Unresolved questions pertaining to DMI-105 textbooks: (preliminary 10-9-2006)

Radiologic Science for Technologists: Physics, Biology, and Protection, Stewart C. Bushong, 2004, 8th ed.
ISBN-13: 978-0-323-02555-3
ISBN-10: 0-323-02555-2

Radiologic Science for Technologists Workbook and Laboratory Manual, Stewart C. Bushong, 2004, 8th ed.
ISBN 0-323-02554-4

This page is about the two textbooks, not physics.  If you don't have the books, this page will not be useful to you.

This page is not intended as an errata to the above textbooks. It  not a complete, nor meticulous review either. I am simply listing some problems I have noted while taking a course in Radiation Physics on a compressed schedule for a diagnostic imaging (healthcare) course. Only chapters 1-12 were covered in the course.

Science textbooks nowadays seem to have an alarming number of errors scattered throughout them. The errors seem to accumulate with succeeding editions. Unwary students stumble into these potholes and spend a great deal of their precious time during the course trying to resolve their confusion, only to develop a sense of frustration that they just cannot master the material. They might not realize that they are dealing with an error in the textbook. Students also resent purchasing medical textbooks that cost hundreds of dollars apiece and which are still littered with known errors and typos even in subsequent editions.

I believe that colleges should demand that a student-friendly  errata site be made available for each textbook they use. This will help students master the course material and also help publishers produce accurate textbooks.

Authors generally welcome feedback on their textbooks. Student feedback is not merely an inconvenience;  the markets for these books exists BECAUSE  students use them. Authors want their books to be as useful, relevant, and as accurate as possible.

The two textbooks listed here are very interesting, very useful,  and offered at a fair price (a rarity these days). I hope my comments below will not deter you from purchasing these books.

If you want to email me, just concatenate the following:      brian fraser 427 @  yahoo .com


Radiologic Science for Technologists Workbook and Laboratory Manual, Stewart C. Bushong, 2004, ISBN 0-323-02554-4

 Workbook Chapter 2

Worksheet 2-3, question 2: off by a factor of 10?

Worksheet 2-5, questions 5 and 15. Curies or Roentgens? Inconsistent.

 Workbook Chapter 3

Worksheet 3-2, question13: Bizarre and unclear question. Only d or e will qualify as force. The Grand Canyon is in Arizona, not Europe. The answer would be in pounds.

 Workbook Chapter 4

Worksheet 4-1, question1: wording of choice b.

Worksheet 4-2, question 2: 18 nucleons or 20 nucleons?

Worksheet 4-3, question 12:  answer in back is missing.

Worksheet 4-3, question 16: Strontium has 36 or 38 total electrons? A valence (?) of 3 is not shown on the classroom Periodic Table chart.

 Workbook Chapter 5

Worksheet 5-1, question 8: What is being modeled? Water? EMR?  Should say EMR is intended.

Worksheet 5-2: no discrepancies found

Worksheet 5-3, question 2 “Attenuation” in glossary involves both absorption and scattering. See also p. 185. Frosted glass is used in projection systems to remove the image of the filament. The intent is scattering, not absorption. Textbook says sandpapered glass is “translucent” (p. 68). I don’t like the wording of the question.

Worksheet 5-3, question 10: "Which statement about visible light is correct?" The "correct" answer is supposedly "e. If visible light is transmitted unattenuated, the matter is opaque."  Whew! What a whopper!

Worksheet 5-4 no discrepancies. (Did not attempt 2,16,17)

Worksheet 5-5, question 1 “Superficial X-rays” for diagnostic imaging ?????? Not defined. Consistent with 20e.

Worksheet 5-6: no discrepancies found

 Workbook Chapter 6

Worksheet 6-1, question 17: substance not specified. Electrons in the atomic substance? Electrons or disintegrations intended? Ion pairs intended? Do we have to know Avogadro’s number too?

Worksheet 6-2, question 13: mAs is charge not current. compare 2-2 intro, or 6-3-14, back page of textbook, p.78, etc.

Worksheet 6-3, question 22: “They never come to rest” versus the textbook’s “the magnitude of the current is zero, indicating that no electrons flow” and “all electrons are at rest” (p. 84) The context of the question is about ordinary electric AC current.

Worksheet 6-4, question 20: both b and c according to textbook p. 87. The neutron also has a magnetic moment of minus 1.91 nuclear magnetons.

 Workbook Chapter 7

Worksheet 7-1, question 11: answer d is not consistent with the wording on p. 99 of textbook, nor the definition of mutual induction given there.

Worksheet 7-2, question 4: Xray tube motors and AC induction motors do NOT require commutators. Probably c was intended.

