Tülin Aras

Comparison of 99mTc(V)-DMSA, 201Tl and 99mTc-MIBI imaging in the follow-up of patients with medullary carcinoma of the thyroid

Radionuclide scanning with tumour-seeking agents such as pentavalent technetium-99m dimercaptosuccinic acid [99mTc(V)-DMSA], thallium-201 and technetium-99m sestamibi (MIBI) has been reported to be useful in the detection of medullary thyroid carcinoma (MTC). We undertook a study in 14 MTC patients to determine the comparative imaging potential of201Tl, MIBI and99mTc(V)-DMSA in the detection of recurrent or metastatic MTC. All patients underwent total thyroidectomy and had persistently elevated serum calcitonin levels after the surgery. Scintigraphic studies were carried out 20 min after the injection of 111 MBq of201Tl or 555 MBq of MIBI and 2 h following the injection of 370 MBq of99mTc(V)-DMSA. All scintigraphic findings were correlated with contemporaneous CT or MRI studies. CT, MRI and bone scans showed 42 (26 bone, 16 soft tissue) metastatic sites in 11 of the 14 patients. In the remaining three patients no lesions were detected during diagnostic evaluation.99mTc(V)-DMSA showed all of the soft tissue metastases but could not show two bone lesions. On the other hand, MIBI imaging was false-negative in 22 (52%) sites and201Tl was false-negative in 34 (80%) sites. Overall, lesion detection sensitivities for99mTc(V)-DMSA, MIBI and201Tl were 95%, 47% and 19% respectively. We conclude that99mTc(V)-DMSA is clearly superior to MIBI and201Tl in the follow-up of MTC patients.

Pentoxifylline Inhibits Overflow and Reduces Intestinal Reperfusion Injury

The aim of this study was to determine the effects of pentoxifylline (Ptx) in reperfusion injury of the small bowel as a leukocyte stabilizer, free radical scavenger, and microcirculatory regulator. Ninety-six male Sprague-Dawley rats were used to determine the biochemical, histopathologic and blood flow changes of the reperfused small intestines after 30 minutes of a warm ischemic insult. Animals were divided into six groups: Sham (S), sham plus Ptx (SP), ischemia (I), ischemia plus Ptx (IP), reperfusion (R), and reperfusion plus Ptx (RP). Pentoxifylline was administered intraperitoneally at a dose of 50 mg/kg 15 minutes before ischemia. The superior mesenteric artery (SMA) was occluded distal to the right colic artery and collateral arcades were ligated as described by Megison. Sixty of the 96 rats (n = 10) were used to determine histopathologic changes, malondialdehyde (MDA), and myeloperoxidase (MPO) levels in tissue. Mucosal lesions were graded on a scale from 0 to 5 as described by Chiu. MDA and MPO levels of the intestinal mucosa were assayed to reflect the free radical formation and neutrophil sequestration, respectively. Thirty-six rats (n = 6) were used to measure blood flow changes of the intestine using 133Xe clearance technique. All data were presented as the mean values plus or minus the standard error of the means (means +/- sem). Although in the R group, mucosal injury score, blood flow, MPO, and MDA levels were higher significantly from the other groups (P < .05), in the RP group blood flow, MPO, and MDA levels were significantly decreased to the basal values (P < .05). Mucosal injury score of the RP group were lower than the reperfusion group but higher than the normal (P < .05). The authors conclude that pentoxifylline pretreatment before reperfusion stabilizes blood flow, decreases MPO and MDA levels to the normal, and attenuates but not completely prevents mucosal damage.

Pentoxifylline improves blood flow to both testes in testicular torsion.

Objectives: Electromagnetic and radioisotopic studies have shown thatunilateral testicular torsion causes a decrease in contralateral testicularblood flow. Pentoxifylline improves microvascular blood flow in conditionsof vascular insufficiency. An experimental study was designed to evaluatethe effects of pentoxifylline (Ptx) on blood flow to both testes duringunilateral testicular torsion and detorsion.Materials and methods: Thirty-six adult male albino Wistar rats wererandomly divided into six groups where each consisted of six rats: group1: sham operation, group 2: sham operation with Ptx, group 3: torsion,group 4: torsion with Ptx, group 5: detorsion, group 6: detorsion with Ptx.After intraperitoneal administration of Ptx at a dose of 50 mg/kg 15minutes before torsion; right testes of the rats underwent 30 minutes oftorsion and 30 minutes of detorsion. Blood flows of both testes weremeasured during torsion and detorsion simultaneously by using 133Xeclearance technique.Results: Unilateral testicular torsion caused decrease in bilateraltesticular blood flow. Pentoxifylline had no effect on testicular blood flowduring torsion. Detorsion caused a partially increase in blood flow toipsilateral (detorted) testis, but had no effect on contralateral (nontorted)testicular blood flow. Pentoxifylline administration during detorsionsignificantly increased blood flow to both testes.Conclusions: Testicular torsion is a pathological process that causesdecreased blood flow to both testes. Pentoxifylline improves blood flow toboth testes during detorsion in a rat model of testicular torsion. Furtherstudies are needed to evaluate the effects of pentoxifylline on testiculartorsion.

