Diagnostic aspects of CT {Miscellaneous (CT).pptx

Miscellaneous (CT)
Urooj Mushtaq Bhat

Basic diagnostic aspects in CT
1. Image Acquisition
CT uses X-rays and computer processing to create cross-sectional images.
Patient lies on a table that moves through a rotating gantry housing the X-ray tube
and detectors.
2. Types of CT Scans
 Non-contrast CT – No contrast agent; useful for trauma, stroke (bleed detection), kidney
stones.
 Contrast-enhanced CT – IV or oral contrast enhances vascular structures or GI tract.
 High-resolution CT (HRCT) – For fine detail, especially in lungs.
 CT Angiography (CTA) – Visualizes blood vessels after contrast injection.
3. Windowing
 Adjusting brightness and contrast to highlight different tissues:
 Bone window – for bones and fractures
 Soft tissue window – for organs
 Lung window – for lung parenchyma

4. Multiplanar Reconstruction (MPR)
 Axial images can be reformatted into sagittal, coronal, and 3D views for better analysis.
5. Common Diagnostic Uses
 Head CT: Trauma, stroke, tumors, hydrocephalus.
 Chest CT: Infections, tumors, embolism, interstitial lung disease.
 Abdomen/Pelvis CT: Appendicitis, tumors, bowel obstructions, trauma.
 CT Angiography: Aneurysms, dissections, vascular occlusions.
6. Artifacts to Consider
 Motion artifact – from patient movement
 Beam hardening – around dense areas like metal or bone
 Streak artifacts – from metal implants
7. Radiation Dose Awareness
 CT delivers higher radiation than X-ray; dose optimization and justification are essential.

Brief history of CT (Computed Tomography) from its
invention to 2025, highlighting key developments:---
1. Origins and Invention (1960s–1970s)
 1967–1972: Sir Godfrey Hounsfield (EMI, UK) and Allan Cormack (Tufts University, USA) independently
developed the mathematical and technical foundations of CT.
 1971: First CT scan of a human brain performed in the UK.
 1979: Hounsfield and Cormack were awarded the Nobel Prize in Physiology or Medicine.
2. First-Generation CT (1970s)
 Translate-rotate system:
 single detector and pencil beam.
 Very slow – one image could take hours.
3. Second & Third Generation CT (Late 1970s–1980s)
 Multiple detectors and fan-beam geometry.
 Whole-body CT scanners introduced.
 Third generation: still the most widely used geometry today.

4. Fourth Generation CT (1980s)
 Stationary ring of detectors; only X-ray tube rotates.
 Fast, but expensive; mostly replaced by third-generation.
5. Spiral (Helical) CT (1990s)
 Introduced continuous patient movement and rotating X-ray tube.
 Allowed for faster and more detailed imaging.
 Enabled 3D reconstruction.
6. Multi-Detector CT (MDCT) (2000s)
 Multiple rows of detectors (4-, 16-, 64-, 128-slice, etc.).
 Improved spatial and temporal resolution.
 Reduced scan times, improved cardiac and trauma imaging.

7. Dual Source & Spectral CT (2010s)
 Dual-source CT:
 Two X-ray tubes and detector arrays for faster imaging and cardiac applications.
 Spectral/dual-energy CT:
 Differentiates materials by energy level, enhancing tissue characterization.
8. AI & Deep Learning Integration (2020s)
 AI-assisted reconstruction for noise reduction and lower radiation.
 Automated detection and diagnosis (e.g., lung nodules, fractures).
 Integration with radiomics and precision medicine.
9. Photon-Counting CT (Early 2020s)
 Breakthrough in detector technology.
 Counts individual photons;
 higher contrast,
 lower dose.
 Provides better differentiation of tissues, especially useful in oncology and cardiology.

10. CT in 2025
 Photon-counting CT is being adopted clinically in major hospitals
 AI and cloud-based PACS systems are fully integrated for faster reporting.
 Ongoing research into real-time CT imaging, hybrid PET/CT and SPECT/CT
enhancements.
 Low-dose pediatric protocols and functional CT imaging are more widely available.

Spiral CT Scan (Helical CT Scan)
 Spiral CT is a type of computed
tomography where the X-ray tube rotates
continuously around the patient while the
patient is moved through the scanner in a
spiral path.
 This allows for continuous data
acquisition, resulting in faster scans and
better image quality.

Key Features of Spiral CT:
1. Continuous Movement
 The patient table moves at a constant speed through the gantry as the X-ray tube rotates
This creates a spiral (helical) path of data collection.
2. Faster Scanning
 Entire regions (e.g., chest, abdomen) can be scanned in seconds.
Crucial for trauma patients, children, or patients who can’t hold their breath long.
3. 3D Image Reconstruction
 Allows generation of multiplanar and 3D images from the continuous data.
Useful in vascular imaging, tumor localization, and surgical planning.
4. Improved Diagnostic Accuracy
 Reduces motion artifacts.
Better coverage of anatomy in a single breath-hold.

