combined scintigraphic, radiographic diag. of bone, joint diseases 2nd ed. - y. bahk (springer)

 To those who acquired their anatomical know- ledge of the skeleton with the aid of clean, dried bone specimens or a plastic mannequin it may appear as a mere inert weight-bearing sca old of the human body. However, like all other or- gans, bone constantly undergoes remodeling and tubulation through the physiological and metabolic activities of osteoblasts and osteo- clasts.  e principal role played by these bone cells is the maintenance of bone integrity and calcium homeostasis by balancing between the ratio of bone collagen production and resorp- tion and by governing mineralization proces- ses. Collagen production is a histological pro- perty common to various connective tissues, but mineralization is unique to bone cells. One of the  rst images of living human bone was a radiograph of the hand of the anatomist Kölliker taken by Wilhelm Conrad Röntgen at Würzburg University on 23 January 1896 (Fig. 1.1). Radiography then became the sole modality for visualizing the skeletal system in vivo, and it remained so until 1961 when Fle- ming and his coworkers produced the  rst Fig. 1.1 One of the  rst radiographs of living human skeleton: anatomist Kolliker’s hand, by Professor Röntgen in January 1896 at Würzburg University Fig. 1.2A, B One of the  rst bone scans made with 85 Sr. A Radiograph of forearm shows bone destruction due to metastasis in the proximal radius. B Dot photoscan reveals intense tracer uptake in the lesional area (from Fleming et al. 1961) 1 Introduction and Fundamentals of Pinhole Scintigraphy 2 Chapter 1: bone scintigraphic image using 85 Sr, a gamma ray-emitting radionuclide (Fig. 1.2). Using bone scintigraphy they successfully diagnosed bone metastasis and fracture. Historically, the event marked the beginning of the clinical use of bone scintigraphy for diagnosing skeletal disorders. During the development stage, bone scintigraphy su ered from many problems, particularly the limited image quality and con- sequent low diagnostic speci city. But with the wide availability of high-technology gamma camera systems furnished with e cient detec- tor-ampli er assemblies, high-resolution colli- mators including  ne pinhole, re ned so ware, and ideal radiopharmaceuticals such as 99m Tc- labeled methylene diphosphonate (MDP) and 99m Tc-labeled hydroxydiphosphonate (HDP), bone scanning has long become established as an indispensable nuclear imaging procedure. Bone scanning is highly valued for two major reasons: exquisite sensitivity and unique ability to assess metabolic, chemical, or molecular pro le of diseased bones, joints, and even so - tissue structures.  e usefulness of nuclear bone imaging modalities have most recently been enriched by the advent of bone marrow scintigraphy and positron emission tomogra- phy (PET) or PET-CT, further expanding the already wide scope of nuclear bone imaging science. Indeed, bone scintigraphy is recognized for its sensitivity in detecting bone metastasis weeks before radiographic change is apparent and even ahead of clinical signs and symptoms. Its useful- ness has also been thoroughly tested in the dia- gnosis of covert fracture, occult trauma with enthesitis, contusion, transient or rheumatoid synovitis, early osteomyelitis and pyogenic ar- thritis, avascular osteonecrosis, and a number of other bone and joint diseases.  e introduc- tion of single photon computed tomo graphy (SPECT) has signi cantly enhanced lesion detectability by enhancing the image contrast through slicing complex structure of the pelvis, hip, spine and skull. In addition, 67 Ga citrate and 111 In- or 99m Tc -labeled granulocyte scans have made important contributions to the dia- gnosis of infective bone diseases. As an adjunct the quanti cation of bone scan chan ges has been proposed (Pitt and Sharp 1985), and data are now automatically processed.  