99mTc-citrate versus 67Ga-citrate for the scintigraphic visualization of inflammatory lesions.

Citric acid was labeled with 99mTc with an efficiency of > 99%. The biodistribution of 99mTc-citrate was studied in mice with turpentine-induced abscesses in comparison to 67Ga-citrate. The max. abscess/muscle concentration ratios were 4.61 +/- 1.92 (3 h) for 99mTc-citrate and 4.76 +/- 2.04 (4 h) for 67Ga-citrate. Arthritis was induced in 10 rabbits by intra-articular injection of ovalbumin Scintigrams obtained 4 days later and at 3 h post-injection of 99mTc-citrate showed increased activity involving the synovium. The max. arthritic/contralateral knee ratio was 3.19 +/- 1.29 (3 h) and 6.47 +/- 3.71 (24 h) for 99mTc- and 67Ga-citrate, respectively. The blood clearance curve of 99mTc-citrate in rabbits was biexponential with a fast (T1/2 = 36 min) and a slow (T1/2 = 18 h) component, compared to mono-exponential clearance of 67Ga-citrate (T1/2 = 23 h). In 10 patients with rheumatoid arthritis whole-body scintigrams and spot images of involved joints indicated localization of the tracer in inflamed tissues. The mean target-to-soft tissue ratios were 3.04 +/- 0.81 and 4.95 +/- 2.56 for 99mTc-citrate and 99mTc-MDP, respectively. Renal clearance of radioactivity was evident from the scintigrams. Our results demonstrated that 99mTc-citrate is effective as a radiopharmaceutical for the visualization of inflammatory lesions and may be preferred to 67Ga-citrate due to the ideal physical characteristics of the radionuclide, easy preparation, low cost, early accumulation and the preference for the renal route of excretion.

Left occipital hypoperfusion in a case with the asperger syndrome

The Asperger syndrome, a less severe variant of autism, has drawn increasing interest among child psychiatrists. Cerebral blood flow studies with autistic subjects have failed to reveal consistent findings. We are reporting a case with the Asperger syndrome, whose single photon emission computed tomography showed left occipital hypoperfusion.

Brain death: determination with brain stem evoked potentials and radionuclide isotope studies.

SummaryThirty-three patients fulfilling the clinical criteria for brain death were tested by Brainstem Auditory Evoked Potentials (BAEP) and Radionuclide Cerebral Angiography and Brain Perfusion Studies. There was a significant correlation between the BAEP and radionuclide study outcomes. All patients with absence of BAEP showed no cerebral perfusion. These findings, added to the clinical findings, resulted in a final diagnosis of brain death in all patients. It is concluded that BAEP and Radionuclide Cerebral Perfusion studies are useful adjuncts for proving that brain death has really occurred.

Evaluation of 99mTc-erythromycin and 99mTc-streptomycin sulphate for the visualization of inflammatory lesions.

99mTc-erythromycin (E) and 99mTc-streptomycin sulphate (SS) were prepared with greater than 98% labelling efficiency. The labels were stable up to 24 h of testing, using ITLC-SG strips and acetone and saline as solvents. The biodistributions of both radiopharmaceuticals versus 67Ga-citrate were studied in mice with turpentine-induced abscesses at 6 days post-induction. The mice were sacrificed at 1, 3 and 6 h post-injection of 15 MBq of 99mTc-E or 99mTc-SS. Mice injected with 67Ga-citrate were sacrificed at 4 and 24 h. The maximum abscess-to-muscle ratios obtained by biodistribution studies were 2.36 +/- 1.04 (6 h), 2.38 +/- 0.38 (6 h) and 4.76 +/- 2.04 (4 h) with 99mTc-E, 99mTc-SS and 67Ga-citrate, respectively. The maximum abscess-to-contralateral tissue ratios by ROIs over respective areas on scintigrams were 2.38 +/- 0.16 (6 h), 3.21 +/- 0.14 (3 h) and 3.24 +/- 0.92 (24 h) for 99mTc-E, 99mTc-SS and 67Ga-citrate, respectively. The uptake mechanism might be infiltration into interstitial space due to increased capillary permeability.

