Multidetector CT

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					 Role of Multidetector CT
         (MDCT)
          Dr. Peter Johnson
       Consultant Radiologist
University Hospital of the West Indies
• What does MDCT mean ?
CT-Principle
  Advantages of MDCT over SDCT
• Improved spatial resolution
• Improved temporal resolution
     MDCT & Spatial Resolution
• 16 Slice scanners : Isotrophic
• No appreciable improvement in quality
  (spatial resolution) with > 16 detectors
Multiplanar Reconstructions (MPR)
Multiplanar Reconstructions (MPR)
Multiplanar Reconstructions (MPR)
Multiplanar Reconstructions (MPR)
Volume Rendering
Surface Rendering
    MDCT & Temporal Resolution
• > number of detectors, greater volume
  covered per unit time
• > number of detectors, faster scanning
• Better for CTA and Cardiac (esp)
• Advantage of 64 slice over 16 slice etc.
           Temporal Resolution
• Useful for:
  – Vascular work eg. CTA, CTV
  – Phased scanning eg. Liver, Kidneys
  – Functional work eg. CT Perfusion, Cardiac CT
• Reduces scan time hence great for:
  – Uncooperative patients
     • SOB
     • Confused (eg. Head injury etc)
     • Paediatric
Reduced Frequency of Sedation of Young
Children with Multisection Helical CT
Pappas John N., Donnelly Lane F., Frush Donald P.

   CONCLUSION: The rate of sedation was reduced threefold
   with multisection helical CT compared with standard helical
   CT, and the need for sedation was eliminated in some age
   groups.

Radiology 2000; 215:897-899
Temporal Resolution
             Clinical Applications
•   General body imaging (Chest, Abdomen & Pelvis)
•   Trauma
•   CT Angiography (CTA)
•   Cardiac CT
•   Virtual Colonoscopy (and other virtual endoscopy)
•   CT perfusion
•   Other
           Clinical Applications
• Cardiac….driving force in MDCT
  – CT Coronary Angiography
  – 4D Cardiac CT…..ventricular function etc.
  – Cardiac calcium scoring
                                             Coronary CTA
Interpreting the evidence: How accurate is coronary computed
tomography angiography?

      Abstract: Coronary CT angiography (CTA) has evolved rapidly into a powerful diagnostic tool. More than
      30 accuracy studies have reported accuracy results in >2000 patients. A meta-analysis of 29 studies
      found per-patient accuracy of 96% sensitivity, 74% specificity, 83% positive predictive value, and 94%
      negative predictive value. Several clinical studies support the safety and accuracy of coronary CTA for
      acute chest pain, after inconclusive stress testing, and in preoperative evaluation of patients before
      cardiac valve surgery. Accuracy studies suffer from selection bias because of the inclusion only of
      patients previously selected to undergo invasive angiography. This increases the incidence of true
      disease, raising apparent sensitivity and lowering negative predictive value, although the latter remains
      high at 94%. CTA has relatively low accuracy for the quantitative assessment of stenosis severity. CTA
      accuracy studies show high figures for sensitivity and negative predictive value in detection of coronary
      lesions. CTA less accurately shows lesion severity, and intermediate-grade lesions require physiologic
      evaluation. Clinical studies support the effectiveness of CTA for exclusion of significant coronary disease.

Gilbert L. Raff
Journal of Cardiovascular Computed Tomography (2007) 1, 73-77
               Coronary CTA
• High sensitivity and negative predictive value
• Good selection tool for excluding patients who
  are not candidates for invasive cardiac
  catheterization
• Good screening tool
• Less acurate at demonstrating lesion severity
  – These patients need intervention anyways !
                                                Coronary CTA
• The greater the detectors….better temporal
  resolution
• MDCT scanners with greater detector numbers
  perform better than lower numbers

Coronary Arteries: Diagnostic Performance of 16-versus 64-Section Spiral CT
Compared with Invasive Coronary Angiography-Meta-Analysis

Conclusion: Sixty-four-section spiral CT has significantly higher specificity and PPV on
a per-patient basis compared with 16-section CT for the detection of greater than
50% stenosis of coronary arteries.

