Pakistan Journal of Nuclear Medicine (PJNM) - Jan 2013 - Volume 03 - Issue 01

No Abstract. Download PDF above

Following the success of PET-CT in the last decade, there have been high expectations regarding the development of new hybrid imaging modalities such as PET-MRI. After years of development, the first simultaneous, fully integrated, wholebody PET-MRI scanner has been released and first clinical results have been published.

PET-MRI offers numerous advantages such as excellent softtissue contrast, significantly lower radiation dose than PET-CT and a wide variety of functional MR imaging combined with PET. However, there are some technical and operational challenges to be addressed. The main objectives of this study were to review the challenges and expectations in the installation, siting, and patient service provision of the Biograph mMR, the first simultaneous wholebody PET-MRI system installed in the UK and to underline the various feasible solutions.

The paper incorporates an extensive literature review, several visits to the installation site and productive discussions with associated scientists and Siemens Healthcare (Biograph mMR manufacturer). With regards to room shielding and siting requirements, several unique characteristics were observed as they had to meet the local regulations for both the PET and the MRI components. Local patient service provision requirements were addressed through developing new clinical examination protocols and through additional safety considerations. Further research will be necessary for optimising these procedures and to ensure widespread clinical adoption of the PET-MRI imaging system.

Aims: The study aimed at: a) characterizing and correcting bowelmotion induced artefacts whilst imaging the region in pre and post drug therapy 18FFDG scans; b)developing a motion model of the gut using a fully 3D nonrigid registration technique for applying to NACT digitised images.

Methods: A motion correction technique for PET-CT scans, particularly those of the abdomen and colon was developed. Attenuation and activity image volumes were generated at different points in the respiratory cycle using the Nonuniform Rational Bspline Cardiac Torso (NCAT) anthropomorphic phantom. The movement of the abdomen was characterised as part of the image registration process and assessment of the motion correction technique was performed quantitatively with Region of Interest (ROI), image fidelity, and image correlation techniques; semiquantitatively with line profile analysis; and qualitatively by overlaying non-motion-corrected and motion-corrected image frames.

Results: Motion correction was successful for frames that were substantially different to the reference (large motion); these frames had considerable differences between the ROI activities in the non-motion-corrected and reference frames. Large motion correction resulted in an improvement in image fidelity factor (from 0.848 to 0.976).

Conclusion: In principle, PET-CT motion correction of the colon can be performed using image registration between different frames in the respiratory cycle. Clinically, frames at different points in the respiratory cycle can be obtained by respiratory gating during PET image acquisition. Future work can concentrate on developing this technique so that it can be applied to clinical data.

Aims: Therapeutic use of unsealed radioisotopes with an objective of providing radiation dose to the target or affected tissue has been in clinical practice for more than 70 years. Oral administration of radioiodine is an established therapy for the treatment of differentiated thyroid cancers. To avoid unacceptably high radiation exposures to patients' family members and other related people by applying ALARA (as low as reasonable achievable) principle, patients who administered the therapeutic dosage of ¹³¹I are required to be hospitalized for some period until the retained radioactivity in the body or the exposure rate at one meter falls to acceptable levels according to national and international limits. The main aim of this study was to investigate the exposure rate patterns of inpatients administered with therapeutic radioiodine and discuss the associated radiation safety issues.

Methods: This work presents the exposure rate patterns in patients treated with ¹³¹I at our institute from 2004 to 2011. A total of 83 patients with thyroid cancer treated with different activities of ¹³¹I ranging from 50 to 150 mCi were included in this study. 76% of the patients were females and 24% male with an age range of 17 to 70 years.

Results: The majority of patients (77.11%) were discharged at the exposure rate of less than 02 mR/hr (milliRoentgen/ hour), whereas only 22.89% patients were discharged at the exposure rate between 02 mR/hr and 05 mR/hr. Only 1.2% of total patients discharged after first 24 hours following ¹³¹I administration whereas 33.73%, 25.3% and 21.67% patients were discharged after 48, 72 and 96 hours after the dose administration. Only 1.2% of the patients stayed the longest duration in isolation (264 hours or 11 days) at the hospital.

Conclusion: With proper radiation safety measurements and pursuance of instructions, reduction in exposure to family members of patients and public can be suitably achieved.

Objective: Methotrexate (MTx) is an anticancer agent used in the treatment of various cancers. The objective of this study was to document the biodistribution of ^99mTc-labelled Mtx (^99mTc-MTx) in normal subjects and patients with breast cancers.

Methods: We prepared the ^99mTc-MTx kit by a direct labelling method and studied its biodistribution in volunteer subjects and patients with breast carcinoma breast. This clinical study was preceded by animal trials.

Results: The normal biodistribution pattern in humans was characterized by nonspecific uptake in the body with the ^99mTc-MTx behaving like a blood pool agent with no evidence of specific organ uptake. The kidneys were seen to be the main route of excretion. Biodistribution data of patients with carcinoma breast showed excellent tracer uptake in the tumour and showed no other nonspecific tracer uptake.

Conclusion: This initial clinical trial showed that ^99mTc-labelled anticancer drug can be successfully used for tumour scintigraphy, which appears to be a major breakthrough as this method of labelling and scanning may be useful in future tumour staging, calculating the sensitivity of tumours to certain anticancer agent and response evaluation during chemotherapy.

Objective: To assess the regional cerebral perfusion changes in patients with major depressive illness, with or without suicidal behavior by ^99mTcHMPAO brain perfusion SPECT.