is analytical approach is based on the calculation of the acti- vity ratios of bone to so tissue, bone to bone, and bone to lesion. Measurement of bone clea- rance of 99m Tc-MDP, photon absorptiometry, and quantitative bone scan are used increasingly in the study of osteoporosis and osteomalacia. Most recently, 18 F FDG-PET has been shown to be a potent imaging method for the detection of not only the early primary cancers but also me- tastases to the bones, lymph nodes, and so tis- sues (Abe et al. 2005; Buck et al. 2004). In spite of unprecedented progress in com- puter technology, electronic engineering, and radiopharmaceuticals, the speci city of bone scintigraphic diagnosis has remained subopti- mal and accordingly for more speci c diagno- sis of many bone and joint diseases additional information is still sought from radiography, CT, MRI and sonography, and  nally such want has led to the hybridization of PET with CT. Silberstein and McAfee (1984) laboriously worked out a scintigraphic appraisal system to raise the speci city, but their success was parti- al.  e factors counted on for scintigraphic di- agnosis in the past were not speci c morpholo- gical features that more or less directly re ected the pathological process in question, but inclu- ded the following: increased or decreased tra- cer uptake, the number of lesions, unilaterality or bilaterality, homogeneity or not, and most problematically approximate anatomy. More essential determinants such as the size, shape, contour, accurate location, and internal texture of lesions cannot be portrayed by tracer uptake and distribution. Clearly, the reason for not analyzing more essential determinants was the relatively low resolution of the scan images made with multiple-hole collimators (O’Conner et al. 1991).  is limitation remained unreme- died even a er the introduction of SPECT. While SPECT is very e ective for the elimina- tion of the overlap of neighboring bones and signi cantly enhances contrast, the resolution remains unimproved. PET, a tomographic mo- dality like SPECT, can sensitively indicate Introduction 3 where increased amounts of FDG are deposi- ted in the cytoplasm of, for example, cancer cells. A PET scan alone, however, cannot iden- tify exact anatomy, needing the help of CT in the form of PET-CT hybridization. It is evident that on the whole the interpretation of scinti- graphy has traditionally relied on nonspeci c or indirect  ndings. Fig. 1.3 Spot scintigraphs (A–D) showing the di erence in the grade of resolution among four scanning methods used for displaying a metastasis (arrows) in the transverse process of L3 vertebra. A LEAP collimator. B Blowup or computer zooming. C Geometric enlargement. D Pinhole magni cation.  e lesion can be localized speci cally in the transverse process only by pinhole scintigraphy (D). E Anteroposterior radiograph shows osteolysis in the trans verse process of the L3 vertebra (arrows) 4 Chapter 1: Fortunately, pinhole bone scintigraphy can in greater detail display pathological changes in the individual disease of bones and joints as well as the so tissues through an optical mag- ni cation with highly improved resolution. It must be remembered that mere blow-up, com- puter zooming or multihole collimator magni-  cation does not truly enhance spatial resolu- tion (Fig. 1.3). Pinhole scintigraphy appears ideal for establishing an improved piecemeal interpretation system at least for skeletal disor- ders.  e level of spatial resolution and image contrast attained by pinhole scintigraphy has been shown to be of an order that is practically comparable to that of radiography both in nor- mal and many pathological conditions (Bahk 1982, 1985, 1988, 1992; Bahk et al. 1987). For example, the small anatomical parts of a verte- bra in adults and a hip joint in children can be distinctly discerned using this method. In an adult vertebra the pedicles, apophyseal joints, neural arches, and spinous process are clearly portrayed and in a pediatric (growing) hip the acetabulum, triradiate cartilage, capital femo- ral epiphysis and physis, and trochanters are regularly discerned (Chap. 4). Clinically, pinhole scanning permits di erent- ial diagnosis, for example, among metastases, compression fractures, and infections of the spine (Bahk et al. 1987).  