Role of Multidetector CT MDCT

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Role of Multidetector CT(MDCT)

• Dr. Peter Johnson
• Consultant Radiologist
• University Hospital of the West Indies

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• What does MDCT mean ?

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CT-Principle
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Advantages of MDCT over SDCT

• Improved spatial resolution
• Improved temporal resolution

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MDCT Spatial Resolution

• 16 Slice scanners Isotrophic
• No appreciable improvement in quality (spatial
  resolution) with gt 16 detectors

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Multiplanar Reconstructions (MPR)
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Multiplanar Reconstructions (MPR)
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Multiplanar Reconstructions (MPR)
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Multiplanar Reconstructions (MPR)
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Volume Rendering
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Surface Rendering
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MDCT Temporal Resolution

• gt number of detectors, greater volume covered per
  unit time
• gt number of detectors, faster scanning
• Better for CTA and Cardiac (esp)
• Advantage of 64 slice over 16 slice etc.

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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

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• 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 215897-899

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Temporal Resolution
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Clinical Applications

• General body imaging (Chest, Abdomen Pelvis)
• Trauma
• CT Angiography (CTA)
• Cardiac CT
• Virtual Colonoscopy (and other virtual endoscopy)
• CT perfusion
• Other

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Clinical Applications

• Cardiac.driving force in MDCT
• CT Coronary Angiography
• 4D Cardiac CT..ventricular function etc.
• Cardiac calcium scoring

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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 gt2000 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

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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 !

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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

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Pulmunary Thrombo-embolism

• CT Pulmunary Angiography (CTPA) /- CT venography
• Recommended by PIOPED II

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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 233806-815

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Virtual Colonoscopy

• Utilizes endo-luminal rendering
• Similar bowel prep as optical colonoscopy
• No need for sedation

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• 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
  2000216331341
• Macari M, Bini EJ, Milano A, et al. Clinical
  significance of missed polyps at CT colonography.
  AJR Am J Roentgenol
• 2004183127134.
• Pickhardt PJ, Choi JR, Hwang I, et al. Computed
  tomographic virtual colonoscopy to screen for
  colorectal neoplasia in
• asymptomatic adults. N Engl J Med
  200334921912200

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Virtual ColonoscopyPatient 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 2003227378-384
• 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 2002222337-345
• 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 2004233328-337

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Virtual Colonoscopy
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Virtual Colonoscopy
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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

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Virtual Colonoscopy

• Problems
• Poor detection rate for flat lesions
• Artefacts
• No consensus in performance and reporting of
  studies
• No tissue sampling
• Patient compliance
• Cost

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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

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Brain Imaging

• MDCT rarely adds to routine brain imaging
• Useful for
• CTA (SAH)
• CT perfusion (Stroke)
• ENT imaging

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Cerebral CTA

• Has replaced catheter angiography as the initial
  evaluation of the cause of acute subarachnoid
  haemorrhage in many centres

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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 188593-602

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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

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Peripheral CTA

• Good non-invasive tool for evaluating peripheral
  arterial disease.

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Peripheral CTA

• Aortoiliac and Lower Extremity Arteries Assessed
  with 16Detector Row CT
• Angiography Prospective Comparison with Digital
  Subtraction Angiography
• In this study, the improved spatial resolution
  obtained with a 16detector 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 20052361083-1093

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Peripheral CTA
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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

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However.

• MDCT is not indicated for everything !
• It isnt indicated at all in certain cicumstances
• Not the study of choice in many circumstances
• Should be used with caution in some circumstances

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e.g.
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Not the study of Choice

• MRI
• Intra and extra-axial intracranial tumours
• Congenital brain anomalies
• Myelopathy Radiculopathy (Traumatic
  Non-traumatic)

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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

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Use with caution

• Pregnant patients (especially 1st trimester)
• Paediatric patients
• Radiation Effects

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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 3572277-2284

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Radiation Risks
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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 188540-546

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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.

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Radiation

• Care and good judgement should be
  excersised.esp. paediatric population.
• Risk/Benefit
• Indications
• Contraindications (including no indication !)

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And so.

• MDCT has revolutionized diagnostic imaging
• Tremendous potential
• High radiation dose
• Not indicated for everything !
• Not a replacement for other modalities

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Thank you