Michele Hamon, MD Remy Morello, MD John W. Riddell, MD Martial Hamon, MD
Radiology: Volume 245: Number 3-December 2007
Pulmunary Thrombo-embolism
– CT Pulmunary Angiography (CTPA) +/- CT
  venography
– Recommended by PIOPED II
                                                    CTPA
Suspected Acute Pulmonary Embolism: Evaluation with Multi-Detector Row
CT versus Digital Subtraction Pulmonary Arteriography


PURPOSE: To determine diagnostic accuracy of four-channel multi-detector row
computed tomography (CT) in emergency room and inpatient populations suspected
of having acute pulmonary embolism (PE) who prospectively underwent both CT and
pulmonary arteriography (PA).

CONCLUSION: Multi-detector row CT has an accuracy of 91% in the depiction of
suspected acute PE when conventional PA is used as the reference standard.

Winer-Muram HT, Rydberg J, Johnson MS, Tarver RD, Williams MD, Shah H, Namyslowski J, Conces D, Jennings SG, Ying J,
Trerotola SO, Kopecky KK.
Radiology 2004; 233:806-815
          Virtual Colonoscopy
• Utilizes endo-luminal rendering
• Similar bowel prep as optical colonoscopy
• No need for sedation
• Several studies demonstrate Virtual Colonoscopy performance on
  par with optical colonoscopy. Some indicate superior performance

Johnson CD, Dachman AH. CT colonography: the next colon screening examination. Radiology 2000;216:331–341

Macari M, Bini EJ, Milano A, et al. Clinical significance of missed polyps at CT colonography. AJR Am J Roentgenol
2004;183:127–134.

Pickhardt PJ, Choi JR, Hwang I, et al. Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in
asymptomatic adults. N Engl J Med 2003;349:2191–2200
                             Virtual Colonoscopy:
                               Patient Tolerance
“Patients undergoing colorectal cancer screening prefer CT colonography to both colonoscopy and DCBE. The
majority of patients experience discomfort and inconvenience with cathartic bowel preparation.”

Thomas M. Gluecker, MD, C. Daniel Johnson, MD, William S. Harmsen, MS, Kenneth P. Offord, MS, Ann M. Harris, BA, Lynn A.
Wilson, RN and David A. Ahlquist, MD
Radiology 2003;227:378-384


“CT colonography was considered less painful and less difficult overall than colonoscopy and was the
preferred examination”
Maria H. Svensson, MD, Elisabeth Svensson, PhD, Anders Lasson, MD and Mikael Hellström, MD, PhD
Radiology 2002;222:337-345


“Patients preferred CT colonography to colonoscopy; however, this preference decreased in time, while
outcome considerations gradually replaced temporary experiences of inconvenience”
Rogier E. van Gelder, MD, Erwin Birnie, PhD, Jasper Florie, MD, Michiel P. Schutter, Joep F. Bartelsman, MD, Pleun Snel, MD, PhD,
Johan S. Laméris, MD, PhD, Gouke J. Bonsel, MD, PhD and Jaap Stoker, MD, Phd
Radiology 2004;233:328-337
Virtual Colonoscopy
Virtual Colonoscopy
          Virtual Colonoscopy
• No established international or even national
  protocol for:
  – Performing study
  – Evaluating and reporting studies
• Some differences in performance of VC
  software by manufacturer
          Virtual Colonoscopy
• Problems:
  – Poor detection rate for “flat” lesions
  – Artefacts
  – No consensus in performance and reporting of
    studies
  – No tissue sampling
  – Patient compliance
  – Cost
            Virtual Colonoscopy
• Current Established Indications:
  – Failed Optical Colonoscopy (OTC)
  – Evaluation of colon proximal to an obstructing
    lesion
  – Patients with contraindications to OTC
• Future:
  – Screening….pending outcomes of Trials
               Brain Imaging
• MDCT rarely adds to routine brain imaging
• Useful for:
  – CTA (SAH)
  – CT perfusion (Stroke)
  – ENT imaging
              Cerebral CTA
• Has replaced catheter angiography as the
  initial evaluation of the cause of acute
  subarachnoid haemorrhage in many centres
                                    Cerebral CTA
MDCT Angiography for Detection and Quantification of Small Intracranial
Arteries: Comparison with Conventional Catheter Angiography

CONCLUSION: Except for the recurrent artery of Heubner and the anterior
choroidal artery, MDCT angiography depicted 90% or more of all examined
small intracranial arteries detected with digital subtraction angiography. The
mean sensitivity was 0.91, and the mean specificity was 0.7.