e “pansy  ower” sign of costosternoclavicular hyperostosis, a pathognomonic “bumpy” appearance of the long bones in infantile cortical hyperostosis, and the “hotter spot within hot area” sign of the nidus of osteoid osteoma are just a few examp- les of diagnoses that can be made by observing characteristic or pathognomonic signs of the individual diseases (Bahk et al. 1992; Kim et al. 1992). To summarize, it appears that, used along with the holistic physicochemical data derived from whole-body, triple-phase, and spot 99m Tc- MDP bone scans, the detailed anatomicometa- bolic pro les of skeletal disorders portrayed by pinhole scintigraphy enormously enhance dia- gnostic feasibility. In addition, it is indeed worth reemphasizing that the diagnostic accu- racy of pinhole scintigraphy can be greatly sharpened if the scintigraphs are read side-by- side with radiographs—the common royal road to all image interpretations (Fig. 1.3D, E). 1.1 A History of Nuclear Bone Imaging Conceptually, the nuclear imaging of bone can be dated from the mid-1920s when the notion of bone-seeking elements evolved from the clinical observation of radium-related osteo- myelitis and bone necrosis (Blum 1924; Ho - man 1925). Shortly following successful isola- tion by the Curies, radium was processed to produce self-luminous materials to be painted on watch dials and instrument panels. During the painting of such radioactive materials with small brushes, workers habitually pointed the brush tip between their lips, and this resulted in chronic ingestion and subsequent bone de- position of hazardous radioactive elements, eventually causing deleterious e ects (Ho - man 1925).  e initial theory was that bone deposition of radium was caused by phagocy- tosis of the reticuloendothelial cells in bone marrow, but soon it was found that bone itself actively accumulates radioelements (Martland 1926).  is was later con rmed by Treadwell et al. (1942) who showed by radioautography that 89 Sr, a beta-emitting bone-seeking element, was laid down in both normal and sarcoma tis- sues. Two decades elapsed until, with the advent of the γ-counter, γ-scanner, and γ-emitting bone-seekers such as 47 Ca and 85 Sr, a new era of nuclear bone imaging was opened. In 1961 Gynning et al. detected the spinal metastases of breast cancer by external counting of the in-vi- vo distribution of 85 Sr.  e data were displayed in a pro le graph so that increased radioactivi- ties in diseased vertebrae were indicated by an acute spike. In the same year, the  rst photo- graphic scintigraph of bone showing selective accumulation of 85 Sr at the site of metastasis with fracture in the radius was published (Fig. Introduction 5 1.2) (Fleming et al. 1961). On the other hand, Corey et al. (1961), using 47 Ca and 85 Sr, showed the possibility of detecting bone pathology by bone scanning before X-ray changes became manifest. However, the 47 Ca scan turned out to be impractical because of the high energy (1.31 MeV) of its principal gamma ray. Accordingly, 85 Sr was then held to be the radionuclide of choice for bone scanning, although it also has drawbacks of a long physical half-life (65 days) and a relatively high-energy gamma emission of 513 keV. Charkes (1969) suggested that 87 Sr might overcome these shortcomings.  e phy- sical half-life of 87 Sr is only 2.8 h, permitting safe administration of a larger dose with incre- ased activity in bone. On the other hand, 18 F, another bone-seeking element, was already in use (Blau et al. 1962).  is is a cyclotron pro- duct possessing a stronger avidity for bone than strontium, with about 50% of an injected dose incorporated into bone. It emits a posit- ron that creates, by annihilation with an elec- tron, two gamma rays having an energy of 511 keV that is suitable for external detection and scanning. Currently, 18 F in the form of 18 F- u- orodeoxyglucose (FDG) is globally used for PET in tumor and many other diseases. Once its high production cost and short physical half-life (1.83 h) prevented popularization, but these problems were solved with the develop- ment of an easily manageable, compact, econo- mical cyclotron.  