Helical CT Research Articles

Cephalometric Analysis of Sphenoid Sinus Dimensions for Sex Identification: A Radiologic Study

Background: Post-mortem identification of human remains with severe crushing and mutilating skeletal injuries from mass burials and natural disasters, is a challenging forensic procedure. Gender determination from skeletal remains requires a comparison between established ante-mortem data and post-mortem findings from mostly intact, easily recoverable parts of the skeleton, like the skull base sphenoid bone. Computed tomography, being the gold standard for radiological assessment of the paranasal sinuses, offers accurate and precise information about skeletal tissues. The aim of the study was to determine the sex of subjects from measurements of the sphenoid sinus using computerized tomography. Materials and Methods: Computerised tomography images of 323 adult sphenoid sinuses, obtained over a six-year period, from individuals whose ages ranged from 18 to 80 years were recruited, and the study was conducted at the Radiology Department of the Usmanu Danfodiyo University Teaching Hospital, Sokoto, following ethical approval. Images were taken with a GE Brightspeed Multidetector Helical CT Scanner, the anteroposterior, craniocaudal and transverse dimensions were measured on sagittal reformatted, axial and coronal reconstructed CT images respectively, and the volumes were determined. Measurements were taken in millimetres, between the widest points at the middle of the sinus walls from three-dimensional reconstructed images using the RadiAnt Version 4.2 (Medixant, 2017), powered by the Digital Imaging and Communication in Medicine (DICOM) viewer software. These images were viewed on bone windows. Results: Sinus volume and the transverse diameter, each correctly classified the sexes of subjects, in 60.4% of cases. However, when all the measured parameters of the sinus were analysed together as a single factor for sex determination, an overall value of 57.6% was obtained. Conclusion: Computerized Tomography measurements of sphenoid sinus dimensions could be useful in support of gender identification in unknown severely damaged human remains with speared sphenoid bone. Keywords: Sex, Sphenoid, CT, Forensic Anthropology

Low-dose helical CT projection data restoration using noise estimation

To build a helical CT projection data restoration model at random low-dose levels. We used a noise estimation module to achieve noise estimation and obtained a low-dose projection noise variance map, which was used to guide projection data recovery by the projection data restoration module. A filtering back-projection algorithm (FBP) was finally used to reconstruct the images. The 3D wavelet group residual dense network (3DWGRDN) was adopted to build the network architecture of the noise estimation and projection data restoration module using asymmetric loss and total variational regularization. For validation of the model, 1/10 and 1/15 of normal dose helical CT images were restored using the proposed model and 3 other restoration models (IRLNet, REDCNN and MWResNet), and the results were visually and quantitatively compared. Quantitative comparisons of the restored images showed that the proposed helical CT projection data restoration model increased the structural similarity index by 5.79% to 17.46% compared with the other restoration algorithms (P < 0.05). The image quality scores of the proposed method rated by clinical radiologists ranged from 7.19% to 17.38%, significantly higher than the other restoration algorithms (P < 0.05). The proposed method can effectively suppress noises and reduce artifacts in the projection data at different low-dose levels while preserving the integrity of the edges and fine details of the reconstructed CT images.

Spiral CT appearances of pancreatic tail insulinoma

Introduction: Insulinomas are the most common category of pancreatic endocrine tumors, with an incidence of 1-7 cases per million people. Material and Methods: Most are intrapancreatic, benign and solitary. Therefore, they have an excellent prognosis after surgical resection. However, the localization diagnosis of insulinomas still poses a challenge to surgeons and radiologists. Results: We present two cases showing classical appearances on helical CT In these two cases the tumors were occult and could not be found by either abdominal enhanced spiral computed tomography (CT) or ultrasonography. We would like to emphasize the need for performing helical CT whenever the diagnosis is suspected, due to the ability to image the pancreas in the early arterial as well as in the equilibrium phase. Conclusions: We reminded of surgeons that insulinomas represent the most frequently found functioning endocrine tumors .Therefore, they have an excellent prognosis after surgical resection. However, the localization diagnosis of insulinomas still poses a challenge to surgeons and radiologists.

