Friday 15 July 2022

TOXIC VIGNETTES


CURRENT CONTENTS:
Antifreeze poisoning
Chemotherapy drugs, cardiotoxicity
Chelation
Danbury shakes (mad hatter syndrome)
Digitalis toxicity
Drugs of abuse
Gadolinium contrast agents
Moonshine
Methylated spirits (3 verses, a 'brief saga')
Workplace pollution (3 verses, a 'brief saga')





Authors' Note  Poisoning with sweet-smelling ethylene glycol is a common toxic problem for humans and pets owing to its wide commercial distribution in products including antifreeze and windshield washer fluid.

 Discovered in 1958, denatonium benzoate (sold under various tradenames, including Bitrex), tastes unbearably bitter to most mammals, even in low concentations, but is not apparently harmful otherwise. It has been used to prevent ingestion of a variety of consumer products. In 2012, all American manufacturers of antifreeze voluntarily agreed to add denatonium to these liquids in order to reduce fatal poisonings.





Author's Note  Anthracycline antibiotics, e.g. doxorubicin (adriamycin) are among the most effective chemotherapy agents; they have been profitably incorporated in multidrug chemotherapy treatment routines for many types of cancer. These advantages are partially offset by a relatively unique adverse effect — the possibility of cardiotoxicity, permanent impairment of the systolic (contracting) function of ventricular heart muscle. 
   Development of this side effect can be minimized by pharmacological manipulations and by monitoring cardiac function periodically during longterm treatment.
   Nuclear medicine techniques have classically been used, but echocardiography may also be of value (see the verse ‘Ejection Fraction’) in monitoring cardiac function.



Authors' Note:

(KEE-layt) / (kee-LAY-shun) Treatment with chelates or chelating agents, has several well-recognized uses in medicine. These include removal of toxic metals from the body, e.g. lead in cases of acute or chronic poisoning, and treatment of iron overload in patients who have received repeated blood transfusions to treat their chronic anemias. The search for drugs of this type which are safer and easier to use is ongoing.
    




  Authors' Note: Erethismus (irritation) mercurialissynonym for mercurialism, was well-known by Lewis Carroll's time, as signs of chronic poisoning had become common among workers in the hatting industry in which salts of mercury were used in the felting of furs; his character, the 'Mad Hatter' reflects the prevalent stereotype.

In the US, hat-making was centered in the Connecticut town of Danbury, where the majority of long-term workers were subject to the 'Danbury shakes' as well as other neuropsychiatric manifestations. The plant continued in operation, including the dumping of wastewater effluent, until the early 1940s. It closed at that time due to staffing shortages and the need for mercury in the armaments industry.

   In 2020, a study of fish populations in Danbury's Still River showed alarming levels of mercury; the persistence of this toxic residue reflects, in part, the concept of biomagnification. 



Authors' Note

(di-JOK-sin)

Digoxin, a cardiac glycoside derived initially from the garden plant digitalis (foxglove), has been used to treat chronic congestive heart failure and to control the heart rate in atrial fibrillation. During the author's professional lifetime, there has been a major reduction in the death-rate and in the incidence of hospital admissions for digoxin poisoning, also known as digitoxicity. This improvement is due to more judicious assessment of factors, e.g. decreasing kidney function, that may result in increasing blood levels of the drug, but also to limitation of the drug's use as alternatives have become available.  


 

Authors' Note:  Occasionally, the shock of reality may help a victim of substance abuse, like Seth, to focus on his plight. A more professional discussion of drug addiction by SheilaB may be enlightening.





Authors' Note  Although the element gadolinium (Gd) is itself toxic, its highly bound chelates make excellent adjunctive agents for diagnostic imaging procedures using magnetic resonance (MR), as they change the magnetic properties of structures with high rates of blood flow, yet allow 'negligible' release of the metal into tissue during the interval following a single intravenous injection. Non-toxic chelates of metallic elements are normally rapidly cleared from the body by urinary excretion. 