Workbook page 79: typo in transformer law; compare textbook p. 102

Worksheet 7-3, question 17: should say “turns” instead of “windings”

Worksheet 7-4, question 7: Trick question? Tube can only conduct if anode can go positive, which it cannot.

Worksheet 7-4, question 9: positive current or electron current? Diodes were defined for positive current. Answer should be b, not a. (p. 119)

Wait a minute. This section is really in chapter 8, not 7!

Workbook Chapter 8

Worksheet 8-1, question 1: answer  e  uses the objectionable term “secondary side”. An autotransformer has only secondary taps or connections, no “side”. Usage is inconsistent with the other questions (11,15)
Worksheet 8-1, question 4: Oerstead’s LAW? His EXPERIMENT had nothing to do with transformers.
Worksheet 8-1, question 18: textbook says “prereading kVp meter” (p. 114) Would have expected  c  to be the answer.
Worksheet 8-3, question 7: unable to find a specific reference for this in the textbook.
Worksheet 8-4, question 1: high voltage GENERATOR?? There are no moving parts here. Meaning is different than that on textbook p. 99. means high voltage SECTION?   (see question 12) But “generator” is a term that is widely used in this context too. Non-physics students might get confused on this.
Worksheet 8-4, question 11: Increased intensity (photon density) or increased average photon energy? I thought intensity had to do with filament power (mostly). Needs clarification.
Worksheet 8-4, crossword puzzle:
5 down “electromagnetic”? Is stated in book (113) but “self induction” would be my answer.

 Workbook Chapter  9

Worksheet 9-1, question 7: Cup is not thoriated (textbook 131). Compare with question 18.
Worksheet 9-1, question 18: Well, ok, but “increases thermionic emission” would be a better answer in my opinion. Also used in welding rods for a similar reason.
Worksheet 9-1, question 20: X rays are emitted from the anode, not filament.
Worksheet 9-2, question 4: choice d seems better than e. Doesn’t anode heat capacity relate better to quantity of x-rays photons than energy of x-ray photons? Questions should have something about higher tube currents and shorter exposure time. (p. 135)
Worksheet 9-2, question 8:  "Molybdenum is used for anode stem material because of which of the following?" The "correct" answer is supposedly "a. It has a high atomic number." But the text book says stem material is “usually made of molybdenum because it is a poor conductor of heat” (p. 136; and therefore reduces heat flow to the bearings; 138 w/m-K)
Worksheet 9-3: questions 1 through 21? 0r 11 to 25?
Worksheet 9-3: question 6: "It is not possible to exceed the heat capacity of the housing without first exceeding that of the anode. True or false." The answer given is "false." Could not find reference in text. Heat capacity of housing is MUCH larger than that of the anode (several million HU versus a few hundred thousand for the anode (p. 145-146). So why is the answer false? The question must really be about cooling rate rather than heat storage capacity.   Approximate numbers for the anode would therefore be 350000HU/15min. For the housing, say 5 million HU/1.5 hours. That means the housing can dissipate the heat faster than the anode can put it in by roughly a factor of two. Hence, the heat capacity of the anode would be exceeded before the heat capacity of the housing. In any case, the presentation needs clarification, regardless of the answer.
Worksheet 9-3: question 7: could not find reference in text. What is the gas? Modern tubes do not use gas. Tungsten vapor deposition? Comes from anode, or filament, or both?

Worksheet 9-3: question 29: could not find reference in text. From what we were taught in class, "a single exposure greatly exceeding those permitted . . ."  would cause the anode to pit or crack (answer a), but the "correct" answer is given as "The tube filament would break" (answer d).

Workbook Chapter 10

Worksheet 10-3: question 5. See question 13 below. I chose c, because production occurs before filtration.
Worksheet 10-3: question 13. My first choice was d (p. 149). Second choice would have been c (p. 157, and Fig 10-15 on 158). The chapter is really not about filtration, and so I would not have chosen a.
Worksheet 10-3: question 14: My choice was b. If a K shell electron is not ejected, there is NO characteristic K line at all. The K shell vacancy can be filled from “any of the outer shells” (p. 150; not just the L shell). Answer a would allow only 57 KeV. But see Fig 10-9.
Worksheet 10-4 Minimum wavelength not in index. Duane-Hunt not in index. What is the source for this material?
Worksheet 10-4 question 5: I would expect to use both Planck’s constant and the speed of light if all I knew was the wavelength.
Worksheet 10-4 question 7: Cannot find reference in textbook.
Worksheet 10-5 question 6: answers a and b both look valid.

Workbook Chapter 11

Worksheet 11-1: no discrepancies found

Worksheet 11-2, question 19: No reference in textbook.

Worksheet 11-2, question 28:  I get (50/70)(2mm) or about 1.33, which is closer to 1.5 than 1.0. Hence my answer would be c instead of b.

