MedicoNotebook: 2015

0 Medical One Liners 431-440

431. Egg shell calcification

Sarcoidosis
Silicosis
Treated Lymphoma

432. Achondroplasia

Champagne glass pelvis
Bullet shaped vertebra
Tombstone iliac wings
Trident hand
Macrocephaly with narrowed foramen magnum

433. In Doppler ultrasound, colour indicates direction of flow, conventionally:

Red: towards the probe
Blue: away from the probe

However, this can be reversed with machine settings.

434. Umbilical artery Doppler

S/D ratio should be < 3 after 34 weeks of pregnancy
S/D ratio in umbilical artery should always be less than that in MCA
IUGR

S/D >3 after 34 weeks gestation
Absent diastolic flow
reversal of diastolic flow

435. Thallium Scan: binds to normal perfused areas of myocardium, therefore infarct looks cold

436. Tecnitium Pyrophophate: binds to myocardial infarct and so it looks hot on nuclear scan.

437. Fibrous dysplasia

Ground glass matrix
Shepherd crook deformity

438. Diaphyseal aclasis = Hereditary multiple exostoses

439. Multiple enchondroma

= Ollier's disease
with Multiple subcutaneous hemangiomas = Maffucci syndrome

440. McCune-Albright syndrome

Polyostotic fibrous dysplasia
Precocious puberty
Cafe au lait spots

1 Important Bone Tumors

Author: Dr Ayush Goel

Important Bone Tumors:

1. Osteosarcoma:

Age: 10-20 yrs (except when its secondary e.g. in Paget's disease in old age)
Metaphyseal
Sunray periosteal reaction

note: sunburst calcification on abdominal X-ray is seen in Pancreatic serous cystadenoma

Codman triangle

note: codman tumor is chondroblastoma

Radioresistant

2. Ewing's sarcoma

Age: 10-20 yrs
laminated periosteal reaction: onion skin
location: diaphyseal
Radiosensitive

3. Giant cell tumor (GCT) = osteoclastoma

Epiphyseal

other epiphyseal lesions - Chondroblastoma, Geode

Soap bubble appearance
Metaepiphyseal: Seen after fusion of epiphysis (age 20-50 yrs)

4. Vertebral hemangioma

X-ray and Sagittal CT: Corduroy cloth appearance
Axial CT: Polka dot appearance

5. Adamantinoma

Mandible (Ameloblastoma): 3rd-5th decade
Tibial diaphysis: 10-20 yrs, typically anterior cortex
Pituitary (Both pituitary stalk and enamel arise from oral epithelium)

6. Above 60 years, multiple lytic lesions

Multiple myeloma

Normal alkaline phosphatase, cold on bone scan
punched out lytic lesions

Metastases

Increased alkaline phosphatase, hot on bone scan i.e. high uptake

7. Metastases

Sclerotic/osteoblastic

Commonly from: Prostate and Breast (can have mixed)
Other: Stomach, Carcinoid

Lytic and expansile

Commonly from Kidney and Thyroid

8. Hyperparathyroidism

subperiosteal bone resorption

radial aspect of proximal and middle phalanges of the 2nd and 3rd fingers
lamina dura: floating teeth

Salt and pepper skull = pepper pot skull
Brown tumor
erosion of lateral end of clavical
rugger jersey spine (secondary hyperparathyroidism due to renal osteodystrophy)

note: picture frame vertebra is seen in Paget's disease of bone (also Cotton wool skull in Paget's)
note: sandwich vertebra is seen in osteopetrosis

9. Eosinophilic granuloma

children
beveled edges
vertebral plana
floating teeth (also seen with hyperparathyroidism)

0 Pulmonary aspergillosis

Pulmonary aspergillosis can present in 3 major forms:

Aspergilloma

fungal ball in an old tuberculous cavity
shows Monad sign (usually also called air crescent sign)

Allergic bronchopulmonary aspergillosis (ABPA)

central bronchiectasis
gloved finger appearance
fleeting opacities

Invasive aspergillosis

in immunocompromised
shows CT halo sign

Note: Reverse CT halo/Atol sign is seen in Cryptogenic organizing pneumonia/bronchiolitis obliterans organising pneumonia (COP/BOOP)

air crescent sign - it defines improvement/recovery in the underlying lesion with increased granulocyte activity (should not be confused with Monad sign which is also called air crescent sign as the air outlining the fungal ball is also in the shape of crescent)

Author: Dr Ayush Goel

421. For lung investigation - CT scan is best, except in Pancoast tumour/Superior sulcus tumour where MRI is investigation of choice to look for brachial plexus involvement.

422. Silhouette's sign or more correctly loss of silhouette sign:

Middle lobe pathology: obscures right heart border
Lower lobe pathology: obscures diaphragm
Lingular pathology: left heart border
Posterior segment of left upper lobe: aortic knuckle
Also see this MCQ: here

423. Lordotic chest X-ray view is used for:

Middle lobe examination (best view)
Lung apex pathology
Interlobar fissural effusion

424. Mammography:

screening in >40 yr females - once yearly
to detect DCIS - MRI is best (done in 2nd week of menstruation)
in young female, mammography is not useful as there is a lot of glandular tissue that makes the breast very dense
Most common sign of malignancy seen on mammogram: microcalcification
Popcorn calcification in breast: Fibroadenoma {Note: Popcorn calcification in lungs - pulmonary hamartoma, it also has fat in the lesion}

425. Radiation doses:

Extremity X-ray = DEXA < Chest X-ray < Mammography < CT head < CT chest < CT Abdomen and pelvis < Coronary CT angiography < PET/CT
Barium studies have doses close to CT head, except Barium enema which has dose just less than CT chest.

