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Kidney: Technique and Protocols Imaging Pearls - Educational Tools | CT Scanning | CT Imaging | CT Scan Protocols - CTisus
Imaging Pearls ❯ Kidney ❯ Technique and Protocols

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  • OBJECTIVE. The purpose of this study is to retrospectively assess the impact of iterative metal artifact reduction (IMAR) with iterative reconstruction (IR) on the image quality and diagnostic performance of CT urography in the evaluation of patients with hip prostheses, compared with IR alone.
    CONCLUSION. The addition of IMAR to IR led to statistically significant improvement in the retrospective diagnostic performance and image quality of CT urography for patients with hip prostheses, compared with IR alone.
    Application of Iterative Metal Artifact Reduction Algorithm to CT Urography for Patients With Hip Prostheses
    Trabzonlu TA et al.
    AJR 2020; 214:137–143
  • “In multiphasic CT, including CT urography, the burden of radiation exposure increases. In patients with metal hardware, increasing the tube current and tube voltage is one of the strategies that has been used to reduce metal artifacts, which increase the radiation exposure more. The IMAR algorithm is the postprocessing method that reduces the degree of visualization of metal artifacts without altering the radiation dose. Thus, applying the IMAR algorithm in multiphasic CT examinations may improve image quality without increasing the radiation exposure.”
    Application of Iterative Metal Artifact Reduction Algorithm to CT Urography for Patients With Hip Prostheses
    Trabzonlu TA et al.
    AJR 2020; 214:137–143
  • “In conclusion, the use of the IMAR technique in combination with IR led to a statistically significant improvement in both objective and subjective image quality in CT urography in patients with unilateral and bilateral hip prosthese.”
    Application of Iterative Metal Artifact Reduction Algorithm to CT Urography for Patients With Hip Prostheses
    Trabzonlu TA et al.
    AJR 2020; 214:137–143
  • “The traditional technique for CTU is to acquire non-contrast images, administer the full contrast bolus and then acquire images in the nephrographic phase (80 to 120 s) and delayed excretory phase (5 to 15 min). Additional image acquisition in the corticomedullary phase (30 to 40 s) is optional and performed at some institutions. Following the image acquisitions, coronal and sagittal reformations are incorporated in most CTU protocols to increase sensitivity and visualization of the kidneys and urothelium. This single bolus technique yields maximal opacification and distension of the urinary tract because the entire administered intravenous contrast volume contributes to the excretory phase. This is also the simplest technique for the technologist to perform, as it only requires a single contrast injection.”
    CT urography: how to optimize the technique
    Karen Cheng et al.
    Abdominal Radiology https://doi.org/10.1007/s00261-019-02111-2
  • “Accordingly, at our institution the corticomedullary phase is not performed; we obtain three acquisitions, beginning with non-contrast images to the level of the pelvic brim, after which we administer 120 mL of Iohexol (Omnipaque 350, GE Healthcare), followed by a bolus of 250 mL of normal saline. Post-contrast images through the abdomen and pelvis are then acquired during nephrographic phase (90 s) and excretory phase (10 min).”
    CT urography: how to optimize the technique
    Karen Cheng et al.
    Abdominal Radiology https://doi.org/10.1007/s00261-019-02111-2
  • “In general, longer delay times of at least 10 min are recommended to increase the likelihood that the distal ureter will be adequately opacified. However, waiting for an excessive time can increase the density of contrast within the ureters and bladder. Although appropriate windowing of images can help in certain cases, resultant streak artifact can be a problem with extremely dense excreted contrast within the collecting system. At our institution, we obtain the excretory phase images at 10 min following the single bolus injection to balance competing concerns of under-distension and excessive contrast density.”
    CT urography: how to optimize the technique
    Karen Cheng et al.
    Abdominal Radiology https://doi.org/10.1007/s00261-019-02111-2 
  • “Split bolus technique is recommended in younger patients because it reduces the radiation dose. However, it is less sensitive for the detection of smaller renal cell carcinomas since fewer post-contrast phases are available and there may be streak artifact present from contrast in the collecting system. Additionally, since only a part of the total contrast bolus contributes to the excretory phase, this technique has poorer contrast opacification and distension of the urinary tract. Despite this limitation, split bolus CTU has been reported to have a similar sensitivity for upper tract urothelial carcinoma as standard single bolus technique.”
    CT urography: how to optimize the technique
    Karen Cheng et al.
    Abdominal Radiology https://doi.org/10.1007/s00261-019-02111-2 
  • “Several different 3D reformation techniques can be utilized to enhance visualization of the urinary tract without increasing radiation exposure, including maximal intensity projection images (MIP), average intensity projection (AIP), volume-rendered reconstruction (VR), and curved planar reformats (CPR).”
    CT urography: how to optimize the technique
    Karen Cheng et al.
    Abdominal Radiology https://doi.org/10.1007/s00261-019-02111-2 
  • “Patient hydration, either with oral fluid administration or intravenous saline, may increase urine output, thereby increasing distension and opacification of the urinary tract and bladder. Adequate distension is critical in the visualization of subtle tumors, which may otherwise be undetectable. Hydration does not significantly hinder workflow and is a relatively safe and easy ancillary technique to most CTU protocols.”
    CT urography: how to optimize the technique
    Karen Cheng et al.
    Abdominal Radiology https://doi.org/10.1007/s00261-019-02111-2 
  • “CTU is a powerful tool and a highly useful imaging technique that allows for the detection and characterization of both benign and malignant conditions involving the urinary tract. The utility of CTU is now widely recognized and has become the imaging of choice in the evaluation of asymptomatic hematuria.”
    CT urography: how to optimize the technique
    Karen Cheng et al.
    Abdominal Radiology https://doi.org/10.1007/s00261-019-02111-2 
  • “ With a three-phase CT urologic protocol, significant dose reduction in the unenhanced and excretory phases can be achieved when these phases are combined with a normal-dose corticomedullary phase.”
    How Much Dose Can Be Saved in Three Phase CT Urography? A Combination of Normal-Dose Corticomedullary Phase With Low Dose Unenhanced and Excretory Phases
    Dahlman P et al.
    AJR 2012; 199:852-860
  • “ It is possible to reduce the total radiation dose for CT urography by 42% by selectively reducing the dose in the unenhanced and excretory phases and systematically evaluating the images obtained in these phases alongside those obtained in the normal dose corticomedullary phase.”
    How Much Dose Can Be Saved in Three Phase CT Urography? A Combination of Normal-Dose Corticomedullary Phase With Low Dose Unenhanced and Excretory Phases
    Dahlman P et al.
    AJR 2012; 199:852-860
  • "Most uroradiologists perform CT urography using multidetector-row CT aline (79%) and use a 3-phase technique (52%) using a single injection (76%) of contrast media at 3 ml/sec (52%) without a compression devise (81%) and with the patient in the supine position (90%)."