    In the late 1990s, a  ‘new’ disease,  nephrogenic systemic fibrosis was found in a small minority of patients, mostly with severe kidney disease, who had received these contrast agents. The problem can be avoided by a simple screening of relevant patients for a history of kidney disease or renal impairment. 






Authors' Note:  The toxic effects of illicit moonshine whiskey often result from the solder of car radiators, items that are conveniently incorporated into clandestine distilling equipment. Chronic kidney failure may be a delayed effect of repeated exposure to lead, cadmium and other heavy metals which leach into the brew from this source, allowing 'Whiskey Rick' and his ilk to escape responsibility for the most devastating effects of their concoctions. 


(Note that the four verses of this "brief saga" can be found in more readily legible format on the blog "Daily Illustrated Nonsense"; click HERE.)
 
(Note that the three verses of this "brief saga" can be found in more readily legible format on the blog "Daily Illustrated Nonsense"; click HERE.) 



Here's a LIST OF LINKS to collections of intriguing poems (over 160 of these!) on medical/dental topics that can now be found on various posts. 


DIRECTION FOR WEB-TRAVELLERS: 
To resume daily titillations on our related blog 'Daily Illustrated Nonsense', click HERE. Once you arrive, you can select your time frame of interest from the calendar-based listings in the righthand margin, and check the daily offerings for any month in the years 2020 to the present. (As of September 2023, there are over 1200 unique entries available on the Daily blog, and most of these are also presented here on 'Edifying Nonsense' in topic-based collections.) The 'Daily' format also has the advantage of including some videos and other material that are not shown here on this topic-based blog.

Sunday 10 July 2022

PALINKUs (poetic novelty): the sixth set


A continuation, proudly displaying more of our poems  ... 

 Go back to review our sets of ten 'palinku' poems, the first one by clicking HERE, and the most recent set , the fifth, HEREAnd if you need a brush-up on palindromes, be sure to follow the links given with the first set for the didactic offering 'Political Palindromes'.






palinku












palinku


You can find a limerick highlighting the classic palindromes, that relates to D. Trump's confidante, the self-confessed 'dirty trickster' Roger Stone, by clicking HERE.













DIRECTION FOR WEB-TRAVELLERS: 
To resume daily titillations on our related blog 'Daily Illustrated Nonsense', click HERE. Once you arrive, you can select your time frame of interest from the calendar-based listings in the righthand margin, and check the daily offerings for any month in the years 2020 to the present. (As of September 2023, there are over 1200 unique entries available on the Daily blog, and most of these are also presented here on 'Edifying Nonsense' in topic-based collections.) The 'Daily' format also has the advantage of including some videos and other material that are not shown here on this topic-based blog.


Tuesday 5 July 2022

Selected Topics in DIAGNOSTIC IMAGING


CURRENT CONTENTS:
Ode to gamma rays
Technetium generators
ECG-gated myocardial SPECT
Parathyroid scintigraphy
A.C. for SPECT
DEXA for bone mineral assessment
Fluorine-18 PET (positron emission tomography)
A.C. for PET imaging
"DOG"-scans (computed axial DOG-graphy)



Authors' Note:   In measuring ionizing radiation such as gamma rays with an instrument such as a  dosimeter, terms such as exposure-rate, flux, and fluence relate to the strength of the source. With regard to possible harm to humans and other biologic creatures, the absorbed dose is more important. The many different units involved in scientific descriptions may, in fact, detract from comprehension by non-experts. A simple rule of thumb, adopted by most professional societies, is to keep exposure "as low as reasonably achievable", as summarized in the acronymic slogan ALARA.










Authors' Note:  SPECT (Single Photon Emission Computed Tomography) imaging of the myocardium (heart muscle), performed at rest and with stress (exercise or drug infusion) is currently the most frequent test performed in hospitals' nuclear imaging departments.

   The 3-dimensional images, a type of computed tomography, are produced with a camera which detects the emission of the single-energy gamma rays following an injection of a radionuclide. By connecting the patient to a system for recording the ECG (electrocardiogram), the images can be "gated", i.e. divided into segments of the cardiac cycle; these show contraction of the ventricles, following each of two injections of the imaging agent. A muscle region showing identically poor blood flow (perfusion) and contractile function at rest and stress represents prior heart damage, and is unlikely to respond to therapy.



