Question

Mr. Smith is 60 years old. He was diagnosed with a prostate cancer five years ago. Over the past few days, Mr. Smith has been feeling weak and increasingly tired and has also been suffering from a headache that did not respond to over-the-counter medications. He scheduled an appointment with his physician.

His physician performed a physical examination and recommended a battery of laboratory tests and imaging procedures.

The table below shows Reference values in the right-hand column. These values reflect the normal range of values for patients without disease or illness. The center column reflects the resulting values for medical test results obtained for Mr. Smith.

Take note whether Mr. Smith’s values are within normal limits.

	Mr. Smith	Reference Values
K+	2.6 mmol/L	3.8-4.9mmol/L
Hb (Hemoglobin)	7.5 g/dL	13.8 to 18.2 g/dL
Hct (Hematocrit)	20.4%	45-52%
Platelet Count	49x109/L	150-400x109/L

After receiving Mr. Smith’s test results, his physician admits him to the hospital. Hospital staff treated him and discharged him.

The following week, Mr. Smith returns to his physician with the same complaint of weakness and a new complaint of shortness of breath. His blood pressure is 160/100 mmHg. MRI reveals metastasis of prostate cancer to osseous tissue. Abdominal CT shows obstruction of intestine due to nodular enlargement of adrenal glands.

Laboratory results from Mr. Smith’s second hospital admission and medical tests show following findings:

Mr. Smith	Reference Values
K+	2.6 mmol/L	3.8-4.9mmol/L
Hb	7.3 g/dl	13.8 to 18.2 g/dL
Hct	20.4%	45-52%
Platelet Count	20x109/L	150-400x109/L
HCO3	38 mmol/l	22-26 mmol/L
Urinary K+	70 mmol/L/24 hr	25-120 mmol/L/24 hr
Blood Glucose	460 mg/dl	64.8-104.4 mg/dL
Serum Aldosterone	1 ng/dl
24 hour Urinary Aldosterone	8.4 mcg/24 hr	2.3-21.0 mcg/24 hr
Renin	2.1 ng/ml/hr	0.65-5.0 ng/ml/hr
ACTH (Adrenocorticotropic Hormone)	1082 pg/ml	9-46 pg/ml
Cortisol	155.5 microg/dL	0-25 microg/dL

CONCLUSION AND DIAGNOSIS

Laboratory findings, MRI and CT confirmed metastatic prostate adenocarcinoma, hypertension and refractory hypokalemia due to ectopic ACTH production. High levels of circulating cortisol caused continuous activation of mineralocorticoid receptors resulting in hypokalemia, metabolic alkalosis and hypertension.

Question:

What imaging procedures did Mr. Smith undergo? Discuss the distinctions and similarities between the two different imaging approaches. What were the results of imaging procedures in Mr. Smith’s case?

Answer 1

MRI and CT were the imaging procedures Mr.Smith underwent

Radiation exposure	The effective radiation dose from CT ranges from 2 to 10 mSv, which is about the same as the average person receives from background radiation in 3 to 5 years. Usually, CT is not recommended for pregnant women or children unless absolutely necessary.	None. MRI machines do not emit ionizing radiation.
Time taken for complete scan	Usually completed within 5 minutes. Actual scan time usually less than 30 seconds. Therefore, CT is less sensitive to patient movement than MRI.	Depending on what the MRI is looking for, and where it is needing to look, the scan may be quick (finished in 10-15 minutes) or may take a long time (2 hours).
Effects on the body	Despite being small, CT can pose the risk of irradiation. Painless, noninvasive.	No biological hazards have been reported with the use of MRI. However, some may be allergic to the contrast dye, which is also inappropriate for those suffering from kidney or liver disorders.
Ability to change the imaging plane without moving the patient	With capability of MDCT, isotropic imaging is possible. After helical scan with Multiplanar Reformation function, an operator can construct any plane.	MRI machines can produce images in any plane. Plus, 3D isotropic imaging also can also produce Multiplanar Reformation.
Application	Suited for bone injuries, Lung and Chest imaging, cancer detection. Widely used on Emergency Room patients.	Suited for Soft tissue evaluation, e.g., ligament and tendon injury, spinal cord injury, brain tumors, etc.
Acronym for	Computed (Axial) Tomography	Magnetic Resonance Imaging.
Details of bony structures	Provides good details about bony structures	Less detailed compared to X-ray
Details of soft tissues	A major advantage of CT is that it is able to image bone, soft tissue and blood vessels all at the same time.	Provides much more soft tissue detail than a CT scan.
Scope of application	CT can outline bone inside the body very accurately.	MRI is more versatile than the X-Ray and is used to examine a large variety of medical conditions.
Principle used for imaging	Uses X-rays for imaging	Uses large external field, RF pulse and 3 different gradient fields
Principle	X-ray attenuation is detected by detector & DAS system, followed by math. model (back projection model) to calculate the value of pixelism that becomes a image.	Body tissues that contain hydrogen atoms (e.g. in water) are made to emit a radio signal which are detected by the scanner. Search for "magnetic resonance" for physics details.
Image specifics	Good soft tissue differentiation especially with intravenous contrast. Higher imaging resolution and less motion artifact due to fast imaging speed.	Demonstrates subtle differences between different kinds of soft tissues.
History	The first commercially viable CT scanner was invented by Sir Godfrey Hounsfield in Hayes, United Kingdom. First patient's brain-scan was done on 1 October 1971.	First commercial MRI was available in 1981, with significant increase in MRI resolution and choice of imaging sequences over time.
Intravenous Contrast Agent	Non-ionic iodinated agents covalently bind the iodine and have fewer side effects. Allergic reaction is rare but more common than MRI contrast. Risk of contrast induced nephropathy (especially in renal insufficiency (GFR<60), diabetes & dehydration).	Very rare allergic reaction. Risk of reaction in those who have or have a history of kidney or liver disorders.
Comfort level for patient	Seldom creates claustrophobia	Anxiety, especially anxiety caused by claustrophobia, is common, as is tiredness or annoyance over having to stay still on a hard table for a long period of time.
Limitation for Scanning patients	Patients with metal implants can get CT scan. A person who is very large (e.g. over 450 lb) may not fit into the opening of a conventional CT scanner or may be over the weight limit for the moving table.	Patients with Cardiac Pacemakers, tattoos and metal implants are contraindicated due to possible injury to patient or image distortion (artifact). Patient over 350 lb may be over table's weight limit. Any ferromagnetic object may cause trauma/burn

Results of imaging procedure:- Laboratory findings, MRI and CT confirmed metastatic prostate adenocarcinoma, hypertension and refractory hypokalemia due to ectopic ACTH production. High levels of circulating cortisol caused continuous activation of mineralocorticoid receptors resulting in hypokalemia, metabolic alkalosis and hypertension