Diagnostic Value of Spiral CT and Magnetic Resonance Imaging Scanning in Gastric Cancer and Precancerous Lesions.

In order to explore the diagnostic value of spiral CT and magnetic resonance imaging scanning in gastric cancer and precancerous lesions, the author selected 56 gastric cancer patients treated in a medical center (group) as the experimental subjects, and all patients underwent MRI, multislice spiral CT scan, and enhanced CT scan two weeks before surgery; at the same time, the gastric cancer staging results of patients were diagnosed according to surgical pathology. All patients were examined under the condition of knowledge and performed breath-holding exercise before examination. The status, location, and extent of tumor lesions were evaluated. In comparison of T staging of gastric cancer patients with magnetic resonance scanning imaging and postoperative pathological examination results, among them, T staging of 3 patients did not match the results of pathological examination, the accuracy rates of T staging on magnetic resonance scanning imaging were T1 = 94.7%, T2 = 87.6%, T3 = 91.2%, and T4 = 94.7%, and the total accuracy was 92.1%. Comparison of helical CT scan imaging and postoperative pathological examination results is as follows. Among them, T staging of 8 patients did not match the results of pathological examination, 3 patients were ulcerative, 5 were protuberance, the accuracy rates of T staging in spiral CT scan imaging were T1 = 90.8%, T2 = 82.2%, T3 = 76.9%, and T4 = 87.6%, and the total accuracy was 84.5%. The total accuracy rate of imaging N staging was 77.5%, and the total accuracy rate of spiral CT scanning imaging N staging was 80.8%. The accuracy rates of M0 and M1 staging in magnetic resonance imaging were 100.0% and 96.5%, respectively, and the accuracy rates of M0 and M1 staging in spiral CT scan imaging were 96.5% and 96.5%, respectively. The accuracy rate of magnetic resonance imaging for the diagnosis of gastric cancer N staging was 77.4%, and the reason for the low accuracy rate was mainly because the enhancement effect was not obvious due to insufficient enhancement. The accuracy rate of spiral CT in diagnosing N staging of gastric cancer was 80.9%, which was mainly due to the small diameter of the middle celiac artery lymph nodes. Magnetic resonance and spiral CT scans have high value in the early diagnosis and staging of gastric cancer.

Systolic or diastolic CT image acquisition for transcatheter aortic valve replacement – An outcome analysis

BackgroundComputed tomography (CT) imaging is the standard of care before transcatheter aortic valve replacement (TAVR). The aortic annulus undergoes conformational changes during the heart cycle. Therefore, the image acquisition time point can impact prosthesis sizing and fit. Clinical outcome data are lacking. The aim of this study was to compare systolic and diastolic cardiac CT data acquisition with regard to procedural and clinical outcomes in patients undergoing TAVR for severe aortic stenosis (AS). MethodsPreprocedural high-pitch helical CT datasets were analyzed in 1954 patients undergoing TAVR between 2013 and 2018 ​at our center. Patients were stratified into two groups according to the acquisition heart phase (979 systolic and 975 diastolic). The study was approved by the local ethics committee. ResultsMedian age was 81.6 [interquartile range 77.5–85.8] years and 964 (49.3%) patients were male. No significant difference was found for the Valve Academic Research Consortium-3 (VARC-3) endpoints of technical failure (systolic, 5.1% vs. diastolic, 5.2%, p ​= ​0.94) or device failure (systolic, 13.7% vs. diastolic, 13.5%, p ​= ​0.92). There was no difference in paravalvular regurgitation. All-cause 30-day mortality was comparable (systolic, 3.6% [95% confidence interval, 2.4–4.7%] vs. diastolic, 3.6% [2.4–4.8%], p ​= ​1.00), while 3-year mortality rates were higher in the diastolic group (Society of Thoracic Surgeons score adjusted hazard ratio, 1.25 [1.07–1.46], p ​< ​0.01). ConclusionsWhile the 30-day technical and clinical outcomes after TAVR are comparable between systolic and diastolic CT imaging, diastolic imaging was associated with higher long-term mortality. Therefore, the data support the guideline recommendation of systolic imaging.