e ready availability of 18 F- FDG and PET-CT is expected to make a signi cant contribution to nuclear imaging, es- pecially in oncology. In the meantime, technetium- 99m ( 99m Tc) tagged compounds were introduced as potent bone scan agents by Subramanian and McAfee (1971). Technetium- 99m is an ideal radiotracer for most scintigraphy with a short physical half-life (6.02 h), a single gamma ray of optimal energy (140 keV), low production cost, and ready availability (Harper et al. 1965; Richards 1960).  e  rst preparation was 99m Tc-triphos- phate salt but this was soon replaced successively by 99m Tc-polyphosphate, 99m Tc-pyro phosphate, 99m Tc-diphosphonates, and  nally 99m Tc-me- thylene diphosphonate (MDP) (Castronovo and Callahan 1972; Subramanian et al. 1972, 1975; Citrin et al. 1975; Fogelman et al. 1977). With the integrated development of a family of ideal radiopharmaceuticals and high-technolo- gy gamma camera systems equipped with an e cient pinhole magni cation device with so ware and SPECT, bone scintigraphy is now  rmly established as the most frequently used and highly rewarding nuclear imaging method. Furthermore, bone marrow scan and the alrea- dy mentioned 18 F FDG PET have been added to the existing large arrays of imaging modali- ties of the musculoskeletal system with almost unlimited diagnostic feasibility, which is tho- roughly noninvasive. Of various bone scintigraphic studies, this book mainly focuses on pinhole scintigraphy, a potent solution to the suboptimal speci city of ordinary bone scan, with commentary discus- sions on the SPECT, PET, and bone marrow scan. It is true that pinhole scintigraphy takes a longer time to perform than planar scintigra- phy, but the longer time is more than compen- sated for by the richness of information. Actu- ally, pinhole scan time is comparable to or even shorter than that of SPECT. As described in the technical section, the re ned pinhole technique using an optimal aperture size of 4 mm, cor- rect focusing, and 99m Tc-MDP or -HDP, the time can now be reduced to as short as 15 min.  e information generated by pinhole scan- ning is unique in many skeletal disorders (Bahk 1982, 1985; Bahk et al. 1987, 1992, 1994, 1995; Kim et al. 1992, 1993, 1999; Yang et al. 1994). Interestingly, historically the pinhole collima- tor was the  rst collimator used for gamma imaging by Anger and Rosenthall (1959). However, for reasons that are not apparent other than its tediousness, it has since largely been ignored and replaced by multihole colli- mators and planar SPECT. It seems that this has occurred within a short period of time without logical reasoning and thorough explo- ration into its utility. Nevertheless, restricted to the diagnosis of hip joint disease, pinhole scan- ning was enthusiastically used by Danigelis et al. (1975), Conway (1993), and Murray in Syd- ney (personal communication), and more re- 6 Chapter 1: cently the Boston group extended its applica- tion to diseases of bone and joints other than the hip in the pediatric domain (Treves et al. 1995). As discussed in detail in Chap. 2, most recently dual-head planar pinhole scintigraphy (Bahk et al. 1998a) and pinhole bone SPECT (Bahk et al. 1998b) have been added to single- head planar pinhole scintigraphy.  e former modi cation signi cantly shortens the scan time and solves the problem of the blind zone that is present on single-head pinhole scans, and the latter can further improve the resoluti- on and contrast by the addition of slicing to magni cation. 1.2 Histology and Physiology of Bone Living bone is continuously renewed by pro- duction and resorption that are mediated through the bioactivities of the osteoblasts and osteoclasts, respectively.  e bone turnover is well balanced and in a state of equilibrium un- less disturbed by disease and/or disuse. When bone production is out-balanced by bone resorption or destruction, as in acute osteomy- elitis, tumor, or immobilization, osteolysis or osteopenia may ensue. In a reverse condition, osteoblastic reaction predominates, resulting in osteosclerosis or increased bone density. Histologically,  ve di erent types of bone cel- ls are known to exist.  