YEAR 03 • BASICS OF RADIOLOGY • 20-MODULE • FULL CHAPTER MASTER

Basics of Radiology Learning Material

20 learning units covering imaging selection, modality fundamentals, patient safety and systematic interpretation across major body systems. Read the chapters, revise the key distinctions, then attempt 10 explained questions per unit in practice or assessment mode.

Academic scope: Original RAHBAR notes for the Year 3 clinical transition, covering foundational diagnostic imaging within the RAHBAR MBBS pathway. Institutional sequencing may differ. Examples are educational; clinical decisions and procedures require appropriate supervision and current local protocols. Sources & further reading ↓

● MODULE 06 / 20

CT, Windows & Cross-Sectional Anatomy

Understand CT attenuation, display windows and contrast phases before interpreting a cross-sectional examination.

Quick revision ↓ Medical Dictionary

FULL CHAPTER EXPLANATION

Deep Learning — Module 06

Connect the clinical question to modality choice, image appearances, limitations and the next decision.

Acquisition and reconstruction

CT collects X-ray measurements around the patient and reconstructs cross-sectional images. Modern acquisitions can support axial, coronal and sagittal displays, but reconstructed views remain dependent on the original data quality. Thin sections improve some anatomical assessments while generating many images that require systematic review. Motion and metal can produce artifacts, and a single selected screenshot is not a substitute for examining the complete study.

Attenuation and Hounsfield units

CT numbers express attenuation relative to reference materials: water is approximately zero Hounsfield units and air approximately minus one thousand. Fat usually has negative values, while bone and many calcifications have higher values than soft tissue. Measurements depend on technique and the region sampled. Partial-volume averaging can mix several tissues within a voxel, so a tiny measurement is not an infallible tissue diagnosis.

Window width and level

Window level selects the center of the displayed attenuation range, and window width controls the span represented across shades of gray. Lung, soft-tissue and bone windows show different aspects of the same data. Changing the display window does not expose the patient to more radiation. An abnormality can be inconspicuous on one window and obvious on another, making appropriate display part of interpretation rather than cosmetic adjustment.

Contrast timing and the question

Noncontrast CT, arterial imaging, portal venous imaging and delayed acquisitions emphasize different findings. Timing affects vascular opacification and lesion appearance. A routine enhanced chest scan is not automatically equivalent to a pulmonary angiogram, and a noncontrast study cannot answer every enhancement question. Additional phases should be justified because each acquisition can add exposure; the radiology team selects the protocol that addresses the referral.

Orientation and systematic review

Use labeled axes and side markers. Axial images are conventionally displayed as though viewed from the patient’s feet, but labels remain the reliable reference. Follow organs and vessels through consecutive sections and use reformats to confirm relationships. Review bones, lung bases and soft tissues even when the referral concerns one abdominal organ. Findings should be described with location, extent and relevant secondary effects before forming an impression.

Visual concept — one CT dataset, several windows

The acquired data can be displayed in different ways. Windowing changes what is emphasized; it does not require another scan.

Typical display purposes — settings vary by examination
Window	Emphasis	Review question
Lung	Aerated lung and air interfaces	What is the lung pattern?
Soft tissue	Differences among soft tissues	What are the organ and mediastinal findings?
Bone	Mineralized tissue detail	Is the cortex or bony alignment abnormal?

Check your understanding: can windowing replace a missing contrast phase?

No. A display change cannot create enhancement information that was never acquired. Protocol selection and window selection are different steps.

High-Yield Revision

Window changes redisplay data without a new exposure.
Contrast phase is part of the diagnostic test.
Review consecutive sections and relevant reformats.

Common Exam & Concept Pitfalls

A single CT screenshot is not a complete examination.
A routine contrast CT is not every type of CT angiogram.

Sources & Further Reading

Curriculum and reference review: 25 September 2026. These original notes teach foundational imaging concepts and clinical reasoning. Interpretation of real studies and procedures requires supervised training. International guidance supports the principles below; local pathways, resources and authorized supervision govern patient care. Faculty review is pending.

Choosing examinations: ACR Appropriateness Criteria
Modality foundations: NIH NIBIB resources on CT, MRI and ultrasound
Safety: IAEA Radiation Protection of Patients · ACR/RSNA RadiologyInfo on contrast materials, MRI safety and ionizing radiation
Chest and vascular questions: Chest radiography and its limitations · Pulmonary embolism imaging
Abdominal and urinary questions: Body CT · ACR acute flank pain criteria summary
Neurological questions: Stroke imaging · Brain MRI
Pelvic and pediatric questions: ACR acute pelvic pain criteria summary · ACOG adnexal torsion and Doppler limitations · Intussusception imaging and treatment
Breast assessment: ACR palpable breast mass criteria summary · Mammography
Nuclear medicine: Understanding a PET-CT report · EANM/SNMMI FDG imaging in infection and inflammation
Image-guided procedures: Catheter angiography · Lung biopsy
Reporting: ACR/RSNA guide to radiology reports

RAHBAR study structure: clinical question → modality → technique → systematic findings → interpretation → communication. Use institutional curriculum and faculty guidance for supervised clinical skills and assessment requirements.