CT FINDINGS OF MALIGNANT NEOPLASTIC MASSES OF SMALL AND LARGE INTESTINE WITH HISTOPATHOLOGICAL CORRELATION: A CROSS SECTIONAL STUDY

AIMS AND OBJECTIVES: To formulate an appropriate scanning protocol technique to evaluate malignant neoplasm of small and large intestine. To dene various CT ndings in malignant bowel neoplasm. To stage bowel neoplasm. To accurately characterize the tumour by histologic type as far as possible. Materials And Methods: In our cross-sectional study, 76 cases of small and large bowel carcinoma were referred to radiology department. After taking informed consent, CECT abdomen of the patients was done. All these patients went for surgical excision of the neoplastic mass; and the mass were sent for HPE examination. Epidemiological data, clinical features, CECT abdominal features were correlated with HPE type of the mass were found out. P-Value&lt;0.05 was considered to be statistically signicant. Results: In Small bowel, ileum was the commonest site of involvement (5.26%), whereas sigmoid colon and rectum (18.42%) was commonest site of involvement in large bowel. Adenocarcinoma was the commonest histological subtype seen in 54 patients (71.05%), followed by lymphoma in 14 patients (18.42%), Mucinous Adenocarcinoma seen in 5 patients (57.5%). and gastrointestinal stromal tumor [GIST] seen in 3 patients(3.94%). Conclusion: Common CT imaging features in malignant bowel neoplasm are bowel Wall thickening &gt;2cm,short Segment Involvementand heterogeneous mixed pattern. Although CT has a high specicity for detection of a metastatic lymph nodes, sensitivity is low.Liver is the commonest site of distant metastasis in malignant bowel neoplasm. Helical CT is a noninvasive, reliable, and accurate technique for imaging the liver and should be considered as the standard preoperative work-up of hepatic metastases from bowel malignant.

Computed tomography venography description of the normal anatomy of the canine hindlimb venous system.

This study was performed to provide a description of the normal anatomy of the canine hindlimb veins using helical CT images. The studies of 30 dogs that underwent CT venography with a 64-slice helical CT scanner were retrospectively reviewed. The dogs were positioned in a head-first prone or head-first supine body position. A topogram CT scan was performed from the pelvic limbs cranial to the iliac wings to the tips of the paws. Bolus-tracking software was used for the dual-phase angiogram, and contrast medium was administered in a cephalic vein. The venous phase was scanned after a delay time of a few seconds after the arterial phase in a caudocranial direction. Three-dimensional images were generated using maximum intensity projections and volume rendering technique. Representative images of three of the 30 dogs were selected and anatomic structures labelled.

SIZE-SPECIFIC DOSE ESTIMATES IN FETAL COMPUTED TOMOGRAPHY.

During fetal computed tomography (CT) imaging, because of differences in the pregnancy period and scanning conditions, different doses of radiation are absorbed by the fetus. We propose a correction coefficient for determining the fetal size-specific dose estimate (SSDE) from the CT dose index (CTDI) displayed on the console at tube voltages of 80-135kVp. The CTDIs corresponding to pregnant women and fetuses were evaluated using a Monte Carlo (MC) simulation, and the ratio of these CTDIs was defined as the Fetus-factor. When the effective diameter of a fetus was approximately 10cm, the Fetus-factor was 1.0. The estimated pregnant SSDE was multiplied by the Fetus-factor to estimate the fetal SSDE, which was compared with the fetal dose obtained by the MC simulation of the image of the fetal CT examination. The fetal dose could be estimated with an error of 31.5% in fetal examinations conducted using helical CT.

Re-evaluating the need for orthopantomography in the management of mandibular trauma: is computed tomography enough?

