CT Scans in Medical Diagnosis

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Questions and Answers

What is a key benefit of using CT scans in trauma cases?

They are a cost-effective tool for diagnosing minor injuries
They reduce the need for radiation therapy
They eliminate the need for surgical biopsies
They help reveal internal injuries and bleeding quickly (correct)

What is the approximate amount of radiation an individual receives from a CT scan?

The same amount as 6 months of background radiation
The same amount as 10 years of background radiation
The same amount as 3 years of background radiation (correct)
The same amount as 1 year of background radiation

What is NOT a factor that affects the radiation dose in CT imaging?

Reconstruction algorithm
Patient age (correct)
Resolution detector efficiency
Slice thickness

What is the term for the amount of radiation energy absorbed by the body?

Absorbed Dose (A) Signup and view all the answers

What is the purpose of CT scans in guiding radiotherapy and other minimally invasive procedures?

To identify normal and abnormal structures (D) Signup and view all the answers

What is a benefit of using CT scans in medical diagnosis?

They can be a cost-effective imaging tool for a wide range of clinical problems (D) Signup and view all the answers

What is the unit of measurement for the field size?

centimeters (C) Signup and view all the answers

What is the conversion coefficient for a field size of 15.3*15.3 cm?

0.12 (B) Signup and view all the answers

What is the formula to calculate the effective dose (E)?

E = fanW (A) Signup and view all the answers

What is the total effective dose (mSv) for a field size of 20.03*20.03 cm?

0.21 (A) Signup and view all the answers

Which of the following is NOT a region where organ and effective doses were measured?

X-ray (D) Signup and view all the answers

What is the purpose of the conversion coefficient?

To calculate the effective dose (A) Signup and view all the answers

What is the parameter measured in the AP direction for the Head protocol?

85 kV (C) Signup and view all the answers

What is the effective dose for the Chest in Lateral direction?

100 mSv (C) Signup and view all the answers

What is the corresponding direction for the Pelvis protocol with an effective dose of 110 mSv?

Lateral (A) Signup and view all the answers

What is the total effective dose calculated for?

Whole body (D) Signup and view all the answers

What is the unit of measurement for the effective dose?

mSv (B) Signup and view all the answers

What was used to determine the conversion coefficients?

Exposure parameters and half value layer of the machine (D) Signup and view all the answers

What is the CTDI volume equivalent to?

(1 / pitch) × CTDIw (D) Signup and view all the answers

What is the unit of measurement for DLP?

mGy cm (C) Signup and view all the answers

What is the purpose of SSDE?

To estimate CT radiation dose that takes a patient's size into account (B) Signup and view all the answers

What is the characteristic shape of the dose delivered by each slice in MSAD?

Bell-shaped (B) Signup and view all the answers

What is the formula to calculate CTDIvol?

CTDIvol = (1 / pitch) × CTDIw (C) Signup and view all the answers

What is the ratio of the patient table increment to the total nominal beam width for the CT scan?

Pitch (B) Signup and view all the answers

What is the primary purpose of CTDI 100?

To measure the dose distribution over a 10 cm pencil ionization chamber (D) Signup and view all the answers

What is the formula for CTDI weighted?

1/3 CTDI100 CENTER + 2/3 CTDI100 PERIPHERAL (D) Signup and view all the answers

What is the purpose of the Computed Tomography Dose Index (CTDI)?

To provide a standardized measure of absorbed dose (B) Signup and view all the answers

What is the difference between CTDI (center) and CTDI (peripheral)?

CTDI (center) measures the dose at the center of the phantom, while CTDI (peripheral) measures the dose at the periphery (D) Signup and view all the answers

What is the significance of the term 'phantom' in the context of CTDI measurement?

It refers to a standardized object used to measure the dose distribution (D) Signup and view all the answers

What is the relationship between CTDI 100 and CTDI weighted?

CTDI 100 is a measure of the dose distribution over a 10 cm pencil ionization chamber, while CTDI weighted is a measure of the weighted average of CTDI (C) Signup and view all the answers

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Study Notes

CT Scan Benefits

CT scans can reveal internal injuries and bleeding quickly, helping save lives in trauma cases.
CT scans can eliminate the need for invasive exploratory surgery and surgical biopsy.
CT scans can identify normal and abnormal structures, making them useful for guiding radiotherapy and other minimally invasive procedures.
CT scans are a cost-effective imaging tool for a wide range of clinical problems.

Risks of CT Scans

CT scans involve exposure to radiation in the form of x-rays, but the benefit of an accurate diagnosis outweighs the risk.
The effective radiation dose from a CT scan is about 10 mSv, similar to the average person's exposure to background radiation over three years.

Factors Affecting Radiation Dose in CT Scans

Slice thickness affects radiation dose.
Noise affects radiation dose.
Resolution detector efficiency affects radiation dose.
Reconstruction algorithm affects radiation dose.
Collimation affects radiation dose.
Filtration affects radiation dose.

Quantification of Dose

Exposure dose is a measure of radiation.
Absorbed dose is a measure of radiation.
Equivalent dose is a measure of radiation.
Effective dose is a measure of radiation.

Measuring Patient Dose

Patient dose can be measured using a panicle chamber.
Patient dose can be measured using a Computed Tomography Dose Index (CTDI) phantom.

CTDI (Computed Tomography Dose Index)

CTDI is a standardized measure of absorbed dose.
CTDI 100 is a measure of dose distribution over a pencil ionization chamber (10 cm).
CTDI weighted measures a weighted average of CTDI from peripheral radial and central dosimetry points within a phantom.
CTDI volume gives a weighted average of CTDI from peripheral radial and central dosimetry points within a phantom, corrected for pitch.

Additional Dose Measurement Quantities

Dose length product (DLP) is the CTDI(vol) multiplied by the scan length in centimeters.
Size-specific dose estimate (SSDE) is a method of estimating CT radiation dose that takes a patient's size into account.
Multiple Scan Average Dose (MSAD) measures radiation dose received by a patient from a series of CT scans.

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