ey are osteoprogenitor cells, osteoblasts, osteocytes, osteoclasts, and bone-lining cells. Osteoprogenitor cells, also known as preosteoblasts, proliferate into osteo- blasts at the osseous surface. Osteoblasts are the main bone-forming cells both in membranous and endochondral ossi cation.  e osteoblast, a mononuclear cell, produces collagen and muco- polysaccharide that form osteoid. It is also close- ly associated with osteoid mineralization.  e osteocytes are the posterity cells of osteoblasts entrapped within bone lacunae.  eir main functions are the nutritional maintenance of the bone matrix and osteocytic osteolysis. Being multinucleated, osteoclasts are involved in bone resorption by osteoclasia. Formerly, the osteo- clast and osteoblast were considered to stem from the same or at least related sources. New evidence, however, has indicated that the cell lines for these two cells are histogenetically di e- rent (Owen 1985). At present, it is widely held that osteoclasts originate from stromal cells of mesenchymal tissue via osteoprogenitor cells, while osteoblasts originate from the mono- cyte-phagocyte line of the hematopoietic system. Bone-lining cells are probably the inactivated form of osteoblasts. Like osteoblasts, these cells line the osseous surface.  e cells are  at and elongated in shape with spindle-shaped nuclei. Although not established yet, their function is probably related to the maintenance of mineral homeostasis and the growth of bone crystals. Osteogenesis is accomplished by minerali- zation of organic matrix or osteoid tissue, which is composed mainly of collagen (90%) and surrounding mucopolysaccharide. Mine- ralization starts with the deposition of inorga- nic calcium and phosphate along the longitudi- nal axis of collagen  brils, a process referred to as nucleation. Nucleation is precipitated by a chemical milieu in which the local phosphate concentration is increased or conversely calci- um salt solubility is decreased. A er nucleati- on, salt exists in a crystalline form and grows in size as more calcium and phosphate precipi- tate. Crystallized salt has resemblance to hy- droxyapatite [Ca  (PO  )·6OH  ]. Bone formation is stimulated by various fac- tors including physical stress and strain and calcium regulatory hormones (parathormone, calcitonin), growth hormone, vitamins A and C, and calcium and phosphate ions. On the other hand, bone resorption occurs as bone matrix is denatured by the proteolytic action of collagenase secreted by osteoclasts. Factors that stimulate osteoclastic activity include bo- dily immobilization, hyperemia, parathor- mone, biochemically active metabolites of vita- min D, thyroid hormone, heparin, interleukin-1, and prostaglandin E.  e skeletal muscles are rich in actin and myosin, the interactions of which cause con- traction.  ey are composed of a large number Introduction 7 of muscle  bers (cells). Muscle  bers, individu- ally invested by the endomysium, are grouped in fascicles enveloped in successive connective tissue sheaths. Variable numbers of fascicles compose a skeletal muscle that is ensheathed by the epimysium. Tendon is a specialized con- nective tissue that unites with muscle belly for- ming the musculotendinous unit on one side and attaches to the periosteum,  brous capsule of the joint, or directly to bone on the other side. 1.3 Mechanism of Bone Adsorption of 99m Tc-Radiopharmaceuticals  e mechanism of 99m Tc-labeled phosphate deposition in bone has not fully been clari ed. However, it is known that the deposition is strongly in uenced by factors such as meta- bolic activity, blood  ow, surface bone area available to extracellular  uid, and calcium content of bone. For example, metabolically active and richly vascular metaphyses retain 1.6 times more 99m Tc than less-active diaphyses of long bones (Silberstein et al. 1975), and such a metabolism- and vascularity-dependent bio- mechanism can be portrayed by scintigraphy of growing bone or highly vascular rachitic or pagetic bones. Another important factor is the nature of calcium phosphate in bone as indi- cated by the Ca/P molar ratio. Francis et al. (1980) experimentally demonstrated that di- phosphonates are more avidly adsorbed to the immature amorphous calcium phosphate (Ca/ P 1.35) than to the mature hydroxyapatite crys- tal (Ca/P 1.66).  