Theses and Dissertations (Companion Animal Clinical Studies)http://hdl.handle.net/2263/322972024-03-29T07:08:15Z2024-03-29T07:08:15ZBeam hardening effects of lead shielding during bone scintigraphy in the horsehttp://hdl.handle.net/2263/838082022-02-12T01:30:02Z2014-10-01T00:00:00ZBeam hardening effects of lead shielding during bone scintigraphy in the horse
Lameness in the horse is one of the most common clinical entities encountered in equine veterinary practice. Obscure lamenesses, equivocal radiographic findings or non–definable lameness that does not respond to regional anaesthesia, often warrant the use of further, more advanced diagnostic imaging modalities such as nuclear scintigraphy.
Bone scintigraphy in the horse is a useful diagnostic imaging modality to help identify sites of active bone metabolism, identified as increased radiopharmaceutical uptake (IRU) in the affected area on a scintigram. The radioactive nuclide, 99mtechnetium (99mTc), is bound to freeze-dried and specially prepared pharmaceutical compounds such as methylene-diphosphonate (MDP) or disodium-oxydronate (HDP) and methylene-hydroxy-diphosphonate (MHDP), resulting in radiopharmaceuticals which are readily absorbed in areas of increased osteogenic activity. Usually, 99mTc–MDP is injected into a horse intravenously and the bone phase initiated approximately 2.5 to 3 hours later. Depending on the presenting complaint and clinicians’ requests, the procedure may involve extensive parts of the horse’s anatomy and thus personnel may be subjected to at least 1.5 to 2 hours of scanning time.
99mTechnetium is a metastable compound which decays by means of gamma ray emission, the majority of which are at an energy peak of 140.5keV. Once injected into the horse, there is extensive interaction within various tissues of the patient, but especially within large masses of muscle and bone. The resulting emitted polychromatic beam emanating from the horse has a vast spectrum of radiation energies. These energies emitted from the surface of the patient reach bystanding personnel with resultant radiation exposure. It is thus of paramount importance to establish the amount of radiation to which personnel are subjected, and whether conventional lead shielding as used in radiography, decreases the exposure during scintigraphic examinations. Due to the fact that there is interaction of the emitted radiation energies within the lead apron itself, resultant characteristic radiation produced by this interaction may theoretically be more harmful than the polychromatic spectrum emitted from the horse. The removal of lower energy radiation and thereby increasing the average energy of a spectrum is known as beam hardening.
Five average sized horses were scanned without lead shields and using combinations of lead shields of varying lead thicknesses on the horse and lead aprons as would be worn by personnel. All resultant energy spectra were measured with a spectrometer and recorded.
The energies emitted from horses injected with 99mTc–MDP differed from the energy spectrum of the pure, non–injected radiopharmaceutical. A large component of lower energies was emitted as a result of patient physical matter interaction. These energies averaged at 88–90keV. Once lead shielding was applied, two energy peaks were seen, one at 83–88keV and another at the typical gamma peak of 140.5keV for 99mTc. Depending on the thickness of the lead shielding, the heights of the two peaks varied. Generally, the thicker the lead coats, or combined lead coats (on the patient and on personnel), the smaller the 140.5keV peak and the higher the 83–88keV peak. This finding was attributed to characteristic x-rays emitted from the lead shielding through the interaction with the 140.5keV of 99mTc. Surprisingly, there was no evidence of the expected beam hardening, the average energy of the spectrum before lead shielding was higher (up to 94.1keV) than the average energy of the spectrum recorded behind lead shielding (up to 88keV). Instead, lead shielding resulted in slight “softening” of the typical 99mTc gamma spectrum. The 140.5keV peak from technetium is theoretically biologically safer than the 83–88keV peak emitted by characteristic radiation of lead coats. Personnel were exposed to lower energy scatter emitted from the horse at any rate, regardless of any application of lead shielding. The overall intensity of radiation exposure behind lead shielding, however, was reduced by 90%.
Therefore, despite altering the gamma spectrum of 99mTc into a biologically potentially more harmful lower peak of 83keV, the wearing of lead shielding during bone scintigraphy is strongly recommended, as it not only reduced the intensity of radiation considerably, but also removes the harmful lower energy scatter emitted from the patient that would otherwise reach bystanding personnel.
Further studies are needed to assess the ability of non-leaded shields to effectively shield the polychromatic energy spectrum emitted from horses during bone scintigraphy, and analyse the characteristic energy spectra emitted by these shields.
Dissertation (MSc)--University of Pretoria, 2014.
2014-10-01T00:00:00ZReticulocyte count and indices in dogs naturally and experimentally infected with Babesia rossihttp://hdl.handle.net/2263/825882021-11-09T01:18:32Z2020-01-01T00:00:00ZReticulocyte count and indices in dogs naturally and experimentally infected with Babesia rossi
Despite haemolytic anaemia being the main consequence of Babesia rossi infection
in dogs, the bone marrow response has been reported to be mild in the face of severe
anaemia. A similar finding has been described in falciparum malaria and has been
ascribed to either a decreased production of erythroid precursors or an inability of
erythroid precursors to respond to hormonal stimulus.
