Interesting Answers and Questions
Question: Sonography and Statistics Accuracy
Answer: Ultrasonography accuracy is relative. Most sonograms result "normal"
in spite of pathology. You can prove a condition exists but, you cannot prove it
does not exist. It is very difficult to get accurate statistics if you cannot do
any biopsy or autopsy to verify your results. There are not ultimate proves
The current technology would let us surpass operator dependence up to some
important level but most manufacturers prefer to stick to known and proven
technology rather than creating new things. The first is more profitable while
the second involves expensive risks.
IMHO, the only way we can honestly protect our patients is by doing our best
at all times while being conscious of the technology limitations and ours as
well. More ...
Question: I am interested in finding out more information about the pros and
cons of using US to diagnose solitary thyroid nodules, what other diagnostic
modalities are available and why US may or may not be the modality of choice.
Please forward to me your opinion or any other information you might have
Answer: Here are the pros of using ultrasonography to diagnose solitary
- It is safe (there is no risk at all) and you can scan the patients
repeatedly and have proper follow-ups
- US can tell the difference between cysts and solid masses
- US can easily tell how close the masses are form important vessels
- US can detect changes consistent with malignancy
- US can easily measure dimensions and volume
- US is less expensive
Disadvantages: US cannot tell when a mass is hypo or hyperactive
Other diagnostic modalities you can use beside lab tests, cytology and
biopsy are CT, Thermography, MRI and Gammagram.
Next 7 questions came from Fiona Soon Chin Fhong; Msc.in Medical Electronics
University Technology of Malaysia.
Question: As a medical electronic student, i would like to seek for your
stand point of view regarding the phenomenon called speckle noise. Does it has
an effect during a scanning especially in early detection of pathologies? And,
what do you think of the speckle effect during a scanning of obese person? Does
the ultrasound machine offers a solution on that or can the sensitivity and
contrast control reduce the problem?
Answer: Speckle noise is an undesirable artifact that masks pathology. It
could be reduced using a phase insensitive technique, or a way to cancel the
undesirable linear-phase representation. You could use a system sampling more
images (more channels and memory needed). You could also consider adding a fuzzy
logic algorithm. Be aware that if you do that, you are changing the image to
meet your needs. That is the way ultrasound post-processing and pre-processing
work though (changing the image to meet your needs).
The hardware requirements are difficult to meet now but if you use fuzzy
logic algorithms, you could get outstanding results.
Speckle phenomena are common when scanning fat patients. Many scanners offer
ways to somehow overcome this effect in a limited approach. One of my scanners -
a digital one- uses special algorithms to cancel the speckle effect, but results
are limited. Of course, digital imaging is a lot better. Gain and contrast
controls offer poor improvement and pre and post-processing are better solutions
(IMHO). The best practical solution now is scanning from different positions and
angles and/or creating artificial acoustic windows.
Question: Through my recent reading in a paper by Dr. Aly A Farag ( IEEE
Transaction in Medical imaging) , I was informed that the accuracy of using
ultrasound diagnosis is about 78%. What about the other 28%? Do you agree with
Answer: I have not heard about it. It depends of the factors included in the
survey. Sonography is a highly operator dependable procedure and results can
vary much. If the statistics you mention consider different scanners,
transducers, different operators, like sonologists, radiologists, sonographers,
general physicians, care of the persons involved in the procedure (Private
practice and research sonograms are more accurate), etc., the 78% would be
accurate. No system is perfect.
In my personal experience, I have found ultrasonography being more accurate
than CT and X-rays when dealing with abdominal and muscle pathology. Also found
breast sonograms being a lot better than X-ray mammography and diagnostic
laparoscopy. But I repeat: This is my experience. I have also seen absolutely
wrong and useless sonograms. It is very relative. More ...
Question: Why are there exist minor cases of radiologist misdiagnosed or made
Answer: Minor - and mayor- cases of radiologists' misdiagnosis and inaccurate
interpretations depend mainly on:
1- Insufficient knowledge.
2- Insufficient scanning time. Many services must scan a high number of
patients a day to be profitable. I know of sites which pay for a pelvic sonogram
less than USA $8.50. In the USA the same sonogram costs about USA $265.