e low Ca/P salt typically exists in the rapidly calcifying front of osteoid matrix in the physes of growing long bones, whereas crystalline hydroxyapatite exists in the cortical bones. Various theories have been proposed regar- ding the site of deposition. Jones et al. (1976) suggested that a small amount of phosphate chemisorbs at kink and dislocation sites on the surface of the hydroxyapatite crystal. On the other hand, the organic matrix is considered to be the site of calcium salt deposition (Rosent- hall and Kaye 1975). Francis et al. (1981) have shown that the deposition of diphosphonate takes place almost exclusively on the surface of the inorganic calcium phosphate. Evidence in support of this  nding has been provided by autoradiographic study (Guillermart et al. 1980). 1.4 Bone Imaging Radiopharmaceuticals  e advantageous properties of 99m Tc were re- ported by Richards (1960) and Harper et al. (1965), but it was not until the introduction of triphosphate complex by Subramanian and McAfee (1971) that 99m Tc became the most promising bone scan agent.  us, this initial work on 99m Tc-labeled phosphate compounds opened a path to the development of a series of novel bone scan agents. Within a short period of time, 99m Tc-labeled polyphosphate, pyro- phosphate, and diphosphonate were developed in series for general use. Chemically, phosphate compounds contain a plural number of phos- phate residues (P–O–P), the simplest form be- ing pyrophosphate with two residues. Phos- phonate has P–C–P bonds instead of P–O–P bonds and diphosphonates are most widely used. Now these are available as 99m Tc-labeled hydroxydiphosphonate (HDP) and 99m Tc-la- beled MDP.  e phosphonate compounds have a strong avidity for hydroxyapatite crystal, es- pecially at the sites where new bone is actively formed as in the physeal plates of growing long bones. Following intravenous injection, 99m Tc- phosphate and 99m Tc-diphosphonate are rapid- ly distributed in the extracellular  uid space of the body, and about half of the injected tracer is  xed by bone and the remainder excreted in the urine by glomerular  ltration (Alazraki 1988). According to Davis and Jones (1976), the amount of radiotracer accumulated in bone 8 Chapter 1: 1 h a er injection is 58% with MDP, 48% with HEDP, and 47% with pyrophosphate.  e latest form of the diphosphonate series is disodium- monohydroxy-methylene diphosphonate (oxidronate sodium, CH 4 Na 2 O 7 P  ) marketed as TechneScan HDP. Its blood and nonosseous clearance is much faster than that of 99m Tc-la- beled MDP, and the blood level is about 10% of the injected dose at 30 min with a rapid fall therea er, reaching 5%, 3%, 1.5%, and 1% at 1 h, 2 h, 3 h, and 4 h, respectively, a er injec- tion (Mallinckrodt 1996). An advantage of this preparation is that an optimum blood level is reached as early as at 1–2 h a er injection; as a result the scan time is conveniently reduced without increasing the tracer dose. 1.5 Bone Marrow Scan Radiopharmaceuticals 99m Tc-nanocolloid and 99m Tc-anti-NCA95 an- tibody are two representative agents for bone marrow scanning.  ese agents image erythro- poietic precursor cells, reticuloendothelial cells (REC), and granulopoietic cells. Phagocytosis is the mechanism by which 99m Tc-colloids vi- sualize REC. Unfortunately, red marrow up- take of currently available 99m Tc-colloids is not large enough to produce marrow image of suf-  cient quality. In addition, disparity may occur between the locations of REC and hematopoi- etic cells in di erent hematological disorders.  eoretically, 52 Fe and 59 Fe can be used for the imaging of erythropoietic bone marrow, but their unsuitable physical characteristics pre- vent practical use. 111 In-chloride has been test- ed as an iron substitute, but has been found not to be satisfactory (Lilien et al. 1973). 111 In- chloride is an expensive agent. 