The first slides emphasize that emergency imaging is a consultation, not an order placed into a queue ^[1]. For an urgent request:

• speak directly with the on-call radiologist when the result is time-critical;
• know the patient, the relevant examination findings, and the decision the scan must inform;
• give the suspected diagnosis and meaningful alternatives, not only a symptom;
• mention instability, pregnancy, prior contrast reaction, renal impairment, implanted devices, and inability to cooperate;
• for an interventional procedure, provide coagulation results, platelet count, medication history, fasting status when relevant, and consent/capacity information;
• agree how a critical result will be communicated and document the discussion.

Fasting or laboratory testing should not become a blanket prerequisite that delays an urgent diagnostic examination. The need depends on whether sedation, anaesthesia, or an invasive procedure is planned.

The slide workflow is:

Clinical history and examination → ABC assessment and haemodynamic stabilization → radiology

This does not mean that every patient must have normal vital signs before imaging. It means that airway, breathing, circulation, monitoring, analgesia, resuscitation, and safe transfer take priority. If the diagnosis is clinical and treatment is immediately lifesaving—such as tension pneumothorax or highly likely testicular torsion—do not delay treatment for a confirmatory image.

The previous note treated an eGFR below 30 mL/min/1.73 m² as an automatic reason to avoid iodinated contrast. That is too absolute. Acute kidney injury and severe chronic kidney disease increase concern, but the decision must weigh the diagnostic benefit, alternative tests, consequences of a missed emergency, hydration status, and current local contrast policy. Consult radiology rather than substituting a less diagnostic study automatically. ^[10]

Non-contrast CT head is the first-line examination when acute intracranial injury is suspected. It is fast, detects acute blood, shows mass effect, and can be reviewed on bone windows for fractures. MRI is more sensitive for selected subtle injuries but is not the first acute examination in most trauma patients.

Current CT indications should follow a validated local rule. For adults, NICE recommends CT within one hour for features including GCS 12 or less, GCS below 15 at two hours, suspected open/depressed or basal skull fracture, post-traumatic seizure, focal neurological deficit, or more than one vomiting episode. Additional delayed criteria apply after loss of consciousness or amnesia. ^[2]

The axial orbital images show a medial orbital-wall fracture through the lamina papyracea. Black locules of gas within the orbit are orbital emphysema and should prompt a careful search for the bony defect, adjacent ethmoid injury, extraocular-muscle entrapment, globe injury, and retrobulbar haematoma ^[1].

The coronal reformations demonstrate why multiplanar review is essential in complex facial trauma. Look for:

• cortical discontinuity and bony step-off;
• displaced orbital-floor or medial-wall fragments;
• sinus opacification or an air–fluid level from blood;
• altered orbital volume and herniation of orbital contents;
• zygomaticomaxillary, nasal, maxillary, and pterygoid-plate involvement.

MRI is a problem-solving examination when CT does not explain persistent neurological impairment. It is more sensitive for diffuse axonal/shear injury, non-haemorrhagic contusion, small brainstem lesions, and subtle oedema or haemorrhage. Dedicated CTA or MRA may be required when blunt cerebrovascular injury is suspected. A normal CT does not exclude concussion or diffuse axonal injury.

For suspected bacterial meningitis, current NICE guidance says ^[3]:

• do not routinely perform neuroimaging before lumbar puncture;
• image first when there is risk of an evolving space-occupying lesion or signs suggesting raised intracranial pressure, such as new focal neurological features, abnormal pupillary reactions, GCS 9 or less, or a progressive/rapid fall in consciousness;
• take blood cultures, give antibiotics, and stabilize the patient before imaging when imaging is required;
• perform lumbar puncture before antibiotics only if it is safe and will not cause a clinically significant treatment delay.

CT cannot certify that lumbar puncture is safe, and a normal CT does not exclude raised intracranial pressure. Conversely, routine CT can delay CSF sampling and antibiotics.

Contrast-enhanced MRI is generally more sensitive for parenchymal infection, posterior-fossa disease, subdural empyema, ventriculitis, and meningitis-related complications. Contrast CT is faster and may be used when MRI is unavailable or unsafe.

The lecture images show:

• Multifocal bacterial abscesses on post-contrast CT: multiple ring-enhancing lesions with low-density centers and surrounding vasogenic oedema at several brain levels.
• TB abscess on MRI: the lesion is inconspicuous on the unenhanced T1-weighted image but has a conspicuous enhancing rim after contrast.