Tl-201 uptake in brown tumors of hyperparathyroidism.

TI-201 chloride bone scans were performed on nine patients with primary hyperparathyroidism just after TI-201 and Tc-99m parathyroid subtraction scintigraphy. Bone lesions accumulate TI-201, especially in sites of brown tumor formation. This was proven by the histopathologic examination of two patients. Eight patients had bone scans with Tc-99m MDP. The lesion-to-background ratio was quantified in seven patients for TI-201 and in four patients for Tc-99m MDP. TI-201 uptake of the lesions were quantified in two patients. The lesion-to-background ratio was 1.63 ± 0.21 and 2.51 ± 0.88 for TI-201 and Tc-99m MDP, respectively. A Ga-67 citrate scan was performed on one patient, and the lesion-to-background ratio was 1.49 ± 0.06. The accumulation of TI-201 in brown tumors of bone might be due to increased blood flow and local metabolic activity. TI-201 chloride was inferior to Tc-99m MDP in lesion detection. It is concluded that bone imaging with TI-201 can easily be performed following parathyroid subtraction scintigraphy to delineate the sites of brown tumor formation.

Short-term effects of somatostatin analogue (SMS 201–995) on left ventricular function in healthy persons: A scintigraphic study

Since somatostatin has been reported to have a negative inotropic and chronotropic effect on atria and positive inotropic effect on ventricle, present study was designed to investigate the acute effects of somatostatin analogue SMS 201–995 infusion on the left ventricular function in healthy volunteers. After labeling the autologous red blood cells with 750–1000 MBq 99mTc-perthecnetate, ECG-gated radionuclide ventriculography was performed. Using Fourier analysis of the left ventricular time-activity curve, ejection fraction (EF), peak ejection rate (PER), peak filling rate (PFR), time to endsystole (TES) and normalized TES/T values were calculated. Study group consisted of 12 healthy volunteers. Somatostatin analogue SMS 201–995 infusion was given at a rate of 100 μg/h during 2h. Baseline, 1st, 2nd h and 4th h imagings were done using the same protocol. Simultaneously heart rate and blood pressure were recorded. The difference between parameters was tested using Kruskall-Wallis test. The mean heart rate, systolic and diastolic blood pressures and did not show any statistically significant change during the somatostatin analogue infusion and 2h later in comparison to baseline values. The mean PER and PFR had a slight decrease at the first hour of infusion, but the change was not significant. However, the significant correlation of PER values with heart rate, EF and TES observed at baseline study were disappeared during the infusion. These results indicate that somatostatin analogue infusion does not appear to change the left ventricular systolic and diastolic function in healthy persons significantly.

Lack of correlation between Tc-99m-sestaMIBI uptake and cadherin expression in infiltrating ductal breast carcinoma as prognostic indicators

Despite using various kinds of prognostic indicators, it is still not possible to predict the biological behavior of breast cancer in all patients. Tc-99m-sestaMIBI (MIBI) uptake determined by breast scintigraphy and cadherin expression of tumor tissue revealed by immunohistochemistry are suggested as potential agents for this purpose. We hypothesize that there can be a correlation between MIBI whose cellular mitochondrial content is claimed to play a significant role in its tumor uptake and cadherin whose downregulation causes an increase in mitochondrial activity in human mammary carcinoma cell lines. The aim of this study was to assess the relationship between the degree of MIBI tumor uptake and cadherin expression in infiltrating ductal breast carcinoma. Correlation with response to chemotherapy and some known prognostic factors of breast cancer such as tumor size, number of metastatic axillary lymph nodes and microscopic grading was also done. Fourteen patients who underwent scintimammography and subsequent surgical excisional biopsy that revealed infiltrating ductal carcinoma were enrolled in this study. Statistical analysis did not show any correlation between MIBI uptake and cadherin expression (p>0.05). Also, no statistically significant correlation was noted between MIBI uptake and tumor size, number of metastatic lymph nodes, microscopic grade, stage of the disease or response to chemotherapy. Similarly, there was no statistically significantly correlation between cadherin expression and tumor size, number of metastatic lymph nodes, microscopic grade, stage of the disease or chemotherapy response. The results of this study imply that there is no correlation between MIBI tumor uptake and cadherin expression with neither of them good enough to be used as prognostic indicators for breast cancer.