Search
CTisus CT Scanning CTisus CT Scanning CTisus CT Scanning CTisus CT Scanning CTisus CT Scanning CTisus CT Scanning CTisus CT Scanning Ask the Fish

Everything you need to know about Computed Tomography (CT) & CT Scanning

July 2018 Imaging Pearls - Educational Tools | CT Scanning | CT Imaging | CT Scan Protocols - CTisus
Imaging Pearls ❯ July 2018

-- OR --

Deep Learning

    • “In conclusion, with the current fast pace in development of machine learning techniques, and deep learning in particular, there is prospect for a more widespread clinical adoption of machine learning in radiology practice. Machine learning and artificial intelligence are not expected to replace the radiologists in the foreseeable future. ese techniques can potentially facilitate radiology work ow, increase radiologist productivity, improve detection and interpretation of findings, reduce the chance of error, and enhance patient care and satisfaction.”


      Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
    • “Radiomics is a process designed to extract a large number of quantitative features from radiology images . Radiomics is an emerging field for machine learning that allows for conversion of radiologic images into mineable high-dimensional data. For instance, Zhang et al evaluated over 970 radiomics features extracted from MR images by using machine learning methods and correlated with features to predict local and distant treatment failure of advanced nasopharyngeal carcinoma.”


      Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
    • “Machine learning approaches to the interrogation of a wide spectrum of such data (sociodemographic, imaging, clinical, laboratory, and genetic) has the potential to further personalize health care, far beyond what would be possible through imaging applications alone. Precision medicine require the use of novel computational techniques to harness the vast amounts of data required to discover individualized disease factors and treatment decisions.”


      Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
    • "Machine learning is a method of data science that provides computers with the ability to learn without being programmed with explicit rules. Machine learning enables the creation of algorithms that can learn and make predictions. In contrast to rules-based algorithms, machine learning takes advantage of increased exposure to large and new data sets and has the ability to improve and learn with experience.” 


      Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
    • “Machine learning tasks are typically classified into three broad categories, depending on the type of task: 
supervised, unsupervised, and reinforcement learning.” 
 Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
      “In supervised learning, data labels are provided to the algorithm in the training phase (there is supervision in training). The expected outputs are usually labeled by human experts and serve as ground truth for the algorithm. The goal of the algorithm is usually to learn a general rule that maps inputs to outputs. In machine learning, ground truth refers to the data assumed to be true. In unsupervised learning, no data labels are given to the learning algorithm.”


      Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
    • “In unsupervised learning, no data labels are given to the learning algorithm. The goal of the machine learning task is to find the hidden structure in the data and to separate data into clusters or groups. In reinforcement learning, a computer program performs a certain task in a dynamic environment in which it receives feedback in terms of positive and negative reinforcement (such as playing a game against an opponent). Reinforcement learning is learning from the consequences of interactions with an environment without being explicitly taught.”


      Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
    • “Artificial neural networks are statistical and math- ematical methods that are a subset of machine learning. These networks are inspired by the way biologic nervous systems process information with a large number of highly interconnected processing elements, which are called neurons, nodes, or cells. An artificial neural network is structured as one input layer of neurons, one or more “hidden layers,” and one output layer. Each hidden layer is made up of a set of neurons, where each neuron is fully connected to all neurons in the previous layer.”


      Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
    • “For the foreseeable future, widespread application of machine learning algorithms in diagnostic radiology is not expected to reduce the need for radiologists. Instead, these techniques are expected to improve radiology work ow, increase radiologist productivity, and enhance patient care and satisfaction.”


      Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
    • “Collection of high-quality ground truth data, development of generalizable and diagnostically accurate techniques, and work ow integration are key challenges for the creation and adoption of machine learning models in radiology practice.”


      Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
    • “In general, machine learning techniques are developed by using a train-test system. Three primary sets of data for training, testing, and validation are ideally needed. The training data set is used to train the model. During training, the algorithm learns from examples. The validation set is used to evaluate different model fits on a separate data and to tune the model parameters. Most training approaches tend to overfit the training data, meaning that they find relationships that fit the training data set well but do not hold in general. Therefore, successive iterations of training and validation may be performed to optimize the algorithm and avoid over fitting. In the testing set, after a machine learning algorithm is initially developed, the final model fit may then be applied to an independent testing data set to assess the performance, accuracy, and generalizability of the algorithm.”


      Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
    • “Fundamentally, machine learning is powerful because it is not “brittle.” A rules-based approach may break when exposed to the real world, because the real world often offers examples that are not captured within the rules that programmer uses to de ne an algorithm. With machine learning, the system simply uses statistical approximation to respond most appropriately based on its training set, which means that it is flexible. Additionally, machine learning is a powerful tool because it is generic, that is, the same concepts are used for self-driving cars as is used for medical imaging interpretation. Generalizability of machine learning allows for rapid expansion in different fields, including medicine.”


      Current Applications and Future Impact of Machine Learning in Radiology 
Garry Choy et al.
 Radiology 2018; 00:1–11
Kidney

    • “Appropriately selected cases of renal angiomyolipoma can be managed by active surveillance. For those patients requiring treatment nephron sparing approaches, including partial nephrectomy and selective arterial embolization, are preferred options. For those with tuberous sclerosis complex mTOR inhibitors may represent a viable approach to control tumor burden while conserving renal parenchyma.”


      Update on the Diagnosis and Management of Renal Angiomyolipoma
Flum, Andrew S. et al.
The Journal of Urology , Volume 195 , Issue 4 , 834 - 846

    • “The recommendation historically has been that patients with AMLs larger than 4 cm undergo intervention, especially in the setting of TSC. This size threshold is based on retrospective series showing that patients with tumors larger than 4 cm more often experienced hemorrhage and other symptoms, had interval growth and required intervention more often than those with AMLs smaller than 4 cm.”


      Update on the Diagnosis and Management of Renal Angiomyolipoma
Flum, Andrew S. et al.
The Journal of Urology , Volume 195 , Issue 4 , 834 - 846

    • “However, the authors argue that 67% of symptomatic patients and 66% with tumors larger than 4 cm could be maintained on surveillance, suggesting that following the historical criteria can result in overtreatment.25 Importantly no patient surveilled who ultimately underwent sur- gical resection had a malignancy on pathological examination.”


      Update on the Diagnosis and Management of Renal Angiomyolipoma
Flum, Andrew S. et al.
The Journal of Urology , Volume 195 , Issue 4 , 834 - 846

    • “Mirroring the evolution of surgical management for renal malignancies, surgery for AML has progressed from nephrectomy to open NSS to minimally invasive NSS. An attempt at NSS should be made in all patients when feasible, as it has been reported in the RCC literature that partial nephrectomy yields superior renal functional 
outcomes and potentially improved overall mortality compared to nephrectomy. Use of NSS is even more critical in patients with TSC, as the multifocal and bilateral disease pattern with a higher rate of recurrence makes renal parenchymal preservation a key concern.”


      Update on the Diagnosis and Management of Renal Angiomyolipoma
Flum, Andrew S. et al.
The Journal of Urology , Volume 195 , Issue 4 , 834 - 846
Liver

    • “ Managing incidental liver lesions depends on the probable importance of the mass. Importance is assessed based on the appearance of the mass and the level of risk that each patient has for developing significant liver masses, realizing that important liver masses are not limited to malignancies. Patient risk for important hepatic masses is stratified as follows: ”


      Hepatic Incidentalomas
Gore RM et al.
Radiol Clin North Am. 2011 Mar;49(2):291-322
    • “When evaluating a small hepatic mass in the oncology patient, 2 important facts must be considered. First, at postmortem examination, benign hepatic lesions are detected in up to 52% of the general population. Second, the liver is the most common site of extranodal metastases, seen in up to 36% of patients. Small hepatic masses are commonly encountered in both populations on cross-sectional imaging. Hepatic cysts including BDHs and HHs are present in nearly 40% of patients. When less than 1.5 cm in size, these lesions can be difficult to characterize and differentiate from metastatic disease.”


      Hepatic Incidentalomas
 Gore RM et al.
Radiol Clin North Am. 2011 Mar;49(2):291-322
    • “The Incidental Findings Committee’s guidance for managing liver incidental findings is illustrated in Figure 3. Managing incidental liver lesions depends on the probable importance of the mass. This is assessed both by the appearance of the mass and the level of risk that each patient has for developing important liver masses. Important liver masses are not limited to malignancies. For example, a benign hepatic adenoma might require surgical intervention.” 


      Managing Incidental Findings on Abdominal CT: White Paper of the ACR Incidental Findings Committee 
Berland LL et al.
J Am Coll Radiol 2010;7:754-773. 