Ring enhancement is a pattern, not a microbiological diagnosis. Differential diagnoses include metastases, toxoplasmosis, tuberculoma/abscess, demyelination, and treatment-related lesions. Restricted diffusion of the cavity on DWI supports a pyogenic abscess but must still be interpreted with the clinical and microbiological context.

MRI is the modality of choice because it shows the spinal cord, CSF space, discs, ligaments, epidural space, vertebral marrow, and soft-tissue masses. The examination should cover the clinically relevant region; in suspected metastatic spinal-cord compression, whole-spine MRI within 24 hours is recommended because non-contiguous disease may occur. ^[4]

The sagittal and axial MRI slides demonstrate two mechanisms:

• Traumatic fracture-dislocation: focal malalignment narrows the canal, effaces the surrounding CSF, and indents the cord. Intramedullary T2 hyperintensity would suggest cord oedema or injury.
• Acute disc prolapse: a focal posterior disc extrusion deforms the ventral cord; the axial view confirms the side and severity better than the sagittal view alone.

For suspected metastatic compression with neurological symptoms or signs, current NICE guidance recommends dexamethasone 16 mg (oral or equivalent parenteral dose) as soon as possible while definitive assessment and treatment are arranged, unless contraindicated; this is not a blanket “high-dose steroids for all back pain” rule. ^[4]

The lecture's older flowchart begins with cervical radiographs, then directs suspected bone injury to CT and suspected cord injury to MRI ^[1]. Current ACR guidance is different ^[5]:

• if CCR/NEXUS indicates that imaging is unnecessary, do not image routinely;
• if adult cervical-spine imaging is indicated after blunt trauma, non-contrast CT is usually appropriate and plain radiography is usually not;
• MRI follows when ligamentous, cord, or nerve-root injury is suspected or confirmed, even if CT shows no fracture.

The lateral radiograph in the slide does not clearly show C7/T1 and is therefore inadequate by the older radiographic standard. The CT multiplanar reformation then reveals a C6/7 fracture-dislocation with translation and canal compromise. This is the visual reason modern trauma pathways prefer high-quality CT when imaging is indicated.

The slide sequence “CXR → CTPA/VQ” is a modality overview, not a complete diagnostic algorithm. In a stable patient:

1. estimate clinical probability with an accepted pathway;
2. use D-dimer to avoid imaging when probability is low/intermediate and the D-dimer is negative, with age-adjustment where locally adopted;
3. perform CTPA when indicated; use V/Q imaging when it is more appropriate or CTPA is unsuitable;
4. in haemodynamic instability, resuscitation and bedside echocardiography/venous ultrasound may inform immediate treatment when definitive CT is unsafe.

Chest radiography usually does not diagnose PE. It helps identify alternative causes and is important when interpreting V/Q imaging. CTPA is a first-line definitive study when clinical probability/D-dimer indicates imaging. ^[6]

• In the lecture CTPA images, the arrows point to low-attenuation intraluminal filling defects surrounded by contrast-opacified blood in pulmonary arteries.
• Check that contrast opacification and breath-hold are adequate before calling a defect.
• Review central, lobar, segmental, and subsegmental arteries in orthogonal planes, then assess RV size, septal contour, reflux of contrast, lung parenchyma, and alternative diagnoses.
• Modern scanners visualize subsegmental vessels better than the historical limitation slide implies; very peripheral isolated defects remain prone to motion artefact and false-positive interpretation.

The V/Q image presents ventilation and perfusion in multiple projections. PE produces a mismatched perfusion defect: segmental perfusion is absent or reduced while ventilation is relatively preserved. Matched defects suggest parenchymal disease and must be correlated with CXR/CT. A normal perfusion scan effectively excludes clinically significant PE.

The sensitivity and specificity values on the 2023 lecture slide reflect older probability-category literature and should be learned as historical slide figures, not applied as standalone post-test probabilities. Modern reporting may use planar V/Q, SPECT, or SPECT/CT and must be integrated with pre-test probability.

The paired ultrasound frames show the key diagnostic maneuver: press the transducer until the artery deforms slightly. A normal vein collapses completely; a thrombosed vein remains open. Non-compressibility is the primary sign of proximal DVT. Colour flow and spectral Doppler are supportive but can be misleading if machine settings are poor.

Lower-limb ultrasound can establish DVT when chest imaging is unsuitable, but a negative proximal study does not exclude PE or isolated calf thrombosis. Serial imaging may be required in selected pathways.

