Myocardial SPECT: what do we gain from attenuation correction (and when)?

AIM: This study aimed at assessing the impact of attenuation correction performed by means of a new hardware device (Beacon(tm)) in the assessment of coronary artery disease with myocardial SPECT and, afterwards, at identifying what specific risk class of patients would mostly benefit from the technique. METHODS: The first 500 consecutive patients, referred to our facility for coronary artery disease (CAD) assessment, were included in this study. Myocardial SPECT was performed after i.v. of 740 MBq of (99m)Tc Tetrofosmin (Myoview, Amersham Health) both after stress and at rest. Studies were acquired by means of a 3 head system (IRIX, Philips Medical System) equipped with the Beacontm option to correct for non-uniform attenuation. Out of the whole population studied, 130 patients underwent coronary angiography (CAG), 108 of which were proven to be affected by significant CAD, defined as a >50% coronary vessel lumen reduction. Attenuation corrected (AC) as well as non-attenuation corrected studies (NAC) were reconstructed, blindly read and qualified as: normal; borderline normal; borderline abnormal and definitely abnormal. RESULTS: In the group of 130 patients who underwent CAG, sensitivity for CAD detection did not vary significantly (96% and 93%, for NAC and AC studies, respectively, p=ns) whereas specificity increased from 73% (NAC studies) to 91% (AC studies), p<0.01. Normalcy rate, assessed in a small subgroup (n=21) with a <5% likelihood for CAD, was found to be 80% for NAC studies vs 93% for AC studies (p<0.05). As regards synthetic clinical judgements, when we grouped normal and probably normal readings into a single ''normal'' category and, conversely, probably abnormal and definitely abnormal into a single ''pathological'' category, we see that after attenuation correction studies reported as ''pathological'' are reclassified as ''normal'' in 17.8% of the cases (25.2% in males and 6.9% in females, p<0.05). The opposite is seen in only 1.6% of the cases (1.3% in males and 4.4% in females). According to established criteria, 155 patients were classified at low risk for CAD (<15%), 115 at intermediate risk (from >15% to <50%) and 230 at high risk (>50%). The intermediate risk class showed the greatest impact: ''normal'' findings increased from 52% to 72%, thus reducing the rate of ''pathological'' reports from 48% to 28%. CONCLUSIONS: This study shows that, while sensitivity for CAD is not affected by attenuation correction, specificity increases significantly, as well as normalcy rate. Out of the whole population studied, the main finding was that attenuation correction increases the rate of normal reports, more frequently in males than in females, and that studies carried out in patients at intermediate risk for CAD are more likely to be affected.

Evaluation of hypertensive patients with a solitary kidney using captopril renal scintigraphy with 99Tcm-MAG3.

The study aimed to evaluate the safety and reliability of captopril renal scintigraphy (CRS) for diagnosing functionally significant renal artery stenosis (RAS) in hypertensive patients with a solitary kidney. Radionuclide studies were carried out using 100 MBq 99Tcm-mercaptoacetyl triglycine (MAG3), 1 h after administration of 50 mg captopril, and repeated in baseline condition when abnormalities were observed in the provocative study. Scintigraphic diagnosis of RAS was based on analysis of captopril-induced changes of the radiorenographs. Overall, 12 patients with a solitary kidney were investigated, and scintigraphic results compared to angiographic findings. All five patients with positive CRS showed an RAS > 50%, whereas only one of the seven patients with negative CRS was affected by RAS. A significant fall in mean arterial pressure was recorded after captopril administration (123 +/- 12 mm Hg before versus 108 +/- 11 after), but no serious side effects were observed. Our results demonstrate that captopril-induced modifications of the renogram could effectively be used to diagnose the presence of RAS. Captopril renal scintigraphy may therefore be suggested as a reliable and safe noninvasive approach to evaluate hypertensive patients with a solitary kidney.

Evaluation of stage 4 neuroblastoma patients by means of MIBG and 99mTc-MDP scintigraphy.

In a group of 22 patients with a stage 4 neuroblastoma, MIBG and 99mTc-MDP scintigraphy and radiological skeletal survey were performed at diagnosis to assess the presence of metastatic skeletal disease. In 20 out of 22 patients the MIBG scan was repeated during follow-up at a time when maximum tumoral regression was expected, i.e. after 3-4 cycles of chemotherapy; scan results were correlated to clinical and laboratory data. At diagnosis MIBG scan showed bone involvement in 19/22 patients, 99mTc-MDP in 20/22 and radiological skeletal survey in 11/22. In 1 patient only marrow aspirate revealed diffusion of disease beyond the primitive lesion. A total of 117/161 (72%) bone lesions were detected by MIBG, 89/161 (55%) by 99mTc-MDP and 47/161 (29%) by radiological skeletal survey. MIBG scintigraphy revealed bone marrow involvement in 11/22 patients in whom either marrow aspirate or bone biopsy were positive. In 5 patients 14 soft tissue lesions were also discovered and all but one primitive lesion accumulated MIBG. Although MIBG scan detected a greater number of bone lesions than 99mTc-MDP, in two patients in whom MIBG scan was negative 99mTc-MDP revealed the presence of bone involvement. Therefore we conclude that 99mTc-MDP scan is necessary to fully assess bone involvement in neuroblastoma at diagnosis. When MIBG scan was repeated after chemotherapy there was a general reduction of the number of detected lesions and in 8/17 patients both bone metastases and marrow involvement could no longer be detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone scan in the evaluation of cementless hip prostheses.