Mandibular fractures are frequent indications for computed tomography (CT) and orthopantomography (OPG) scans in emergency rooms. Numerous studies found CT to have higher sensitivity and enhanced accuracy compared to OPG in diagnosing mandible fractures. Controversy exists regarding additional need for OPG when evaluating dental trauma. This study investigates whether OPG adds diagnostic value to CT in mandibular trauma and whether additional OPG significantly alters management. A retrospective chart review identified 100 patients ≥ 18years of age with known mandibular trauma who received CT and OPG in the emergency department between May 2015 and January 2020. All patients demonstrated a fracture in at least one study. CT and OPG studies were anonymized and randomized. A single attending surgeon evaluated mandible fracture and dental trauma characteristics and subsequently compared findings. One hundred patient CT and OPG scans were reviewed. CT detected mandible fractures in all patients and OPG detected fractures in 93% (p = 0.01). Twenty-eight patients had different findings between scans. CT demonstrated 1 or more additional fracture(s) than OPG in 20 patients and dental trauma not seen on OPG in 4. OPG detected 1 fracture and no dental trauma that was not seen on CT. CT drove treatment-determining differences in 17 cases and OPG in 0 cases. CT appears efficacious in detecting clinically significant mandible fractures and dental trauma with little additional benefit from OPG in emergency settings. Helical CT may be the only imaging necessary in evaluating patients with such trauma.

Intensity-based iterative reconstruction for helical grating interferometry breast CT with static grating configuration.

Grating interferometry breast computed tomography (GI-BCT) has the potential to provide enhanced soft tissue contrast and to improve visualization of cancerous lesions for breast imaging. However, with a conventional scanning protocol, a GI-BCT scan requires longer scanning time and higher operation complexity compared to conventional attenuation-based CT. This is mainly due to multiple grating movements at every projection angle, so-called phase stepping, which is used to retrieve attenuation, phase, and scattering (dark-field) signals. To reduce the measurement time and complexity and extend the field of view, we have adopted a helical GI-CT setup and present here the corresponding tomographic reconstruction algorithm. This method allows simultaneous reconstruction of attenuation, phase contrast, and scattering images while avoiding grating movements. Experiments on simulated phantom and real initial intensity, visibility and phase maps are provided to validate our method.

Impact of acquisition time and misregistration with CT on data-driven gated PET

Objective. Data-driven gating (DDG) can address patient motion issues and enhance PET quantification but suffers from increased image noise from utilization of <100% of PET data. Misregistration between DDG-PET and CT may also occur, altering the potential benefits of gating. Here, the effects of PET acquisition time and CT misregistration were assessed with a combined DDG-PET/DDG-CT technique. Approach. In the primary PET bed with lesions of interest and likely respiratory motion effects, PET acquisition time was extended to 12 min and a low-dose cine CT was acquired to enable DDG-CT. Retrospective reconstructions were created for both non-gated (NG) and DDG-PET using 30 s to 12 min of PET data. Both the standard helical CT and DDG-CT were used for attenuation correction of DDG-PET data. SUVmax, SUVpeak, and CNR were compared for 45 lesions in the liver and lung from 27 cases. Main results. For both NG-PET (p = 0.0041) and DDG-PET (p = 0.0028), only the 30 s acquisition time showed clear SUVmax bias relative to the 3 min clinical standard. SUVpeak showed no bias at any change in acquisition time. DDG-PET alone increased SUVmax by 15 ± 20% (p < 0.0001), then was increased further by an additional 15 ± 29% (p = 0.0007) with DDG-PET/CT. Both 3 min and 6 min DDG-PET had lesion CNR statistically equivalent to 3 min NG-PET, but then increased at 12 min by 28 ± 48% (p = 0.0022). DDG-PET/CT at 6 min had comparable counts to 3 min NG-PET, but significantly increased CNR by 39 ± 46% (p < 0.0001). Significance. 50% counts DDG-PET did not lead to inaccurate or biased SUV—increased SUV resulted from gating. Improved registration from DDG-CT was equally as important as motion correction with DDG-PET for increasing SUV in DDG-PET/CT. Lesion detectability could be significantly improved when DDG-PET used equivalent counts to NG-PET, but only when combined with DDG-CT in DDG-PET/CT.