• Haemodynamically stable major trauma: contrast-enhanced CT is the principal examination for abdominal and pelvic injury and may be part of whole-body trauma CT. ^[7]
• Unstable or transiently responding patient: resuscitation, bedside radiography/eFAST, and the fastest route to haemorrhage control take priority. Whether a patient proceeds to CT, interventional radiology, or theatre depends on response, suspected bleeding site, available hybrid facilities, and the trauma protocol.

FAST detects free fluid; it does not grade a solid-organ injury and is insensitive for retroperitoneal, hollow-viscus, diaphragmatic, and small-volume injury. A negative FAST is not a trauma clearance test.

The lecture suggests oral contrast in a conscious patient. Routine positive oral contrast is not required for modern initial blunt-trauma CT and can delay scanning; IV contrast is the crucial component for parenchymal perfusion and active bleeding. ^[7]

• detects organ and vascular injury;
• shows active contrast extravasation and pseudoaneurysm;
• grades anatomical severity;
• identifies haemoperitoneum and retroperitoneal haematoma;
• guides surgery, angioembolization, or monitored non-operative management;
• provides arterial, portal-venous, delayed excretory, bone, and lung information when appropriately protocolled.

An injury grade informs management but does not decide it alone; haemodynamics, ongoing transfusion need, associated injuries, age/comorbidity, and local capability also matter.

• Non-pregnant adults: CT abdomen/pelvis is generally the most accurate initial examination; ultrasound or MRI may precede it depending on patient factors and local expertise. ^[8]
• Children: graded-compression ultrasound is usually first; MRI or low-dose CT follows an equivocal/non-diagnostic study according to the local pathway.
• Pregnancy: ultrasound and non-contrast MRI are both appropriate; CT is reserved for situations where the benefit outweighs fetal radiation risk and alternatives are inadequate. ^[8]

On CT, the arrow identifies an enlarged tubular appendix with wall thickening/enhancement and surrounding periappendiceal fat stranding. Look for an appendicolith, focal wall defect, extraluminal gas, phlegmon, abscess, and free fluid.

On ultrasound, seek a blind-ending, non-compressible tubular structure arising from the caecum. An outer diameter above 6 mm supports appendicitis, but diameter alone is not diagnostic; assess tenderness under the probe, hyperaemia, echogenic inflamed surrounding fat, appendicolith, fluid, and abscess. Non-visualization is not the same as a negative study.

The lecture's “non-contrast CT first, contrast if time” sequence is historical. Current ESVS guidance recommends prompt CTA of the thoraco-abdominal aorta and access vessels for suspected rupture because it confirms the diagnosis and determines open-versus-endovascular anatomy ^[9]. If the patient is too unstable for transfer to CT, do not delay haemorrhage control; a bedside ultrasound may rapidly confirm an aneurysm but cannot reliably show or exclude rupture or map repair anatomy.

• Non-contrast axial CT: a large calcified aneurysm is accompanied by left retroperitoneal blood. Acute blood may be hyperattenuating; a high-attenuation crescent within mural thrombus is another warning sign.
• Contrast-enhanced axial CT: dense contrast outside the expected aortic lumen represents active extravasation into the retroperitoneal haematoma. Distinguish the opacified lumen from non-enhancing mural thrombus.
• Coronal reformation: demonstrates the longitudinal extent, proximal neck, iliac involvement, and access anatomy needed for EVAR planning.

Ultrasound remains the standard first-line test for screening and surveillance of an asymptomatic AAA, not for defining rupture extent. “Mycotic aneurysm” means an infected aneurysm and does not imply a fungal cause.

Testicular salvage falls with duration and degree of twisting; the lecture's six-hour warning is a useful urgency marker, not a binary point at which viability suddenly ends. When clinical suspicion is high, obtain urgent urological assessment and proceed to exploration without waiting for imaging. Doppler ultrasound is useful when it can be obtained immediately without delaying intervention. ^[11]

The lecture compares both testes side by side. The affected testis has absent intratesticular colour and spectral arterial signals while the contralateral testis demonstrates flow. Also assess for:

• enlarged, hypoechoic or heterogeneous testis;
• high-riding/horizontal lie;
• twisted spermatic cord or whirlpool sign;
• reactive hydrocele and scrotal-wall thickening;
• reduced rather than absent flow in partial torsion.

Preserved arterial flow does not fully exclude early, partial, or intermittent torsion. Epididymitis more often causes increased epididymal/testicular vascularity, but age and clinical context remain essential.