Recently, more information has become available on the use of various reticulocyte
indices in an attempt to describe and explain the underlying pathogenesis of various
anaemias as their release describes the recent functional state of the bone marrow.
The objective of this study was to compare the admission absolute reticulocyte count
(ARC) and reticulocyte indices in dogs naturally infected with B. rossi with dogs
suffering from immune-mediated haemolytic anaemia (IMHA), unrelated to babesiosis,
as well as healthy control dogs. The ARC and reticulocyte indices were also evaluated
in five experimentally B. rossi infected dogs throughout the disease course.
This was a retrospective observational study looking at the records generated on a
haematology analyser, the ADVIA 2120 (Siemens, Munich, Germany). The
haematocrit (HCT), ARC and other reticulocyte indices for 103 dogs, naturally infected
with B. rossi was compared to 16 dogs with IMHA and 14 control dogs. The
experimentally infected dogs consisted of five purpose-bred beagles that were infected
with high and low dose B. rossi parasite inoculum. Differences between groups were
assessed using the Mann-Whitney U test, whereas the Friedman’s ANOVA was used
to assess the change over time during the disease course in the experimentally
infected dogs. The Wilcoxon Signed Ranks test was then used to determine the
differences within the experimentally infected groups.
The median (IQR) HCT for the Babesia (0.16 L/L; 0.12 – 0.27; P < 0.001) and IMHA
(0.15 L/L; 0.12 – 0.17; P < 0.001) groups were significantly lower than the control group (0.52 L/L; 0.45 – 0.57). For the Babesia and IMHA groups the HCT did not differ
significantly. Compared to the control group (42.1 x109/L; 33.8 – 62.6), the median
(IQR) ARC was significantly higher in the Babesia (82.1 x109/L; 48.6 – 174.9; P =
0.006) and IMHA (256.7 x109/L; 79.0 – 436.9; P = 0.004) groups. The ARC was
significantly lower in the Babesia group compared to the IMHA group (P = 0.011),
despite no significant difference for HCT between groups.
On day four of the experimentally infected group, approximately 24 – 48 hours after a
peripheral parasitaemia was observed, there was a sudden decrease in the ARC to
less than its value on day one, which was inappropriate for the degree of anaemia
observed.
The reticulocytes of B. rossi naturally infected dogs were larger and more hypochromic
with a greater difference in cellular haemoglobin (CH) between reticulocytes and
mature erythrocytes compared to the control group, whereas the reticulocytes of the
experimentally infected dogs were smaller and more hypochromic than day one of
infection. All reticulocyte indices demonstrated significant differences on day four
compared to day one of the experimental study. The changes noted in the reticulocyte
indices are postulated to be a contribution of anaemia of inflammation (AID), shift
reticulocytosis and iron-restricted erythropoiesis.
This study concludes that the regenerative response in dogs naturally infected with B.
rossi is inappropriate, despite the severity of anaemia observed, compared to dogs
with IMHA. Furthermore, the findings of the experimentally group may indicate a
possible direct suppressive action of the Babesia parasite on the bone marrow during
the time of parasitaemia, resulting in insufficient erythropoiesis. Similar findings have
been reported in falciparum malaria and other factors will require further investigation.
Dissertation (MSc)--University of Pretoria, 2020.
2020-01-01T00:00:00ZEffect of acupuncture on heart rate variability at rest and on stride length and frequency at gallop in thoroughbred racehorseshttp://hdl.handle.net/2263/813092022-02-17T13:27:29Z2021-08-01T00:00:00ZEffect of acupuncture on heart rate variability at rest and on stride length and frequency at gallop in thoroughbred racehorses
The aim of this study was to determine whether three acupuncture treatments affected thoroughbred racehorses in training. Heart rate variability (HRV) at rest and stride parameters (SP) during a 600m gallop were measured. Needles were inserted for 20 minutes into pre-selected acupuncture points in the treatment horses while those in the non-treatment group were haltered.
The delta values (post-treatment minus pre-treatment) of the groups were compared. There were no significant changes (p < 0.05) in the HRV indicators. The treatment group showed (delta median of treatment vs. non-treatment group) that the parasympathetic (PNS) indicators shifted towards inhibition of the vagal system (RMSSD = - 2.19 vs. 1.47; HF = - 37.19 vs. 19.42; SD1 = - 1.56 vs. 1.04). The delta medians of indicators associated with the combined effect of the PNS and sympathetic nervous system (SDNN = 4.39 vs. - 4.00; LF = 179.48 vs. - 397.26; SD2 = 8.55 vs. - 7.48); cardiac autonomic balance (LF/HF = 0.26 vs. - 0.32; LF norm = 14.23 vs. - 0.80; HF norm = - 4.78 vs. 3.54) and heart rate measures (Mean HR = 3.96 vs. - 3.00; Mean RR = - 169.72 vs. 107.54) showed a shift in opposite directions.