1.6 Fundamentals of Pinhole Scintigraphy  is section considers the spatial resolution and sensitivity of the pinhole collimator as related to aperture size and aperture-to-target distance. In addition, the parameters that a ect image quality are brie y discussed. For those interested in a mathematical presen- tation of this subject, a separate chapter is appended. A scintigraphic image is the cumulative re- sult of a number of physical parameters inclu- ding (a) radionuclide, (b) amount of radioacti- vity, (c) collimator design, (d) detector e ciency, and (e) image display and recording devices. Other factors such as patient move- ment during scanning and various artifacts can also a ect the spatial resolution, object con- trast, and sensitivity, which all seriously a ect lesion detectability (Appendix and Chap. 5).  e tracer must be localized to bone and deliver a low radiation dose while permitting a high count density in the target. In this respect, 99m Tc with a half-life of 6.02 h and a monoenergetic gamma ray of 140 keV labeled to phosphates is ideally suited for bone scan- ning. As a rule, 740–925 MBq (20–25 mCi), or a slightly higher dose in the elderly who have Fig. 1.4 Schematic diagram showing inversion and mag- ni cation of pinhole image. D Diameter of detector or crystal, t thickness of detector, a collimator length or de- tector-to-aperture distance, d aperture-to-object distance, a acceptance angle Introduction 9 reduced bone metabolic function, of 99m Tc- MDP or 99m Tc- HDP is injected with satisfactory results and an acceptably low radiation dose. Basically, a gamma camera system consists of a scintillation detector with collimator, electron- ic devices, and image display and recording de- vices. Of these, the collimator is probably the most important variable that a ects image res- olution.  e primary objective of a collimator is to direct the gamma rays emitted from a se- lected source to scintillation detector in a spe- ci cally desired manner. Four di erent types of collimators are used: pinhole collimator, and parallel-hole, converging and diverging multi- hole collimators.  e pinhole collimator is a cone-shaped heavy-metal shield that tapers into a small aperture perforated at the tip at a distance a from the detector face, which may be either circular or rectangular in shape (Fig. 1.4).  e geometry of the pinhole is such that it optically creates an inverted image of the object on the crystal detector from the photons traveling through the small aperture.  e design is based on aperture diameter, acceptance angle α, colli- mator length a, and collimator material.  e aperture diameter of a pinhole collima- tor is the most important and direct determi- nant of the system’s resolution and sensitivity. Evidently, the collimator with a smaller aper- ture diameter can produce a scan image with a higher resolution, but at the expense of sen- sitivity, and vice versa.  erefore, optimization of the two contradicting parameters is necessa- ry. In practice, a collimator with an aperture diameter of 3 or 4 mm is optimal.  e magni - cation, resolution, and sensitivity of a pinhole collimator acutely change with the aperture- to-target distance.  us, image magni cation with a true gain in both resolution and sen- sitivity can be achieved by placing the collima- tor tip close to the target. Fig. 1.5A, B Local recurrence of colon carcinoma. A Lateral planar bone scintigraph shows no abnormal tracer uptake (?). B Lateral pinhole scintigraph demon- strates minimal uptake in the presacral so tissue, de- noting recurrence (arrow) A B [...]