transmission-reflection optoacoustic ultrasound

Development of imaging methods capable of furnishing tumor-specific morphological, functional, and molecular information is paramount for early diagnosis, staging, and treatment of breast cancer. Ultrasound (US) and optoacoustic (OA) imaging methods exhibit excellent traits for tumor imaging in terms of fast imaging speed, ease of use, excellent contrast, and lack of ionizing radiation. Here, we demonstrate simultaneous tomographic whole body imaging of optical absorption, US reflectivity, and speed of sound (SoS) in living mice. In vivo studies of 4T1 breast cancer xenografts models revealed synergistic and complementary value of the hybrid imaging approach for characterizing mammary tumors. While neovasculature surrounding the tumor areas were observed based on the vascular anatomy contrast provided by the OA data, the tumor boundaries could be discerned by segmenting hypoechoic structures in pulse-echo US images. Tumor delineation was further facilitated by enhancing the contrast and spatial resolution of the SoS maps with a full-wave inversion method. The malignant lesions could thus be distinguished from other hypoechoic regions based on the average SoS values. The reported findings corroborate the strong potential of the hybrid imaging approach for advancing cancer research in small animal models and fostering development of new clinical diagnostic approaches.

The role of cardiac magnetic resonance in diagnosis of cardiac sarcoidosis.

Sarcoidosis is a systemic granulomatous disease with a high prevalence of cardiac involvement in autopsic studies. Cardiac sarcoidosis is associated with increased cardiovascular morbidity and mortality. Endomyocardial biopsy is a specific technique, but unfortunately not sensitive enough. Non-invasive cardiac imaging has an important role in the evaluation of patients with suspected or confirmed cardiac sarcoidosis. Echocardiography remains the first choice imaging technique because of its availability and low cost. However, this method could not provide tissue characterization or evaluation of disease activity level. 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has essential role in diagnosis and monitoring of patients with suspected or confirmed cardiac sarcoidosis. Nevertheless, more recently it has been shown that cardiac magnetic resonance (CMR) might provide useful information about cardiac sarcoidosis. Hybrid imaging approach that includes PET-CMR and PET-CT is particularly interesting for diagnosis, assessment of activity and follow-up in these patients. Diagnostic algorithm in sarcoidosis patients should include clinical data, hybrid imaging and biopsy. Use of different CMR sequences such as cine imaging, late gadolinium enhancement, T1 and T2 mapping, as well as strain imaging, may significantly contribute to diagnosis and monitoring of patients with cardiac sarcoidosis. However, validation of these techniques and particularly T1 and T2 mapping in sarcoidosis patients in large studies is necessary. This review aimed to summarize current knowledge about clinical usefulness of CMR in patients with cardiac sarcoidosis.

Positron emission tomography/MRI for cardiac diseases assessment.

Functional imaging tools have emerged in the last few decades and are increasingly used to assess the function of the human heart in vivo. Positron emission tomography (PET) is used to evaluate myocardial metabolism and blood flow. Magnetic resonance imaging (MRI) is an essential tool for morphological and functional evaluation of the heart. In cardiology, PET is successfully combined with CT for hybrid cardiac imaging. The effective integration of two imaging modalities allows simultaneous data acquisition combining functional, structural and molecular imaging. After PET/CT has been successfully accepted for clinical practices, hybrid PET/MRI is launched. This review elaborates the current evidence of PET/MRI in cardiovascular imaging and its expected clinical applications for a comprehensive assessment of cardiovascular diseases while highlighting the advantages and limitations of this hybrid imaging approach.

A Hybrid Deep Learning and Handcrafted Feature Approach for Cervical Cancer Digital Histology Image Classification

Cervical cancer is the second most common cancer affecting women worldwide but is curable if diagnosed early. Routinely, expert pathologists visually examine histology slides for assessing cervix tissue abnormalities. A localized, fusion-based, hybrid imaging and deep learning approach is explored to classify squamous epithelium into cervical intraepithelial neoplasia (CIN) grades for a dataset of 83 digitized histology images. Partitioning the epithelium region into 10 vertical segments, 27 handcrafted image features and rectangular patch, sliding window-based convolutional neural network features are computed for each segment. The imaging and deep learning patch features are combined and used as inputs to a secondary classifier for individual segment and whole epithelium classification. The hybrid method achieved a 15.51% and 11.66% improvement over the deep learning and imaging approaches alone, respectively, with a 80.72% whole epithelium CIN classification accuracy, showing the enhanced epithelium CIN classification potential of fusing image and deep learning features.

Hybrid T2 - and T1 -weighted radial acquisition for free-breathing abdominal examination.