Methods: ^99mTc HMPAO brain SPECT was performed in 40 subjects including 10 controls in Group A. There were 30 patients with major depression meeting the DSM-IV criteria scoring > 17 on the Hamilton Rating Scale. The patients were subclassified into groups B and C. Group B included 16 patients suffering from major depression. Group C included 14 patients with major depression and attempted suicide or who had moderate to severe suicidal risk as assessed by Intent Score Scale. Semiquantitative assessment of cerebral perfusion was perfromed through a brain quantification software program. The cortextocerebellum ratios were calculated in 16 ROIs drawn on coronal section in all the patients.

Results: The scintigraphic evaluation of the cerebral perfusion in the Group B (nonsuicidal) showed significant hypoperfusion in the prefrontal (p < 0.001), orbitofrontal (p < 0.01), frontal motor (p < 0.01) and the temporal lobes (p < 0.01). In the Group C (suicidal), significant hypoperfusion was noticed in the prefrontal (p < 0.001), orbitofrontal (p < 0.01) and frontal motor areas (p < 0.001). The temporal lobe showed hyperperfusion (p < 0.001).

Conclusion: In major depressive illness, the prefrontal, the orbitofrontal and the frontal motor areas, are markedly hypoperfused. In severe depression not associated with any suicidal behavior, there is hypoperfusion in the temporal lobes, whereas the temporal lobes are hyperperfused in suicidal behavior, with the degree of hyperperfusion related to the severity of the suicidal behaviour.

A 63-year-old lady presented with breath lessness of over five weeks. Lung perfusion scan illustrated bilateral mismatched perfusion defects consistent with multiple pulmonary emboli. Six months later, the patient presented with dyspnoea and was assessed for ischaemic heart disease with a myocardial perfusion SPECT scan. The scan images did not show any evidence of ischaemia or infarction. However, the scan showed prominent right ventricular uptake and a D-shaped left ventricle (Movahed's sign). Repeat perfusion lung scan demonstrated persistent bilateral pumonary embolism. Echocardiogram confirmed marked right heart enlargement, significant pulmonary hypertension with pulmonary artery pressure in excess of 80 mmHg. This case illustrates diagnostic value of left ventricular shape on a myocardial perfusion scan.

Thoracic kidney is a very rare form of renal ectopia representing less than 5% of all ectopic kidneys. Ealry visualisation through functional radionuclide imaging, both preand postsurgery, helps in assessing the function and the location of the organs involved. We present a case of a 7-month-old boy with surgical closure of leftsided congenital diaphragmatic hernia. ^99mTc-DMSA scan was performed to localise the kidney and estimate the split renal function and a ^99mTc-MAA lung perfusion scan was performed to assess the relative lung function. The DMSA scan confirmed the presence of the left kidney in the left hemithorax and the perfusion lung scan showed reduced pulmonary perfusion on the left secondary to the left diaphragmatic renal hernia.

Congenital diaphragmatic hernias are most commonly diagnosed as lethal anomalies in neonates or infants. In adults, congenital hernias can present as an incidental finding or may be associated with nonspecific symptoms. The presence of a basal lung mass due to the presence of herniated abdominal contents in the thoracic cavity can appear dramatic on imaging and the unwary can be led into making a wrong diagnosis. We report a case of an incidentally diagnosed rightsided Bochdalek hernia in a young woman and discuss the developmental anomalies leading to this pathology.

Ischial tuberosity avulsion fracture usually occurs between puberty and late adolescence where the ischial tuberosity apophysis remains open and nonossified. Avulsion commonly occurs in young athletes resulting from sudden forcible contraction of the hamstrings during sudden forceful physical activity or chronic repetitive traction. Misdiagnosing ischial tuberosity avulsion is not uncommon since the clinical presentation closely mimics that of a hamstring injury. Early recognition of the fracture is important as this will enable proper management and prevent the development of chronic pain. However, ccasionally, the diagnosis is missed on plain radiographs since the radiographic features may be absent, suble or nonspecific. We present such a case of an unsuspected ischial tuberosity avulsion fracture diagnosed on SPECT-CT.

Peritoneal scintigraphy is a useful radionuclide technique in assessing the drainage function and for evaluating anatomical problems in patients on CAPD. Occasionally a patient on CAPD will present with scrotal swelling when radionuclide technique helps diagnose the cause of the swelling. We present a report of peritoneal scintigraphy in two patients on CAPD with scrotal swelling where the planar and SPECT-CT images demonstrated a connection between the peritoneal cavity and the peritesticular tunica vaginalis. This is the first report of a SPECT-CT peritoneal scintigram.

Medullary thyroid carcinoma (MTC) is a distinct C-cell tumour of the thyroid gland that produces calcitonin in high quantities. Various imaging techniques are available in nuclear medicine to image MTC which include ¹³¹I-MIBG and somatostatin receptor imaging agent ¹¹¹In-Octreotide.Due to the nonavailability of these agents in Pakistan, we tried using locally prepared ^99mTc-labelled pentavalent dimercaptosuccinic acid (^99mTc(V)-DMSA) in a patient suspected of advanced MTC. CT with contrast could not be performed in this patient due to raised serum urea and creatinine levels indicating renal impairment. ^99mTc(V)-DMSA was prepared by modification of a locally formulated kit of renal DMSA. Significant accumulation of the tracer was seen in the gross disease present in the neck and mediastinum. The resolution and good physical characteristics of ^99mTc(V)-DMSA make it a useful agent for MTC imaging, where other modalities are not available.

No Abstract. Download PDF above

No Abstract. Download PDF above

No Abstract. Download PDF above

No Abstract. Download PDF above

No Abstract. Download PDF above