Worksheet 11-2, question 32: No reference.  I used 1/2^3

Workbook Chapter 12

Worksheet 12-1: no discrepancies found

Worksheet 12-2, question 6:

Worksheet 12-2, question 8:

Worksheet 12-3, question 26: Mass attenuation coefficient ????  Not defined. Seems to contradict answer to 25.

Worksheet 12-3, question 29: Is discussed in ch 15 instead of 12. Answer is not apparent from text. Workbook gives  e  but why wouldn't a be a.better choice?

Worksheet 12-3, question 30:

Radiologic Science for Technologists: Physics, Biology, and Protection, Stewart C. Bushong, 2004, 8th ed., ISBN-13: 978-0-323-02555-3, ISBN-10: 0-323-02555-2

p. 22 “semilogarithmic scale on one axis”; probably “logarithmic scale on one axis” is meant.

p. 34, example in lower right about portable (35 kg, 25 m hall, 9  seconds, final v of 3 m/s). Method of calculation seems to be roundabout. Why not just take final KE as the measure of the total work, then divide by the time to get the power? But that gives 17.5 watts, not 32.  Problem appears to have inconsistent info. Acceleration and time values give a hallway length of 13.4 meters (S = 1/2at^2) not 25 meters. Instructor says we won’t be tested on this.

p. 59 Greeks called light a photon? (term was given by physical chemist Gilbert Lewis in 1926)

p. 61: this section is very confusing and poorly explained. The “distance from one crest to another” should be called a “cycle”. A cycle is defined by the wave itself. It is not dependent on the units that are used for distance or time. “Frequency is the number of wavelengths . . .” is confusing. The definition in the text on page 60 is much better. The archer illustration is also confusing.
p. 95 Diagram 7-2a leaves the impression that the copper and zinc are both in direct contact and also separated by wet paper. The diagram appears to combine the concepts of the voltaic pile with the "crown of cups".



Fig 8-8, p114: are BOTH filaments always on? Shouldn't switch be shown on secondary side?  Figure 9-4B on page 132 is more accurate; notice the separate transformer cores.
Fig 8-31, p126: high voltage section appears to have an extra line segment between the top two diodes. This means the tube anode is directly connected to the AC transformer. 

p. 121 Fig 8-20. This does not appear to be an accurate diagram. The mA meter cannot measure current within the tube. And the bottom diode is either redundant or useless. What might have been intended is a circuit with the cathodes of both diodes connected together (the bottom diode has to be reversed) and both connected so they are pointing into the X-ray tube anode, and the cathode of the tube grounded. This will give full wave rectification with only two diodes, but requires a center tap on the transformer, which is not usually done on systems like this (because transformers are far more expensive than diodes). The mA meter would then be at ground potential and still be in the anode-cathode circuit of the X-ray tube. For more information see: http://www.allaboutcircuits.com/vol_3/chpt_3/4.html

p. 131:  Light bulb filaments ARE made of tungsten.

p. 135: Thermal conductivity of tungsten is 174 w/m-K; copper is 400 w/m-K. Thermal conductivity of tungsten is less than HALF that for copper, not “nearly equal.” 

p. 165: An example application of "the square law, a corollary to the inverse square law" is given here. But Bushong does not  usethe formula in his example. The example does not include squares, nor does it include distances. Instead, he relates the mAs ratio directly to the Roentgens ratio. Better exposition is needed here!

p. 166:  Fig 11-3 and the Question associated with it. "One half of 94 is 47 . . ." Ok. But where does the 94 come from? The number should be 118, not 94.

p. 174: Compton effect. The presentation here seems quite different from that in physics textbooks. Those assume free electrons (negligible binding energy). The Compton wavelength is only 0.0243 Angstroms, and so even at 180 degrees deflection the max wavelength shift is only 0.0243 Angstroms. Diagnostic X-ray wavelengths are around 1 Angstrom.  But the presentation in the textbook includes the Compton effect itself, plus binding energy, plus ejected electron kinetic energy (of several keV), and it is all called the “Compton effect”. Confusing.

p. 175:  "The probability of the Compton effect does not depend on the atomic number of the atom involved." (See also p. 182) Compare that with this one from another textbook: "The likelihood of Compton scatter is proportional to the atomic number; therefore there is more Compton scattering in high atomic number materials." (Nuclear Medicine and PET Technology and Techniques, Christian, Bernier, and Langan, 2004, 5th ed., p. 53)  Which expert is the student to believe?  And this is just physics!  Can you imagine what healthcare must be like!?

p. 182 Fig 12-13 change “change” to “chance”?

p. 186 “Is it obvious that the assumed HVL in soft tissue was 5 cm?”  No, it is not obvious. Half of 1000 is 500. But at 5 cm, the value on the graph is about 30. Looks like HVL is 1 cm.