Most clinical MR examinations require acquisition of different image contrasts. For abdominal exams, the scans are conventionally performed as separate acquisitions using respiratory gating or repeated breath holding, which can be time-inefficient and challenging for patients. Here, a hybrid imaging approach is described that creates T2 - and T1 -weighted images from a single scan and allows for free-breathing acquisition. T2 -weighted data is collected using 3D fast spin-echo (FSE) acquisition with motion-robust radial stack-of-stars sampling. The wait time between the FSE trains is used to acquire T1 -weighted gradient-echo (GRE) data. Improved robustness is achieved by extracting a respiratory signal from the GRE data and using it for motion-weighted reconstruction. As validated in simulations and phantom scans, GRE acquisition in the wait time has minor effect on the signal strength and contrast. Volunteer scans at 1.5T showed that T2 - and T1 -weighted hybrid imaging is feasible during free-breathing. Furthermore, it has been demonstrated in a patient that hybrid imaging with T1 -weighted Dixon acquisition is possible. The described hybrid sequence enables comprehensive T2 - and T1 -weighted imaging in a single scan. In addition to free-breathing abdominal examination, it promises value for clinical applications that are frequently affected by motion artifacts.

The contributions of the actin machinery to endocytic membrane bending and vesicle formation.

Branched and cross-linked actin networks mediate cellular processes that move and shape membranes. To understand how actin contributes during the different stages of endocytic membrane reshaping, we analyzed deletion mutants of yeast actin network components using a hybrid imaging approach that combines live imaging with correlative microscopy. We could thus temporally dissect the effects of different actin network perturbations, revealing distinct stages of actin-based membrane reshaping. Our data show that initiation of membrane bending requires the actin network to be physically linked to the plasma membrane and to be optimally cross-linked. Once initiated, the membrane invagination process is driven by nucleation and polymerization of new actin filaments, independent of the degree of cross-linking and unaffected by a surplus of actin network components. A key transition occurs 2 s before scission, when the filament nucleation rate drops. From that time point on, invagination growth and vesicle scission are driven by an expansion of the actin network without a proportional increase of net actin amounts. The expansion is sensitive to the amount of filamentous actin and its cross-linking. Our results suggest that the mechanism by which actin reshapes the membrane changes during the progress of endocytosis, possibly adapting to varying force requirements.

Nonlinear ultrasonic stimulated thermography for damage assessment in isotropic fatigued structures

Traditional non-destructive evaluation (NDE) and structural health monitoring (SHM) systems are used to analyse that a structure is free of any harmful damage. However, these techniques still lack sensitivity to detect the presence of material micro-flaws in the form of fatigue damage and often require time-consuming procedures and expensive equipment. This research work presents a novel "nonlinear ultrasonic stimulated thermography" (NUST) method able to overcome some of the limitations of traditional linear ultrasonic/thermography NDE-SHM systems and to provide a reliable, rapid and cost effective estimation of fatigue damage in isotropic materials. Such a hybrid imaging approach combines the high sensitivity of nonlinear acoustic/ultrasonic techniques to detect micro-damage, with local defect frequency selection and infrared imaging. When exciting structures with an optimised frequency, nonlinear elastic waves are observed and higher frictional work at the fatigue damaged area is generated due to clapping and rubbing of the crack faces. This results in heat at cracked location that can be measured using an infrared camera. A Laser Vibrometer (LV) was used to evaluate the extent that individual frequency components contribute to the heating of the damage region by quantifying the out-of-plane velocity associated with the fundamental and second order harmonic responses. It was experimentally demonstrated the relationship between a nonlinear ultrasound parameter (βratio) of the material nonlinear response to the actual temperature rises near the crack. These results demonstrated that heat generation at damaged regions could be amplified by exciting at frequencies that provide nonlinear responses, thus improving the imaging of material damage and the reliability of NUST in a quick and reproducible manner.

A hybrid numerical and imaging approach for characterizing defects in composite structures

In this study, a hybrid approach coupling hyperspectral near infrared imaging with a progressive finite element method is proposed for characterization of the elastic and failure response of composites with non-uniform variations of the wrinkles profile through the thickness and across the structure dimensions. In this approach, hyperspectral near infrared spectroscopy is used to create a 3D profile of the surface resin pockets with the capability of measuring resin thickness from approximately 125 to 2500μm. These resin pockets are directly correlated to underlying ply level wrinkling as confirmed by optical microscopy. The 3D mapped resin plane obtained from the hyperspectral imaging is used to morph a ply-by-ply finite element model of a carbon-fiber/epoxy resin laminated plate using a progressive damage failure methodology. The results show the capability of the hybrid method to predict the structural response in laminated composites containing spatially distributed and non-uniform ply-level wrinkling.

Whole-body live mouse imaging by hybrid reflection-mode ultrasound and optoacoustic tomography.

We present a hybrid preclinical imaging scanner that optimally supports image acquisition in both reflection-mode ultrasonography and optoacoustic (OA) tomography modes. The system comprises a quasi-full-ring tomographic geometry capable of the simultaneous dual-mode imaging through entire cross sections of mice with in-plane spatial resolution in the range of 150 and 350 μm in the respective OA and ultrasound (US) imaging modes with an imaging speed of up to 10 two-dimensional frames per second. Three-dimensional whole-body data is subsequently rendered by rapid scanning of the imaged plane. The system further incorporates rapid laser wavelength tuning for real-time acquisition of multispectral OA data, which enables studies of longitudinal dynamics as well as fast kinetics and biodistribution of contrast agents. In vivo imaging performance is demonstrated by label-free hybrid anatomical scans through living mice, as well as real-time visualization of optical contrast agent perfusion. By setting new standards for whole-body tomographic imaging performance in both the OA and pulse-echo US modes, the developed hybrid imaging approach is expected to benefit numerous applications where the availability of high-quality structural information provided by the tomographic reflection-mode US can ease interpretation of the functional and molecular imaging results attained by the OA modality.