New and emerging technology in the diagnosis and treatment of pancreatic cysts.

Pancreatic cysts have always presented as a diagnostic dilemma due to the difficulties in identifying patients with current imaging modalities that could most benefit from surgical intervention. Intraductal papillary mucinous neoplasms (IPMNs) and mucinous cystadenomas (MCNs) carry the highest malignant potential of all pancreatic cysts and pancreatic adenocarcinoma carries a high mortality as the fourth leading cause of cancer-related deaths. However, surgery to remove benign cysts also carries a high morbidity and occasional mortality. Opportunities to identify and reduce pre-cancer lesions must be aggressively pursued. Multidetector helical CT (MDHCT) or an up-to-date MRI is the first diagnostic tool to evaluate a suspected pancreatic lesion. Currently, review by a multidisciplinary group who specialize in pancreatic cysts and pancreatic cancer is advised to review factors such as a patient's comorbidities, the type of surgery needed to remove the cyst and the estimated morbidity and mortality associated with the procedure. Some recent data are emerging to assist with identifying those at highest risk such as cyst fluid analysis, laser endomicroscopy, and artificial intelligence (AI). This article reviews the current status, benefits, challenges and future prospects on diagnosis and treatment of pancreatic cysts. Further prospective randomized control trials are needed to determine the optimal management and treatment for patients with pancreatic cysts.

Computed Tomography Assessment of Tidal Lung Overinflation in Domestic Cats Undergoing Pressure-Controlled Mechanical Ventilation During General Anesthesia.

ObjectiveThis study aimed to evaluate lung overinflation at different airway inspiratory pressure levels using computed tomography in cats undergoing general anesthesia.Study DesignProspective laboratory study.AnimalsA group of 17 healthy male cats, aged 1.9–4.5 years and weighing 3.5 ± 0.5 kg.MethodsSeventeen adult male cats were ventilated in pressure-controlled mode with airway pressure stepwise increased from 5 to 15 cmH2O in 2 cmH2O steps every 5 min and then stepwise decreased. The respiratory rate was set at 15 movements per min and end-expiratory pressure at zero (ZEEP). After 5 min in each inspiratory pressure step, a 4 s inspiratory pause was performed to obtain a thoracic juxta-diaphragmatic single slice helical CT image and to collect respiratory mechanics data and an arterial blood sample. Lung parenchyma aeration was defined as overinflated, normally-aerated, poorly-aerated, and non-aerated according to the CT attenuation number (−1,000 to −900 HU, −900 to −500 HU, −500 to −100 HU, and −100 to +100 HU, respectively).ResultAt 5 cmH2O airway pressure, tidal volume was 6.7± 2.2 ml kg−1, 2.1% (0.3–6.3%) of the pulmonary parenchyma was overinflated and 84.9% (77.6%−87.6%) was normally inflated. Increases in airway pressure were associated with progressive distention of the lung parenchyma. At 15 cmH2O airway pressure, tidal volume increased to 31.5± 9.9 ml kg−1 (p < 0.001), overinflated pulmonary parenchyma increased to 28.4% (21.2–30.6%) (p < 0.001), while normally inflated parenchyma decreased 57.9% (53.4–62.8%) (p < 0.001). Tidal volume and overinflated lung fraction returned to baseline when airway pressure was decreased. A progressive decrease was observed in arterial carbon dioxide partial pressure (PaCO2) and end-tidal carbon dioxide (ETCO2) when the airway pressures were increased above 9 cmH2O (p < 0.001). The increase in airway pressure promoted an elevation in pH (p < 0.001).Conclusions and Clinical RelevanceVentilation with 5 and 7 cmH2O of airway pressure prevents overinflation in healthy cats with highly compliant chest walls, despite presenting acidemia by respiratory acidosis. This fact can be controlled by increasing or decreasing respiratory rate and inspiratory time.