The authors report the data obtained in a bone scan study conducted in 15 patients with cementless total hip arthroplasty. The study was conducted a minimum of 6 months and a maximum of 46 months postsurgery. Contrary to what occurs for cemented prostheses, we used bone scan not as a diagnostic aid for complications, but in order to evaluate the osteogenetic response of the bone to a cementless prosthetic implant. Zonal bone scan high uptake revealed specific areas of overloading, or, when localized in the para-articular region, they anticipated the presence of ossifications before they became visible radiographically. Bone scan was also useful in monitoring the incorporation and remodelling phases of the auto and/or homoplastic bone grafts used.

75Se HCAT test in the detection of bile acid malabsorption in functional diarrhoea and its correlation with small bowel transit.

The purpose of this study was to evaluate whether bile acid malabsorption assessed by the 75SeHCAT test, had a pathogenetic role in functional chronic diarrhoea and to ascertain whether the small bowel transit time (SBTT) could be correlated with the 75SeHCAT test results. The test was based on the counting of the abdominal retention of a 75-selenium labelled homotaurocholic acid. The 75SeHCAT test was carried out in a control group of 23 healthy adults and in 46 patients, 38 of whom were suffering from irritable bowel syndrome (IBS) of diarrhoeic form and eight patients who had undergone cholecystectomy and were suffering from chronic diarrhoea. Faecal bile acid loss was determined in nine patients, and in 14, serum bile acid increase after a standard meal was measured. In 17, SBTT was studied by hydrogen breath test after lactulose administration (21 g in 300 ml water). In 15 patients, choledochocaecal transit time was estimated by Tc99m-HIDA (111 MBq) cholescintigraphy. In 20 of 46 subjects, 75SeHCAT retention was below normal level, and in 19 cholestyramine administration relieved diarrhoea. 75SeHCAT results were related to faecal bile acid loss, while no correlation was found with serum bile acids and SBTT. The data suggest a possible wider use of the 75SeHCAT test in chronic diarrhoea to estimate bile acid malabsorption in irritable bowel syndrome, diarrhoeic form, and provide an effective treatment. In our patients small bowel transit velocity does not seem to be a pathogenetic factor of bile acid malabsorption.

Scintigraphic evaluation of enterogastric reflux using 75Se-HCAT: methodology and first clinical observations.

The aim of this study was to assess the possibility of detecting enterogastric reflux (EGR) by 75Se-HCAT cholescintigraphy. The lowest detectable activity in the gastric area at different concentrations of the radiotracer in the gallbladder was preliminary measured both in a plastic phantom and in an in vivo model. Ten patients were studied after a single oral administration of 1480 KBq 75Se-HCAT. Gamma camera imaging was carried out for five consecutive days during both fasting and after meal ingestion. In our in vivo model an EGR corresponding to 1% of gallbladder content on day one and 8% on day five was detected. In three out of five patients in whom bile was present in the stomach at endoscopy, 75Se-HCAT cholescintigraphy demonstrated an EGR, while in three out of five patients in whom endoscopy was negative, 75Se-HCAT cholescintigraphy detected EGR either during fasting or after meal ingestion. As EGR is not constant, 75Se-HCAT may be a useful tracer of bile to detect EGR over a prolonged period of time and in different physiological conditions.

Use of 23-selena-25-homocholyltaurine to detect bile acid malabsorption in patients with illeal dysfunction or diarrhea.

Abdominal gamma-counting after oral administration of 23-selena-25-homocholyltaurine (75SeHCAT) was carried out on 23 healthy volunteers and 66 patients: 33 with distal ileum resections, 3 with Crohn's disease of the ileum, 17 suffering from various intestinal diseases but with normal ileum, and 13 with chronic diarrhea syndrome but without evident intestinal or extraintestinal pathology. The percentage value of 75SeHCAT abdominal retention was assessed by analysis of the activity versus time curve, obtained by single exponential least-squares fit in five consecutive measurements (time zero and 1, 3, 5, and 7 days after 75SeHCAT administration) and directly by the gamma-camera countings on days 3, 5, and 7. The percentage values obtained from the curve on the third day were found to be the most suitable for differentiating between the groups, giving the 75SeHCAT test a 94% sensitivity and a 100% specificity. Our data show that this test is a valid indicator of bile acid loss: actually, it gave evidence of idiopathic malabsorption of bile salts in 6 patients with diarrhea of unknown origin who responded to cholestyramine and showed a correlation (correlation index = 0.585) with the residual ileum of the last meter in resected patients. Moreover, the 75SeHCAT test is easy to perform in any hospital with gamma-counting facilities and has negligible radiation risk.

Scintigraphic study of the evolution of cortical homografts in the treatment of fractures.

Twelve patients who had undergone osteosynthesis with a metal plate combined with a frozen homoplastic bone graft for the treatment of fractures or pseudarthrosis were subjected to bone scintigraphy with 99 Tc MDP. This investigation showed the graft to be a site of early and specific accumulation of the tracer. This finding supports early colonization of the graft by vascular structures and osteoblastic cells. In view of the small number of cases studied and our incomplete knowledge of the metabolic processes involved these considerations must remain hypotheses but given the excellent clinical results obtained, the relationships between homoplastic bone and host bone merit further investigation.

[Supervision of the postoperative period in biliary shunt operations: validity of sequential hepato-biliary scintiphotography with 99mTc-HIDA]. / Controllo del decorso post-operatorio negli interventi di derivazione biliare: validita' della scintifotografia sequenziale epato-biliare con 99mTc-HIDA.

The Authors' aim was to assess the effectiveness of Sequential Scintiphotography of the Liver with 99mTc-HIDA (SSFH) in the evaluation of post operative jaundice, in operations of biliary derivation (43 observations in 28 patients). SSFH proved to be highly reliable even in comparison with more laborious procedures (such as Transhepatic Cholangiography), and superior to equally simple procedures such as Echo Tomography and Computerised Tomography, evidencing itself as the investigation of choice for the study of this pathology, especially in long-term follow-ups.