426. HRCT Lung - uses bone algorithm for image reconstruction, useful for:

interstitial lung diseases and bronchiectasis

--> HRCT in Alveolar proteinosis: Crazy pavement appearance (see also: MCQ)

--> HRCT is also used in temporal bone imaging.

for Bony labyrinth: do CT
Membranous labyrinth: do MRI

427. All fractures are well visualized on CT except stress fracture which is best seen on MRI due to edema.

428. MRI uses free induction decay to receive signals.

Absolute contraindication:

Pacemaker
Metallic (ferromagnetic) implant/foreign body

429. Substances that are white/hyperintense on T1 Weighted MRI:

fat
subacute haemorrhage
posterior pituitary
melanoma and its metastases

430. CSF is white on T2 weighted image and dark on T1 weighted image.

0 X-ray photon interaction with matter

X-ray photon interaction with matter can occur in various forms:

Photoelectric effect {low energy photon (energy just greater than binding energy of electron) interacts with innermost shell electron}- MCQ

directly proportional to atomic number of matter
inversely proportional to cube of incident photon energy
maximum with tightly bound electrons (i.e. innermost shell - K)

Compton scattering/effect

is the cause of scatter radiation and thus increase radiation dose
does not depend on atomic number
inversely proportional to photon energy

Coherent scattering
Pair production (not important in diagnostic radiology)

Author: Dr Ayush Goel

0 Stroke

Author: Dr Ayush Goel

Stroke (cerebrovascular accident) is a neurological deficit that can occur due to:

ischemia (ischaemic stroke)
haemorrhage (haemorrhagic stroke)

lobar haemorrhage
hypertensive haemorrhage

Imaging

CT scan

First investigation to be undertaken is CT scan, to rule out haemorrhage. It is thus the investigation of choice for haemorrhagic stroke.

Axial Non contrast CT image showing left capsuloganglionic haemorrhage as hyperdense area
Image courtesy: Dr Ayush Goel

Hyperacute/early Ischaemic stroke is best evaluated on MRI (see below), however, there are subtle signs that may be present on CT to help make a diagnosis:

Hyperdense MCA sign: shows clot in MCA (earliest sign on CT)
Loss if Insular ribbon
Loss of grey-white matter differenciation

Red - loss of insular ribbon and grey-white matter differentiation; green - normal insular ribbon, blue - normal deep grey matter.
Image courtesy: Dr Ayush Goel

Later, even CT can demonstrate the infarcted area very well as wedge shaped hypodensity in the particular vascular territory.

Chronic infarct in left MCA terriotory
Image courtesy: Dr Ayush Goel

MRI

It is the investigation of choice for ischaemic stroke.

Diffusion weighted MR imaging is the earliest to detect ischaemic region as hyperintense on DWI and hypointense on ADC maps.

ADC (Red circle) and DWI (Blue circle)
Image courtesy: Dr Garima Goel

MedicoNotebook - Founder : DrShiviMudgal (Goel) , Co-Founder : DrAyushGoel

0 Medical One Liners 411-420

411. Bulging fissure sign: Klebsiella pneumonia

412. Venous sinus thrombosis CT:

Non contrast - dense delta sign
Contrast CT - empty delta sign

413. Worst headache of life: Subarachnoid haemorrhage

414. Investigation of choice for

aneurysm - angiography
aortic aneurysm - CT scan as there may be intraluminal thrombus
aortic dissection - MRI

415. Basal exudates on CT seen in: Tuberculous meningitis and cryptococcal meningitis.

416. Contrast of X-ray image is inversely related to kVp.

417. Radiation intensity is inversely proportional to square of distance from the radiation.

418. Chest X-ray PA view is taken with film to focus distance of 180 cm. Chest AP view and other X-rays are taken at 100 cm.

419. Golden S sign: Right upper lobe collapse due to hilar mass.

420. Most common lung carcinoma with cavitation: Squamous cell carcinoma

MedicoNotebook - Founder : DrShiviMudgal (Goel) , Co-Founder : DrAyushGoel

0 Myocardial perfusion and viability

Author: Dr Ayush Goel

Myocardial perfusion and viability assessment is important for many reasons:

to diagnose, locate and grade the severity of coronary artery disease
to identify candidates who would benefit from re-vascularization
to evaluate response of re-vascularization

Terminology

Stunned myocardium

It refers to a state in which there is wall dysfunction but the perfusion (resting and stress) is normal.

Myocardial ischemia

It refers to a state in which there is decreased perfusion on stress but normal during rest (seen as reversible perfusion defect). These patients will significantly benefit with treatment.

Hibernating myocardium

In this the myocardium shows decreased perfusion on both stress and resting phase (seen as fixed defect) but the myocytes are viable and will benefit from revascularization.

Myocardial infarct

In this there is absent perfusion on both stress and resting phase (seen as fixed defect) and the myocytes are not viable. There will be no benefit from revascularization.

Imaging techniques

thallium-201 SPECT
- excessive radiation dose (c.f. 99mTc-MIBI)
- redistribution may occur
- single injection for stress and resting phase
99mTc-Sestamibi SPECT
- less radiation dose
- no redistribution
- separate injections for stress and resting phase
FDG-PET (for viability)
- based on the fact that myocardium utilizes glucose for metabolism when under effect of ischemia (hence the ischemic myocardium will show greater uptake than normal cells)
- under normal circumstances, it utilizes fatty acids for energy
- non-viable myocardium will not show any uptake
Cardiac MR perfusion imaging