THE EFFECT OF OUT-OF-PLANE PATIENT SHIELDING ON CT RADIATION EXPOSURE AND TUBE CURRENT MODULATIONS: A PHANTOM STUDY ACROSS THREE VENDORS.

The aim of this study was to evaluate how out-of-plane patient shielding affects radiation exposure parameters and tube current modulation on different vendors' computed tomography (CT) scanners. Helical CT scans were performed using two homogenous phantoms to mimic patient attenuation. Four CT scanners from three vendors were investigated by varying the distance of the patient shield from the border of the imaging volume. Scans were performed with a shield placed before and after the localizer. Changes in volume computed tomography dose index (CTDIvol), dose-length product (DLP) and tube current-time products were studied. Out-of-field lead shield increased the CTDIvol and DLP values for each scanner at least for one scan setting when the shield was present in the localizer. The most notable changes were recorded with >1.3 pitch values when the shield was closest to the scanned volume (2.5cm), and the scan direction was towards the shield. The usage of patient shields in the localizer CT scans can disturb TCM even when placed 7.5cm away from the edge of the scan.

Significance of Coronary Artery Calcification in Medical Examination Lung Helical CT

Significance of Coronary Artery Calcification in Medical Examination Lung Helical CT

Diagnostic Performance of Multi-Direction Adjusted Multi-Planar Reconstruction with Helical CT for Evaluating Continuity of the Anterior Cruciate Ligament

To analyze the diagnostic performance of MDA-MPR with CT for evaluating ACL structural continuity. A total of 145 patients with highly suspected ACL injury admitted to our hospital between January 2016 and May 2021 were retrospectively enrolled. All patients had undergone examination with MRI, CT, and arthroscopy. Taking arthroscopy results as the gold standard, the diagnostic accuracy for identifying ACL rupture by MRI and MDA-MPR with CT were compared. The receiver operator characteristic curves demonstrated that both MRI and MDA-MPR with CT performed well in the diagnosis of ACL tears. The sensitivities of MRI and MDA-MPR with CT for diagnosing complete ACL tears were 95.16% (59/62) and 90.32% (56/62), respectively. Their specificities in this regard were 77.11% (64/83) and 84.34% (70/83), respectively. MRI had a higher sensitivity but MDA-MPR with CT had a higher specificity for detecting complete ACL tears, and the differences were statistically significant (p <.05). The sensitivities of diagnosing partial ACL tears using MRI and MDA-MPR with CT were 78.79% (26/33) and 75.76% (25/33), respectively, while the specificities were 86.61% (97/112) and 90.18% (101/112), respectively. These differences were non-significant (p >.05). MDA-MPR with CT has high diagnostic efficiency for ACL injuries, especially in the diagnosis of complete ACL tears.

Soil macroporosity and water flow in the root zone of oases in hyper‐arid regions

AbstractThe characteristics of soil macropores and water infiltration are closely connected to the growth of plant roots and their root zone environment. However, it is unclear how the root zone environment of oasis farmlands regulates the development of soil macropores and water flow in hyper‐arid regions. The objective of this study was to investigate soil macropores and their effect on water flow under irrigated oasis farmlands using a combination of X‐ray computed tomography (CT) and dye tracer. It was hypothesized that the integration of CT and dye tracer could clearly reveal preferential flow through biopores and large pores of oasis soils. A helical medical CT scanner was used to quantify more information about soil macropores in the root zone, along with an in situ single‐ring dye infiltration experiment to reveal water flow in three different oasis farmlands (piedmont oasis farmland, marginal oasis farmland, and old oasis farmland). Soil macroporosity was 0.44% under crop rows, while soil macroporosity in the interrows was only 0.30% across the oasis farmlands. Biopores contributed 73% of the volume of the total macropores under crop rows. The stable infiltration rate in the interrows was 0.3 mm min−1, which was significantly (p &lt; 0.05) less than that under crop rows (0.7 mm min−1). Water flow under crop rows were mainly transported in biopores and large pores. The contribution of macropores to preferential flow under crop rows was 4.8 times larger than interrows. The integration of CT and dye tracer was a more holistic technique, which adequately revealed that oases had preferential flow affected by biopores and large pores, resulting in higher solute and contaminant transport.Key Points Soil macropores and preferential flow affected by crop roots were investigated in hyper‐arid regions. The integration of CT and dye tracer adequately identified preferential flowpaths of oasis soils. Biopores were larger under crop rows than interrows. Preferential flow transported in biopores and large soil pores under crop rows.