Applications
 Chest: CT (lung cancer, pulmonary embolism)
 Abdomen/pelvis CT (appendicitis, tumors)
 CT angiography
 Virtual colonoscopy

Advantages of Spiral CT:
 Reduced scan time
 More accurate Continuous rotation allows scanning in a single breath-hold,
reducing motion artifacts and improving patient comfort.
 Better Image Quality: Produces high-resolution 3D images with reduced slice
gaps, improving diagnostic accuracy.
 Improved Detection: Ideal for detecting small lesions, vascular abnormalities, and
subtle pathology due to isotropic imaging.
 Enhanced Contrast Timing: Allows better synchronization with contrast
administration for angiographic studies (e.g., CT angiography).
 Volume Imaging: Enables multiplanar reconstruction (MPR) and 3D visualization,
useful in surgical planning and oncology.
 Efficient Workflow: Shorter scan times improve patient throughput and reduce
examination delays.

disadvantages of Spiral (Helical) CT:
1. Increased Radiation Dose:
 Continuous scanning during spiral CT results in higher radiation exposure compared to conventional
CT.
2. Motion Artifacts:
 Though faster, spiral CT can still be affected by patient movement, especially in uncooperative
patients or children.
3. Higher Cost:
 Spiral CT systems are more expensive due to their advanced technology and software.
4. Complex Image Reconstruction:
 The continuous data requires sophisticated algorithms, which may introduce artifacts or distortions
if not properly calibrated.
5. Overlapping Data:
 There's a risk of redundant information or image artifacts due to overlapping spiral paths.
6. Contrast Media Issues:
 As scans are faster, timing of contrast injection must be precise; errors can affect image quality or
miss enhancement phases.

2D and 3D imaging in CT:---
2D Imaging (Two-Dimensional Imaging)
 2D imaging in CT refers to the standard cross-sectional or “slice” images acquired in axial, sagittal, or
coronal planes.
Key Features:
 Axial slices: Most CT scanners acquire images in the axial (horizontal) plane.
 Reconstruction: These slices can be reconstructed into sagittal (side view) or coronal (front view) images.
 Grayscale display: Each image pixel represents a CT number (Hounsfield Unit), correlating with tissue
density.
 Diagnosis: Most clinical diagnoses are made using high-resolution 2D images.
 Faster to interpret: Radiologists are trained primarily in reading 2D sections.
Limitations:
 Lack of depth perception.
 Difficult to visualize complex anatomical relationships.

3D Imaging in CT
(Three-Dimensional Imaging)
 3D imaging involves volumetric reconstruction
from multiple 2D slices to create life like images
of internal structures.
Techniques:
 Volume Rendering (VR):
 Generates realistic 3D views by projecting
intensity values through the volume.

Maximum Intensity
Projection (MIP):
Displays highest value
pixels (e.g., blood
vessels in angiography).

Surface Rendering (Shaded
Surface Display - SSD):
Outlines surfaces
like bones or
organs for
modeling.

Multiplanar
Reconstruction
(MPR):
 Converts axial slices into
coronal, sagittal, or oblique
planes.

Applications:
 Surgical planning (e.g., tumor resection, orthopedic implants)
 CT Angiography (visualizing blood vessels)
 Virtual colonoscopy or bronchoscopy
 Facial trauma and dental planning

Advantages:
 Enhanced visualization of spatial relationships
 Aids in understanding complex anatomy
 Useful for educational and communication purposes

Limitations:
 Requires high computational power
 Time-consuming rendering
 May obscure details if improperly adjusted

CT Scan Imaging Documentation
 Proper documentation in CT (Computed Tomography) is crucial for patient care, legal
compliance, radiation safety, and audit purposes
1. Patient Identification and Demographics
 Full name
 Date of birth
 Unique patient ID
 Gender
 Referring physician's name
 Date and time of scan.

2. Clinical Information
 Indication for the scan (e.g., trauma, suspected stroke, tumor evaluation)
 Relevant clinical history
 Previous imaging studies (to compare findings)-
3. Scan Protocol
 Details
 Type of scan performed (e.g., head CT, chest CT, CT angiography)
 Scan region/anatomy covered
 Scan mode used (conventional, spiral/helical, high-resolution)
 Slice thickness and intervals
 Patient positioning.

