Cone-beam pair-wise data consistency conditions in helical CT.

Purpose: During diagnostic x‐ray CT imaging procedures or image guided radiotherapy, image quality will be degraded if target organs move during the data acquisition. This can be caused by patients' occasional motion or by intrinsic motion like cardiac and respiratory motion. The inconsistency in the projection data is the major reason for the image quality degradation. We present and validate a method to improve the consistency of the projections using a novel Fan‐beam Data Consistency Condition (FDCC) such that the image quality can be improved. Method and Materials: Computer‐simulated dynamic phantoms are generated and projection data are acquired from these dynamic phantoms. Using the FDCC, individual projection data from one view of fan‐beam projections can be estimated from filtering all the other projection data acquired from different view angles. Then those projections contaminated by motion are re‐estimated using the FDCC, resulting in a corrected sinogram. A standard Fan‐beam Filtered Back Projection (FBP) reconstruction algorithm is then used to reconstruct images from the corrected sinograms. Motion artifacts can be alleviated using this procedure. Results: Images are reconstructed from both the original sinogram where projections are contaminated by motion and the corrected sinogram after applying the FDCC. Strong motion artifacts are observed in the images reconstructed from the contaminated sinogram while improvement can be found in the reconstructed images using the corrected sinogram. Conclusions: A novel method using the new FDCC is proposed to combat the motion artifacts due to the temporal inconsistency in the projection data. Numerical simulations were conducted to demonstrate the potential of this correction scheme to mitigate motion artifacts. Thus, the preliminary numerical results indicate that the FDCC has potential use in combating both cardiac and respiratory motion in CT imaging.

In medical x ray computed tomography (CT) imaging devices, the x ray tube usually emits a polychromatic spectrum of photons resulting in beam-hardening artifacts in the reconstructed images. The bone-correction method has been widely adopted to compensate for beam-hardening artifacts. However, its correction performance is highly dependent on the empirical determination of a scaling factor, which is used to adjust the ratio of the reconstructed value in the bone region to the actual mass density of bone-tissue. A significant problem with bone-correction is that a large number of physical experiments are routinely required to accurately calibrate the scaling factor. In this article, an improved bone-correction method is proposed, based on the projection data consistency condition, to automatically determine the scaling factor. Extensive numerical simulations have verified the existence of an optimal scaling factor, the sensitivity of bone-correction to the scaling factor, and the efficiency of the proposed method for the beam-hardening correction.

"High-precision, reconstructed 3D model" of skull scanned by conebeam CT: Reproducibility verified using CAD/CAM data.

There is increasing scientific evidence that whole-body Gallium-68 prostate-specific membrane antigen (68 Ga-PSMA) positron emission tomography/computed tomography (PET/CT) improves the sensitivity of prostate cancer detection above standard staging radiology. Diagnostic IV-contrasted CT scanning offers high-quality recognition and delineation of organs and structures with a high sensitivity and specificity for diagnoses of many non-prostate pathologies. At our institution, imaging for prostate cancer staging and restaging involves a 68 Ga-PSMA PET/CT scan combined with a diagnostic IV-contrasted CT scan of the head, neck, chest, abdomen and pelvis. In this study, we aimed to determine the incidence of significant findings unrelated to prostate cancer identified when this combined imaging approach is utilized for prostate cancer imaging. In this single-centre retrospective review, 68 Ga-PSMA PET/CT and diagnostic IV-contrasted CT scans undertaken for prostate cancer staging over a 12-month period (n=1200) were reviewed for significant findings not related to prostate cancer. In cases with a significant other finding, follow-up imaging and/or pathology results were reviewed, where available. The overall incidence of significant other non-prostate cancer findings was determined, as was the incidence of unsuspected neoplasms. Significant findings, unrelated to prostate cancer, were identified in a total of 5.7% of scans (n=68) with 3.2% (n=38) of findings being unsuspected neoplasms. Diagnostic quality IV-contrasted CT combined with 68 Ga-PSMA PET/CT for staging of prostate cancer identified significant other non-prostate cancer findings, including renal, lung, gastrointestinal and haematological malignancies. Many of these conditions impact on patient management and required further investigation or treatment prior to management of the prostate cancer.

To evaluate the use of dual-phase helical computed tomography (CT) (with or without CT angiography) to assess resectability in patients suspected to have pancreatic cancer. Tumor resectability was prospectively evaluated in 89 patients who later underwent surgery for suspected pancreatic cancer. Helical CT scans were obtained in the vascular phase and a phase of maximal hepatic enhancement. CT angiograms were produced with multiprojection volume reconstruction and maximum-intensity projection. CT results were correlated with surgical and histopathologic results. Helical CT allowed detection of pancreatic cancer in 74 of 76 cases (97%). There were six false-positive results (positive predictive value, 92%). For prediction of irresectability, helical CT had an accuracy of 91%, negative predictive value of 79%, and sensitivity of 91%. Helical CT allowed detection of liver metastases in 21 of 28 cases (75%), nodal involvement in 13 of 24 cases (54%), and vascular invasion in 35 of 40 cases (88%). CT angiography demonstrated 30 of the 35 cases of vascular invasion detected with helical CT (86%). Use of dual-phase helical CT improves prediction of resectability in patients with pancreatic cancer. CT angiography cannot show all of the findings seen on helical scans.

