Iranian Journal of Nuclear Medicine
Volume:13 Issue: 2, 2006

Amyloidosis is characterized by an abnormal extracellular deposition of amyloid in different organs, where it usually causes some type of dysfunction. Its cause is unknown. Five different types of amyloidosis have been described according to the underlying disease; immunoglobulin amyloidosis, familial amyloidosis, senile systemic amyloidosis, secondary amyloidosis and hemodialysis-associated amyloidosis. We report a case of hemodialysis-associated amyloidosis in a 56-year-old man that radionuclide imaging demonstrated intense uptake of Tc-99m MDP within the myocardium. The diagnosis of amyloidosis was established by analysis of aspirated abdominal fat, although other non- invasive modalities didn’t reveal any positive findings. The first clue to the possible presence of amyloidosis in this case was provided by the radionuclide bone scan performed, which revealed intense tracer uptake in the heart suggesting amyloid deposit. We conclude that in cases of extraosseous accumulation of Tc-99 MDP especially as a diffuse pattern of myocardial uptake, a diagnosis of amyloidosis should be considered, in an appropriate clinical setting.

With the arrival of increasingly higher resolution PET systems, small amounts of motion can cause significant blurring in the images, compared to the intrinsic resolutions of the scanners. In this work, we have reviewed advanced correction methods for the three cases of (i) unwanted patient motion, as well as motions due to (ii) cardiac and (iii) respiratory cycles. For the first type of motion (most often studies in PET brain imaging), conventional motion-correction algorithms have relied on extraction of the motion information from the emission data itself. However, the accuracy of motion compensation in this approach is degraded by the noisy nature of the emission data. Subsequently, advanced methods, as reviewed in this work, make use of external real-time measurements of motion. Various image-based and projection-based correction methods have been discussed and compared. The paper also reviews recent and novel applications that perform corrections for cardiac and respiratory motions. Unlike conventional gating schemes, in which the cardiac and respiratory gated frames are independently reconstructed (resulting in noisy images), the reviewed methods are seen to follow a common trend of seeking to produce images of higher quality by making collective use of all the gated frames (and the estimated motion). As an observation, a general theme in motion-correction methods is seen to be the use of increasingly sophisticated software to make use of existing advanced hardware. In this sense, this field is very open to future novel ideas (hardware, and especially software) aimed at improving motion detection, characterization and compensation.

There is a limited number of case reports published in the past decade confirming the radio-iodine presence in the tear. These observations as well as reported cases of salivary and lacrimal gland dysfunction after radioiodine therapy stimulated investigators to clarify whether lacrimal gland function can be affected post-radioiodine therapy. Hence we planned a historical cohort study to evaluate this effect. We studied 100 eyes of 50 patients who were referred to the nuclear medicine department of Dr. Shariati hospital from 01.1383 to 02.1384 and had received high doses (accumulative dose: 100-450mCi) of I-131 treatment of differentiated thyroid carcinoma with their latest admission at least 3 months previously. Dry eye symptoms (obtained via a standard questionnaire) and Schirmer I test results (mm/5min) of this group were compared with those of an unexposed group (100 eyes of 50 individuals) matched by sex and age. Cases with another known cause(s) of dry eye were not included in either group. 51% of the exposed eyes and 50% of the unexposed ones revealed at least one of the dry eye symptoms in the questionnaire. Data analysis showed no significant difference between the number of symptoms of two groups, but 2 symptoms (burning, unrelated to light and erythema) were significantly higher in the exposed eyes. From 9 exposed eyes complaining of erythema, Schirmer test result was abnormal only in 2 (one patient). Also among the 10 eyes with burning symptom (unrelated to light) one patient (2 eyes) revealed abnormal Schirmer test result. The study also demonstrated a significantly lower wetting amount of the Schirmer paper in exposed group compared to others. In the patients undergone radio-iodine therapy, results were 0-4 mm in 21%, 5-9 mm in 20% and 10 mm or more in 59%. These results were seen in the unexposed group in 6%, 17% and 77%, respectively. File review of the 21 exposed eyes with 0-4 mm Schirmer test results revealed presence of the migraine history in five (4 woman) surprisingly and 131I-avid skull metastasis in another patient (2 eyes). Long-term reduction in the tear secretion from major and/or minor lacrimal glands is seen after high-dose radio-iodine therapy, which seems to be severe in the majority of patients; however these patients complain of dry eye symptoms no more than unexposed population. Conditions such as migraine may be unknown causes of impaired tear secretion and need further investigation.

Non-uniformity test is essentially the only required daily QC procedure in nuclear medicine practice. Noise creates statistical variation or random error in a flood image. Non-uniformity on the other hand does not have statistical nature and may be regarded as systemic error. The present methods of non-uniformity calculation do not distinguish between these two types of error. The Jarque-Bera and Kolmogorov-Smirnov tests were examined as alternative methods in calculation of non-uniformity in flood test images. Using the Monte carol method, uniform and non-uniform flood images of different matrix sizes and count density were generated. The uniformity of the images was calculated using the present and proposed methods. The results were also tested using 1300 planar images of 128x128 matrix size. The proposed methods were more accurate and sensitive to non-uniformity at low count density. However, their precisions were less than the conventional methods. There were no significant differences between these procedures at high count density. The integral and differential uniformity do not distinguish between noise always present in the data or in occasional non-uniformity. In a uniform intact flood image, the difference between maximum and minimum pixel count (the value of integral uniformity) is much more than recommended values for non-uniformity. After filtration of image this difference decreases but still remains high. The proposed methods are more sensitive to non-uniformity at low count density and may be used as alternative methods in daily uniformity test.