    • Incidental Liver Mass Detected on CT


    • “The core objectives of the Incidental Findings Project are to (1) develop consensus on patient characteristics and imaging features that are required to characterize an incidental finding, (2) provide guidance to manage such findings in ways that balance the risks and benefits to patients, (3) recommend reporting terms that reflect the level of confidence regarding a finding, and (4) focus future research by proposing a generalizable management framework across practice settings.”


      Management of Incidental Liver Lesions on CT: A White Paper of the ACR Incidental Findings Committee.
Gore RM, Pickhardt PJ, Mortele KJ, Fishman EK, Horowitz JM, Fimmel CJ, Talamonti MS, Berland LL, Pandharipande PV.
J Am Coll Radiol. 2017 Nov;14(11):1429-1437
    • “The algorithm should only be applied to incidental liver lesions in asymptomatic adult patients (!18 years of age) for whom CT was requested for an unrelated reason. As described earlier, the algorithm is designed for use in patients with varied underlying risk levels (low versus high) for a malignant hepatic lesion. However, the algo- rithm should not be applied when index CT (i.e., that which demonstrates the incidental lesion) was requested to evaluate a known or suspected liver lesion or hepatic abnormality. There are some hepatic lesions that present with associated vascular invasion, biliary dilation, or adenopathy. Patients with these associated findings should be referred directly for oncologic evaluation.”

      
Management of Incidental Liver Lesions on CT: A White Paper of the ACR Incidental Findings Committee.
Gore RM, Pickhardt PJ, Mortele KJ, Fishman EK, Horowitz JM, Fimmel CJ, Talamonti MS, Berland LL, Pandharipande PV.
J Am Coll Radiol. 2017 Nov;14(11):1429-1437
    • Reporting Considerations of a Hepatic Lesion
      1. Lesion size
      
2. Lesion attenuation

      3. Lesion homogeneity versus complexity
      4. Lesion enhancement pattern

      5. Lesion margin

      6. Lesion multiplicity

      7. Lesion growth pattern
      
8. Lesion location
    • “Specific regions of the liver are susceptible to effects of perfusional changes and fatty infiltration or sparing; such effects may mimic liver lesions . Peripherally, so-called THADs (transient hepatic attenuation differ- ences, seen on CT) and THIDs (transient hepatic intensity differences, seen on MRI) reflect changes in enhancement of the parenchyma due to relative differ- ences in hepatic arterial versus portal venous supply. Near the falciform ligament and the gallbladder fossa, alterations in venous drainage can result in focal fatty deposition or sparing.”

      
Management of Incidental Liver Lesions on CT: A White Paper of the ACR Incidental Findings Committee.
Gore RM, Pickhardt PJ, Mortele KJ, Fishman EK, Horowitz JM, Fimmel CJ, Talamonti MS, Berland LL, Pandharipande PV.
J Am Coll Radiol. 2017 Nov;14(11):1429-1437
    • “In low-risk patients, incidental liver lesions less than 1 cm generally do not require further workup and can be considered benign. Incidental liver lesions that are 1.0 to 1.5 cm and have benign or flash-filling features also do not require further workup. Prompt MRI is advised for lesions with suspicious features that are 1.0 to 1.5 cm.”


      Management of Incidental Liver Lesions on CT: A White Paper of the ACR Incidental Findings Committee.
Gore RM, Pickhardt PJ, Mortele KJ, Fishman EK, Horowitz JM, Fimmel CJ, Talamonti MS, Berland LL, Pandharipande PV.
J Am Coll Radiol. 2017 Nov;14(11):1429-1437
    • “In high-risk patients with incidental liver lesions less than 1 cm, MRI is advised in 3 to 6 months to both characterize the lesion and document the presence or absence of growth. For lesions that are 1.0 to 1.5 cm and have benign features, no further workup with MRI is necessary; for lesions of this size with suspicious or flash-filling features, we recommend prompt MRI.”