Effect of detector in-plane rotation misalignment on dimensional measurements using helical CT acquisition.

One of the critical factors that may significantly contribute to X-ray computed tomography measurement uncertainty is the misalignment of CT system components from ideal geometry assumed by tomographic reconstruction. It is proven to cause image artifacts, inhomogeneous magnification, thus leading to dimensional measurement errors. There is a lack of studies on helical trajectory scanning in metrological applications, focusing on the detector's angular misalignments. We will present results of CT measurements with misaligned detector by in-plane rotation for circular, double-helix, and space-filling trajectory. They prove that such misalignment may cause significant measurements errors, depending on the misalignments magnitude and applied acquisition trajectory.

Clinical Value of Helical CT, Energy Spectrum CT, and MRI in the Diagnosis of Primary Liver Cancer

Clinical Value of Helical CT, Energy Spectrum CT, and MRI in the Diagnosis of Primary Liver Cancer

Using previously registered cone beam computerized tomography images to facilitate online computerized tomography to cone beam computerized tomography image registration in lung stereotactic body radiation therapy.

PurposeIn our conventional image registration workflow, the four‐dimensional (4D) CBCT was directly registered to the reference helical CT (HCT) using a dual registration approach within the Elekta XVI software. In this study, we proposed a new HCT–CBCT auto‐registration strategy using a previously registered CBCT (CBCTpre) as the reference image and tested its clinical feasibility.MethodsFrom a previous CBCT session, the registered average 4D CBCT was selected as CBCTpre and the HCT–CBCTpre registration vector from the clinician's manual registration result was recorded. In the new CBCT session, auto‐registration was performed between the new average 4D CBCT (CBCTtx) and CBCTpre (CBCTpre‐CBCTtx). The overall HCT–CBCTtx registration result was then derived by combing the results from two registrations (i.e., HCT–CBCTpre + CBCTpre–CBCTtx). The results from the proposed method were compared with clinician's manually adjusted HCT–CBCTtx registration results (“ground truth”) to evaluate its accuracy using a test dataset consisting of 32 challenging registration cases.ResultsThe uncertainty of the proposed auto‐registration method was −0.1 ± 0.5, 0.1 ± 1.0, and −0.1 ± 0.7 mm in three translational directions (lateral, longitudinal, and vertical) and 0.0° ± 0.9°, 0.3° ± 0.9°, and 0.4° ± 0.7° in three rotation directions, respectively. Two patients (6.3%) had translational uncertainty > 2 mm (max = 3.1 mm) and both occurred in the longitudinal direction. Meanwhile, the uncertainty of the conventional direct HCT–CBCTtx auto‐registration was −0.4 ± 2.6, −0.2 ± 7.4, −1.4 ± 3.6 mm for translations and −0.3° ± 1.2°, 0.0° ± 1.6°, and 0.1 ± 1.1° for rotations. Eleven patients (34.4%) had translation uncertainty > 2 mm (max = 26.2 mm) in at least one direction. Accuracy in translation was improved with the new method, while rotation accuracy stayed in the same order.ConclusionWe demonstrated the feasibility of incorporating prior clinical registration knowledge into the online HCT–CBCT registration process. The proposed auto‐registration method provides a quick and reliable starting solution for online HCT–CBCT registration.