Maximizing throughput in label-free microspectroscopy with hybrid Raman imaging.

Raman spectroscopy is an optical method providing sample molecular composition, which can be analyzed (by point measurements) or spatially mapped by Raman imaging. These provide different information, signal-to-noise ratios, and require different acquisition times. Here, we quantitatively assess Raman spectral features and compare the two measurement methods by multivariate analysis. We also propose a hybrid method: scanning the beam through the sample but optically binning the signal at one location on the detector. This approach generates significantly more useful spectral signals in terms of peak visibility and statistical information. Additionally, by combination with a complementary imaging mode such as quantitative phase microscopy, hybrid imaging allows high throughput and robust spectral analysis while retaining sample spatial information. We demonstrate the improved ability to discriminate between cell lines when using hybrid scanning compared to typical point mode measurements, by quantitatively evaluating spectra taken from two macrophage-like cell lines. Hybrid scanning also provides better classification capability than the full Raman imaging mode, while providing higher signal-to-noise signals with shorter acquisition times. This hybrid imaging approach is suited for various applications including cytometry, cancer versus noncancer detection, and label-free discrimination of cell types or tissues.

Diagnosis of Pulmonary Embolism: Conventional Ventilation/Perfusion SPECT Is Superior to the Combination of Perfusion SPECT and Nonenhanced CT

Background: Ventilation/perfusion single-emission photon CT (V/P-SPECT) is widely used to detect pulmonary embolism (PE). Any pathological deficit on P-SPECT with a corresponding unremarkable V-SPECT is considered an embolism. This means that a deficit on P-SPECT with a corresponding deficit on the ventilation scan correlates with other lung pathologies such as pneumonia, bullous emphysema or tumor. In principle, it is possible to identify any of these lung pathologies on nonenhanced chest CT and so this technique has the potential to replace V-SPECT in the diagnosis of PE. Today, SPECT/CT hybrid imaging systems are increasingly applied in clinical routines. Objectives: We investigated whether embolism can be diagnosed using a combined P-SPECT/CT hybrid imaging approach without V-SPECT. Methods: Ninety-three patients with clinically suspected embolism were investigated with standard V/P-SPECT and a nonenhanced CT scan on a combined SPECT/CT system. A diagnosis of embolism was based on V/P-SPECT (gold standard). P-SPECT/CT datasets were blinded and analyzed without any knowledge of the V-SPECT data. The accuracy of P-SPECT/CT was compared to the gold standard. Results: Embolism was diagnosed in 24/93 patients using V/P-SPECT. In total, 57 lung lobes were affected. P-SPECT/CT significantly (p < 0.01) overdiagnosed embolism in nonaffected patients. In total, 36 cases with 88 affected lung lobes were shown. The sensitivity was 95.8%, the specificity 82.6%, the false-negative rate 4.2% and the false-positive rate 17.3%. Conclusions: Our results demonstrate that a nonenhanced CT scan in a novel hybrid imaging system cannot replace V-SPECT in the scintigraphy-based diagnosis of PE. V-SPECT increases specificity and reduces the number of false-positive results when compared to ‘perfusion-only' SPECT/CT.

Intravenous urography supplemented with computerised tomography urogram: A pragmatic hybrid imaging approach to hydronephrosis

Background:Image quality in an Intravenous Urogram (IVU) can occasionally be compromised by variables like bowel preparation, renal function and radiographic factors, posing a challenge to all Uroradiologists. The Computerised Tomography Urogram (CTU) yields better diagnostic information than an IVU, due to its inherent superior anatomic delineation and contrast sensitivity, against a trade-off involving radiation dose and cost. Our study was conducted to assess the utility and timing of performing a single-phase CTU, as a problem-solving tool, to clear the diagnostic dilemma in a selected subset of patients, in whom an ongoing IVU could potentially be inconclusive.Material and Methods:Five hundred and twelve patients who underwent IVU studies for urologic referrals at a tertiary care hospital, during the period of January to December 2009, formed the subject of the study, of whom 33 patients with inconclusive IVU findings after the first three radiographs underwent a single-phase CTU, to reach definitive imaging diagnoses.Results:The percentage of inconclusive IVU studies amounted to only 33 / 512 (6.4%), in whom a CTU study revealed definitive diagnoses in 30 patients and no abnormality in three patients, thus conclusively clearing the ambiguities raised on the IVU in all the selected patients.Conclusions:The concept of a CTU limited to a single-phase study to supplement an inconclusive IVU optimizes the contrast and radiation dose to the affected patients. It is a cost-effective, timely, and definitive ‘imaging intervention’ and should be considered a viable hybrid technique to be utilized selectively and judiciously.