    Current Use of Computed Tomographic Urography: Survey of the Society of Uroradiology
    Townsend BA et al.
    J Comput Assist Tomogr 2009; 33:96-100

  • CT Urography: Indications per Society of Uroradiology
    - Painless gross and microscopic hematuria
    - Suspected transitional cell carcinoma
    - Followup of transitional cell carcinoma
    - Recurrent UTI’s
    - Congenital anomalies
    - Renal trauma
  • "Most uroradiologists use CT Urography in their practice today; some no longer perform IV urography. Variability in multidetector-row CT technique suggests that more research is needed to determine the optimal protocol."

    Current Use of Computed Tomographic Urography: Survey of the Society of Uroradiology
    Townsend BA et al.
    J Comput Assist Tomogr 2009; 33: 96-100

  • "CT Urography is essentially defined as a CT examination of the urinary tract before and after the administration of intravenous contrast material that includes excretory phase images."

    What is the Current Role of CT Urography and MR Urography in the Evaluation of the Urinary Tract
    Silverman SS, Leyendecker JR, Amis Jr ES
    Radiology 2009; 250:309-323

  • Split Bolus Technique for CT Urography (Maheshwari E et al.)
    - Scan without contrast from top of kidneys thru the base of the bladder
    - Inject 50 ml of iodixanol at 3 cc/sec
    - Wait 5 minutes
    - Inject 80 ml of iodixanol at 3 cc/sec
    - Wait 100 seconds and then scan the patient from the top of the kidneys thru the pelvis (combined nephrographic and excretory phase)
  • " In conclusion, in patients with hematuria, split bolus MDCT urography and oral hydration provide complete opacification of the majority of upper urinary tract segments and are accurate for the diagnosis of upper tract urothelial tumors."