Clinical radiation nephropathy can result in considerable morbidity and/or mortality. Renal tolerance (TD5/5) has been stated to be 20 Gy when irradiation has been delivered to both kidneys in 3-5 weeks. Therefore to minimize renal toxicity in these patients, localization and shielding of the kidneys are essential. This study was carried out to evaluate the role of 99mTc-DTPA renal scintigraphy in renal localization for perfect shielding. From April 2000 to March 2001, thirteen patients had complete history, physical examination, serum creatinine level, complete blood count, urinalysis and abdominal sonography. Then the patients were referred to nuclear medicine department. After I.V. injection of 10 mCi 99mTc-DTPA, the kidneys were localized by gamma camera and marked on skin. All patients received abdominal radiation with A-P and P-A fields with cobalt 60 machine up to 3000-5000CGY. Kidneys were shielded posteriorly after 1500cGY with 5 HVL (Half value layer) blocks. After minimum follow-up of 24 months, no evidence of increasing blood pressure, edema, proteinuria, rising in serum creatinin or changing in kidney size was found. The results show that localization of kidneys by 99mTc-DTPA is a useful, easy and safe method to shield kidneys in these patients.

Various radiopharmaceuticals, including 67Ga, 201Tl, and 99mTc-sestamibi have been used to differentiate benign from malignant thyroid nodules. 99mTc-Tetrofosmin, a lipophilic cationic radiotracer, and 99mTc-sestamibi have also been reported to accumulate in thyroid tumors. In this study, we evaluated the role of 99mTc-Tetrofosmin in the differentiation of malignant from benign thyroid nodules. We prospectively studied 108 patients with solitary cold thyroid nodule on 99mTc-pertechnetate scintigraphy (33 malignant and 75 benign) to investigate the diagnostic value of 99mTc-Tetrofosmin scintigraphy. 99mTc-Tetrofosmin scintigraphy was performed 15, 60, and 120 minutes following IV injection of 20 mCi (740 MBq) of radiotracer in the anterior planar mode with a gamma camera equipped with LEAP collimator. The scans were visually analyzed by two experienced nuclear physician. The nodules with late tracer retention (activity more than adjacent thyroid tissue) were classified as positive and nodules without late retention were interpreted as negative for malignancy. Fine needle aspiration (FNA) was performed in all patients in 3-7 days interval. 52 patients were subsequently operated on while 56 patients refused surgery. These 56 patients, however, had at least two negative FNA results. 45 out of 108 nodules show high 99mTc-Tetrofosmin uptake on delayed images; 27 of them were malignant. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated to be 81.8%, 76.0%, 54.0%, and 90.4% respectively. Accuracy of the test was also determined to be 77.7%. We concluded that 99mTc-Tetrofosmin scintigraphy is a relatively sensitive, but not enough specific, method in diagnosing malignant thyroid nodules. This agent could be of value in the presence of FNA limitations.

Acceptance test is a necessary procedure after SPECT system installation. The goal of this test is to reveal system''s present condition, to compare it with manufacturer''s specifications and also as a base for later tests. This study investigated four SPECT systems in Tehran. All of the quality control tests are performed on the basis of NEMA and IAEA recommendations and by a same group. These tests include intrinsic spatial resolution, intrinsic energy resolution, temporal resolution, intrinsic linearity, maximum count rate, pixel size, intrinsic and extrinsic uniformity, sensitivity, reconstruction spatial resolution with and without scatter and centre of rotation. Results of this investigation show that three systems have minimum acceptance conditions, but the fourth one due to it''s suboptimal energy resolution and spatial resolution lacked the required specifications for acceptance. It was shown during the next six months after installation that this system showed frequent impairments and even had been out of service for a while. However, other systems did not show any considerable problems. The acceptance test is an essential step after installation of any SPECT system. If there is no considerable deficits at the initial acceptance test of a SPECT system, it won''t become troublesome for a long time.

Ionizing radiations are the hazardous agents in the workplace and all forms of ionizing radiation produce some type of injuries. Awareness of application of protection guidelines and knowledge of the principles of radiation protection can play an important role in health of employees. Survey of radiation employee’s levels of awareness and practical behavior is essential and should be standardized. The hospitals were visited to determine the number of radiation employees and to select the samples. Data was collected by questionnaire and analyses were performed by EPI6 software. The employee’s awareness about protection in the radiation room was 70%, about application of film badge was more than 85%. The employee’s awareness of periodic inspection of atomic energy organization expert was 54% and their knowledge of long term and short term radiation effects were 98% and 95%, respectively. There was a meaningful relation concerning the level of education and awareness of the employees about MPD or principles of radiation protection (P<0.0007 and P<0.003 respectively). Our results reveal that the employees have acceptable knowledge about the use of film badges, however, they lack enough awareness concerning other issues of radiation protection. Proper and periodic educational courses for radiation workers are mandatory.