Subarachnoid hemorrhage: tips #1,6,7,8 (Fig 2)

By narrowing the window, the findings become easier to see(Fig A), and they can be  identified more easily in the bottom slice (Fig B). In supratentorial area, by comparing with a previous image, you can recognize a slight enlargement of the inferior horn of the lateral (niko-niko sign), which is associated with SAH (Fig C).

Narrow the window setting. Look at the images thoroughly. Compare with past images to identify subtle changes.

Cerebellar infarction: tips #1,10 (Fig 3)

In narrow window, a low-density area is seen in the right cerebellar hemisphere (Fig A). This corresponds to the area of AICA (Fig B), indicating a cerebellar infarction (Fig C). Even a faint focus of infarction can be detected by adjustingthe window level and width with an awareness of anatomical vascular territory. 

Narrow the window setting when reading a head CT to check for infarct focus along the vascular territory.

Cerebral venous sinus thrombosis: tips #1,9 (Fig 4)

By narrowing the window, high-density area can be detected in venous sinus (Fig A). With contrast enhancement, the area becomes dark which indicates thrombosis (Fig B). 

When high-density area is seen within the venous sinus on NCECT, consider differential diagnoses such as post-contrast agent use or dehydration. When there is infarction or subcortical hemorrhage, the signs of cerebral venous sinus thrombosis should be checked for, because it’s rare.

Always look for high-density in the venous sinus in NCECT.

Epidural hematoma: tips #1,2,10 (Fig 5)

When a patient complains neck pain or back pain,  the focus tends to be on vascular disorders such as vertebral dissection or aortic dissection. However, it’s crucial to pay attention to intraspinal abnormality. By windowing, hemorrhages become whiter, while other normal structures within the spinal canal are dark (Fig A). Sagittal reconstructed images should be created not only under bone setting but also under soft tissue setting (Fig B). In most cases, MRI reveals epidural hematoma more clearly.

Pay attention to intraspinal construction. Detect the hemorrhage by windowing and using MPR.

Pulmonary thromboembolism: tips #1,7,9 (Fig 6)

In general, CECT is used to diagnose pulmonary thromboembolism, but fresh thrombi may appear as a high-density area in NCECT.  However, they may not be visible with a usual window setting, so it’s important to use a narrow window setting (WW40 WL60) to identify thrombi (Fig A). Artifacts can also appear as high-density areas, making it difficult to distinguish.

The golden standard is CECT, but it’s also important to evaluate indirect findings, such as IVC/right ventricular enlargement  (Fig C) and retrograde flow of the contrast agent into IVC.

Aortic dissection: tips #1,7,9 (Fig 7)

Narrowing the window reveals a high-density area extending from the aortic root to the periphery of the pulmonary artery (Fig A), suggesting aortic bleeding. Contrast agent makes the flap of dissection more visible and it can be diagnosed as Stanford type A dissection (Fig B). Pericardial hematoma as an indirect finding is important for both diagnosis and assessing severity (Fig C).

In cases of open false lumen type and no calcification of the detached intima, it’s difficult to diagnose. When aortic dissection needs to be ruled out, CECT should be performed.

SMA embolism: tips #1,2,5,9 (Fig 8)

By narrowing the window, the superior mesenteric artery(SMA) becomes high-density (Fig A). In CECT, thrombus is observed and a decrease in contrast enhancement is evident in some portions of the intestinal tract (Fig B). SMA embolism occurs when embolic material from the heart becomes lodged, so the thrombus is often found more than 5-8cm distal to the branching point from the aorta. 

Pay attention to the blood vessels even in NCECT. Thrombi should be observed by narrowing the window.

SMA dissection: tips #1,5,9 (Fig 9)

By narrowing the window, a part of the superior mesenteric artery(SMA) becomes visible as high-density. This finding suggests thrombus in a portion of SMA, raising suspicion of dissection(Fig A). In CECT, this area is observed as a contrast defect (Fig B). There may be an increase in the density of surrounding adipose tissue as an indirect finding of SMA dissection. (although not very common).

Pay attention to the blood vessels even in NCECT. Thrombi should be observed by narrowing the window.

Ovarian torsion: tips #2,3,5,9  (Fig 10)

Important differentials for abdominal pain in women of reproductive age include ovarian hemorrhage, ovarian torsion, and ectopic pregnancy. Ovarian hemorrhage and ectopic pregnancy often involve the presence of an intraperitoneal hematoma as a diagnostic clue. However, telling if the ovary is enhanced or not isn’t easy in the case of ovarian torsion, so it is crucial to track the vascular structures twisted at the ovary (Fig C).

It is important to find vascular structures toward the knot-like twisted segment (Fig A,B), using thin slices and MPR.

Gastrointestinal tract perforation: tips #2,5  (Fig 11)

Gastrointestinal tract perforation can be fatal, especially for the elderly who may have limited preserves. So even when it isn’t suspected clinically, always consider the possibility. First, confirm the presence of free air or mucosal abnormality in the stomach and duodenum. And then, trace the colon (especially the sigmoid colon) from the anus to confirm that the bowel contents (feces) are retained in the digestive tract, utilizing MPR (fig A,B). As the feces from the perforation site may be covered by the mesentery, there may be a minimal amount of free air.

Even when there is no obvious free air, track the colon from the anus utilizing MPR .

Strangulation obstruction: tips #2,7,9 (Fig 12)

Strangulation obstruction should be considered in all cases of acute abdominal pain. Territorial bowel and mesenteric edema (TBME), which indicates venous congestion in the mesentery, is the early sign of intestinal ischemia (Fig A,B). In coronal CECT, Bowel wall edema becomes more evident (Fig B). TBME is the most important sign in diagnosing strangulation obstruction rather than closed loop obstruction (Fig C) or intestinal dilation. 

It’s important to look for TBME, which is the early sign of intestinal ischemia (Fig A,B).

NOMI: tips #7,9  (Fig 13)

The symptoms and clinical findings are nonspecific in NOMI and it can be fatal. Therefore, always look for indicators of the early stage of NOMI, such as intravascular dehydration (smaller SMV sign, collapse of IVC) (Fig A,B) ,dilatation of intestinal loops with the decrease of intestinal tonus (Fig C) and insufficient or patchy contrast enhancement of the intestines. However, it’s important to be aware that the signs of intravascular dehydration may appear to be corrected by transfusion.

Be aware of the indicators of the early stage of NOMI, such as smaller SMV sign and collapse of IVC (Fig A,B).