... References Bahk YW (1988) Pinhole scintigraphy as applied to bone and joint studies In: Proceedings of Fourth Asia and Oceania Congress of Nuclear Medicine and Biology, Taipei, pp 93–95 Bahk YW (1992) Scintigraphic and radiographic imaging of inflammatory bone and joint diseases Pre-Congress Teaching Course of Fifth Asia and Oceania Congress of Nuclear Medicine and Biology, Jakarta, pp 19–35 Bahk YW,... (1982) Usefulness of pinhole scintigraphy in bone and joint diseases (abstract) Jpn J Nucl Med 29:1307–1308 Bahk YW (1985) Usefulness of pinhole collimator scintigraphy in the study of bone and joint diseases (abstract) European Nuclear Medicine Congress London, p 262 Bahk YW (1988) Pinhole scintigraphy as applied to bone and joint studies In: Proceedings of Fourth Asia and Oceania Congress of Nuclear Medicine... Taipei, pp 93–95 Bahk YW (1992) Scintigraphic and radiographic imaging of inflammatory bone and joint diseases Pre-Congress Teaching Course of Fifth Asia and Oceania Congress of Nuclear Medicine and Biology, Jakarta, pp 19–35 Bahk YW, Kim OH, Chung SK (1987) Pinhole collimator scintigraphy in differential diagnosis of metastasis, fracture, and infections of the spine J Nucl Med 28:447–451 Bahk YW, Chung... views include Water’s view of the paranasal sinuses, Towne’s view of the occiput, seated view of the sacrum and coccyx, butterfly view of the sacroiliac joint, frog-leg view of the hip joints, sunrise view of the patella, and tunnel view of the intercondylar notch of the distal femur (see respective figures in Chap 4) Understandably, it is important to maintain the assured quality of individual scan parameters... scan time (sensiti- vity) In general, pinhole scanning is efficiently performed with aperture-to-skin distance of 0–10 cm For example, one vertebra or two with intervertebral disk, the hip or knee joint, fingers with small joints are imaged at no distance, while the whole cervical spine is imaged at a distance of about 10 cm A total of 400–450 k-counts are accumulated over a period of 15– 12 Chapter... posterior tibiofibular joint, st sustentaculum tali, stj subtalar joint, t talus, tfj talofibular joint, tncj talonaviculocuneiform joint, tnj talonavicular joint, tnl talonavicular ligament, trs trochlear surface, ttj tibiotalar joint (from Bahk et al 1998b, with permission) 20 min The scan time has been reduced from the previous 30–60 min by optimizing scan parameters and using 99mTc-HDP It is worth... atlantoaxial (aa) joints are relatively photopenic because they are larger than the other joints B Open-mouth anteroposterior radiograph identifies the atlantooccipital joints (ao), lateral masses of the atlas (lm), the dens or odontoid process (d), and the atlantoaxial joints (aa) tal joint, the median atlantoaxial joint, and the base of the dens Generally, tracer uptake in the apophyseal joints and spinous... anatomical detail and the clarity of the metabolic profile, and hence, the diagnostic efficacy of bone scintigraphy For example, important anatomical landmarks can be portrayed on a pair of anterior and posterior scans of the hip The anterior scan visualizes the femoral head, acetabular so- 16 A Chapter 2: B A C Fig 2.1A–C Paired dual-head pinhole scans of a normal hip joint A Anterior scan clearly showing... sacroiliac joints (thin arrows) (from Bahk et al 1998a, with permission) Thus, for example, in acute pyogenic synovitis of the ankle, paired medial and lateral pinhole scans permit an objective three-dimensional analysis of inflamed synovia in the anterior, posterior, medial, and lateral compartments of the ankle (Fig 2.4A, B) At present, this is probably the best imaging examination of bone and joint diseases. .. SPECT is related to the optical design of the parallel-hole collimator, which primarily focuses on the enhancement of the system’s sensitivity and not so much on the resolution In addition, the resolution of a gamma camera system is impaired by a finite cut-off frequency of the reconstruction filter, limited interval of angular sampling, and restricted sizes of the display matrix In general, planar . particularly the limited image quality and con- sequent low diagnostic speci city. But with the wide availability of high-technology gamma camera systems furnished with e cient detec- tor-ampli. hydroxyapatite crys- tal (Ca/P 1.66).  e low Ca/P salt typically exists in the rapidly calcifying front of osteoid matrix in the physes of growing long bones, whereas crystalline hydroxyapatite. physiologically reduced bone tur- nover rate. As the scrutiny of the preliminary scan dictates, the study may be augmented with the pinhole technique. It is advocated that as many apparently