3- Bad technique
4- Old and unreliable machines
Question: What are the difficulties found with the images by radiologist
during an interpretation?
Answer: The most you talk with your patients, the better diagnosis you do.
You could even get the diagnosis just by talking with the patient and practicing
a limited physical examination. That is what I usually try to do, confirming my
clinical diagnosis with my scanner but ...
Moved by technology, I set up a telesonography service over the Internet: I
receive sonogram pictures images, some data relating patient symptoms and give
back my diagnosis. I also set up a secondary and inexpensive ultrasound service,
helped by a sonographer. I must be honest though: Both services are relatively
cheap for the users because I cannot get as good results as doing the sonograms
by my self. I will keep trying to get best and more economical results though,
but also will keep my private practice scanning my patients.
Question: Is there something wrong with the machine resolving power or due to
other reasons? I'm very curious about that.
Answer: Most of the time scanners work perfectly. Let me tell you something I
saw years ago:
I was attending an ultrasound meeting. Manufactures came from many countries
with their best machines. Important professors came from all over the world.
They set up a live demonstration and presented a pregnant woman to be scanned in
front of the audience. She told she was in her 18th week. A famous professor
scanned the woman using a well known French machine. He -and us- saw nothing.
Several slave monitors showed no pregnancy at all. The professor, using the
microphone told: "This machine is not working well. It is useless. Please, could
any one give a good machine?". A big "OOOOOOOOOOH" was heard coming from the
astonished audience. The professor immediately got another equipment. Neither
worked. He got another equipment, and other, and other, etc. None worked for the
I realized the woman's bladder was overfilled and displacing the pregnant
uterus upwards out of the pelvis. I left my seat and went behind the scenes, and
told them what was happening. Incidentally, the woman was the wife of a friend
of mine and I could verify that she really was in her 18 week.. The professors
also verified it .... behind the scenes . . .
Note a single word was told to the audience.
Question: During my last visit to Batu Pahat General Hospital in Malaysia, I
was told by the radiologist that what is to be solved is to resolve the
parenchymal changes on tissue and if possible find a solution in early detection
of Hepatitis B. Do you agree with him?
Answer: You can resolve parenchymal changes that could be consistent with
hepatitis, but you cannot assure it is hepatitis.... yet
Question: Last question, how much does a radiologist depend on the clinical
test report during the scanning?
Answer: A lot. Non only on the scan report, but on the questions and answers
the radiologist and patients exchange and on the limited physical examination
the radiologist should perform before scanning
Question: How accurate are obstetric sonograms?
Answer: It depends mainly on these factors:
- Gestational age: Individual differences increase as pregnancy progresses so,
measurements taken early in pregnancy are most accurate
- Used measurement: CRL measurement is more accurate than gestational sac
volume, gestational sac volume is more accurate than measure just one GS
- Operator skill and experience: To get precise measurements, you must place
the calipers according to proper anatomic landmarks
- Scanning time: Faster examinations are less accurate that dedicated
- Hardware: Intracavitary probes provide higher frequency, so their resolution
is better. Digital machines also do it better than analog machines
- Software: Its precision depends of statistics accuracy and on the
software algorithm. Dedicated external software is more accurate that the
software the ultrasound scanners provide
Next statistics come from my own experience, when doing my own sonograms,
considering that I have 19+ year sonography experience, dedicate necessary time
for each examination (just private practice), use a very good digital machine
with probes from 2.5 MHZ up to 8.5 MHz , and dedicated and updated software
developed by myself, out of statistics obtained with appropriate feedback.
Although they are very accurate, keep in mind that the decimal factor result
from calculations and they does not mean accuracy. For example, 4.1 days, does
not mean that accuracy goes as high as 0.1 day (2 hours. 24 minutes). They are
displayed because they are used for calculations precision.
Weeks Error (days)
3.9 ---> 3.0
6.1 ---> 2.6
7.2 ---> 3.0
9.8 ---> 4.1
13.1 ---> 5.5
15.0 ---> 6.3
27.4 ---> 14.2
39.5 ---> 20.5
I have been reluctant to use my own software when providing obstetric
telesonography service because conditions are different and I could not rely on