The purpose of this study was to evaluate the use of gadolinium and barium-enhanced magnetic resonance (MR) imaging in detecting intestinal and extraintestinal Crohn's disease and compare MRI with contrast-enhanced helical computed tomography (CT). Twenty-six patients with Crohn's disease underwent imaging examinations, including gadolinium-enhanced, fat suppressed fast multiplanar spoiled gradient-recalled (FMPSPGR) MR imaging with oral 2% barium sulfate and rectal water and with helical CT using i.v. and positive (13) or negative (13) intestinal contrast material. MR images and CT scans were reviewed separately by two radiologists for bowel wall thickness and enhancement, presence of abscess, phlegmon, and fistula. MR images and CT scans were then compared side by side. Surgical, endoscopic, and histopathologic findings and results of barium studies were reviewed to determine the location and severity of involvement of intestinal Crohn's disease. Depiction of mural thickening and/or enhancement was superior on the MR images, which showed 55 (85%) and 52 (80%) of 65 abnormal bowel segments for the two observers, compared with helical CT, which showed 39 (60%) and 42 (65%; P < 0.001, P < 0.05) of bowel segments affected by Crohn's disease. Segments of bowel with moderate or marked mural thickening were depicted equally on MR imaging and helical CT. In mildly diseased segments of bowel, with only slight thickening and enhancement, MR imaging depicted 22 (79%) and 19 (68%) of 28 segments, compared with helical CT, which depicted 9 (32%; P < 0.01), and 13 (46%; P > 0.05) of 28 segments. In the side-by side comparison, MR imaging was preferred over helical CT for depicting normal bowel wall (MR 71%, CT 4%, equal 25%; P < 0.001), mural thickening (MR 41%, CT 11% equal 48%; P < 0.01), mural enhancement (MR 89%, equal 11%; P < 0.001), and overall GI tract evaluation (MR 52%, CT 10%, equal 38%; P < 0.001). Gadolinium-enhanced MR imaging with oral dilute barium sulfate and rectal water depicts intestinal and extraintestinal changes of Crohn's disease and shows promise as a clinically useful tool.

We are developing an automated method for the detection of lung nodules in helical computed tomography (CT) images. This technique incorporates 2D and 3D analyses to exploit the volumetric image data acquired during a CT examination. Gray-level thresholding is used to segment the lungs within the thorax. A rolling ball algorithm is applied to more accurately define the segmented lung regions. The set of segmented CT sections, which represents the complete lung volume, is iteratively thresholded, and a 10-point connectivity scheme is used to identify contiguous 3D structures. Structures with volumes less than a predefined maximum value comprise the set of nodule candidates, which is then subjected to 2- and 3-D feature analysis. To distinguish between candidates representing nodule and non- nodule structures, the values of the features are merged through linear discriminant analysis. When applied to a database of 17 helical thoracic CT cases, gray-level thresholding combined with the volume criterion detected 82% of the lung nodules. Linear discriminant analysis yielded an area under the receiver operating characteristic curve of 0.93 in the task of distinguishing between nodule and non- nodule structures within this set of nodule candidates.

Accurate noninvasive measurement of the volume of the liver has many potential clinical applications and is an important element in the preoperative evaluation of the liver transplant recipient. Helical (or spiral) computed tomography (CT) has theoretical advantages over conventional CT in this application because the entire liver can be imaged in a single breath-hold, limiting inaccuracies related to patient motion and respiratory variation. We compared liver volumes measured by conventional CT and helical CT in 22 patients undergoing preoperative evaluation for liver transplantation. The mean volume for helical CT is 1328 ml (SD 405) and conventional CT is 1323 ml (SD 417). We found no significant difference between the helical CT and conventional CT volumes for each patient.