    Split-Bolus MDCT Urography: Upper Tract Opacification and Performance for Upper Tract Tumors in Patients with Hematuria
    Maheshwari E et al.
    AJR 2010; 194:453-458

  • "We believe that oral hydration is a simple method of aiding urinary tract opacification while maintaining an effective workflow, as has been advocated previously by Kawamoto et al."

    Split-Bolus MDCT Urography: Upper Tract Opacification and Performance for Upper Tract Tumors in Patients with Hematuria
    Maheshwari E et al.
    AJR 2010; 194:453-458

  • "The negative predictive value of MDCT urography for upper tract tumors was 99.5% and 100% for two reviewers and 100% for the prospective interpretations."

    Split-Bolus MDCT Urography: Upper Tract Opacification and Performance for Upper Tract Tumors in Patients with Hematuria
    Maheshwari E et al.
    AJR 2010; 194:453-458

  • "Split-bolus MDCT urography provided at least 50% opacification of the majority of upper urinary tract segments and had high sensitivity, specificity, and accuracy for the detection of upper urinary tract tumors"

    Split-Bolus MDCT Urography: Upper Tract Opacification and Performance for Upper Tract Tumors in Patients with Hematuria
    Maheshwari E et al.
    AJR 2010; 194:453-458

  • Split Bolus Technique for the Kidneys (Zamboni GA et al.)
    - Inject 50 ml of IV contrast
    - Wait 3 minutes
    - Inject 100 ml of contrast at 4-6 ml/sec
    - Begin acquisition 5 seconds after trigger point of 200 HU is reached
    - Obtain a single acquisition
  • Excretory Phase (4-8 minutes): Optimal Phase For Detection of-
    - Transitional cell carcinoma
    - Collecting system obstruction
    - Pyelonephritis
    - Changes in perfusion
    - Measure lesion de-enhancement
  • Nephrographic Phase (60-140 sec): Optimal Phase For Detection of-
    - Renal lesion detection
    - Pyelonephritis
    - Tumor invasion (renal vein/IVC)
    - Characterize lesion density
    - Perfusion changes
    - Renal vein or IVC thrombus
  • Corticomedullary Phase (25-50sec) : Optimal Phase For Detection of-
    - Evaluate arterial strutures
    - Preoperative planning for nephron sparing surgery
    - Define tumor vascularity
    - Changes in perfusion
    - Tumor detection  
  • Unenhanced CT of the Kidney: Optimal Phase For Detection of-
    - Calculus
    - Cyst vs mass (HDRC vs solid tumor)
    - High density renal cyst
    - Identify location of the kidneys to define coverage 
  • "The regions of altered perfusion on nephrographic or excretory contrast enhanced acquisitions would actually appear as regions of hyperattenuation if the kidney was imaged 3-6 hours after the initial CT, owing to a decreased rate of contrast transit through the tubules."

    Optimizing Detectability of Renal Pathology with MDCT: Protocols, Pearls and Pitfalls
    Johnson PT, Horton KM, Fishman EK
    AJR 2010; 194:1001-1012

  • "Underdistension or inadequate opacification of the ureter may prevent identification of a small transitional cell carcinoma."

    Optimizing Detectability of Renal Pathology with MDCT: Protocols, Pearls and Pitfalls
    Johnson PT, Horton KM, Fishman EK
    AJR 2010; 194:1001-1012

  • "With the goal of refining interpretive performance, this pictorial essay shows the patterns of conspicuity unique to each genitourinary pathologic abnormality, presents experience-based recommendations to improve detection and characterization using multiphasic MDCT, and describes pitfalls to avoid."

    Optimizing Detectability of Renal Pathology with MDCT: Protocols, Pearls and Pitfalls
    Johnson PT, Horton KM, Fishman EK
    AJR 2010; 194:1001-1012

  • Optimizing Detectability of Renal Pathology With MDCT: Protocols, Pearls, and Pitfalls

    Pamela T. Johnson, Karen M. Horton and Elliot K. Fishman

    OBJECTIVE. The purpose of this article is to review MDCT acquisition protocol parameters and interpretative practices for evaluating genitourinary lesions other than classic renal cell carcinoma, to optimize lesion detectability and accurately characterize pathologic abnormalities.

