Thursday, March 19, 2015

Radiology ER cheat sheet: Important Radiology Numbers

The following lists important radiology numbers that radiologists, residents, and other medical professionals can use as reference.

Click here for ACR recommendations

Maximum size for paratracheal stripe  4mm
Nodule <3cm  Mass >3 cm
ET tube should be 3-5 cm from the carina
Pulmonary artery diameter <28mm (similar to aorta)


Maximum pancreatic duct diameter  3 mm
Maximum size for spleen 13 cm (superior to inferior)
Maximum size for liver 15.5 cm (superior to inferior, mid clavicular line).
Normal size of CBD  6mm; after Age 60, add 1mm per decade.
Size for appendix (raising concern for appendicitis)  6 mm

Liver Lacerations

GRADE 1: hematoma: subcapsular, < 10% surface area and laceration: capsular tear, < 1cm depth
GRADE 2:  hematoma: subcapsular, 10 - 50% surface area, intraparenchymal hematoma < 10cm diameter, laceration: capsular tear, 1 - 3cm depth, < 10cm length
GRADE 3: hematoma: subcapsular, > 50% surface area, or ruptured with active bleeding, hematoma: intraparenchymal > 10 cm diameter, laceration: capsular tear, > 3 cm depth
GRADE 4:  hematoma: ruptured intraparenchymal with active bleeding, laceration: parenchymal distruption involving 25 - 75% hepatic lobes or involves up to 3 Couinaud segments (within one lobe)
GRADE 5: laceration: parenchymal distruption involving >75% hepatic lobe or involves > 3 Couinaud segments, vascular: juxtahepatic venous injuries (IVC, major hepatic vein)
GRADE 6: vascular avulsion

Grading of liver injury based on American Association of Surgery for trauma

Splenic Lacerations
GRADE 1: less than 1 cm. Subcapsular hematoma <1cm
GRADE 2:  about 2 cm (1-3 cm). . Subcapsular or central hematoma 1-3cm
GRADE 3: more than 3 cm. Subcapsular or central hematoma  3-10cm
GRADE 4: more than 10 cm. Subcapsular or central hematoma 10cm <
GRADE 5: total devascularization or emaceration.


Maximum obstructing calculus size before urologic surgery -6 mm
AML is at risk for bleeding  if greater than 4 cm
Average Renal Size 9-13 cm

Ascending aorta is dilated at 4 cm and aneurysmal at 5cm.
Descending aorta is aneurysmal at 3 cm.
Important Desending Aortic Sizes: If  size 5.5 cm (or grows ≥ 0.6-0.8 cm per year), surgery needed
Illiac artery aneurysm:   Common Illiac Artery is aneurysmal when   Female >1.5 cm; Male > 1.7 cm , Internal illiac > 0.8cm; Elective surgery > 3 cm
Aortic balloon best 2cm below top of arch
Anemia- Noncontrast of Aorta <45 HU (women)  <50 HU (men) or Superior sagittal sinus <35


Ac joint wide if > 8 mm or >4mm asymmetry

Coracoclavicluar distance wide if > 13 mm or > 5 mm asymmetry

Scapholunate interval >4mm is abnormal

Common missed ankle fractures
 Anterior calcaneal process
 Lateral talus
 Posterior malleolus fracture

Lateral clear space of ankle should be <5.5mm at 1 cm above the plafond, greater => syndesmotic injury

Medial clear space of ankle should be <4mm

Weber classification
Type A : Fibular fracture below the tibial plafond
Type B : Fibular fracture at level of tibial plafond
Type C : Fibular fracture above the tibial plafond

Bohlers angle of calcaneus should be 20-40 degrees

PCL on MRI thicker than 6 mm is concerning for tear.


Normal Liver <15 cm

Normal Spleen <11 cm cranial caudal

Maximum gallbladder wall thickness 2mm

Gallbladder polyps 10mm< or symptomatic RESECTION
Gallbladder polyp 5mm< IGNORE
Gallbladder polyp 6-10mm FOLLOWUP

Ultrasound Endometrial post menopausal thickness, Consider tissue sampling if
  1. Nonbleeding  with endometrial stripe 11mm<
  2. Bleeding with endometrial stripe 5mm
(Ultrasound Obstet Gynecol. 2004 Oct;24(5):558-65.)

Scrotal Pain: Lack of flow in the testis is torsion.  Make sure to check the contralateral testis for bell clapper deformity. Increased flow in the epididymis is concerning epididymitis.  Differential also includes torsion of the testicular appendage.

Enlarged ovary with peripheral follicles and pelvic pain is concerning for torsion.