We retrospectively compared the accuracy of somatostatin receptor scintigraphy (SRS) with that of helical computed tomography (CT) in the detection and localization of primary and metastatic neuroendocrine tumors. A medical record search identified 27 patients with known or clinically suspected neuroendocrine tumors who underwent helical CT and SRS within 3 months of one another at our institution. CT images were evaluated retrospectively by two blinded radiologists who used consensus reading. Images were evaluated for the presence or absence of primary tumor and hepatic and extrahepatic metastases. CT results were compared with the SRS report as interpreted by the nuclear medicine physicians. The results of the surgical, clinical follow-up, and pathologic findings were considered as the gold standard. Sensitivity, specificity, and accuracy were calculated for both imaging techniques. In addition, McNemar analysis was performed to determine statistically significant differences between CT and SRS. Helical CT was more sensitive than SRS in the detection of extrahepatic metastases, and the difference between the two imaging modalities was statistically significant (p = 0.0312) as determined by the McNemar chi-square test. However, the difference between CT and SRS in detecting primary neuroendocrine tumors, hepatic metastasis, and combined hepatic and extrahepatic metastasis was not statistically significant (p = 0.625, 1.000, and 1.000, respectively). Helical CT and SRS have similar sensitivity, specificity, and accuracy in detecting primary neuroendocrine tumor and hepatic metastasis. However, helical CT appears to be more sensitive in detecting extrahepatic metastasis from primary neuroendocrine tumors.

Renal lymphoma is most often seen in conjunction with multisystemic, disseminated lymphoma or as tumor recurrence. Renal lymphoma may also be seen in immunocompromised patients or, rarely, as primary disease. Computed tomography (CT) is the most sensitive, efficient, and comprehensive examination for evaluation of the kidneys in patients with suspected renal lymphoma. Helical CT in particular improves detection and characterization of lymphomatous renal involvement by optimizing contrast dynamics and data acquisition and is the current modality of choice for accurate staging of lymphoma. Typical CT patterns in renal lymphoma include single and multiple masses, invasion from contiguous retroperitoneal disease, perirenal disease, and diffuse renal infiltration. Atypical CT patterns may also be encountered and provide a diagnostic challenge. These include spontaneous hemorrhage, necrosis, heterogeneous attenuation, cystic transformation, and calcification. Solid renal masses including renal cell carcinoma and metastases are the most commonly encountered entities that mimic renal lymphoma at CT and require biopsy for definitive diagnosis. CT (particularly helical CT) is useful in the evaluation of patients with suspected renal lymphoma, and familiarity with the spectrum of findings in renal lymphoma is important for accurate diagnosis.

To assess prospectively the clinical effectiveness of helical computed tomography (CT) in the evaluation of patients with unresolved suspicion for pulmonary embolism (PE). Helical CT was performed in 164 consecutive patients suspected of having acute PE, intermediate probability at ventilation-perfusion (V-P) scintigraphy, and normal findings at duplex ultrasonography (US) of the legs. Fifteen patients also underwent pulmonary angiography. Helical CT results were analyzed immediately to help plan anticoagulant treatment. If helical CT did not show PE, anticoagulant treatment was not indicated. Clinical outcome for these patients was assessed during 3-month follow-up. In 40 (24.4%) of 164 patients, the diagnosis of PE was based on results at helical CT (n = 39) or pulmonary angiography (n = 1). Repeated Doppler US of the legs depicted one thrombus in the calf of three patients with normal results at helical CT that could have been responsible for PE. During 3-month follow-up, three patients experienced recurrent PE (one death, two recurrences). Therefore, PE occurred in six (5.4% [95% confidence interval, 1.3%, 9.7%]) of 112 patients with normal findings at helical CT who did not receive anticoagulant treatment. Findings at helical CT allowed accurate diagnosis of acute PE in patients with intermediate probability at V-P scintigraphy and without deep venous thrombosis at duplex sonography of the legs.

Background: The majority of injuries are the result of blunt trauma. For these individuals, CT has emerged as the main diagnostic tool. The development of computer technology and slip ring gantry design has made it possible to scan much faster thanks to the availability of helical or spiral CT scanners. These advancements have also made rapid picture reconstruction possible with faster microprocessors.Aim: the aim of the study was to assess the role of helical CT in evaluation of patients with blunt abdominal trauma.Materials and Methods: Total 39 patients after taking written informed consent were studied with Helical CT Scanner using GE, Hi-Speed CT/i Scanner. (General Electric) at tertiary care district hospital of Jammu.Results: A total of 39 patients with mean age of 34 years were studied. The CT examination was conducted at an average of 2.6 days after sustaining blunt trauma. The accuracy of CT was confirmed by surgical, clinical and radiological follow up for an average period of 7.9 months. The major cause of injury in our study was road traffic accident. The most frequently involved viscera in our study were kidneys which comprised 33.33%. This was followed by bowel/mesentery 15.15%, liver 8.24%, spleen 8.24% pancreas, 8.24%, urinary bladder 8.24% and diaphragm 3.03%.Conclusion: Helical CT has become a major advancement to assess the trauma patients, because of fast scans and also image reconstruction time have reduced patient turn-around time for abdominal trauma. CT having the advantage over other imaging methods like excretory urography, sonography, and radionuclide imaging because superior contrast resolution and ability to visualize all organs as well as simultaneously the peritoneal cavity and retroperitoneum can be visualized.