      Management of Incidental Liver Lesions on CT: A White Paper of the ACR Incidental Findings Committee.
Gore RM, Pickhardt PJ, Mortele KJ, Fishman EK, Horowitz JM, Fimmel CJ, Talamonti MS, Berland LL, Pandharipande PV.
J Am Coll Radiol. 2017 Nov;14(11):1429-1437
    • TAKE-HOME POINTS
      • Forgo workup of incidental hepatic lesions less than 1 cm in low-risk patients.
      • Forgo workup of incidental hepatic lesions with distinctly benign features regardless of risk level.
      • Pursue workup of incidental hepatic lesions that are over 1 cm and without distinctly benign features in high-risk patients

      Management of Incidental Liver Lesions on CT: A White Paper of the ACR Incidental Findings Committee.
Gore RM et al.

      J Am Coll Radiol. 2017 Nov;14(11):1429-1437
      Incidental Liver Mass Detected on CT
Pancreas

    • “Pancreatic ductal adenocarcinoma (PDA) accounts for over 90% of all pancreatic malignancies and is the second most common digestive-system cancer after colorectal cancer in the United States. PDA is the third cause of cancer deaths in the United States, with about 53670 new diagnoses and 43090 deaths in 2017. PDA has a sharply rising incidence and is predicted to become the second most common cause of cancer deaths in the United States by 2020 .”

      
Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390
    • “The risk factors associated with PDA include smoking, long-standing diabetes, obesity, and nonhereditary chronic pancreatitis. Over 80% of PDAs are due to sporadic mutations and fewer than 10% are due to inherited germline mutations.”


      Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390
    • “Genetic syndromes and genes known to be associated with an increased risk of PDA are hereditary pancreatitis (PRSS1, SPINK1), familial atypical multiple mole melanoma syndrome (p16), hereditary breast and ovarian cancer syndromes (BRCA1, BRCA2, PALB2), Peutz-Jeghers syndrome (STK11), and hereditary nonpolyposis colon cancer or Lynch syndrome (MLH1, MSH2, MSH6).”


      Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390
    • “Patients with pancreatic ductal adenocarcinoma (PDA) must be selected for first-line surgery based on the likelihood of achieving complete curative resection with negative margins (R0); in doubtful cases and when the risk of incomplete resection (R1 or R2) is high, neoadjuvant chemotherapy and radiation therapy should be performed.”


      Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390
    • “Excellent spatial resolution makes multidetector CT the reference standard for initial PDA staging; multidetector CT is particularly effective in assessing unresectability criteria related to vascular spread.”


      Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390
    • “In patients undergoing neoadjuvant therapy, a radiologic response, however limited, and more specifically decreased vascular involvement and/or tumor size, indicate high likelihood of complete resection with negative margins and therefore support resection surgery.”

      
Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390
    • “PDA is diagnosed at an advanced stage (T3 or T4) in the majority of patients. Thus, at diagnosis, only 20% of patients meet the criteria for complete resection surgery, which offers the only chance for a cure, with 5-year survival rates of up to 15%–25% in high-volume centers.”


      Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390


    • Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390


    • Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390
    • “Multidetector CT depicts peri- neural invasion as infiltrating extrapancreatic soft tissue extending directly from the intrapancreatic tumor along an established perineural pathway of PDA spread. In some patients with R0 resection, perineural invasion may explain the occurrence of rapid systemic subclinical spread to pre- viously unaffected pancreatic zones or to the retroperitoneum leading to early treatment failure.”


      Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390
    • “This body of evidence establishes that neoadjuvant therapy in patients with borderline resectable or even locally advanced PDA can induce a response that allows secondary nega- tive-margin resection of the primary tumor, with acceptable morbidity and survival rates that compare favorably with those obtained in patients who have initially resectable tumors.”


      Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390
    • “The mechanisms underlying the diminished performance of imaging studies after neoadjuvant therapy are related to the nature of PDA. The tumor is composed of extensive and dense fibrous stroma containing varying densities of tumor cells. When successful, CRT decreases or eliminates the cancer cells but leaves the preexisting fibrotic tissue and may induce the development of additional fibrosis. This fibrotic component results in persistent high attenu- ation of the perivascular fat, which may be mistakenly interpreted as indicating persistent vascular invasion.”


      Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390
    • “Initial PDA staging relies chiefly on optimal-quality multiphasic multidetector CT of the pancreas. The findings serve to help accurately classify the tumor based on relationships with the blood vessels, thereby guiding treatment decisions. MR imaging should be performed routinely if the tumor is potentially resectable to look for liver metastases or not visualized at multidetector CT. Evaluating the treatment response to first-line CRT remains extremely challenging with current imaging techniques. The high risk of underestimating the histologic response warrants surgery in most patients without indisputable evidence of disease progression after CRT.”