    CONCLUSION. With the goal of refining interpretative performance, this pictorial essay shows the patterns of conspicuity unique to each genitourinary pathologic abnormality, presents experience-based recommendations to improve detection and characterization using multiphasic MDCT, and describes pitfalls to be avoided.

  • How Not to Miss or Mischaracterize a Renal Cell Carcinoma: Protocols, Pearls, and Pitfalls

    Pamela T. Johnson, Karen M. Horton and Elliot K. Fishman

    OBJECTIVE. MDCT protocol optimization for renal cell carcinoma requires attention to several data acquisition, reconstruction, and display parameters. Specifically, multiple acquisitions with varying coverage, careful timing of each contrast-enhanced phase, and use of 2D and 3D multiplanar displays are required. This article reviews these parameters, supplemented by experience-based pearls and pitfalls.

    CONCLUSION. Proper data acquisition and utilization of postprocessing tools are essential to avoid missed diagnoses or misinterpretation when imaging renal cell carcinoma.

  • "MDCT protocol optimization for renal cell carcinoma requires attention to several data acquisition, reconstruction, and display parameters. Specifically multiple acquisitions with varying coverage, careful timing of each contrast enhanced phase, and use of 2D and 3D multiplanar displays are required."

    How Not to Miss or Mischaracterize a Renal Cell Carcinoma: Protocols, Pearls and Pitfalls
    Johnson PT, Horton KM, Fishman EK
    AJR 2010; 194: W307-315

     

  • "Although this study was designed to evaluate urinary system opacification and image quality by using a triple bolus technique, our sample size did not allow assignment of its diagnostic performance. A larger test group is needed to assign diagnostic abilities of this protocol."

    Kidney and Urinary Tract Imaging: Triple Bolus Multidetector CT Urography as a One-Stop Shop-Protocol Design, Opacification, and Image Quality Analysis
    Kekelidze M et al.
    Radiology 2010; 255:508-516

  • "Multidetector CT Urography with a timed triple bolus scanning technique reduces effective radiation dose to about half of that caused by single bolus three phase multidetector CT urographic protocols without comprimising image quality of the kidneys and the urinary tract."

    Kidney and Urinary Tract Imaging: Triple Bolus Multidetector CT Urography as a One-Stop Shop-Protocol Design, Opacification, and Image Quality Analysis
    Kekelidze M et al.
    Radiology 2010; 255:508-516

  • "Triple bolus multidetector CT urography is a dose efficient protocol acquiring corticomedullary-nephrographic-excretory and vascular enhancement phases in a single acquisition and provides sufficient opacification and distention of the upper urinary tract. Simultaneously adequate image quality of renal parenchyma and vascular anatomy is achieved."

    Kidney and Urinary Tract Imaging: Triple Bolus Multidetector CT Urography as a One-Stop Shop-Protocol Design, Opacification, and Image Quality Analysis
    Kekelidze M et al.
    Radiology 2010; 255:508-516

  • "The average time to generate simple MIPs at the console was 3.4 minutes (range 1.7-4.4 minutes), and 22.3 minutes (range 15-30 minutes) to create images at the 3D workstation."

    Semiautomated MIP Images Created Directly on 16 Section Multidtector CT Console for Evaluation of Living Renal Donors
    Singh AK et al.
    Radiology 2007; 244:583-590
  • "In conclusion our study revealed that the MIPs from a predesigned protocol on the scanner console were much quicker to generate than similar images from 3D workstations, and postprocessing demands(eg, the needs of renal donors) can be quickly fulfilled at the scanner console itself."

    Semiautomated MIP Images Created Directly on 16 Section Multidtector CT Console for Evaluation of Living Renal Donors
    Singh AK et al.
    Radiology 2007; 244:583-590
  • "When protocols involving multiple scans are designed, an effort should be made to obtain as much diagnostic information as necessary with a sufficient but not unnecessary amount of radiation whenever possible."

    Patient Radiation Dose at CT Urography and Conventional Urography
    Nawfel RD et al.
    Radiology 2004; 232:126-132
  • "Measurements made from curved planar images are typically inaccurate because of the geometric distortion that occurs at increasing distances from the centerline."

    Value of Curved Planar Reformations in MDCT of Abdominal Pathology
    Desser TS et al.
    AJR 2004;182:1477-1484

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