Authors' Note:   Attacks of renal colic (spasmodic intermittent pain) may occur due to blockage of urine flow by stones in the ureters. In adult patients, stones consisting of calcium salts are most likely. If a high serum calcium level is found (this situation prevails in only a minority of cases of kidney stones), overactivity of the tiny parathyroid (PT) glands may be responsible. Milder cases of excessive parathyroid hormone secretion may also occur without symptoms, but can lead to loss of bone mass and increased risk of bone fracture.
   A single functioning adenoma (benign tumor)  of one of the PT glands is most commonly responsible, but hyperplasia (overgrowth) of all four glands may also result in inappropriate PT hormone secretion, detected by increased blood levels. The radiotracer Tc-99m sestamibi is taken up selectively by overactive PT glands, and may help plan surgery to explore the neck and remove the tumor.



Authors' Note: Absorption of rays by body tissues complicates theinterpretation of medical imaging with nuclear techniques. ‘Hybrid' scanners combine the nuclear camera with a CT x-ray unit that provides maps of attenuation; this technique for correction of attenuation (known to workers in the field as A.C.), makes the nuclear scan more accurate in the detection of various lesions, in particular, abnormalities in blood flow to the heart muscle, and studies of deeply-located tumors, e.g. somatostatin scans.

   The combination of the two scanners (nuclear and X-ray CT) has been given the puzzling name “SPECT-CT”


 

Authors' Note  DEXA, or Dual Energy X-ray Absorptiometry, is a simple standardized imaging test to assess bone mass in the context of osteoporosis. It actually measures bone mass in a peculiar form, i.e, mass per unit area (rather than volume) of tissue; differential attenuation (blocking by tissue) for the 2 photons of different energies is assessed for each spatial element in a planar field. The technique is however, excellent for serial tests in the same patient, and is now used  so widely that its results are regarded as synonymous with Bone Mineral Density (BMD).










Authors' Note:   Absorption of rays by body tissues complicates the interpretation of medical imaging with Positron Emission Tomography (PET). In equipment development since the year 2000, 'hybrid' scanners combine the nuclear camera with a CT x-ray unit that provides maps of attenuation; this technique for correction of attenuation (known to workers in the field as A.C.), makes PET more accurate in the detection of cancer. A potential limitation, the much lower energy of the photons used for x-ray CT, turns out to have little degrading effect in practical usage.

   Moreover, anatomic localization of the lesion can be obtained at the same session, enabling techniques such as superposition of the ‘hot’ focus on a 3D anatomic body-map. This technique has been given  the difficult and somewhat redundant term ‘PET-CT’.



Authors' Note:   The confusing terminology for advanced, i.e. 3D medical imaging, uses acronyms that may be historically based or poorly explained. The development of a method of imaging known as ‘DOGgraphy’ is apocryphal. 

CAT: computerized axial tomography, X-ray imaging of a body section; better described in modern terms as ‘x-ray CT’
PET: positron (dual-photon) emission tomography; a Nuclear Medicine technique involving prior injection of a positron-emitting radionuclide ('isotope'); becoming an important modality in cancer assessment
Holography: processing of fields of light or other radiation scattered from objects; well developed with lasers, but with limited current application in medical imaging.


Here's a LIST OF LINKS to collections of intriguing poems (over 160 of these!) on medical/dental topics that can now be found on various posts. 


DIRECTION FOR WEB-TRAVELLERS: 
To resume daily titillations on our related blog 'Daily Illustrated Nonsense', click HERE. Once you arrive, you can select your time frame of interest from the calendar-based listings in the righthand margin, and check the daily offerings for any month in the years 2020 to the present. (As of September 2023, there are over 1200 unique entries available on the Daily blog, and most of these are also presented here on 'Edifying Nonsense' in topic-based collections.) The 'Daily' format also has the advantage of including some videos and other material that are not shown here on this topic-based blog.