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Proportional Anatomy and Anatomical Pathway
Proportional Anatomy and Anatomical Pathway
AP Knee = AP Shoulder = AP Clavicle
Lateral Ankle = (+ 5% kVP) PA Hand
AP Hip = AP L-Spine = AP Oblique Ribs = (15% increase in kVP) AP Knee
PA Caldwell= (15% increase in kVp) AP Hip
Lateral Chest= (+10 kVp + 15% twice in kVp) AP knee
Justification and Calculations
Justification and Calculations
1st:
EXPLANATION: We started with the AP knee optimal exposure from a previous lab experiment.
CALCULATIONS: Since we were using a different color/ material phantom in the previous lab experiment, our deviation index value came out to 3. Meaning it was overexposed.
2nd: Optimal Technique
EXPLANATION: To maintain penetration of the grid we kept kVp the same. We used the mAs formula of decreasing the mAs by 20% to decrease the DI value by about 1. We decreased mAs by 20% 3 times to lower the DI value by about 3 to try to reach 0, optimal exposure.
CALCULATIONS:
- 20% of 10 is 2. 10-2=8mAs
- 20% of 8 is 1.6. 8-1.6= 6.4mAs
- 20% of 6.4 is 1.28. 6-1.26= 4.72mAs ~5mAs
Justification and Calculations
Justification and Calculations
1st:
EXPLANATION: Since the knee and shoulder are similar in density, we kept the technique the same as the AP knee.
CALCULATIONS: We received a DI value of –3.5, meaning it was under-exposed.
2nd: Optimal Technique
EXPLANATION: We measured the shoulder at 15cm, where the knee was 8cm. We doubled the mAs to compensate for the thickness. And received a DI value within the optimal range. We used the mAs formula of increasing the mAs by 25% to decrease the DI value by about 1, three times.
CALCULATIONS:
- 25% of 5 is 1.25. 5+1.25= 6.25mAs
- 25% of 6.25 is 1.56. 6.25+1.56= 7.81mAs
- 25% of 7.81 is 1.95. 7.81+1.95= 9.76 ~10mAs
Justification and Calculations
Justification and Calculations
1st:
EXPLANATION: Since the shoulder and clavicle are similar in density, we kept the technique the same as the AP shoulder.
CALCULATIONS: We received a DI value of –1.6, meaning it was under-exposed.
2nd:
EXPLANATION: We used the mAs formula by increasing the mAs by 25% to try to increase the DI value by about one. It still was not within optimal range.
CALCULATIONS:
-25% of 10 is 2.5. 10+2.5= 12.5mAs
3rd: Optimal Technique
EXPLANATION: Since we only wanted the DI value to increase by about .5, instead of increasing mAs by 25%, we only increased mAs by 12.5%.
CALCULATIONS:
-12.5% of 12.5 is 1.56. 12.5+1.5= 14mAs
Justification and Calculations
Justification and Calculations
1st:
EXPLANATION: The hand was the first non-grid anatomy we moved onto. We used the technique provided by the system for an average hand.
CALCULATIONS: We received a DI value of 1, meaning it was overexposed.
2nd: Optimal Technique
EXPLANATION: We only needed to decrease the DI value by about 1. We increased the kVp for a slight increase in penetration but decreased the mAs by 20% since the image was slightly overexposed.
CALCULATIONS:
- 20% of 1 is 0.2. 1-0.2= 0.8mAs
Justification and Calculations
Justification and Calculations
1st:
EXPLANATION: Since the ankle is about twice the density of the hand, we started by doubling the mAs.
CALCULATIONS:
- .8 hand mAs x 2 = 1.6mAs
2nd: Optimal Technique
EXPLANATION: Since we only wanted the DI value to increase by about .5, instead of increasing mAs by 25%, we only increased mAs by 12.5%.