Objectives: To assess the impact of an emergency department (ED) guideline employing selective use of helical computed tomography (CT) on clinical outcomes of female patients with suspected appendicitis. Methods: All patients presenting with suspected appendicitis were prospectively enrolled and managed in accordance with a guideline incorporating selective use of helical CT. Although not the objective of this investigation, male patients were included for purposes of comparison. Patients with clinically evident appendicitis were referred to the surgical service, and patients with equivocal presentations were studied with helical CT. Patients were followed to final surgical or clinical outcomes. Outcome measures included time from ED presentation to laparotomy and rate of appendiceal perforation. These measures were compared with those of a historical cohort of patients preceding the use of helical CT. Results: A total of 310 consecutive patients with suspected appendicitis were enrolled; 92 had appendicitis. Sixty patients were referred to the surgical service without helical CT, and 41 had appendicitis (68%). Helical CT was performed on 250 patients; 51 had appendicitis (20%). For males, the mean interval from ED presentation to laparotomy was 559 minutes (95% CI = 444 to 674 minutes) during guideline use and 480 minutes (95% CI = 405 to 555 minutes) before. This interval for females was 433 minutes (95% CI = 326 to 540 minutes) during guideline use and 710 minutes (95% CI = 558 to 862 minutes) before. Appendiceal perforation rate for males was 0.25 (95% CI = 0.14 to 0.36) during guideline use and 0.38 (95% CI = 0.29 to 0.47) before; perforation rate for females was 0.06 (95% CI =−0.05 to 0.17) during guideline use and 0.23 (95% CI = 0.14 to 0.32) before. Helical CT had 92% sensitivity, 97% specificity, and 96% accuracy in diagnosing appendicitis. Conclusions: Helical CT is highly accurate in detecting appendicitis in patients with equivocal ED presentations. The use of a guideline employing selective helical CT was associated with a decline in the time from ED presentation to operative intervention in females.

To compare ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI) in the diagnosis and determination of resectability of pancreatic adenocarcinoma. Articles reporting US, CT, or MRI data of patients with known or suspected pancreatic adenocarcinoma and at least 20 patients verified with histopathology, surgical findings, or follow-up were included. A bivariate random effects approach was used to calculate sensitivity and specificity for diagnosis and resectability of pancreatic adenocarcinoma. Sixty-eight articles fulfilled all inclusion criteria. For diagnosis, sensitivities of helical CT, conventional CT, MRI, and US were 91%, 86%, 84%, and 76% and specificities were 85%, 79%, 82%, and 75% respectively. Sensitivities for MRI and US were significantly lower compared with helical CT (P = 0.04 and P = 0.0001). For determining resectability, sensitivities of helical CT, conventional CT, MRI, and US were 81%, 82%, 82, and 83% and specificities were 82%, 76%, 78%, and 63% respectively. Specificity of US was significantly lower compared with helical CT (P = 0.011). Helical CT is preferable as an imaging modality for the diagnosis and determination of resectability of pancreatic adenocarcinoma.

To perform meta-analysis of literature about the role of helical computed tomography (CT) and ventilation-perfusion (V-P) scanning in detection of acute pulmonary embolism (PE) by using summary receiver operating characteristic (ROC) curve analysis. V-P scanning articles published from January 1985 to March 2003 and helical CT articles published from January 1990 to March 2003 in MEDLINE and EMBASE databases were included if (a) tests were performed for evaluation of acute PE, (b) conventional angiography was the reference standard, and (c) absolute numbers of true-positive, false-negative, true-negative, and false-positive results were available. Sensitivity analysis was conducted by excluding articles published before 1995. A total of 12 articles discussing helical CT and/or V-P scanning were included. With a random-effects model, pooled sensitivity for helical CT was 86.0% (95% confidence interval [CI]: 80.2%, 92.1%), and specificity was 93.7% (95% CI: 91.1%, 96.3%). V-P scanning yielded low sensitivity of 39.0% (95% CI: 37.3%, 40.8%) but high specificity of 97.1% (95% CI: 96.0%, 98.3%) with high probability threshold. V-P scanning yielded high sensitivity of 98.3% (95% CI: 97.2%, 99.5%) and low specificity of 4.8% (95% CI: 4.7%, 4.9%) with normal threshold. Regression coefficients for helical CT angiography were 0.588 (95% CI: -1.55, 2.74) and 4.14 (95% CI: -0.002, 8.28) versus V-P scanning with high and normal thresholds, respectively. Regression coefficients for helical CT angiography were 0.588 (95% CI: -1.55, 2.74) and 4.14 (95% CI: -0.002, 8.28) versus V-P scanning with high and normal thresholds, respectively. Helical CT has greater discriminatory power than V-P scanning with normal and/or near-normal threshold to exclude PE, while helical CT and V-P scanning with high probability threshold had similar discriminatory power in the diagnosis of PE.