4. Contrast Media Documentation
 Type of contrast agent used (e.g., non-ionic iodinated)
 Route of administration (IV, oral, rectal)
 Dose and concentration
 Injection rate and timing
 Pre-contrast and post-contrast scan phases
 Any contrast reactions or complications

5. Radiation Dose Information
 CTDIvol (Computed Tomography Dose Index volume)
 DLP (Dose-Length Product)
 Estimated effective dose (if available)
 Dose optimization comments (especially for pediatric or high-risk patients)
6. Imaging Findings and Interpretation
 Structured description of findings
 Normal anatomy
 Pathological observations (lesions, fractures, hemorrhage, etc.)
 Comparative notes (if previous CT/MRI/X-rays available)
 Measurement of abnormalities (size, attenuation, etc.)Radiologist’s impression/conclusion.
7. Technical Parameters (Optional but Recommended)
 kVp and mAs settings
 Reconstruction algorithms
 Window settings used (e.g., soft tissue, bone, lung windows)

Safety Considerations in Terms of
Radiation Dose in CT Scanning
1. ALARA Principle "As Low As Reasonably Achievable" is the guiding
safety principle.
 Balances diagnostic image quality with the lowest possible radiation
dose.
2. Justification of the Scan
 CT should only be performed if the benefits outweigh the risks.
 Avoid unnecessary repeat scans.
 Use alternative imaging modalities (MRI, ultrasound) when appropriate.
3. Optimization of Scan Parameters
 Adjust kVp and mAs based on patient size, age, and clinical need.
 Use automatic exposure control (AEC) and dose modulation software.
 Minimize scan length to the area of interest only.

4. Shielding
 Use lead aprons or gonadal shields when possible (especially in pediatrics).
 Protect radiosensitive organs (breasts, thyroid, eyes) when not part of the scan.
5. Special Considerations for Vulnerable Populations
 Pediatric patients: More sensitive to radiation; use pediatric protocols.
 Pregnant women: Avoid CT unless absolutely necessary; consider ultrasound or MRI.
 Repeated scans: Maintain dose records and assess cumulative exposure.
6. Dose Monitoring and Reporting
 Record CTDIvol and DLP in patient records.
 Use dose-tracking software and compare with diagnostic reference levels (DRLs).
 Review high-dose cases in safety committees or audits.
7. Use of Low-Dose CT Protocols
 For specific indications like:
 Lung cancer screening (Low-dose Chest CT)
 Renal stones (Low-dose Abdominal CT)
 Follow-up of known lesions

8. Staff Safety
 Operators should remain outside the CT room during
exposure.
 Use intercom systems to communicate with patients.
 Wear personal dosimeters and review exposure levels
regularly.
9. Patient Communication and Consent
 Inform patients about the purpose of the scan and
associated risks.
 Obtain informed consent especially for contrast-enhanced or
high-dose procedures.
 Provide post-scan instructions when needed (hydration after
contrast, etc.)
10. Equipment Maintenance and QA
Routine calibration and maintenance of CT machines.
Regular quality assurance (QA) tests to ensure accurate dose delivery.
Use dose-reduction software and AI-assisted image reconstruction when available.

11. Patient Safety Exposure
a. Risk Awareness and Communication
 Inform patients about the benefits and risks of radiation exposure in CT.
 Use simple language to explain that while CT provides excellent diagnostic information, it
also involves ionizing radiation.
 Provide comparisons to natural background radiation for perspective (e.g., "This scan
equals about 3 months of background exposure").
b. Cumulative Dose Consideration
 Maintain a record of the patient’s imaging history, especially for those undergoing multiple
or repeated CT scans.
 Use dose tracking systems to avoid unnecessary repeat imaging.
 Encourage referring physicians to consider prior imaging before requesting new scans.---

c. Justification of Each Scan
 Every scan should be clinically justified.
 Evaluate whether alternative, non-ionizing modalities (like MRI or ultrasound) can provide the
required information.
d. Scan Area Limitation
 Always limit the scan region to only the area of interest.
 Avoid scanning unnecessary adjacent areas to reduce dose exposure.
e. Pediatric and Pregnant Patients
 Children are more radiosensitive—use pediatric dose protocols with adjusted kVp and mAs.
 For pregnant patients, avoid CT unless absolutely essential; shielding and modified protocols
should be applied if performed.
f. Protocol Optimization
 Tailor scan parameters (kVp, mAs, pitch, rotation time) to the patient's body habitus and diagnostic
need.
 Use automatic exposure control (AEC) and iterative reconstruction algorithms to reduce dose
without compromising image quality.

g. Radiation Dose Indicators
 Include CTDIvol (Computed Tomography Dose Index) and DLP (Dose-Length Product) in the
scan report.
 Compare with diagnostic reference levels (DRLs) to ensure doses are within recommended
limits.
h. Use of Shielding
 Apply gonadal, thyroid, breast, or fetal shields whenever applicable and safe.
 Especially important in children and younger adults.
i. Education and Training
ii. Radiologists and technologists should undergo regular training on dose optimization.
iii. Awareness of dose reduction strategies is essential for staff safety and patient protection.

Diagnostic aspects of CT {Miscellaneous (CT).pptx

Diagnostic aspects of CT {Miscellaneous (CT).pptx

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