CALCULATIONS:
- 12.5% of 1.6 is 0.2. 1.6+0.2= 1.8mAs
Justification and Calculations
Justification and Calculations
1st:
EXPLANATION: We started the AP hip by increasing the kVp 15% from the AP knee, but since it measured about the same as the shoulder, we used the same mAs.
CALCULATIONS:
- 15% of 70 is 10.5. 70+10.5= 80.5kVp
2nd: Optimal Technique
EXPLANATION: Since we were only slightly underexposed in the previous image, we only increased our mAs by 12.5% to obtain an image within the optimal range.
CALCULATIONS:
- 25% of 10 is 2.5. 10+2.5= 12.5mAs
Justification and Calculations
Justification and Calculations
1st:
EXPLANATION: We believed since the L-spine was about the same thickness as the hip, we could use the same technique.
CALCULATIONS: We received a DI value of -2.1, meaning it was under-exposed.
2nd: Optimal Technique
EXPLANATION: We used the mAs formula by increasing the mAs by 25% twice to increase the DI value by 2. We received a DI value of –0.2, within the optimal range.
CALCULATIONS:
- 25% of 12.5 is 3.125. 12.5+3.125= 16.625mAs
- 25% of 16.625 is 3.9. 16.625+3.9= 20 mAs
Justification and Calculations
Justification and Calculations
1st:
EXPLANATION: We used the technique from the L-spine since it had a similar thickness. However, it was overexposed due to the lungs and less density.
CALCULATIONS: We received a DI value of 4.7
2nd: Optimal Technique
EXPLANATION: Since we were overexposed with a DI value of 4.7, we needed to come down with the mAs by 20% at least 3.
CALCULATIONS:
- 20% of 20 is 4. 20-4=16mAs
- 20% of 16 is 3.2. 16-3.2= 12.8mAs
- 20% of 12.8 is 2.56. 12.8—2.56= 10.24mAs ~10mAs
Justification and Calculations
Justification and Calculations
1st:
EXPLANATION: We used the technique from the RPO oblique ribs since they had similar thicknesses.
CALCULATIONS: We received a DI value of –4.4, meaning it was under-exposed.
2nd:
EXPLANATION: We used the mAs formula to increase the mAs by 25% three times to increase the DI value by about 1 each time. It was still slightly underexposed.
CALCULATIONS:
- 25% of 10 is 2.5. 10+2.5=12.5mAs
- 25% of 12.5 is 3.125. 12.5+3.125= 15.625mAs
- 25% of 15.625 is 3.9. 15.625+19.5= 19.5mAs ~20mAs
3rd: Optimal Technique
EXPLANATION: Instead of increasing mAs and patient dose, we increased the kVp by 15% and decreased the mAs by 20%.
CALCULATIONS:
- kVp: 15% of 80 is 12. 80+ 12= 92kVp ~90kVp
- mAs: 20% of 20 is 4. 20-4 =16 mAs
Justification and Calculations
Justification and Calculations
1st:
EXPLANATION: Using the proportional anatomy table, it states the PA chest is equivalent to AP knee + 10 kVp. Since we are doing the lateral, it states to “double the mAs and up 10kVp”.
CALCULATIONS: We received a DI value of 2.8
2nd:
EXPLANATION: We used the 15% rule, but still were over exposed.
CALCULATIONS:
- Using the 15% rule:
- kVp: 15% of 90 is 13.5. 90+13.5= 103.5kVp ~104
- mAs: 10mAs/ 2= 5mAs
3rd:
EXPLANATION: We kept kVp the same but decreased mAs by 20% twice to lower the DI value by about 1 each time.
CALCULATIONS:
- 20% of 5 is 1. 5-1= 4mAs
- 20% of 4 is 0.8. 4-0.8= 3.2mAs
4th:
EXPLANATION: Since we were still not in the desired DI value range, we decided to use the 15% rule again.
CALCULATIONS:
- Using the 15% rule
- kVp: 15% of 104 is 15.6. 104+15.6= 119.6kVp ~120kVp
- mAs: 3.2mAs/ 2= 1.6mAs
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