Villablanca JP, Rodriguez FJ, Stockman T, Dahliwal S, Omura M, Hazany S, Sayre J.
AJR 2007; 188:593-602
                                     Cerebral CTA
Intracranial Aneurysms: Role of Multidetector CT Angiography
in Diagnosis and Endovascular Therapy Planning

Conclusion: Multidetector CT angiography offers high diagnostic accuracy-
equivalent to that of DSA-in the detection of intracranial aneurysms. Also,
the possibility of coil embolization can be reliably determined with
multidetector CT angiography.

Karsten Papke, MD Christian K. Kuhl, MD Martin Fruth, MD Cornel Haupt, MD Martin Schlunz-Hendann, MD
Dieter Sauner, MD Martin Fiebich, PhD Alan Bani, MD Friedhelm Brassel, MD
Radiology: Volume 244: Number 2-August 2007
              Peripheral CTA
• Good non-invasive tool for evaluating
  peripheral arterial disease.
                                  Peripheral CTA
Aortoiliac and Lower Extremity Arteries Assessed with 16–Detector Row CT
Angiography: Prospective Comparison with Digital Subtraction Angiography

“In this study, the improved spatial resolution obtained with a 16–detector row CT
scanner is reflected in the total sensitivity and specificity (96% and 97%, respectively,
for both readers) in the detection of hemodynamically significant arterial stenosis of
aortoiliac and lower extremity arteries. In particular, excellent sensitivities (ie, 96% and
97% for readers 1 and 2, respectively) and specificities (ie, 95% and 96% for readers 1
and 2, respectively) for grading small popliteocrural arteries were obtained in this
study”

Jürgen K. Willmann, MD, Bernhard Baumert, MD, Thomas Schertler, MD, Simon Wildermuth, MD, Thomas Pfammatter, MD,
Francis R. Verdun, PhD, Burkhardt Seifert, PhD, Borut Marincek, MD and Thomas Böhm, MD
Radiology 2005;236:1083-1093
Peripheral CTA
                          Whole Body CT
Cost-effectiveness of Whole-Body CT Screening

“Compared with routine care, whole-body CT
screening provided minimal gains in life expectancy
(0.016 6 years or 6 days) at an average additional cost
of $2513 per patient, or an incremental cost
effectiveness ratio of $151 000 per life-year gained”
Molly T. Beinfeld, MPH, Eve Wittenberg, PhD and G. Scott Gazelle, MD, MPH, PhD
                   However….
•   MDCT is not indicated for everything !
•   It isn’t indicated at all in certain cicumstances
•   Not the study of choice in many circumstances
•   Should be used with caution in some
    circumstances
e.g.
         Not the study of Choice:
• MRI:
  – Intra and extra-axial intracranial tumours
  – Congenital brain anomalies
  – Myelopathy & Radiculopathy (Traumatic & Non-
    traumatic)
       Not the study of Choice:
• Ultrasound:
  – Initial evaluation of neonatal intracranial events
    e.g. Germinal Matrix Haemorrhage (CT not
    indicated for this pathology), ? Hydrocephalus.
  – Acute gynecologic events e.g. ? Ectopic, ruptured
    ovarian cysts, ovarian torsion
          Use with caution……
• Pregnant patients (especially 1st trimester)
• Paediatric patients

                Radiation Effects
                           Radiation Dose
“On the basis of such risk estimates and data on CT use from 1991 through
1996, it has been estimated that about 0.4% of all cancers in the United
    States
may be attributable to the radiation from CT studies. By adjusting this
estimate for current CT use, this estimate might now be in the range of 1.5 to
2.0%”

David J. Brenner, Ph.D., D.Sc., and Eric J. Hall, D.Phil., D.Sc.
NEJM 2007; 357:2277-2284
Radiation Risks
                        Radiation Dose
“Relative to CT scanners from the early 1990s,
present-day MDCT scanners result in doses that
are ~1.5 and -1.7 higher per unit mAs in head
and body phantoms, respectively.”

Huda W, Vance A
AJR 2007; 188:540-546
              However……..
• To date, no example of cancer definitely
  attributable to exposure to diagnostic x-ray
  doses has been reported.
• Data represent extrapolated risk estimates
  related to known cancer incidences from
  exposure at Hiroshima and “therapeutic Xray
  treatments” in the early 20th century.
                  Radiation
• Care and good judgement should be
  excersised….esp. paediatric population.
• Risk/Benefit
• Indications
• Contraindications (including no indication !)
                  And so…….
•   MDCT has revolutionized diagnostic imaging
•   Tremendous potential
•   High radiation dose
•   Not indicated for everything !
•   Not a replacement for other modalities
Thank you

				
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posted:7/25/2011
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