The SP results showed a significant increase in maximum stride count (p = 0.004). The delta medians showed a shift in opposite directions i.e., average stride length (-0.06 vs. 0.05), average stride count (0.31 vs. -0.26), maximum stride count (0.84 vs. -5.70), maximum speed (1.30 vs. -0.80) and stride length at maximum speed (0.13 vs. -0.01).
Thus, the non-treatment group seemed to perform better and were calmer, suggesting that a withdrawal period may be appropriate following acupuncture treatments.
Dissertation (MSc (Veterinary Sciences))--University of Pretoria, 2021.
2021-08-01T00:00:00ZComparison of etorphine-midazolam and etorphine-azaperone for African buffalo (Syncerus caffer) immobilisationhttp://hdl.handle.net/2263/807392023-05-31T10:01:17Z2020-01-01T00:00:00ZComparison of etorphine-midazolam and etorphine-azaperone for African buffalo (Syncerus caffer) immobilisation
Objective To compare physiological and time variables of etorphine-azaperone (EA) to etorphine-midazolam (EM) immobilisation in African buffalo bulls.
Study design Randomised crossover study
Animal population A group of ten adult buffalo bulls of mean ± standard deviation 49 ± 19 months old and weighing 353 ± 97 kg.
Method Each buffalo was administered, by dart, EA and EM once, one week apart. Once recumbent, the buffalo was instrumented, and physiological variables were recorded at 5-minute intervals, starting at 5 minutes until 20 minutes after recumbence. Opioid antagonist (naltrexone 20 mg mg-1 etorphine dose) was administered at 40 minutes. Induction (dart placement to recumbent) and recovery (naltrexone administration to standing) times were recorded. Arterial and jugular venous blood samples were analysed for gases, acid-base status, and electrolytes at 5 and 20 minutes using a portable blood gas analyser. The arterial to end-tidal carbon dioxide gradient and alveolar to arterial partial pressure of oxygen gradient were calculated. Data were compared between combinations using a general linear mixed model and reported as mean (± standard deviation). Significant findings were set to p < 0.05.
Results The doses of etorphine, azaperone and midazolam administered were 0.015 ± 0.001, 0.15 ± 0.01 and 0.16 ± 0.02 mg kg-1, respectively. Induction times for buffalo immobilised with EA was 326 ± 304 seconds (5.4 ± 5.1 minutes) and not different to 247 ± 162 seconds (4.1 ± 2.7 minutes) for EM. The overall mean heart rate for the buffalo immobilised with EA was 113 ± 27 beats minute-1, which was significantly faster compared to 79 ± 22 beats minute-1 for EM (p < 0.001). The respiratory rate, when buffalo were immobilised with EA, was 18 ± 4 breaths minute-1 which was significantly slower compared to 23 ± 7 breaths minute-1 for EM (p < 0.001). The overall mean arterial blood pressure for buffalo immobilised with EA was 102 ± 25 mmHg, which was significantly lower compared to 163 ± 18 mmHg for EM (p < 0.001). The overall mean arterial partial pressure of oxygen for buffalo immobilised with EA was 37 ± 12 mmHg which was not different compared to 43 ± 8 mmHg for EM (p = 0.062). The potassium concentrations of both arterial and venous samples of the EM immobilised buffalo were 4.0 ± 0.4 mmol L-1 and within expected reference intervals, but significantly different compared to 3.7 ± 0.3 mmol L-1 for EA immobilised buffalo (p < 0.01). The other measured electrolytes (sodium, chloride, and ionised calcium) were not different between EA and EM buffalo nor between arterial and venous blood samples within a combination. The majority of the buffalo demonstrated a negative arterial to end-tidal carbon dioxide gradient with alveolar to arterial partial pressure of oxygen gradients greater than 20 mmHg in both EA and EM, however, there were no significant differences between drug combinations. Recovery times were 71 ± 27 seconds (1.2 ± 0.5 minutes) for EA and not different to 86 ± 44 seconds (1.4 ± 0.7 minutes) for EM immobilisation.
Conclusion and clinical relevance EM produced an equally effective and reliable immobilisation as EA in buffalo bulls. However, systemic arterial hypertension was a concern in EM and both combinations caused clinically relevant hypoxaemia. However, treatment of this hypoxaemia is questioned as no clinical variables indicated that life-threatening interventions were required. We speculate that an early compensatory response to severe hypoxaemia was most likely present. Astute monitoring is advised with both drug combinations, especially if supplemental oxygen is administered.
Mini Dissertation (MMedVet (Anaesthesiology))--University of Pretoria, 2020.
2020-01-01T00:00:00Z