Findings diagnostic of pregnancy failure:
  • Crown-rump length of ≥ 7 mm and no heartbeat
  • Mean sac diameter of ≥ 25 mm and no embryo
  • Absence of embryo with heartbeat ≥ 2 weeks after a scan that showed a gestational sac without a yolk sac
  • Absence of embryo with heartbeat ≥ 11 days after a scan that showed a gestational sac with a yolk sac
Findings suspicious for but not diagnostic of pregnancy failure:
  • Crown-rump length of < 7 mm and no heartbeat
  • Mean sac diameter of 16-24 mm and no embryo
  • Absence of embryo with heartbeat 7-13 days after a scan that showed a gestational sac without a yolk sac
  • Absence of embryo with heartbeat 7-10 days after a scan that showed a gestational sac with a yolk sac
  • Absence of embryo ≥ 6 weeks after last menstrual period
  • Empty amnion (amnion seen adjacent to yolk sac, with no visible embryo)
  • Enlarged yolk sac (> 7 mm)
  • Small gestational sac in relation to the size of the embryo (< 5 mm difference between mean sac diameter and crown-rump length)
For the finding of no intrauterine fluid collection and normal (or near-normal) adnexa on ultrasonography:
  • A single measurement of human chorionic gonadotropin (hCG), regardless of its value, does not reliably distinguish between ectopic and intrauterine pregnancy (viable or nonviable).
  • If a single hCG measurement is < 3,000 mIU/mL, presumptive treatment for ectopic pregnancy with the use of methotrexate or other pharmacologic or surgical means should not be undertaken, in order to avoid the risk of interrupting a viable intrauterine pregnancy.
  • If a single hCG measurement is ≥ 3,000 mIU/mL, a viable intrauterine pregnancy is possible but unlikely. The most likely diagnosis is a nonviable intrauterine pregnancy, so it is generally appropriate to obtain at least one follow-up hCG measurement and follow-up ultrasonogram before undertaking treatment for ectopic pregnancy.

Bradycardia <80 bpm sustained

( NEJM October 10, 2013, Vol. 369:15, pp. 1443-1451

Maximum diameter of portal vein before portal hypertension -13 mm
Normal Doppler flow in TIPS  90-190 cm/s

Postmenopausal age group:
Simple Cyst <1 cm no followup;  1-7 cm  yearly followup, 7cm <  MRI or surgery consultation
Compex Cyst:  (thick septation, nodule, vascularity)- surgery
Complex Cyst:   Uniform internal echos/reticulation- 6 week f/u or Surgery consultation
World J Radiol. 2013 March 28; 5(3): 113–125.


Normal Thyroid scan uptake values- Early 18%(4 hrs)  Late 36%(24 hrs)
Gastric Emptying over 10% at 4 hrs is delayed.

SFU Grading of Infant Hydronephrosis

Grade 0  No Splitting
Grade 1 Urine in pelvis barely splits sinus
Grade 2 Urine fills intrarenal pelvis or extra renal pelvis, major calyces dilated
Grade 3 SFU grade 2 and minor calyces uniformly dilated and parenchyma preserved
Grade 4 SFU Grade 3 and parenchyma thin

Hydroureter (on sagittal image)
Grade 1:  <7 mm
Grade 2: 7-10 mm
Grade 3: >10 mm


Anterior atlantodental interval  >3 mm in adults >4 mm children is abnormal.

Craniocervical Injury (Pediatrics)
  • >5mm between occipital condyles and the condylar surface of the atlas
  • Powers ratio  Normal <1  The ratio of the distance from the basion to the spinolaminar line of the atlas divided by the distance from the anterior tubercle (atlas) to the the foramen magnum         
  • a line drawn from C2 Body(posterior aspect) should come within 12 mm of the basion 
Jefferson Fracture (C2)  6 mm or greater between the lateral mass of C1 and the odontoid process is suggestive of ligamentous injury on open mouth odontoid view.

Displacement of C1 on C2:   > 5 mm between the anterior cortex of the dens and the posterior cortex of the C1 anterior ring suggests ligamentous disruption

Abnormal prevetebral soft tissue thickness >7mm at C2   >22mm at C6

MRI Evolution of Hemorrhage
Hyperacute  (24 hrs)     T1 (isointense)  T2 (bright)
Acute   (1-3 days)         T1 (isointense)  T2 (dark)
Early Subacute (3-7 days) T1 (bright)  T2 (dark)
Late Subacute  (7-14 days) T1 (bright)  T2  (bright)
Chronic   (14 days +)        T1 (dark)    T2 (dark)

Modic Type 1  T1 dark T2 bright (edema)
Modic Type 2  T1 bright T2 bright (fat)
Modic Type 3 T1 dark T2 dark (fibrosis)

Acute stroke -  DWI images are most sensitive within 2 hours to 2 weeks

Basal ganglia calcification in kids include MELAS, Fahr disease, endocrine disorders, prior hypoxic injury


Thyroid Nodules :  DUKE's 3-Tiered System.  CT/MRI/PET-CT Features
Category 1:
Thyroid nodule PET avid or Thyroid nodule locally invasive or
Suspicious lymph nodes
Strongly consider workup with US for anysize nodule
Category 2:
Solitary thyroid nodule in patient <35 years age
Consider workup with US if ≥1 cm in adults.
Consider workup with ultrasound for any size in pediatric patients.
Category 3:
Solitary thyroid nodule in patient, ≥35 years age
Consider workup with ultrasound if ≥1.5 cm
Multiple nodules
Consider ultrasound with recommendations prioritized on
basis of criteria (in order listed) for solitary nodule
( AJR AM J Roentgenol .2014 Jan;202(1):18-24. doi: 10.2214/AJR.13.10972.)

Maximum insufflation for air enema reduction 120 Hg

Need atleast 12 French  for chest tubes
Need 8 French for Nephrostomy

Hope these important radiology numbers are helpful.  Please comment if there is anything that needs to be updated.  Thanks.

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