# Imaging of Choice for Common Conditions > Investigation of choice across systems for NEET-PG Radiology: CT, MRI, USG and nuclear indications from stroke and stones to osteomyelitis. - Canonical URL: https://prepelephant.com/topics/neet-pg/radiology/imaging-of-choice-common-conditions - Exam / course: NEET-PG · Subject: Radiology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Imaging of Choice for Common Conditions", PrepElephant, https://prepelephant.com/topics/neet-pg/radiology/imaging-of-choice-common-conditions ## Direct answer Selecting the investigation of choice is the highest-yield radiology skill for NEET-PG: non-contrast CT for acute head injury and stroke exclusion, CT pulmonary angiography for pulmonary embolism, non-contrast CT KUB for ureteric colic, ultrasound for gallstones, obstructive jaundice and first-line obstetric evaluation, MRI for spinal cord compression, disc disease, osteomyelitis, early avascular necrosis and demyelination, and plain radiographs for pneumothorax, intestinal obstruction and most fractures. Matching modality physics to the clinical question — density detail and speed for CT, soft-tissue contrast for MRI, availability and zero radiation for ultrasound — converts a long list into a logical algorithm. ## What you must remember - Neuro: acute head trauma and stroke — non-contrast CT first; early or posterior fossa infarction — MRI DWI; spinal cord compression and cauda equina — MRI urgent; epilepsy focus, pituitary and posterior fossa — MRI. - Chest: pneumothorax and effusion — erect chest radiograph; pulmonary embolism — CTPA (V/Q if renal impairment, contrast allergy, often pregnancy with normal radiograph); bronchiectasis — HRCT; hilar adenopathy evaluation — CT chest. - Abdomen: gallstones and obstructive jaundice — ultrasound first line; renal colic — non-contrast CT KUB; appendicitis — ultrasound first in children and pregnancy, CT in typical adults; blunt abdominal trauma — FAST then CT if stable, laparotomy if unstable; pancreatic disease — CT (and MRCP for duct detail); intestinal obstruction — erect abdominal radiograph with CT for cause. - Musculoskeletal: fracture — radiographs; occult scaphoid or sacral fracture — CT or MRI; osteomyelitis and discitis — MRI; early avascular necrosis — MRI; Charcot versus osteomyelitis in diabetic foot — MRI; internal derangement of knee — MRI. - Genitourinary and obstetric: ectopic pregnancy and viability — transvaginal ultrasound; fetal anomaly — ultrasound; prostate — MRI; testicular torsion — Doppler ultrasound. - Small parts and vascular: thyroid nodule — ultrasound with TI-RADS; DVT — compression Doppler; carotid stenosis screening — Doppler ultrasound; aortic aneurysm screening — ultrasound, CT for planning. - Oncology staging generally relies on contrast CT with MRI for brain, spine and liver lesions, plus PET-CT for metabolically active tumours such as lymphoma. - Pregnancy and children: ultrasound or MRI first to avoid radiation whenever diagnostically equivalent. ## Common confusion The recurring error is defaulting to MRI as the "best" test; the exam rewards the right question, not the strongest magnet — scaphoid fracture needs CT or MRI only after negative radiographs with persistent suspicion, and simple pneumothorax needs an erect film, not CT. A second error is forgetting pregnancy modifications: appendicitis moves from CT to ultrasound/MRI, and renal colic from CT to ultrasound. Finally, remember which CTs are non-contrast (head, renal colic) versus contrast-enhanced (trauma, PE, staging) — the distinction changes answers. ## Exam-focused takeaway This page condenses the most repeated one-liner format in radiology: "investigation of choice for..." — memorise each pair above, especially CT stroke, MRI cord compression, NCCT KUB, USG gallstones, HRCT bronchiectasis, MRI osteomyelitis and Doppler for DVT and torsion. Pregnancy- and paediatric-specific substitutions are favourites, as is the sequence FAST-then-CT in trauma. Rehearse by system so the whole list reconstructs logically. ## Frequently asked questions ### What is the investigation of choice for renal colic? Non-contrast CT of the kidneys, ureters and bladder, detecting virtually all stones with high sensitivity. Ultrasound is preferred first-line in pregnancy, children and young patients. ### Which imaging is chosen for spinal cord compression? Urgent MRI of the spine, demonstrating the cord, the compressing lesion and soft-tissue involvement in one study; CT is used for bony surgical anatomy after MRI defines the pathology. ### How is pulmonary embolism investigated? With CT pulmonary angiography as first line; ventilation-perfusion scintigraphy is chosen when contrast is contraindicated (renal impairment, allergy) or in pregnancy with a normal chest radiograph. ### What imaging follows a negative radiograph for suspected scaphoid fracture? Repeat radiographs after immobilisation, proceeding to CT or MRI if clinical suspicion persists; MRI demonstrates occult fracture lines and marrow oedema earliest. ### Which modalities are first-line in the pregnant patient? Ultrasound for abdominal, pelvic and obstetric questions, and MRI without gadolinium for soft-tissue problems; ionising-radiation studies are reserved for emergencies where the benefit clearly exceeds the small fetal risk.