      Pancreatic adenocarcinoma staging in the era of Preoperative Chemotherapy and Radiation therapy 
Zins M et al.
Radiology 2018; 287:374–390
Small Bowel

    • “In the emergent setting, CT may yield criti- cal information regarding the presence, location, and cause of active bleeding—data that can guide the choice of subsequent therapy. Recent developments in the use of and techniques for performing CT angiography have made it a potential first-line tool for evaluating acute GI bleeding.”

      
CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)

    • “Acute gastrointestinal (GI) bleeding is a common problem, occurring in the upper GI tract of 100–200 per 100000 persons annually and in the lower GI tract of 20.5–27.0 per 100000 persons annually. Although 80%–85% of cases of GI bleeding resolve spontaneously, it can result in massive hemorrhage and death. Most causes of acute GI bleeding are identifiable and treatable.” 


      CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)

    • “In the current nomenclature, upper GI bleeding (UGIB) is defined as bleeding originating proximal to the Treitz ligament, and lower GI bleeding (LGIB) is defined as bleeding originating from the colon or rectum. The term suspected small-bowel bleeding is used when the upper and lower GI tracts have been evaluated (typically with endoscopy) and no bleeding site has been identified. The term obscure GI bleeding is used when no bleeding source is found after the entire GI tract has been examined with advanced techniques.” 


      CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)

    • “Endoscopy is highly useful for diagnosing the cause of UGIB, with 92%–98% sensitivity and 3%–100% specificity, and enables effective treatment of bleeding in the majority of cases.” 


      CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)

    • “CT angiography is an accurate examination for identifying the source of acute GI bleeding. A meta-analysis of data from 672 patients with moderate to severe UGIB and/or LGIB revealed an overall sensitivity of 85% and a specificity of 92% for detection of the bleeding site.” 


      CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)

    • “Most complications of GI hemorrhage result from hypotension; therefore, the patient must be stabilized and his or her blood volume must be restored before a diagnostic workup is initiated (6,7). Reversal of anticoagulant medication and correction of the coagulation abnormality may be performed. However, before these measures are implemented, a risk-versus- bene t analysis in which the severity of bleed- ing, severity of coagulation abnormalities, and risk associated with discontinuing prophylactic medications are taken into account must be performed.” 


      CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)
    • “Radiologic methods have a role in assessing UGIB only when upper endoscopy is not feasible or yields inconclusive results. Upper GI endoscopy may be contraindicated in the setting of shock, substantial comorbidity, or massive hemorrhage. Adequate endoscopic evaluation of the bleeding source may not be possible when extensive luminal blood obscures visualization or the bleeding originates from a difficult anatomic location such as the distal duodenum.”

      
CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)
    • “Colonoscopy has several limitations. Patients must have undergone adequate colon preparation before proceeding to colonoscopy. Colonoscopy without colon preparation is not recommended by the American College of Gastroenterology. In emergent situations, a rapid colon preparation involving the administration of 4–6 L of a polyethylene glycol–based solution for 3–4 hours may be attempted. However, this procedure is frequently difficult to perform, and it may result in an incomplete or nondiagnostic endoscopic evaluation.” 


      CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)
    • “Detecting extraluminal disease in a bleeding patient maybe helpful in influencing treatment and goals of care—for example, in a case of a bleeding small- bowel neoplasm with metastatic disease. CT may also be used to identify complications of hypoperfusion (eg, signs of bowel ischemia or infarction) or the risk of organ disease exacerbation due to hypoperfusion (eg, findings of heart failure, arterial stenosis or coronary atherosclerosis, or renal parenchymal disease).”

      
CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)
    • “Dual-energy CT techniques offer potential bene ts for evaluation of GI bleeding. Acquiring both high- and low-energy datasets through a volume of tissue enables one to estimate the radiation attenuation caused by iodine in each pixel of the image by using material-decomposition algorithms. Attenuation due to iodine can be subtracted from an image by means of VNC image reconstruction. A VNC image set can be used in place of a traditional nonenhanced image series to lower the radiation dose 
of an examination.”


      CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)
    • “Optimal sensitivity for identification of active extravasation is achieved by evaluating the arterial phase and portal venous phase images together. The finding of intraluminal enhancement that changes in attenuation and shape between the arterial and portal venous phases is specific for active extravasation.”


      CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)
    • “A positive result at CT angiography is predictive of a positive result at subsequently performed fluoroscopic angiography. Sun et al found that among 26 patients with positive CT angiography results who subsequently underwent fluoroscopic angiography, the fluoroscopic findings were positive in 85% of cases. Compared with RBC scintigraphy, CT angiography has similar capability in the prediction of positive fluoroscopic angiography results but is better for localizing the site of bleeding.”

      
CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)
    • “CT angiography and multiphase CT enterography yield a large volume of images that must be reviewed 
efficiently in the emergent setting. A consistent approach to these examinations facilitates effective interpretation of imaging findings. In addition to the routine scan pattern, the radiologist must add specific attention to the bowel and its vasculature for sources of GI hemorrhage. Thin-section reconstructions in the coronal plane are typically preferred for primary image review because more bowel is displayed at a given time. Additional planes are used for further evaluation of any suspicious findings. Review of coronal MIP images is helpful for identifying subtle enhancement associated with active extravasation, vascular anomalies, and tumors.”
CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)


    • 









CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)
      












    • CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)
    • “Anatomic locations where abnormalities are commonly seen are initially reviewed. Beginning with the arterial phase images, the ileocolic vessels are examined from their origin to the cecum. The ileocolic vein is examined for appropriate caliber and early filling; the findings of this evaluation may indicate a shunt through a vascular malformation or mass. The cecum is then reviewed for the presence of a mass or vascular malformation. Similarly, the inferior mesenteric artery is followed through the superior rectal artery and superior rectal vein to the rectum. The anus and rectum are examined for vascular malformations or masses.”

      
CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)
    • “The causes of acute GI bleeding and the ex- pected associated imaging findings vary according to the segment of the GI tract.The most common causes of acute GI bleeding are categorized according to bowel segment in Tables 4 and 5 (3,59,60). Important points regarding the sources of bleed- ing in the upper GI tract, lower GI tract, and small bowel are reviewed in the following sections.”

      
CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press)


    • 










CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:000–0000 (in press)
      





    • CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:000–0000 (in press)




      







    • CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:000–0000 (in press)




      



 




    • “Many common causes of bleeding in the esophagus and upper GI tract, such as peptic ulcer disease, cannot be optimally evaluated with CT. When the cause of UGIB is not found, identification of a high-attenuating hematoma or active hemorrhage is still clinically helpful and may lead to repeat endoscopy .Ulcers can be identified by carefully searching for defects in the enhancing gastric and duodenal mucosa.”


      CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press) 





CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:000–0000 (in press)




    • 




“In younger patients, the most common cause of small-bowel bleeding is Crohn disease. Although mild GI bleeding is very common in patients with Crohn disease, severe GI hemorrhage is relatively rare, with a prevalence of 0.6%–4.0%.The bleeding associated with Crohn disease is most commonly attributed to diffuse areas of inflammation, but it can be due to a focal con- dition such as a bleeding ulcer or pseudopolyp. Inflammatory findings of Crohn disease include subtle wall thickening, mural enhancement, and ulcerations, which are best detected at CT enterography.” 


      CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press) 





CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:000–0000 (in press)




      




    • 




“Acute GI bleeding is a common problem that warrants expert clinical decision making and advanced diagnostic testing.The urgency of the diagnostic workup and the type of examination chosen are dependent on many factors, including suspected rate of bleeding, level of hemodynamic stability, and risk factors for complications. Endoscopy is currently the method of 
 choice for initial diagnostic evaluation and therapeutic intervention in patients with UGIB and LGIB. Rapid and comprehensive CT assessment enables fast detection of GI bleeding and abnormalities 
of extraenteric structures, which can affect clinical decision making.”


      CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:0000–0000 (in press) 




CT for Evaluation of Acute Gastrointestinal Bleeding 
Michael L.Wells et al.
RadioGraphics 2018; 38:000–0000 (in press)




    • “Diverticulosis is the most common cause of acute LGIB, and the endoscopic evaluation of this condition can be particularly problematic. Attempts to locate a bleeding diverticulum among dozens or hundreds of diverticula and suboptimal bowel preparation can lead to hours of tedious endoscopic evaluation and nondiagnostic examinations. Preoperative localization of the bleeding source with CT may be invaluable for enabling targeted endoscopy.”
© 1999-2018 Elliot K. Fishman, MD, FACR. All rights reserved.